Make DOOM work

I think I lost this work originally

.github/workflows/build-test.yml

@@ -10,7 +10,7 @@ jobs:
   build:
     strategy:
       matrix:
-        os: [ubuntu-latest, windows-latest]
+        os: [ubuntu-latest, windows-latest, macos-latest]
 
     runs-on: ${{ matrix.os }}
 

Avalonia.Base/Avalonia.Base.csproj

@@ -0,0 +1,7 @@
+<Project Sdk="Microsoft.NET.Sdk">
+
+    <PropertyGroup>
+        <TargetFramework>net5.0</TargetFramework>
+    </PropertyGroup>
+
+</Project>

Avalonia.Base/README.md

@@ -0,0 +1,2 @@
+See `Robust.Client/UserInterface/XAML/RiderNotes.md` for why this project exists.
+We are not actually using Avalonia (yet).

MSBuild/Robust.Engine.props

@@ -4,5 +4,6 @@
         <TargetFramework>net5.0</TargetFramework>
         <LangVersion>9</LangVersion>
         <Nullable>enable</Nullable>
+        <WarningsAsErrors>nullable</WarningsAsErrors>
     </PropertyGroup>
 </Project>

OpenToolkit.GraphicsLibraryFramework/OpenToolkit.GraphicsLibraryFramework.csproj

@@ -14,12 +14,6 @@
     <PackageReference Condition="'$(TargetFramework)' == 'net472'" Include="System.Memory" Version="4.5.3" />
   </ItemGroup>
 
-  <ItemGroup>
-    <Content Include="OpenToolkit.GraphicsLibraryFramework.dll.config">
-      <CopyToOutputDirectory>PreserveNewest</CopyToOutputDirectory>
-    </Content>
-  </ItemGroup>
-
   <ItemGroup>
     <ProjectReference Include="..\Robust.Shared\Robust.Shared.csproj" />
   </ItemGroup>

OpenToolkit.GraphicsLibraryFramework/OpenToolkit.GraphicsLibraryFramework.dll.config

@@ -1,5 +0,0 @@
-<configuration>
-    <!-- I actually have no idea whether this works on FreeBSD but it can't hurt to set it as such. -->
-    <dllmap os="linux,freebsd" dll="glfw3.dll" target="glfw.so.3" />
-    <dllmap os="osx" dll="glfw3.dll" target="glfw.3.dylib" />
-</configuration>

README.md

@@ -1,25 +1,16 @@
 ![Robust Toolbox](https://raw.githubusercontent.com/space-wizards/asset-dump/3dd3078e49e3a7e06709a6e0fc6e3223d8d44ca2/robust.png)
 
-[![Build status](https://ci.appveyor.com/api/projects/status/ygb7t8hsj3wt7pnm/branch/master?svg=true)](https://ci.appveyor.com/project/Silvertorch5/space-station-14/branch/master)
-[![Coverage](https://sonarcloud.io/api/project_badges/measure?project=ss14&metric=coverage)](https://sonarcloud.io/dashboard?id=ss14)
+Robust Toolbox is an engine primarily being developed for [Space Station 14](https://github.com/space-wizards/space-station-14), although we're working on making it usable for both [singleplayer](https://github.com/space-wizards/RobustToolboxTemplateSingleplayer) and [multiplayer](https://github.com/space-wizards/RobustToolboxTemplate) projects.
 
-Robust Toolbox is a client/server backend for [Space Station 14](https://github.com/space-wizards/space-station-14).
+Use the [content repo](https://github.com/space-wizards/space-station-14) for actual development, even if you're modifying the engine itself.
 
-### *This repository is the *engine* section of SS14. This is the base engine all SS14 servers will be built on. As such, it does not start on its own: it needs the [content repo](https://github.com/space-wizards/space-station-14). Use said repo for actual development, even if you're modifying the engine itself. Think of Robust Toolbox as BYOND in the context of Spacestation 13.*
+## Project Links
 
-## Getting in Touch
+[Website](https://spacestation14.io/) | [Discord](https://discord.gg/t2jac3p) | [Forum](https://forum.spacestation14.io/) | [Steam](https://store.steampowered.com/app/1255460/Space_Station_14/) | [Standalone Download](https://spacestation14.io/about/nightlies/)
 
-* Website: [spacestation14.io](https://spacestation14.io/)
-* Discord: [Invite Link](https://discord.gg/t2jac3p)
-* IRC: `irc.rizon.net#spacebus`
-* Code Analysis: [Sonar Cloud](https://sonarcloud.io/dashboard?id=ss14)
-* Automatic Content Builds: [builds.spacestation14.io](https://builds.spacestation14.io/jenkins/)
+## Documentation/Wiki
 
-The IRC is setup to relay back and forth to the Discord server so [IRC nerds](https://xkcd.com/1782/) will not be left out.
-
-## Documentation
-
-We have various technical documentation articles on the [HackMD Wiki](https://hackmd.io/@ss14/docs/%2F%40ss14%2Ftechnical-documentation-overview).
+The [HackMD Wiki](https://hackmd.io/@ss14/docs/wiki) has documentation on SS14s content, engine, game design and more. We also have lots of resources for new contributors to the project.
 
 ## Contributing
 
@@ -27,8 +18,8 @@ We are happy to accept contributions from anybody. Get in Discord or IRC if you
 
 ## Building
 
-**In practice, you usually don't build this repository directly.**
+This repository is the **engine** part of SS14. It's the base engine all SS14 servers will be built on. As such, it does not start on its own: it needs the [content repo](https://github.com/space-wizards/space-station-14). Think of Robust Toolbox as BYOND in the context of Spacestation 13.
 
 ## Legal Info
 
-See `legal.md` for licenses and copyright.
+See [legal.md](https://github.com/space-wizards/RobustToolbox/blob/master/legal.md) for licenses and copyright.

Resources/Locale/en-US/console.ftl

@@ -0,0 +1 @@
+console-line-edit-placeholder = Command Here

Resources/Locale/en-US/input.ftl

@@ -0,0 +1,54 @@
+input-key-Escape = Escape
+input-key-Control = Control
+input-key-Shift = Shift
+input-key-Alt = Alt
+input-key-Menu = Menu
+input-key-F1 = F1
+input-key-F2 = F2
+input-key-F3 = F3
+input-key-F4 = F4
+input-key-F5 = F5
+input-key-F6 = F6
+input-key-F7 = F7
+input-key-F8 = F8
+input-key-F9 = F9
+input-key-F10 = F10
+input-key-F11 = F11
+input-key-F12 = F12
+input-key-F13 = F13
+input-key-F14 = F14
+input-key-F15 = F15
+input-key-Pause = Pause
+input-key-Left = Left
+input-key-Up = Up
+input-key-Down = Down
+input-key-Right = Right
+input-key-Space = Space
+input-key-Return = Return
+input-key-NumpadEnter = Num Enter
+input-key-BackSpace = Backspace
+input-key-Tab = Tab
+input-key-PageUp = Page Up
+input-key-PageDown = Page Down
+input-key-End = End
+input-key-Home = Home
+input-key-Insert = Insert
+input-key-Delete = Delete
+input-key-MouseLeft = Mouse Left
+input-key-MouseRight = Mouse Right
+input-key-MouseMiddle = Mouse Middle
+input-key-MouseButton4 = Mouse 4
+input-key-MouseButton5 = Mouse 5
+input-key-MouseButton6 = Mouse 6
+input-key-MouseButton7 = Mouse 7
+input-key-MouseButton8 = Mouse 8
+input-key-MouseButton9 = Mouse 9
+
+input-key-LSystem-win = Left Win
+input-key-RSystem-win = Right Win
+input-key-LSystem-mac = Left Cmd
+input-key-RSystem-mac = Right Cmd
+input-key-LSystem-linux = Left Meta
+input-key-RSystem-linux = Right Meta
+
+input-key-unknown = <unknown key>

Resources/Prototypes/dbg_rotationMarker.yml

@@ -1,40 +0,0 @@
-- type: entity
-  id: debugRotation1
-  name: dbg_rotation1
-  components:
-  - type: Clickable
-  - type: InteractionOutline
-  - type: Sprite
-    netsync: false
-    visible: true
-    sprite: debugRotation.rsi
-    state: direction1
-  placement:
-    mode: AlignTileAny
-
-- type: entity
-  id: debugRotation4
-  name: dbg_rotation4
-  components:
-  - type: Clickable
-  - type: InteractionOutline
-  - type: Sprite
-    netsync: false
-    visible: true
-    sprite: debugRotation.rsi
-    state: direction4
-  placement:
-    mode: AlignTileAny
-
-- type: entity
-  id: debugRotationTex
-  name: dbg_rotationTex
-  components:
-  - type: Clickable
-  - type: InteractionOutline
-  - type: Sprite
-    netsync: false
-    visible: true
-    texture: debugRotation.rsi/direction1.png
-  placement:
-    mode: AlignTileAny

Resources/Prototypes/dummy_entity.yml

@@ -1,4 +0,0 @@
-- type: entity
-  name: blank entity
-  id: BlankEntity
-  abstract: true

Resources/Shaders/Internal/fov-lighting.swsl

@@ -28,5 +28,10 @@ void fragment()
 
     highp float occlusion = ChebyshevUpperBound(occlDist, ourDist);
 
+    if (occlusion >= 1.0)
+    {
+        discard;
+    }
+
     COLOR = vec4(0.0, 0.0, 0.0, 1.0 - occlusion);
 }

Resources/Shaders/Internal/light-soft.swsl

@@ -1,5 +1,11 @@
 #include "/Shaders/Internal/light_shared.swsl"
 
+highp vec4 calcGaussianWeights(highp float sigma, highp vec4 offset)
+{
+    highp vec4 eExp = offset * offset / (2.0 * sigma * sigma);
+    return exp(-eExp) / (sigma * sqrt(2.0 * PI));
+}
+
 highp float createOcclusion(highp vec2 diff)
 {
     // Calculate vector perpendicular to light vector.
@@ -8,23 +14,57 @@ highp float createOcclusion(highp vec2 diff)
 
     highp float ourDist = length(diff);
 
-    highp vec2 occlDist = occludeDepth(diff, shadowMap, lightIndex);
+    // Sample 7 points on a line perpendicular to the light source.
+    // Depending on the closest point, we change the gaussian weights down below
+    // to change the "narrowness" of the samples.
+    perpendicular *= lightSoftness * 1.5;
+
+    // Get all the samples we need.
+    highp vec2 sample1 = occludeDepth(diff, shadowMap, lightIndex);
+    highp vec2 sample2 = occludeDepth(diff + perpendicular, shadowMap, lightIndex);
+    highp vec2 sample3 = occludeDepth(diff - perpendicular, shadowMap, lightIndex);
+    highp vec2 sample4 = occludeDepth(diff + perpendicular * 2.0, shadowMap, lightIndex);
+    highp vec2 sample5 = occludeDepth(diff - perpendicular * 2.0, shadowMap, lightIndex);
+    highp vec2 sample6 = occludeDepth(diff + perpendicular * 3.0, shadowMap, lightIndex);
+    highp vec2 sample7 = occludeDepth(diff - perpendicular * 3.0, shadowMap, lightIndex);
+
+    highp float mindist =
+        min(sample1.x,
+        min(sample2.x,
+        min(sample3.x,
+        min(sample4.x,
+        min(sample5.x,
+        min(sample6.x,
+            sample7.x))))));
+
+    mindist = max(0.001, mindist);
 
     // Change soft shadow size based on distance from primary occluder.
-    highp float distRatio = (ourDist - occlDist.x) / occlDist.x / 2.0;
+    highp float distRatio = (ourDist - mindist);
 
-    perpendicular *= distRatio * lightSoftness;
+    // Sigma can never be zero so make sure to clamp.
+    // TODO: Scaling the dist ratio here in a more sane way might make shadows look better buuuut I'm lazy.
+    // Shadows look pretty nice already.
+    highp float sigma = max(0.001, distRatio * 0.75);
+    highp vec4 weights = calcGaussianWeights(sigma, vec4(0.0, 1.0, 2.0, 3.0));
 
-    // Totally not hacky PCF on top of VSM.
-    highp float occlusion = smoothstep(0.1, 1.0, ChebyshevUpperBound(occlDist, ourDist));
+    // Calculation of gaussian weights here is broken because it doesn't add up to 1.
+    // Fixing this is hard and if I had to guess too expensive for GPU shaders.
+    // So instead we add up the total weights and scale the result with that,
+    // so that we still end up with 0-1.
+    highp float totalWeigths = weights.x + weights.y * 2.0 + weights.z * 2.0 + weights.w * 2.0;
 
-    occlusion += shadowContrib(diff + perpendicular);
-    occlusion += shadowContrib(diff - perpendicular);
-    occlusion += shadowContrib(diff + perpendicular * 2.0);
-    occlusion += shadowContrib(diff - perpendicular * 2.0);
-    occlusion += shadowContrib(diff + perpendicular * 3.0);
-    occlusion += shadowContrib(diff - perpendicular * 3.0);
+    highp float occlusion = 0.0;
 
-    return occlusion / 7.0;
+    // Calculate actual occlusion with new weights.
+    occlusion += ChebyshevUpperBound(sample1, ourDist) * weights.x;
+    occlusion += ChebyshevUpperBound(sample2, ourDist) * weights.y;
+    occlusion += ChebyshevUpperBound(sample3, ourDist) * weights.y;
+    occlusion += ChebyshevUpperBound(sample4, ourDist) * weights.z;
+    occlusion += ChebyshevUpperBound(sample5, ourDist) * weights.z;
+    occlusion += ChebyshevUpperBound(sample6, ourDist) * weights.w;
+    occlusion += ChebyshevUpperBound(sample7, ourDist) * weights.w;
+
+    return occlusion / totalWeigths;
 }
 

Robust.Benchmarks/Program.cs

@@ -0,0 +1,12 @@
+using BenchmarkDotNet.Running;
+
+namespace Robust.Benchmarks
+{
+    internal class Program
+    {
+        public static void Main(string[] args)
+        {
+            BenchmarkSwitcher.FromAssembly(typeof(Program).Assembly).Run();
+        }
+    }
+}

Robust.Benchmarks/Robust.Benchmarks.csproj

@@ -0,0 +1,18 @@
+<Project Sdk="Microsoft.NET.Sdk">
+    <Import Project="..\MSBuild\Robust.Properties.targets" />
+    <Import Project="..\MSBuild\Robust.Engine.props" />
+    <PropertyGroup>
+        <IsPackable>false</IsPackable>
+        <AppendTargetFrameworkToOutputPath>false</AppendTargetFrameworkToOutputPath>
+        <OutputPath>../bin/Benchmarks</OutputPath>
+        <OutputType>Exe</OutputType>
+    </PropertyGroup>
+    <ItemGroup>
+      <ProjectReference Include="..\Robust.Server\Robust.Server.csproj" />
+      <ProjectReference Include="..\Robust.Shared\Robust.Shared.csproj" />
+    </ItemGroup>
+    <ItemGroup>
+      <PackageReference Include="BenchmarkDotNet" Version="0.12.1" />
+    </ItemGroup>
+    <Import Project="..\MSBuild\Robust.Engine.targets" />
+</Project>

Robust.Benchmarks/Serialization/Copy/SerializationCopyBenchmark.cs

@@ -0,0 +1,115 @@
+using System.IO;
+using System.Linq;
+using BenchmarkDotNet.Attributes;
+using Robust.Benchmarks.Serialization.Definitions;
+using Robust.Shared.Serialization.Manager;
+using Robust.Shared.Serialization.Markdown;
+using Robust.Shared.Serialization.Markdown.Mapping;
+using Robust.Shared.Serialization.Markdown.Sequence;
+using Robust.Shared.Utility;
+using YamlDotNet.RepresentationModel;
+
+namespace Robust.Benchmarks.Serialization.Copy
+{
+    public class SerializationCopyBenchmark : SerializationBenchmark
+    {
+        public SerializationCopyBenchmark()
+        {
+            InitializeSerialization();
+
+            DataDefinitionWithString = new DataDefinitionWithString {StringField = "ABC"};
+
+            var yamlStream = new YamlStream();
+            yamlStream.Load(new StringReader(SeedDataDefinition.Prototype));
+
+            var seedMapping = yamlStream.Documents[0].RootNode.ToDataNodeCast<SequenceDataNode>().Cast<MappingDataNode>(0);
+
+            Seed = SerializationManager.ReadValueOrThrow<SeedDataDefinition>(seedMapping);
+        }
+
+        private const string String = "ABC";
+
+        private const int Integer = 1;
+
+        private DataDefinitionWithString DataDefinitionWithString { get; }
+
+        private SeedDataDefinition Seed { get; }
+
+        [Benchmark]
+        public string? CreateCopyString()
+        {
+            return SerializationManager.CreateCopy(String);
+        }
+
+        [Benchmark]
+        public int? CreateCopyInteger()
+        {
+            return SerializationManager.CreateCopy(Integer);
+        }
+
+        [Benchmark]
+        public DataDefinitionWithString? CreateCopyDataDefinitionWithString()
+        {
+            return SerializationManager.CreateCopy(DataDefinitionWithString);
+        }
+
+        [Benchmark]
+        public SeedDataDefinition? CreateCopySeedDataDefinition()
+        {
+            return SerializationManager.CreateCopy(Seed);
+        }
+
+        [Benchmark]
+        public SeedDataDefinition BaselineCreateCopySeedDataDefinition()
+        {
+            // ReSharper disable once UseObjectOrCollectionInitializer
+            var copy = new SeedDataDefinition();
+
+            copy.ID = Seed.ID;
+            copy.Name = Seed.Name;
+            copy.SeedName = Seed.SeedName;
+            copy.SeedNoun = Seed.SeedNoun;
+            copy.DisplayName = Seed.DisplayName;
+            copy.RoundStart = Seed.RoundStart;
+            copy.Mysterious = Seed.Mysterious;
+            copy.Immutable = Seed.Immutable;
+
+            copy.ProductPrototypes = Seed.ProductPrototypes.ToList();
+            copy.Chemicals = Seed.Chemicals.ToDictionary(p => p.Key, p => p.Value);
+            copy.ConsumeGasses = Seed.ConsumeGasses.ToDictionary(p => p.Key, p => p.Value);
+            copy.ExudeGasses = Seed.ExudeGasses.ToDictionary(p => p.Key, p => p.Value);
+
+            copy.NutrientConsumption = Seed.NutrientConsumption;
+            copy.WaterConsumption = Seed.WaterConsumption;
+            copy.IdealHeat = Seed.IdealHeat;
+            copy.HeatTolerance = Seed.HeatTolerance;
+            copy.IdealLight = Seed.IdealLight;
+            copy.LightTolerance = Seed.LightTolerance;
+            copy.ToxinsTolerance = Seed.ToxinsTolerance;
+            copy.LowPressureTolerance = Seed.LowPressureTolerance;
+            copy.HighPressureTolerance = Seed.HighPressureTolerance;
+            copy.PestTolerance = Seed.PestTolerance;
+            copy.WeedTolerance = Seed.WeedTolerance;
+
+            copy.Endurance = Seed.Endurance;
+            copy.Yield = Seed.Yield;
+            copy.Lifespan = Seed.Lifespan;
+            copy.Maturation = Seed.Maturation;
+            copy.Production = Seed.Production;
+            copy.GrowthStages = Seed.GrowthStages;
+            copy.HarvestRepeat = Seed.HarvestRepeat;
+            copy.Potency = Seed.Potency;
+            copy.Ligneous = Seed.Ligneous;
+
+            copy.PlantRsi = Seed.PlantRsi == null
+                ? null!
+                : new ResourcePath(Seed.PlantRsi.ToString(), Seed.PlantRsi.Separator);
+            copy.PlantIconState = Seed.PlantIconState;
+            copy.Bioluminescent = Seed.Bioluminescent;
+            copy.BioluminescentColor = Seed.BioluminescentColor;
+            copy.SplatPrototype = Seed.SplatPrototype;
+
+            return copy;
+        }
+    }
+}

Robust.Benchmarks/Serialization/Definitions/DataDefinitionWithString.cs

@@ -0,0 +1,11 @@
+using Robust.Shared.Serialization.Manager.Attributes;
+
+namespace Robust.Benchmarks.Serialization.Definitions
+{
+    [DataDefinition]
+    public class DataDefinitionWithString
+    {
+        [field: DataField("string")]
+        public string StringField { get; init; } = default!;
+    }
+}

Robust.Benchmarks/Serialization/Definitions/SeedDataDefinition.cs

@@ -0,0 +1,119 @@
+using System.Collections.Generic;
+using Robust.Shared.Maths;
+using Robust.Shared.Prototypes;
+using Robust.Shared.Serialization.Manager.Attributes;
+using Robust.Shared.Utility;
+
+namespace Robust.Benchmarks.Serialization.Definitions
+{
+    /// <summary>
+    ///     Arbitrarily large data definition for benchmarks.
+    ///     Taken from content.
+    /// </summary>
+    [Prototype("seed")]
+    public class SeedDataDefinition : IPrototype
+    {
+        public const string Prototype = @"
+- type: seed
+  id: tobacco
+  name: tobacco
+  seedName: tobacco
+  displayName: tobacco plant
+  productPrototypes:
+    - LeavesTobacco
+  harvestRepeat: Repeat
+  lifespan: 75
+  maturation: 5
+  production: 5
+  yield: 2
+  potency: 20
+  growthStages: 3
+  idealLight: 9
+  idealHeat: 298
+  chemicals:
+    chem.Nicotine:
+      Min: 1
+      Max: 10
+      PotencyDivisor: 10";
+
+        [DataField("id", required: true)] public string ID { get; set; } = default!;
+
+        #region Tracking
+        [DataField("name")] public string Name { get; set; } = string.Empty;
+        [DataField("seedName")] public string SeedName { get; set; } = string.Empty;
+        [DataField("seedNoun")] public string SeedNoun { get; set; } = "seeds";
+        [DataField("displayName")] public string DisplayName { get; set; } = string.Empty;
+        [DataField("roundStart")] public bool RoundStart { get; set; } = true;
+        [DataField("mysterious")] public bool Mysterious { get; set; }
+        [DataField("immutable")] public bool Immutable { get; set; }
+        #endregion
+
+        #region Output
+        [DataField("productPrototypes")]
+        public List<string> ProductPrototypes { get; set; } = new();
+        [DataField("chemicals")]
+        public Dictionary<string, SeedChemQuantity> Chemicals { get; set; } = new();
+        [DataField("consumeGasses")]
+        public Dictionary<Gas, float> ConsumeGasses { get; set; } = new();
+        [DataField("exudeGasses")]
+        public Dictionary<Gas, float> ExudeGasses { get; set; } = new();
+        #endregion
+
+        #region Tolerances
+        [DataField("nutrientConsumption")] public float NutrientConsumption { get; set; } = 0.25f;
+        [DataField("waterConsumption")] public float WaterConsumption { get; set; } = 3f;
+        [DataField("idealHeat")] public float IdealHeat { get; set; } = 293f;
+        [DataField("heatTolerance")] public float HeatTolerance { get; set; } = 20f;
+        [DataField("idealLight")] public float IdealLight { get; set; } = 7f;
+        [DataField("lightTolerance")] public float LightTolerance { get; set; } = 5f;
+        [DataField("toxinsTolerance")] public float ToxinsTolerance { get; set; } = 4f;
+        [DataField("lowPressureTolerance")] public float LowPressureTolerance { get; set; } = 25f;
+        [DataField("highPressureTolerance")] public float HighPressureTolerance { get; set; } = 200f;
+        [DataField("pestTolerance")] public float PestTolerance { get; set; } = 5f;
+        [DataField("weedTolerance")] public float WeedTolerance { get; set; } = 5f;
+        #endregion
+
+        #region General traits
+        [DataField("endurance")] public float Endurance { get; set; } = 100f;
+        [DataField("yield")] public int Yield { get; set; }
+        [DataField("lifespan")] public float Lifespan { get; set; }
+        [DataField("maturation")] public float Maturation { get; set; }
+        [DataField("production")] public float Production { get; set; }
+        [DataField("growthStages")] public int GrowthStages { get; set; } = 6;
+        [DataField("harvestRepeat")] public HarvestType HarvestRepeat { get; set; } = HarvestType.NoRepeat;
+        [DataField("potency")] public float Potency { get; set; } = 1f;
+        [DataField("ligneous")] public bool Ligneous { get; set; }
+        #endregion
+
+        #region Cosmetics
+        [DataField("plantRsi", required: true)] public ResourcePath PlantRsi { get; set; } = default!;
+        [DataField("plantIconState")] public string PlantIconState { get; set; } = "produce";
+        [DataField("bioluminescent")] public bool Bioluminescent { get; set; }
+        [DataField("bioluminescentColor")] public Color BioluminescentColor { get; set; } = Color.White;
+        [DataField("splatPrototype")] public string? SplatPrototype { get; set; }
+        #endregion
+    }
+
+    public enum HarvestType
+    {
+        NoRepeat,
+        Repeat
+    }
+
+    public enum Gas
+    {
+    }
+
+    [DataDefinition]
+    public struct SeedChemQuantity
+    {
+        [DataField("Min")]
+        public int Min;
+
+        [DataField("Max")]
+        public int Max;
+
+        [DataField("PotencyDivisor")]
+        public int PotencyDivisor;
+    }
+}

Robust.Benchmarks/Serialization/Initialize/SerializationInitializeBenchmark.cs

@@ -0,0 +1,21 @@
+using BenchmarkDotNet.Attributes;
+using Robust.Shared.Serialization.Manager;
+
+namespace Robust.Benchmarks.Serialization.Initialize
+{
+    public class SerializationInitializeBenchmark : SerializationBenchmark
+    {
+        [IterationCleanup]
+        public void IterationCleanup()
+        {
+            SerializationManager.Shutdown();
+        }
+
+        [Benchmark]
+        public ISerializationManager Initialize()
+        {
+            InitializeSerialization();
+            return SerializationManager;
+        }
+    }
+}

Robust.Benchmarks/Serialization/Read/SerializationReadBenchmark.cs

@@ -0,0 +1,59 @@
+using System.IO;
+using BenchmarkDotNet.Attributes;
+using Robust.Benchmarks.Serialization.Definitions;
+using Robust.Shared.Serialization.Markdown;
+using Robust.Shared.Serialization.Markdown.Mapping;
+using Robust.Shared.Serialization.Markdown.Sequence;
+using Robust.Shared.Serialization.Markdown.Value;
+using YamlDotNet.RepresentationModel;
+
+namespace Robust.Benchmarks.Serialization.Read
+{
+    public class SerializationReadBenchmark : SerializationBenchmark
+    {
+        public SerializationReadBenchmark()
+        {
+            InitializeSerialization();
+
+            StringDataDefNode = new MappingDataNode();
+            StringDataDefNode.Add(new ValueDataNode("string"), new ValueDataNode("ABC"));
+
+            var yamlStream = new YamlStream();
+            yamlStream.Load(new StringReader(SeedDataDefinition.Prototype));
+
+            SeedNode = yamlStream.Documents[0].RootNode.ToDataNodeCast<SequenceDataNode>().Cast<MappingDataNode>(0);
+        }
+
+        private ValueDataNode StringNode { get; } = new("ABC");
+
+        private ValueDataNode IntNode { get; } = new("1");
+
+        private MappingDataNode StringDataDefNode { get; }
+
+        private MappingDataNode SeedNode { get; }
+
+        [Benchmark]
+        public string? ReadString()
+        {
+            return SerializationManager.ReadValue<string>(StringNode);
+        }
+
+        [Benchmark]
+        public int? ReadInteger()
+        {
+            return SerializationManager.ReadValue<int>(IntNode);
+        }
+
+        [Benchmark]
+        public DataDefinitionWithString? ReadDataDefinitionWithString()
+        {
+            return SerializationManager.ReadValue<DataDefinitionWithString>(StringDataDefNode);
+        }
+
+        [Benchmark]
+        public SeedDataDefinition? ReadSeedDataDefinition()
+        {
+            return SerializationManager.ReadValue<SeedDataDefinition>(SeedNode);
+        }
+    }
+}

Robust.Benchmarks/Serialization/SerializationBenchmark.cs

@@ -0,0 +1,43 @@
+using System;
+using Robust.Server;
+using Robust.Shared.Configuration;
+using Robust.Shared.ContentPack;
+using Robust.Shared.IoC;
+using Robust.Shared.Reflection;
+using Robust.Shared.Serialization.Manager;
+
+namespace Robust.Benchmarks.Serialization
+{
+    public abstract class SerializationBenchmark
+    {
+        public SerializationBenchmark()
+        {
+            IoCManager.InitThread();
+            ServerIoC.RegisterIoC();
+            IoCManager.BuildGraph();
+
+            var assemblies = new[]
+            {
+                AppDomain.CurrentDomain.GetAssemblyByName("Robust.Shared"),
+                AppDomain.CurrentDomain.GetAssemblyByName("Robust.Server"),
+                AppDomain.CurrentDomain.GetAssemblyByName("Robust.Benchmarks")
+            };
+
+            foreach (var assembly in assemblies)
+            {
+                IoCManager.Resolve<IConfigurationManagerInternal>().LoadCVarsFromAssembly(assembly);
+            }
+
+            IoCManager.Resolve<IReflectionManager>().LoadAssemblies(assemblies);
+
+            SerializationManager = IoCManager.Resolve<ISerializationManager>();
+        }
+
+        protected ISerializationManager SerializationManager { get; }
+
+        public void InitializeSerialization()
+        {
+            SerializationManager.Initialize();
+        }
+    }
+}

Robust.Benchmarks/Serialization/Write/SerializationWriteBenchmark.cs

@@ -0,0 +1,98 @@
+using System.Globalization;
+using System.IO;
+using BenchmarkDotNet.Attributes;
+using Robust.Benchmarks.Serialization.Definitions;
+using Robust.Shared.Serialization.Manager;
+using Robust.Shared.Serialization.Markdown;
+using Robust.Shared.Serialization.Markdown.Mapping;
+using Robust.Shared.Serialization.Markdown.Sequence;
+using Robust.Shared.Serialization.Markdown.Value;
+using YamlDotNet.RepresentationModel;
+
+namespace Robust.Benchmarks.Serialization.Write
+{
+    public class SerializationWriteBenchmark : SerializationBenchmark
+    {
+        public SerializationWriteBenchmark()
+        {
+            InitializeSerialization();
+
+            DataDefinitionWithString = new DataDefinitionWithString {StringField = "ABC"};
+
+            var yamlStream = new YamlStream();
+            yamlStream.Load(new StringReader(SeedDataDefinition.Prototype));
+
+            var seedMapping = yamlStream.Documents[0].RootNode.ToDataNodeCast<SequenceDataNode>().Cast<MappingDataNode>(0);
+
+            Seed = SerializationManager.ReadValueOrThrow<SeedDataDefinition>(seedMapping);
+        }
+
+        private const string String = "ABC";
+
+        private const int Integer = 1;
+
+        private DataDefinitionWithString DataDefinitionWithString { get; }
+
+        private SeedDataDefinition Seed { get; }
+
+        [Benchmark]
+        public DataNode WriteString()
+        {
+            return SerializationManager.WriteValue(String);
+        }
+
+        [Benchmark]
+        public DataNode WriteInteger()
+        {
+            return SerializationManager.WriteValue(Integer);
+        }
+
+        [Benchmark]
+        public DataNode WriteDataDefinitionWithString()
+        {
+            return SerializationManager.WriteValue(DataDefinitionWithString);
+        }
+
+        [Benchmark]
+        public DataNode WriteSeedDataDefinition()
+        {
+            return SerializationManager.WriteValue(Seed);
+        }
+
+        [Benchmark]
+        public DataNode BaselineWriteSeedDataDefinition()
+        {
+            var mapping = new MappingDataNode();
+
+            mapping.Add("id", Seed.ID);
+            mapping.Add("name", Seed.Name);
+            mapping.Add("seedName", Seed.SeedName);
+            mapping.Add("displayName", Seed.DisplayName);
+            mapping.Add("productPrototypes", Seed.ProductPrototypes);
+            mapping.Add("harvestRepeat", Seed.HarvestRepeat.ToString());
+            mapping.Add("lifespan", Seed.Lifespan.ToString(CultureInfo.InvariantCulture));
+            mapping.Add("maturation", Seed.Maturation.ToString(CultureInfo.InvariantCulture));
+            mapping.Add("production", Seed.Production.ToString(CultureInfo.InvariantCulture));
+            mapping.Add("yield", Seed.Yield.ToString(CultureInfo.InvariantCulture));
+            mapping.Add("potency", Seed.Potency.ToString(CultureInfo.InvariantCulture));
+            mapping.Add("growthStages", Seed.GrowthStages.ToString(CultureInfo.InvariantCulture));
+            mapping.Add("idealLight", Seed.IdealLight.ToString(CultureInfo.InvariantCulture));
+            mapping.Add("idealHeat", Seed.IdealHeat.ToString(CultureInfo.InvariantCulture));
+
+            var chemicals = new MappingDataNode();
+            foreach (var (name, quantity) in Seed.Chemicals)
+            {
+                chemicals.Add(name, new MappingDataNode
+                {
+                    ["Min"] = new ValueDataNode(quantity.Min.ToString(CultureInfo.InvariantCulture)),
+                    ["Max"] = new ValueDataNode(quantity.Max.ToString(CultureInfo.InvariantCulture)),
+                    ["PotencyDivisor"] = new ValueDataNode(quantity.PotencyDivisor.ToString(CultureInfo.InvariantCulture))
+                });
+            }
+
+            mapping.Add("chemicals", chemicals);
+
+            return mapping;
+        }
+    }
+}

Robust.Client.NameGenerator/XamlUiPartialClassGenerator.cs

@@ -247,7 +247,6 @@ namespace {nameSpace}
                                 DiagnosticSeverity.Error,
                                 true),
                             Location.None));
-                    return null;
                 }
             }
 

Robust.Client/Audio/Midi/MidiManager.cs

@@ -15,6 +15,7 @@ using Robust.Shared.Maths;
 using Robust.Shared.Physics;
 using Robust.Shared.Physics.Broadphase;
 using Robust.Shared.Utility;
+using Robust.Shared.ViewVariables;
 using Logger = Robust.Shared.Log.Logger;
 
 namespace Robust.Client.Audio.Midi
@@ -33,24 +34,6 @@ namespace Robust.Client.Audio.Midi
         /// </returns>
         IMidiRenderer? GetNewRenderer();
 
-        /*
-        /// <summary>
-        ///     Checks whether the file at the given path is a valid midi file or not.
-        /// </summary>
-        /// <remarks>
-        ///     We add this here so content doesn't need to reference NFluidsynth.
-        /// </remarks>
-        bool IsMidiFile(string filename);
-
-        /// <summary>
-        ///     Checks whether the file at the given path is a valid midi file or not.
-        /// </summary>
-        /// <remarks>
-        ///     We add this here so content doesn't need to reference NFluidsynth.
-        /// </remarks>
-        bool IsSoundfontFile(string filename);
-        */
-
         /// <summary>
         ///     Method called every frame.
         ///     Should be used to update positional audio.
@@ -58,6 +41,11 @@ namespace Robust.Client.Audio.Midi
         /// <param name="frameTime"></param>
         void FrameUpdate(float frameTime);
 
+        /// <summary>
+        ///     Volume, in db.
+        /// </summary>
+        float Volume { get; set; }
+
         /// <summary>
         ///     If true, MIDI support is available.
         /// </summary>
@@ -76,6 +64,7 @@ namespace Robust.Client.Audio.Midi
 
         private SharedBroadPhaseSystem _broadPhaseSystem = default!;
 
+        [ViewVariables]
         public bool IsAvailable
         {
             get
@@ -86,12 +75,29 @@ namespace Robust.Client.Audio.Midi
             }
         }
 
-        private readonly List<MidiRenderer> _renderers = new();
+        [ViewVariables]
+        private readonly List<IMidiRenderer> _renderers = new();
 
         private bool _alive = true;
         private Settings? _settings;
         private Thread? _midiThread;
         private ISawmill _midiSawmill = default!;
+        private float _volume = 0f;
+        private bool _volumeDirty = true;
+
+        [ViewVariables(VVAccess.ReadWrite)]
+        public float Volume
+        {
+            get => _volume;
+            set
+            {
+                if (MathHelper.CloseTo(_volume, value))
+                    return;
+
+                _volume = value;
+                _volumeDirty = true;
+            }
+        }
 
         private static readonly string[] LinuxSoundfonts =
         {
@@ -118,6 +124,7 @@ namespace Robust.Client.Audio.Midi
         private NFluidsynth.Logger.LoggerDelegate _loggerDelegate = default!;
         private ISawmill _sawmill = default!;
 
+        [ViewVariables(VVAccess.ReadWrite)]
         public int OcclusionCollisionMask { get; set; }
 
         private void InitializeFluidsynth()
@@ -176,18 +183,6 @@ namespace Robust.Client.Audio.Midi
             _sawmill.Log(rLevel, message);
         }
 
-        /*
-        public bool IsMidiFile(string filename)
-        {
-            return SoundFont.IsMidiFile(filename);
-        }
-
-        public bool IsSoundfontFile(string filename)
-        {
-            return SoundFont.IsSoundFont(filename);
-        }
-        */
-
         public IMidiRenderer? GetNewRenderer()
         {
             if (!FluidsynthInitialized)
@@ -251,7 +246,9 @@ namespace Robust.Client.Audio.Midi
                 }
 
                 lock (_renderers)
+                {
                     _renderers.Add(renderer);
+                }
 
                 return renderer;
             }
@@ -269,69 +266,79 @@ namespace Robust.Client.Audio.Midi
             }
 
             // Update positions of streams every frame.
-            lock (_renderers)
-                foreach (var renderer in _renderers)
+            foreach (var renderer in _renderers)
+            {
+                if (renderer.Disposed)
+                    continue;
+
+                if(_volumeDirty)
+                    renderer.Source.SetVolume(Volume);
+
+                if (!renderer.Mono)
                 {
-                    if (renderer.Disposed)
-                        continue;
-
-                    if (!renderer.Mono)
-                    {
-                        renderer.Source.SetGlobal();
-                        continue;
-                    }
-
-                    MapCoordinates? mapPos = null;
-                    if (renderer.TrackingCoordinates != null)
-                    {
-                        mapPos = renderer.TrackingCoordinates.Value.ToMap(_entityManager);
-                    }
-                    else if (renderer.TrackingEntity != null)
-                    {
-                        mapPos = renderer.TrackingEntity.Transform.MapPosition;
-                    }
-
-                    if (mapPos != null)
-                    {
-                        var pos = mapPos.Value;
-                        if (pos.MapId != _eyeManager.CurrentMap)
-                        {
-                            renderer.Source.SetVolume(-10000000);
-                        }
-                        else
-                        {
-                            var sourceRelative = _eyeManager.CurrentEye.Position.Position - pos.Position;
-                            var occlusion = 0f;
-                            if (sourceRelative.Length > 0)
-                            {
-                                occlusion = _broadPhaseSystem.IntersectRayPenetration(
-                                    pos.MapId,
-                                    new CollisionRay(
-                                        pos.Position,
-                                        sourceRelative.Normalized,
-                                        OcclusionCollisionMask),
-                                    sourceRelative.Length,
-                                    renderer.TrackingEntity);
-                            }
-                            renderer.Source.SetOcclusion(occlusion);
-                        }
-
-                        if (renderer.Source.SetPosition(pos.Position))
-                        {
-                            continue;
-                        }
-
-                        if (float.IsNaN(pos.Position.X) || float.IsNaN(pos.Position.Y))
-                        {
-                            // just duck out instead of move to NaN
-                            renderer.Source.SetOcclusion(float.MaxValue);
-                            continue;
-                        }
-
-                        _midiSawmill?.Warning("Interrupting positional audio, can't set position.");
-                        renderer.Source.StopPlaying();
-                    }
+                    renderer.Source.SetGlobal();
+                    continue;
                 }
+
+                MapCoordinates? mapPos = null;
+                if (renderer.TrackingCoordinates != null)
+                {
+                    mapPos = renderer.TrackingCoordinates.Value.ToMap(_entityManager);
+                }
+                else if (renderer.TrackingEntity != null)
+                {
+                    mapPos = renderer.TrackingEntity.Transform.MapPosition;
+                }
+
+                if (mapPos != null)
+                {
+                    var pos = mapPos.Value;
+                    if (pos.MapId != _eyeManager.CurrentMap)
+                    {
+                        renderer.Source.SetVolume(-10000000);
+                    }
+                    else
+                    {
+                        var sourceRelative = _eyeManager.CurrentEye.Position.Position - pos.Position;
+                        var occlusion = 0f;
+                        if (sourceRelative.Length > 0)
+                        {
+                            occlusion = _broadPhaseSystem.IntersectRayPenetration(
+                                pos.MapId,
+                                new CollisionRay(
+                                    pos.Position,
+                                    sourceRelative.Normalized,
+                                    OcclusionCollisionMask),
+                                sourceRelative.Length,
+                                renderer.TrackingEntity);
+                        }
+
+                        renderer.Source.SetOcclusion(occlusion);
+                    }
+
+                    if (renderer.Source.SetPosition(pos.Position))
+                    {
+                        continue;
+                    }
+
+                    if (renderer.TrackingEntity != null)
+                    {
+                        renderer.Source.SetVelocity(renderer.TrackingEntity.GlobalLinearVelocity());
+                    }
+
+                    if (float.IsNaN(pos.Position.X) || float.IsNaN(pos.Position.Y))
+                    {
+                        // just duck out instead of move to NaN
+                        renderer.Source.SetOcclusion(float.MaxValue);
+                        continue;
+                    }
+
+                    _midiSawmill?.Warning("Interrupting positional audio, can't set position.");
+                    renderer.Source.StopPlaying();
+                }
+            }
+
+            _volumeDirty = false;
         }
 
         /// <summary>
@@ -342,6 +349,7 @@ namespace Robust.Client.Audio.Midi
             while (_alive)
             {
                 lock (_renderers)
+                {
                     for (var i = 0; i < _renderers.Count; i++)
                     {
                         var renderer = _renderers[i];
@@ -349,10 +357,11 @@ namespace Robust.Client.Audio.Midi
                             renderer.Render();
                         else
                         {
-                            ((IMidiRenderer)renderer).InternalDispose();
+                            renderer.InternalDispose();
                             _renderers.Remove(renderer);
                         }
                     }
+                }
 
                 Thread.Sleep(1);
             }
@@ -363,9 +372,13 @@ namespace Robust.Client.Audio.Midi
             _alive = false;
             _midiThread?.Join();
             _settings?.Dispose();
-            foreach (var renderer in _renderers)
+
+            lock (_renderers)
             {
-                renderer?.Dispose();
+                foreach (var renderer in _renderers)
+                {
+                    renderer?.Dispose();
+                }
             }
 
             if (FluidsynthInitialized && !_failedInitialize)
@@ -420,6 +433,7 @@ namespace Robust.Client.Audio.Midi
                 var span = new Span<byte>(buf.ToPointer(), length);
                 var stream = _openStreams[(int) sfHandle];
 
+                // Fluidsynth's docs state that this method should leave the buffer unmodified if it fails. (returns -1)
                 try
                 {
                     // Fluidsynth does a LOT of tiny allocations (frankly, way too much).
@@ -443,6 +457,7 @@ namespace Robust.Client.Audio.Midi
                 {
                     return -1;
                 }
+
                 return 0;
             }
 
@@ -464,10 +479,12 @@ namespace Robust.Client.Audio.Midi
 
             public override int Close(IntPtr sfHandle)
             {
-                var stream = _openStreams[(int) sfHandle];
+                if (!_openStreams.Remove((int) sfHandle, out var stream))
+                    return -1;
+
                 stream.Dispose();
-                _openStreams.Remove((int) sfHandle);
                 return 0;
+
             }
         }
     }

Robust.Client/Audio/Midi/MidiRenderer.cs

@@ -8,6 +8,7 @@ using Robust.Shared.IoC;
 using Robust.Shared.Log;
 using Robust.Shared.Map;
 using Robust.Shared.Utility;
+using Robust.Shared.ViewVariables;
 using MidiEvent = NFluidsynth.MidiEvent;
 
 namespace Robust.Client.Audio.Midi
@@ -21,6 +22,17 @@ namespace Robust.Client.Audio.Midi
 
     public interface IMidiRenderer : IDisposable
     {
+
+        /// <summary>
+        ///     The buffered audio source of this renderer.
+        /// </summary>
+        internal IClydeBufferedAudioSource Source { get; }
+
+        /// <summary>
+        ///     Whether this renderer has been disposed or not.
+        /// </summary>
+        bool Disposed { get; }
+
         /// <summary>
         ///     This controls whether the midi file being played will loop or not.
         /// </summary>
@@ -110,6 +122,11 @@ namespace Robust.Client.Audio.Midi
         /// </summary>
         void StopAllNotes();
 
+        /// <summary>
+        ///     Render and play MIDI to the audio source.
+        /// </summary>
+        internal void Render();
+
         /// <summary>
         ///     Loads a new soundfont into the renderer.
         /// </summary>
@@ -159,7 +176,7 @@ namespace Robust.Client.Audio.Midi
         internal void InternalDispose();
     }
 
-    public class MidiRenderer : IMidiRenderer
+    internal class MidiRenderer : IMidiRenderer
     {
         [Dependency] private readonly IClydeAudio _clydeAudio = default!;
         [Dependency] private readonly ITaskManager _taskManager = default!;
@@ -188,8 +205,12 @@ namespace Robust.Client.Audio.Midi
         private readonly object _playerStateLock = new();
         private SequencerClientId _synthRegister;
         public IClydeBufferedAudioSource Source { get; set; }
+        IClydeBufferedAudioSource IMidiRenderer.Source => Source;
+
+        [ViewVariables]
         public bool Disposed { get; private set; } = false;
 
+        [ViewVariables(VVAccess.ReadWrite)]
         public byte MidiProgram
         {
             get => _midiProgram;
@@ -203,6 +224,7 @@ namespace Robust.Client.Audio.Midi
             }
         }
 
+        [ViewVariables(VVAccess.ReadWrite)]
         public byte MidiBank
         {
             get => _midiBank;
@@ -216,6 +238,7 @@ namespace Robust.Client.Audio.Midi
             }
         }
 
+        [ViewVariables(VVAccess.ReadWrite)]
         public uint MidiSoundfont
         {
             get => _midiSoundfont;
@@ -229,10 +252,16 @@ namespace Robust.Client.Audio.Midi
             }
         }
 
+        [ViewVariables(VVAccess.ReadWrite)]
         public bool DisablePercussionChannel { get; set; } = true;
+
+        [ViewVariables(VVAccess.ReadWrite)]
         public bool DisableProgramChangeEvent { get; set; } = true;
 
+        [ViewVariables(VVAccess.ReadWrite)]
         public int PlayerTotalTick => _player?.GetTotalTicks ?? 0;
+
+        [ViewVariables(VVAccess.ReadWrite)]
         public int PlayerTick
         {
             get => _player?.CurrentTick ?? 0;
@@ -243,12 +272,19 @@ namespace Robust.Client.Audio.Midi
             }
         }
 
+        [ViewVariables(VVAccess.ReadWrite)]
         public uint SequencerTick => _sequencer?.Tick ?? 0;
+
+        [ViewVariables(VVAccess.ReadWrite)]
         public double SequencerTimeScale => _sequencer?.TimeScale ?? 0;
 
+        [ViewVariables(VVAccess.ReadWrite)]
         public bool Mono { get; set; }
+
+        [ViewVariables]
         public MidiRendererStatus Status { get; private set; } = MidiRendererStatus.None;
 
+        [ViewVariables(VVAccess.ReadWrite)]
         public bool LoopMidi
         {
             get => _loopMidi;
@@ -260,10 +296,11 @@ namespace Robust.Client.Audio.Midi
             }
         }
 
+        [ViewVariables(VVAccess.ReadWrite)]
         public IEntity? TrackingEntity { get; set; } = null;
-        public EntityCoordinates? TrackingCoordinates { get; set; } = null;
 
-        internal bool Free { get; set; } = false;
+        [ViewVariables(VVAccess.ReadWrite)]
+        public EntityCoordinates? TrackingCoordinates { get; set; } = null;
 
         internal MidiRenderer(Settings settings, SoundFontLoader soundFontLoader, bool mono = true)
         {
@@ -294,7 +331,11 @@ namespace Robust.Client.Audio.Midi
             Status = MidiRendererStatus.Input;
             StopAllNotes();
 
-            _driver = new MidiDriver(_settings, MidiDriverEventHandler);
+            lock (_playerStateLock)
+            {
+                _driver = new MidiDriver(_settings, MidiDriverEventHandler);
+            }
+
             return true;
         }
 
@@ -332,8 +373,13 @@ namespace Robust.Client.Audio.Midi
         {
             if (Status != MidiRendererStatus.Input) return false;
             Status = MidiRendererStatus.None;
-            _driver?.Dispose();
-            _driver = null;
+
+            lock (_playerStateLock)
+            {
+                _driver?.Dispose();
+                _driver = null;
+            }
+
             StopAllNotes();
             return true;
         }
@@ -357,7 +403,8 @@ namespace Robust.Client.Audio.Midi
 
         public void StopAllNotes()
         {
-            _synth.AllNotesOff(-1);
+            lock(_playerStateLock)
+                _synth.AllNotesOff(-1);
         }
 
         public void LoadSoundfont(string filename, bool resetPresets = false)
@@ -372,7 +419,12 @@ namespace Robust.Client.Audio.Midi
         public event Action<Shared.Audio.Midi.MidiEvent>? OnMidiEvent;
         public event Action? OnMidiPlayerFinished;
 
-        internal void Render(int length = SampleRate / 250)
+        void IMidiRenderer.Render()
+        {
+            Render();
+        }
+
+        private void Render(int length = SampleRate / 250)
         {
             if (Disposed) return;
 
@@ -452,6 +504,7 @@ namespace Robust.Client.Audio.Midi
             var timestamp = SequencerTick;
             var midiEv = (Shared.Audio.Midi.MidiEvent) midiEvent;
             midiEv.Tick = timestamp;
+            midiEvent.Dispose();
             SendMidiEvent(midiEv);
             return 0;
         }
@@ -462,6 +515,7 @@ namespace Robust.Client.Audio.Midi
             var timestamp = SequencerTick;
             var midiEv = (Shared.Audio.Midi.MidiEvent) midiEvent;
             midiEv.Tick = timestamp;
+            midiEvent.Dispose();
             SendMidiEvent(midiEv);
             return 0;
         }

Robust.Client/BaseClient.cs

@@ -8,10 +8,12 @@ using Robust.Client.Utility;
 using Robust.Shared;
 using Robust.Shared.Configuration;
 using Robust.Shared.Enums;
+using Robust.Shared.GameObjects;
 using Robust.Shared.IoC;
 using Robust.Shared.Log;
 using Robust.Shared.Map;
 using Robust.Shared.Network;
+using Robust.Shared.Players;
 using Robust.Shared.Timing;
 using Robust.Shared.Utility;
 
@@ -24,6 +26,7 @@ namespace Robust.Client
         [Dependency] private readonly IPlayerManager _playMan = default!;
         [Dependency] private readonly INetConfigurationManager _configManager = default!;
         [Dependency] private readonly IClientEntityManager _entityManager = default!;
+        [Dependency] private readonly IEntityLookup _entityLookup = default!;
         [Dependency] private readonly IMapManager _mapManager = default!;
         [Dependency] private readonly IDiscordRichPresence _discord = default!;
         [Dependency] private readonly IGameTiming _timing = default!;
@@ -96,6 +99,25 @@ namespace Robust.Client
             _net.ClientDisconnect(reason);
         }
 
+        /// <inheritdoc />
+        public void StartSinglePlayer()
+        {
+            DebugTools.Assert(RunLevel < ClientRunLevel.Connecting);
+            DebugTools.Assert(!_net.IsConnected);
+            _playMan.Startup();
+            _playMan.LocalPlayer!.Name = PlayerNameOverride ?? _configManager.GetCVar(CVars.PlayerName);
+            OnRunLevelChanged(ClientRunLevel.SinglePlayerGame);
+            GameStartedSetup();
+        }
+
+        /// <inheritdoc />
+        public void StopSinglePlayer()
+        {
+            DebugTools.Assert(RunLevel == ClientRunLevel.SinglePlayerGame);
+            DebugTools.Assert(!_net.IsConnected);
+            GameStoppedReset();
+        }
+
         /// <inheritdoc />
         public event EventHandler<RunLevelChangedEventArgs>? RunLevelChanged;
 
@@ -132,7 +154,7 @@ namespace Robust.Client
             var userId = _net.ServerChannel.UserId;
             _discord.Update(info.ServerName, userName, info.ServerMaxPlayers.ToString());
             // start up player management
-            _playMan.Startup(_net.ServerChannel!);
+            _playMan.Startup();
 
             _playMan.LocalPlayer!.UserId = userId;
             _playMan.LocalPlayer.Name = userName;
@@ -145,16 +167,13 @@ namespace Robust.Client
         ///     receiving states when they join the lobby.
         /// </summary>
         /// <param name="session">Session of the player.</param>
-        private void OnPlayerJoinedServer(IPlayerSession session)
+        private void OnPlayerJoinedServer(ICommonSession session)
         {
             DebugTools.Assert(RunLevel < ClientRunLevel.Connected);
             OnRunLevelChanged(ClientRunLevel.Connected);
 
-            _entityManager.Startup();
-            _mapManager.Startup();
+            GameStartedSetup();
 
-            _timing.ResetSimTime();
-            _timing.Paused = false;
             PlayerJoinedServer?.Invoke(this, new PlayerEventArgs(session));
         }
 
@@ -162,7 +181,7 @@ namespace Robust.Client
         ///     Player is joining the game
         /// </summary>
         /// <param name="session">Session of the player.</param>
-        private void OnPlayerJoinedGame(IPlayerSession session)
+        private void OnPlayerJoinedGame(ICommonSession session)
         {
             DebugTools.Assert(RunLevel >= ClientRunLevel.Connected);
             OnRunLevelChanged(ClientRunLevel.InGame);
@@ -189,10 +208,25 @@ namespace Robust.Client
             PlayerLeaveServer?.Invoke(this, new PlayerEventArgs(_playMan.LocalPlayer?.Session));
 
             LastDisconnectReason = args.Reason;
+            GameStoppedReset();
+        }
 
+        private void GameStartedSetup()
+        {
+            _entityManager.Startup();
+            _mapManager.Startup();
+            _entityLookup.Startup();
+
+            _timing.ResetSimTime();
+            _timing.Paused = false;
+        }
+
+        private void GameStoppedReset()
+        {
             IoCManager.Resolve<INetConfigurationManager>().FlushMessages();
             _gameStates.Reset();
             _playMan.Shutdown();
+            _entityLookup.Shutdown();
             _entityManager.Shutdown();
             _mapManager.Shutdown();
             _discord.ClearPresence();
@@ -249,6 +283,11 @@ namespace Robust.Client
         ///     The client is now in the game, moving around.
         /// </summary>
         InGame,
+
+        /// <summary>
+        ///     The client is now in singleplayer mode, in-game.
+        /// </summary>
+        SinglePlayerGame,
     }
 
     /// <summary>
@@ -259,12 +298,12 @@ namespace Robust.Client
         /// <summary>
         ///     The session that triggered the event.
         /// </summary>
-        private IPlayerSession? Session { get; }
+        private ICommonSession? Session { get; }
 
         /// <summary>
         ///     Constructs a new instance of the class.
         /// </summary>
-        public PlayerEventArgs(IPlayerSession? session)
+        public PlayerEventArgs(ICommonSession? session)
         {
             Session = session;
         }

Robust.Client/ClientIoC.cs

@@ -14,6 +14,7 @@ using Robust.Client.Prototypes;
 using Robust.Client.Reflection;
 using Robust.Client.ResourceManagement;
 using Robust.Client.State;
+using Robust.Client.Timing;
 using Robust.Client.UserInterface;
 using Robust.Client.Utility;
 using Robust.Client.ViewVariables;
@@ -27,8 +28,7 @@ using Robust.Shared.Network;
 using Robust.Shared.Players;
 using Robust.Shared.Prototypes;
 using Robust.Shared.Reflection;
-using Robust.Shared.Serialization;
-using Robust.Shared.Serialization.Manager;
+using Robust.Shared.Timing;
 
 namespace Robust.Client
 {
@@ -38,11 +38,18 @@ namespace Robust.Client
         {
             SharedIoC.RegisterIoC();
 
+            IoCManager.Register<IGameTiming, ClientGameTiming>();
+            IoCManager.Register<IClientGameTiming, ClientGameTiming>();
             IoCManager.Register<IPrototypeManager, ClientPrototypeManager>();
+            IoCManager.Register<IMapManager, ClientMapManager>();
+            IoCManager.Register<IMapManagerInternal, ClientMapManager>();
+            IoCManager.Register<IClientMapManager, ClientMapManager>();
             IoCManager.Register<IEntityManager, ClientEntityManager>();
+            IoCManager.Register<IEntityLookup, EntityLookup>();
             IoCManager.Register<IComponentFactory, ClientComponentFactory>();
             IoCManager.Register<ITileDefinitionManager, ClydeTileDefinitionManager>();
             IoCManager.Register<IClydeTileDefinitionManager, ClydeTileDefinitionManager>();
+            IoCManager.Register<GameController, GameController>();
             IoCManager.Register<IGameController, GameController>();
             IoCManager.Register<IGameControllerInternal, GameController>();
             IoCManager.Register<IReflectionManager, ClientReflectionManager>();
@@ -52,7 +59,8 @@ namespace Robust.Client
             IoCManager.Register<IResourceCacheInternal, ResourceCache>();
             IoCManager.Register<IClientNetManager, NetManager>();
             IoCManager.Register<IClientEntityManager, ClientEntityManager>();
-            IoCManager.Register<IEntityNetworkManager, ClientEntityNetworkManager>();
+            IoCManager.Register<IClientEntityManagerInternal, ClientEntityManager>();
+            IoCManager.Register<IEntityNetworkManager, ClientEntityManager>();
             IoCManager.Register<IClientGameStateManager, ClientGameStateManager>();
             IoCManager.Register<IBaseClient, BaseClient>();
             IoCManager.Register<IPlayerManager, PlayerManager>();
@@ -66,8 +74,6 @@ namespace Robust.Client
             IoCManager.Register<IDiscordRichPresence, DiscordRichPresence>();
             IoCManager.Register<IClientConsoleHost, ClientConsoleHost>();
             IoCManager.Register<IConsoleHost, ClientConsoleHost>();
-            IoCManager.Register<IFontManager, FontManager>();
-            IoCManager.Register<IFontManagerInternal, FontManager>();
             IoCManager.Register<IMidiManager, MidiManager>();
             IoCManager.Register<IAuthManager, AuthManager>();
             switch (mode)
@@ -94,8 +100,9 @@ namespace Robust.Client
                     throw new ArgumentOutOfRangeException();
             }
 
+            IoCManager.Register<IFontManager, FontManager>();
+            IoCManager.Register<IFontManagerInternal, FontManager>();
             IoCManager.Register<IEyeManager, EyeManager>();
-
             IoCManager.Register<IPlacementManager, PlacementManager>();
             IoCManager.Register<IOverlayManager, OverlayManager>();
             IoCManager.Register<IOverlayManagerInternal, OverlayManager>();

Robust.Client/Console/Commands/Debug.cs

@@ -280,12 +280,12 @@ namespace Robust.Client.Console.Commands
     internal class SnapGridGetCell : IConsoleCommand
     {
         public string Command => "sggcell";
-        public string Help => "sggcell <gridID> <vector2i> [offset]\nThat vector2i param is in the form x<int>,y<int>.";
+        public string Help => "sggcell <gridID> <vector2i>\nThat vector2i param is in the form x<int>,y<int>.";
         public string Description => "Lists entities on a snap grid cell.";
 
         public void Execute(IConsoleShell shell, string argStr, string[] args)
         {
-            if (args.Length != 2 && args.Length != 3)
+            if (args.Length != 2)
             {
                 shell.WriteLine(Help);
                 return;
@@ -293,7 +293,6 @@ namespace Robust.Client.Console.Commands
 
             string gridId = args[0];
             string indices = args[1];
-            string offset = args.Length == 3 ? args[2] : "Center";
 
             if (!int.TryParse(args[0], out var id))
             {
@@ -307,29 +306,17 @@ namespace Robust.Client.Console.Commands
                 return;
             }
 
-            SnapGridOffset selectedOffset;
-            if (Enum.IsDefined(typeof(SnapGridOffset), offset))
-            {
-                    selectedOffset = (SnapGridOffset)Enum.Parse(typeof(SnapGridOffset), offset);
-            }
-            else
-            {
-                shell.WriteError("given offset type is not defined");
-                return;
-            }
-
             var mapMan = IoCManager.Resolve<IMapManager>();
 
             if (mapMan.GridExists(new GridId(int.Parse(gridId, CultureInfo.InvariantCulture))))
             {
                 foreach (var entity in
-                    mapMan.GetGrid(new GridId(int.Parse(gridId, CultureInfo.InvariantCulture))).GetSnapGridCell(
+                    mapMan.GetGrid(new GridId(int.Parse(gridId, CultureInfo.InvariantCulture))).GetAnchoredEntities(
                         new Vector2i(
                             int.Parse(indices.Split(',')[0], CultureInfo.InvariantCulture),
-                            int.Parse(indices.Split(',')[1], CultureInfo.InvariantCulture)),
-                        selectedOffset))
+                            int.Parse(indices.Split(',')[1], CultureInfo.InvariantCulture))))
                 {
-                    shell.WriteLine(entity.Owner.Uid.ToString());
+                    shell.WriteLine(entity.ToString());
                 }
             }
             else
@@ -678,10 +665,10 @@ namespace Robust.Client.Console.Commands
         public string Description => "Gets the system clipboard";
         public string Help => "getclipboard";
 
-        public void Execute(IConsoleShell shell, string argStr, string[] args)
+        public async void Execute(IConsoleShell shell, string argStr, string[] args)
         {
             var mgr = IoCManager.Resolve<IClipboardManager>();
-            shell.WriteLine(mgr.GetText());
+            shell.WriteLine(await mgr.GetText());
         }
     }
 
@@ -1097,15 +1084,8 @@ namespace Robust.Client.Console.Commands
                 var key = (Keyboard.Key) parsed!;
 
                 var name = clyde.GetKeyName(key);
-                var scanCode = clyde.GetKeyScanCode(key);
-                var nameScanCode = clyde.GetKeyNameScanCode(scanCode);
 
-                shell.WriteLine($"name: '{name}' scan code: '{scanCode}' name via scan code: '{nameScanCode}'");
-            }
-            else if (int.TryParse(args[0], out var scanCode))
-            {
-                var nameScanCode = clyde.GetKeyNameScanCode(scanCode);
-                shell.WriteLine($"name via scan code: '{nameScanCode}'");
+                shell.WriteLine($"name: '{name}' ");
             }
         }
     }

Robust.Client/Console/Commands/MonitorCommands.cs

@@ -0,0 +1,72 @@
+using System.Linq;
+using JetBrains.Annotations;
+using Robust.Client.Graphics;
+using Robust.Shared.Console;
+using Robust.Shared.IoC;
+
+namespace Robust.Client.Console.Commands
+{
+    [UsedImplicitly]
+    public sealed class LsMonitorCommand : IConsoleCommand
+    {
+        public string Command => "lsmonitor";
+        public string Description => "";
+        public string Help => "";
+
+        public void Execute(IConsoleShell shell, string argStr, string[] args)
+        {
+            var clyde = IoCManager.Resolve<IClyde>();
+
+            foreach (var monitor in clyde.EnumerateMonitors())
+            {
+                shell.WriteLine(
+                    $"[{monitor.Id}] {monitor.Name}: {monitor.Size.X}x{monitor.Size.Y}@{monitor.RefreshRate}Hz");
+            }
+        }
+    }
+
+    [UsedImplicitly]
+    public sealed class MonitorInfoCommand : IConsoleCommand
+    {
+        public string Command => "monitorinfo";
+        public string Description => "";
+        public string Help => "Usage: monitorinfo <id>";
+
+        public void Execute(IConsoleShell shell, string argStr, string[] args)
+        {
+            if (args.Length < 1)
+            {
+                shell.WriteError("Expected one argument.");
+                return;
+            }
+
+            var clyde = IoCManager.Resolve<IClyde>();
+            var monitor = clyde.EnumerateMonitors().Single(c => c.Id == int.Parse(args[0]));
+
+            shell.WriteLine($"{monitor.Id}: {monitor.Name}");
+            shell.WriteLine($"Video modes:");
+
+            foreach (var mode in monitor.VideoModes)
+            {
+                shell.WriteLine($"  {mode.Width}x{mode.Height} {mode.RefreshRate} Hz {mode.RedBits}/{mode.GreenBits}/{mode.BlueBits}");
+            }
+        }
+    }
+
+    [UsedImplicitly]
+    public sealed class SetMonitorCommand : IConsoleCommand
+    {
+        public string Command => "setmonitor";
+        public string Description => "";
+        public string Help => "Usage: setmonitor <id>";
+
+        public void Execute(IConsoleShell shell, string argStr, string[] args)
+        {
+            var clyde = IoCManager.Resolve<IClyde>();
+
+            var id = int.Parse(args[0]);
+            var monitor = clyde.EnumerateMonitors().Single(m => m.Id == id);
+            clyde.SetWindowMonitor(monitor);
+        }
+    }
+}

Robust.Client/Console/Commands/QuitCommand.cs

@@ -1,11 +1,12 @@
 using System;
 using Robust.Shared.Console;
+using Robust.Shared.IoC;
 
 namespace Robust.Client.Console.Commands
 {
-    class QuitCommand : IConsoleCommand
+    class HardQuitCommand : IConsoleCommand
     {
-        public string Command => "quit";
+        public string Command => "hardquit";
         public string Description => "Kills the game client instantly.";
         public string Help => "Kills the game client instantly, leaving no traces. No telling the server goodbye";
 
@@ -14,4 +15,16 @@ namespace Robust.Client.Console.Commands
             Environment.Exit(0);
         }
     }
+
+    class QuitCommand : IConsoleCommand
+    {
+        public string Command => "quit";
+        public string Description => "Shuts down the game client gracefully.";
+        public string Help => "Properly shuts down the game client, notifying the connected server and such.";
+
+        public void Execute(IConsoleShell shell, string argStr, string[] args)
+        {
+            IoCManager.Resolve<IGameController>().Shutdown("quit command used");
+        }
+    }
 }

Robust.Client/Console/ScriptClient.cs

@@ -30,7 +30,8 @@ namespace Robust.Client.Console
 
             var console = new ScriptConsoleServer(this, session);
             _activeConsoles.Add(session, console);
-            console.Open();
+            // FIXME: When this is Open(), resizing the window will cause its position to get NaN'd.
+            console.OpenCentered();
         }
 
         private void ReceiveScriptResponse(MsgScriptResponse message)

Robust.Client/ContentStart.cs

@@ -5,10 +5,15 @@ namespace Robust.Client
         public static void Start(string[] args)
         {
 #if FULL_RELEASE
-            throw new System.InvalidOperationException("ContentStart is not available on a full release.");
+            throw new System.InvalidOperationException("ContentStart.Start is not available on a full release.");
 #else
             GameController.Start(args, true);
 #endif
         }
+
+        public static void StartLibrary(string[] args, GameControllerOptions options)
+        {
+            GameController.Start(args, true, null, options);
+        }
     }
 }

Robust.Client/Debugging/DebugDrawing.cs

@@ -8,9 +8,11 @@ using Robust.Shared;
 using Robust.Shared.Configuration;
 using Robust.Shared.GameObjects;
 using Robust.Shared.IoC;
+using Robust.Shared.Map;
 using Robust.Shared.Maths;
 using Robust.Shared.Physics;
 using Robust.Shared.Physics.Broadphase;
+using Robust.Shared.Physics.Dynamics.Joints;
 using Robust.Shared.Prototypes;
 
 namespace Robust.Client.Debugging
@@ -19,11 +21,10 @@ namespace Robust.Client.Debugging
     public class DebugDrawing : IDebugDrawing
     {
         [Dependency] private readonly IOverlayManager _overlayManager = default!;
-        [Dependency] private readonly IComponentManager _componentManager = default!;
         [Dependency] private readonly IEyeManager _eyeManager = default!;
         [Dependency] private readonly IPrototypeManager _prototypeManager = default!;
-        [Dependency] private readonly IPhysicsManager _physicsManager = default!;
         [Dependency] private readonly IEntityManager _entityManager = default!;
+        [Dependency] private readonly IMapManager _mapManager = default!;
         [Dependency] private readonly IInputManager _inputManager = default!;
 
         private bool _debugColliders;
@@ -44,8 +45,8 @@ namespace Robust.Client.Debugging
 
                 if (value && !_overlayManager.HasOverlay<PhysicsOverlay>())
                 {
-                    _overlayManager.AddOverlay(new PhysicsOverlay(_componentManager, _eyeManager,
-                        _prototypeManager, _inputManager, _physicsManager));
+                    _overlayManager.AddOverlay(new PhysicsOverlay(_eyeManager,
+                        _prototypeManager, _inputManager, _mapManager));
                 }
                 else
                 {
@@ -80,10 +81,9 @@ namespace Robust.Client.Debugging
 
         private class PhysicsOverlay : Overlay
         {
-            private readonly IComponentManager _componentManager;
             private readonly IEyeManager _eyeManager;
+            private readonly IMapManager _mapManager;
             private readonly IInputManager _inputManager;
-            private readonly IPhysicsManager _physicsManager;
 
             public override OverlaySpace Space => OverlaySpace.WorldSpace | OverlaySpace.ScreenSpace;
             private readonly ShaderInstance _shader;
@@ -93,12 +93,11 @@ namespace Robust.Client.Debugging
             private List<IPhysBody> _hoverBodies = new();
 
 
-            public PhysicsOverlay(IComponentManager compMan, IEyeManager eyeMan, IPrototypeManager protoMan, IInputManager inputManager, IPhysicsManager physicsManager)
+            public PhysicsOverlay(IEyeManager eyeMan, IPrototypeManager protoMan, IInputManager inputManager, IMapManager mapManager)
             {
-                _componentManager = compMan;
                 _eyeManager = eyeMan;
                 _inputManager = inputManager;
-                _physicsManager = physicsManager;
+                _mapManager = mapManager;
 
                 _shader = protoMan.Index<ShaderPrototype>("unshaded").Instance();
                 var cache = IoCManager.Resolve<IResourceCache>();
@@ -106,22 +105,23 @@ namespace Robust.Client.Debugging
             }
 
             /// <inheritdoc />
-            protected override void Draw(DrawingHandleBase handle, OverlaySpace currentSpace)
+            protected internal override void Draw(in OverlayDrawArgs args)
             {
-                switch (currentSpace)
+                switch (args.Space)
                 {
                     case OverlaySpace.ScreenSpace:
-                        DrawScreen((DrawingHandleScreen) handle);
+                        DrawScreen(args);
                         break;
                     case OverlaySpace.WorldSpace:
-                        DrawWorld((DrawingHandleWorld) handle);
+                        DrawWorld(args);
                         break;
                 }
 
             }
 
-            private void DrawScreen(DrawingHandleScreen screenHandle)
+            private void DrawScreen(in OverlayDrawArgs args)
             {
+                var screenHandle = args.ScreenHandle;
                 var lineHeight = _font.GetLineHeight(1f);
                 Vector2 drawPos = _hoverStartScreen + new Vector2(20, 0) + new Vector2(0, -(_hoverBodies.Count * 4 * lineHeight / 2f));
                 int row = 0;
@@ -134,7 +134,7 @@ namespace Robust.Client.Debugging
                         row++;
                     }
 
-                    DrawString(screenHandle, _font, drawPos + new Vector2(0, row * lineHeight), $"Ent: {body.Entity}");
+                    DrawString(screenHandle, _font, drawPos + new Vector2(0, row * lineHeight), $"Ent: {body.Owner}");
                     row++;
                     DrawString(screenHandle, _font, drawPos + new Vector2(0, row * lineHeight), $"Layer: {Convert.ToString(body.CollisionLayer, 2)}");
                     row++;
@@ -146,38 +146,47 @@ namespace Robust.Client.Debugging
 
             }
 
-            private void DrawWorld(DrawingHandleWorld worldHandle)
+            private void DrawWorld(in OverlayDrawArgs args)
             {
+                var worldHandle = args.WorldHandle;
                 worldHandle.UseShader(_shader);
                 var drawing = new PhysDrawingAdapter(worldHandle);
 
                 _hoverBodies.Clear();
                 var mouseScreenPos = _inputManager.MouseScreenPosition;
                 var mouseWorldPos = _eyeManager.ScreenToMap(mouseScreenPos).Position;
-                _hoverStartScreen = mouseScreenPos;
+                _hoverStartScreen = mouseScreenPos.Position;
 
                 var viewport = _eyeManager.GetWorldViewport();
 
                 if (viewport.IsEmpty()) return;
 
                 var mapId = _eyeManager.CurrentMap;
+                var sleepThreshold = IoCManager.Resolve<IConfigurationManager>().GetCVar(CVars.TimeToSleep);
+                var colorEdge = Color.Red.WithAlpha(0.33f);
+                var drawnJoints = new HashSet<Joint>();
 
                 foreach (var physBody in EntitySystem.Get<SharedBroadPhaseSystem>().GetCollidingEntities(mapId, viewport))
                 {
                     // all entities have a TransformComponent
-                    var transform = physBody.Entity.Transform;
+                    var transform = physBody.Owner.Transform;
 
-                    var worldBox = physBody.GetWorldAABB();
+                    var worldBox = physBody.GetWorldAABB(_mapManager);
                     if (worldBox.IsEmpty()) continue;
 
-                    var colorEdge = Color.Red.WithAlpha(0.33f);
-                    var sleepThreshold = IoCManager.Resolve<IConfigurationManager>().GetCVar(CVars.TimeToSleep);
-
                     foreach (var fixture in physBody.Fixtures)
                     {
                         var shape = fixture.Shape;
                         var sleepPercent = physBody.Awake ? physBody.SleepTime / sleepThreshold : 1.0f;
-                        shape.DebugDraw(drawing, transform.WorldMatrix, in viewport,  sleepPercent);
+                        shape.DebugDraw(drawing, transform.WorldMatrix, in viewport, sleepPercent);
+                    }
+
+                    foreach (var joint in physBody.Joints)
+                    {
+                        if (drawnJoints.Contains(joint)) continue;
+                        drawnJoints.Add(joint);
+
+                        joint.DebugDraw(drawing, in viewport);
                     }
 
                     if (worldBox.Contains(mouseWorldPos))
@@ -194,9 +203,9 @@ namespace Robust.Client.Debugging
             {
                 var baseLine = new Vector2(pos.X, font.GetAscent(1) + pos.Y);
 
-                foreach (var chr in str)
+                foreach (var rune in str.EnumerateRunes())
                 {
-                    var advance = font.DrawChar(handle, chr, baseLine, 1, Color.White);
+                    var advance = font.DrawChar(handle, rune, baseLine, 1, Color.White);
                     baseLine += new Vector2(advance, 0);
                 }
             }
@@ -272,11 +281,11 @@ namespace Robust.Client.Debugging
                 _eyeManager = eyeManager;
             }
 
-            protected override void Draw(DrawingHandleBase handle, OverlaySpace currentSpace)
+            protected internal override void Draw(in OverlayDrawArgs args)
             {
                 const float stubLength = 0.25f;
 
-                var worldHandle = (DrawingHandleWorld) handle;
+                var worldHandle = (DrawingHandleWorld) args.DrawingHandle;
                 foreach (var entity in _entityManager.GetEntities())
                 {
                     var transform = entity.Transform;

Robust.Client/Debugging/DebugDrawingManager.cs

@@ -87,8 +87,9 @@ namespace Robust.Client.Debugging
                 _owner = owner;
             }
 
-            protected override void Draw(DrawingHandleBase handle, OverlaySpace currentSpace)
+            protected internal override void Draw(in OverlayDrawArgs args)
             {
+                var handle = args.WorldHandle;
                 foreach (var ray in _owner.raysWithLifeTime)
                 {
                     handle.DrawLine(

Robust.Client/Debugging/DebugPhysicsSystem.cs

@@ -125,11 +125,11 @@ namespace Robust.Client.Debugging
             _physics = system;
         }
 
-        protected override void Draw(DrawingHandleBase handle, OverlaySpace currentSpace)
+        protected internal override void Draw(in OverlayDrawArgs args)
         {
             if (_physics.Flags == PhysicsDebugFlags.None) return;
 
-            var worldHandle = (DrawingHandleWorld) handle;
+            var worldHandle = args.WorldHandle;
 
             if ((_physics.Flags & PhysicsDebugFlags.Shapes) != 0)
             {

Robust.Client/GameController/GameController.Standalone.cs

@@ -1,25 +1,31 @@
 using System;
+using System.Threading;
 using Robust.LoaderApi;
+using Robust.Shared;
 using Robust.Shared.IoC;
 using Robust.Shared.Log;
 using Robust.Shared.Timing;
+using Robust.Shared.Utility;
 
 namespace Robust.Client
 {
     internal partial class GameController
     {
-        private IGameLoop _mainLoop = default!;
+        private IGameLoop? _mainLoop;
 
         [Dependency] private readonly IGameTiming _gameTiming = default!;
+        [Dependency] private readonly IDependencyCollection _dependencyCollection = default!;
 
         private static bool _hasStarted;
 
+        private Thread? _gameThread;
+
         public static void Main(string[] args)
         {
             Start(args);
         }
 
-        public static void Start(string[] args, bool contentStart = false, IMainArgs? loaderArgs=null)
+        public static void Start(string[] args, bool contentStart = false, IMainArgs? loaderArgs=null, GameControllerOptions? options = null)
         {
             if (_hasStarted)
             {
@@ -30,11 +36,11 @@ namespace Robust.Client
 
             if (CommandLineArgs.TryParse(args, out var parsed))
             {
-                ParsedMain(parsed, contentStart, loaderArgs);
+                ParsedMain(parsed, contentStart, loaderArgs, options);
             }
         }
 
-        private static void ParsedMain(CommandLineArgs args, bool contentStart, IMainArgs? loaderArgs)
+        private static void ParsedMain(CommandLineArgs args, bool contentStart, IMainArgs? loaderArgs, GameControllerOptions? options)
         {
             IoCManager.InitThread();
 
@@ -42,23 +48,18 @@ namespace Robust.Client
 
             InitIoC(mode);
 
-            var gc = (GameController) IoCManager.Resolve<IGameController>();
+            var gc = IoCManager.Resolve<GameController>();
             gc.SetCommandLineArgs(args);
             gc._loaderArgs = loaderArgs;
+            if(options != null)
+                gc.Options = options;
 
             // When the game is ran with the startup executable being content,
             // we have to disable the separate load context.
             // Otherwise the content assemblies will be loaded twice which causes *many* fun bugs.
-            gc._disableAssemblyLoadContext = contentStart;
-            if (!gc.Startup())
-            {
-                Logger.Fatal("Failed to start game controller!");
-                return;
-            }
-            gc.MainLoop(mode);
+            gc.ContentStart = contentStart;
 
-            Logger.Debug("Goodbye");
-            IoCManager.Clear();
+            gc.Run(mode);
         }
 
         public void OverrideMainLoop(IGameLoop gameLoop)
@@ -66,52 +67,68 @@ namespace Robust.Client
             _mainLoop = gameLoop;
         }
 
-        public void MainLoop(DisplayMode mode)
+        public void Run(DisplayMode mode, Func<ILogHandler>? logHandlerFactory = null)
         {
-            if (_mainLoop == null)
+            if (!StartupSystemSplash(logHandlerFactory))
             {
-                _mainLoop = new GameLoop(_gameTiming)
-                {
-                    SleepMode = mode == DisplayMode.Headless ? SleepMode.Delay : SleepMode.None
-                };
+                Logger.Fatal("Failed to start game controller!");
+                return;
             }
 
-            _mainLoop.Tick += (sender, args) =>
+            if (_clyde.SeparateWindowThread)
             {
-                if (_mainLoop.Running)
-                {
-                    Tick(args);
-                }
-            };
+                var stackSize = _configurationManager.GetCVar(CVars.SysGameThreadStackSize);
+                var priority = (ThreadPriority) _configurationManager.GetCVar(CVars.SysGameThreadPriority);
 
-            _mainLoop.Render += (sender, args) =>
-            {
-                if (_mainLoop.Running)
+                _gameThread = new Thread(() => GameThreadMain(mode), stackSize)
                 {
-                    _gameTiming.CurFrame++;
-                    _clyde.Render();
-                }
-            };
-            _mainLoop.Input += (sender, args) =>
-            {
-                if (_mainLoop.Running)
-                {
-                    Input(args);
-                }
-            };
+                    IsBackground = false,
+                    Priority = priority,
+                    Name = "Game thread",
+                };
 
-            _mainLoop.Update += (sender, args) =>
-            {
-                if (_mainLoop.Running)
-                {
-                    Update(args);
-                }
-            };
+                _gameThread.Start();
 
-            // set GameLoop.Running to false to return from this function.
-            _mainLoop.Run();
+                // Will block until game exit
+                _clyde.EnterWindowLoop();
+
+                if (_gameThread.IsAlive)
+                {
+                    Logger.Debug("Window loop exited; waiting for game thread to exit");
+                    _gameThread.Join();
+                }
+            }
+            else
+            {
+                ContinueStartupAndLoop(mode);
+            }
 
             Cleanup();
+
+            Logger.Debug("Goodbye");
+            IoCManager.Clear();
+        }
+
+        private void GameThreadMain(DisplayMode mode)
+        {
+            IoCManager.InitThread(_dependencyCollection);
+
+            ContinueStartupAndLoop(mode);
+
+            // Game thread exited, make sure window thread unblocks to finish shutdown.
+            _clyde.TerminateWindowLoop();
+        }
+
+        private void ContinueStartupAndLoop(DisplayMode mode)
+        {
+            if (!StartupContinue(mode))
+            {
+                Logger.Fatal("Failed to start game controller!");
+                return;
+            }
+
+            DebugTools.AssertNotNull(_mainLoop);
+            _mainLoop!.Run();
         }
     }
 }

Robust.Client/GameController/GameController.cs

@@ -1,4 +1,5 @@
-using System;
+using System;
+using System.Collections.Generic;
 using System.IO;
 using System.Net;
 using System.Threading.Tasks;
@@ -48,6 +49,7 @@ namespace Robust.Client
         [Dependency] private readonly IClientConsoleHost _console = default!;
         [Dependency] private readonly ITimerManager _timerManager = default!;
         [Dependency] private readonly IClientEntityManager _entityManager = default!;
+        [Dependency] private readonly IEntityLookup _lookup = default!;
         [Dependency] private readonly IPlacementManager _placementManager = default!;
         [Dependency] private readonly IClientGameStateManager _gameStateManager = default!;
         [Dependency] private readonly IOverlayManagerInternal _overlayManager = default!;
@@ -59,17 +61,18 @@ namespace Robust.Client
         [Dependency] private readonly IFontManagerInternal _fontManager = default!;
         [Dependency] private readonly IModLoaderInternal _modLoader = default!;
         [Dependency] private readonly IScriptClient _scriptClient = default!;
-        [Dependency] private readonly IComponentManager _componentManager = default!;
-        [Dependency] private readonly IPlayerManager _playerManager = default!;
         [Dependency] private readonly IRobustMappedStringSerializer _stringSerializer = default!;
         [Dependency] private readonly IAuthManager _authManager = default!;
         [Dependency] private readonly IMidiManager _midiManager = default!;
+        [Dependency] private readonly IEyeManager _eyeManager = default!;
 
         private CommandLineArgs? _commandLineArgs;
-        private bool _disableAssemblyLoadContext;
+
         // Arguments for loader-load. Not used otherwise.
         private IMainArgs? _loaderArgs;
 
+        public bool ContentStart { get; set; } = false;
+        public GameControllerOptions Options { get; private set; } = new();
         public InitialLaunchState LaunchState { get; private set; } = default!;
 
         public bool LoadConfigAndUserData { get; set; } = true;
@@ -79,14 +82,126 @@ namespace Robust.Client
             _commandLineArgs = args;
         }
 
-        public bool Startup(Func<ILogHandler>? logHandlerFactory = null)
+        private bool StartupContinue(DisplayMode displayMode)
+        {
+            _clyde.InitializePostWindowing();
+            _clyde.SetWindowTitle(Options.DefaultWindowTitle);
+
+            _taskManager.Initialize();
+            _fontManager.SetFontDpi((uint) _configurationManager.GetCVar(CVars.DisplayFontDpi));
+
+            // Disable load context usage on content start.
+            // This prevents Content.Client being loaded twice and things like csi blowing up because of it.
+            _modLoader.SetUseLoadContext(!ContentStart);
+            _modLoader.SetEnableSandboxing(false && Options.Sandboxing);
+
+            if (!_modLoader.TryLoadModulesFrom(new ResourcePath("/Assemblies/"), Options.ContentModulePrefix))
+            {
+                Logger.Fatal("Errors while loading content assemblies.");
+                return false;
+            }
+
+            foreach (var loadedModule in _modLoader.LoadedModules)
+            {
+                _configurationManager.LoadCVarsFromAssembly(loadedModule);
+            }
+
+            IoCManager.Resolve<ISerializationManager>().Initialize();
+
+            // Call Init in game assemblies.
+            _modLoader.BroadcastRunLevel(ModRunLevel.PreInit);
+            _modLoader.BroadcastRunLevel(ModRunLevel.Init);
+
+            _resourceCache.PreloadTextures();
+            _userInterfaceManager.Initialize();
+            _eyeManager.Initialize();
+            _networkManager.Initialize(false);
+            IoCManager.Resolve<INetConfigurationManager>().SetupNetworking();
+            _serializer.Initialize();
+            _inputManager.Initialize();
+            _console.Initialize();
+            _prototypeManager.Initialize();
+            _prototypeManager.LoadDirectory(Options.PrototypeDirectory);
+            _prototypeManager.Resync();
+            _mapManager.Initialize();
+            _entityManager.Initialize();
+            _gameStateManager.Initialize();
+            _placementManager.Initialize();
+            _viewVariablesManager.Initialize();
+            _scriptClient.Initialize();
+
+            _client.Initialize();
+            _discord.Initialize();
+            _modLoader.BroadcastRunLevel(ModRunLevel.PostInit);
+
+            if (_commandLineArgs?.Username != null)
+            {
+                _client.PlayerNameOverride = _commandLineArgs.Username;
+            }
+
+            _authManager.LoadFromEnv();
+
+            GC.Collect();
+
+            // Setup main loop
+            if (_mainLoop == null)
+            {
+                _mainLoop = new GameLoop(_gameTiming)
+                {
+                    SleepMode = displayMode == DisplayMode.Headless ? SleepMode.Delay : SleepMode.None
+                };
+            }
+
+            _mainLoop.Tick += (sender, args) =>
+            {
+                if (_mainLoop.Running)
+                {
+                    Tick(args);
+                }
+            };
+
+            _mainLoop.Render += (sender, args) =>
+            {
+                if (_mainLoop.Running)
+                {
+                    _gameTiming.CurFrame++;
+                    _clyde.Render();
+                }
+            };
+            _mainLoop.Input += (sender, args) =>
+            {
+                if (_mainLoop.Running)
+                {
+                    Input(args);
+                }
+            };
+
+            _mainLoop.Update += (sender, args) =>
+            {
+                if (_mainLoop.Running)
+                {
+                    Update(args);
+                }
+            };
+
+            _clyde.Ready();
+
+            if (!Options.DisableCommandLineConnect &&
+                (_commandLineArgs?.Connect == true || _commandLineArgs?.Launcher == true)
+                && LaunchState.ConnectEndpoint != null)
+            {
+                _client.ConnectToServer(LaunchState.ConnectEndpoint);
+            }
+
+            return true;
+        }
+
+        private bool StartupSystemSplash(Func<ILogHandler>? logHandlerFactory)
         {
             ReadInitialLaunchState();
 
             SetupLogging(_logManager, logHandlerFactory ?? (() => new ConsoleLogHandler()));
 
-            _taskManager.Initialize();
-
             // Figure out user data directory.
             var userDataDir = GetUserDataDir();
 
@@ -99,7 +214,7 @@ namespace Robust.Client
 
             if (LoadConfigAndUserData)
             {
-                var configFile = Path.Combine(userDataDir, "client_config.toml");
+                var configFile = Path.Combine(userDataDir, Options.ConfigFileName);
                 if (File.Exists(configFile))
                 {
                     // Load config from user data if available.
@@ -123,7 +238,12 @@ namespace Robust.Client
 
             _resourceCache.Initialize(LoadConfigAndUserData ? userDataDir : null);
 
-            ProgramShared.DoMounts(_resourceCache, _commandLineArgs?.MountOptions, "Content.Client", _loaderArgs != null);
+            var mountOptions = _commandLineArgs != null
+                ? MountOptions.Merge(_commandLineArgs.MountOptions, Options.MountOptions) : Options.MountOptions;
+
+            ProgramShared.DoMounts(_resourceCache, mountOptions, Options.ContentBuildDirectory,
+                _loaderArgs != null && !Options.ResourceMountDisabled, ContentStart);
+
             if (_loaderArgs != null)
             {
                 _stringSerializer.EnableCaching = false;
@@ -131,77 +251,21 @@ namespace Robust.Client
                 _modLoader.VerifierExtraLoadHandler = VerifierExtraLoadHandler;
             }
 
+            _clyde.TextEntered += TextEntered;
+            _clyde.MouseMove += MouseMove;
+            _clyde.KeyUp += KeyUp;
+            _clyde.KeyDown += KeyDown;
+            _clyde.MouseWheel += MouseWheel;
+            _clyde.CloseWindow += args =>
+            {
+                if (args.Window == _clyde.MainWindow)
+                {
+                    Shutdown("Main window closed");
+                }
+            };
+
             // Bring display up as soon as resources are mounted.
-            if (!_clyde.Initialize())
-            {
-                return false;
-            }
-
-            _clyde.SetWindowTitle("Space Station 14");
-
-            _fontManager.Initialize();
-
-            // Disable load context usage on content start.
-            // This prevents Content.Client being loaded twice and things like csi blowing up because of it.
-            _modLoader.SetUseLoadContext(!_disableAssemblyLoadContext);
-            _modLoader.SetEnableSandboxing(true);
-
-            if (!_modLoader.TryLoadModulesFrom(new ResourcePath("/Assemblies/"), "Content."))
-            {
-                Logger.Fatal("Errors while loading content assemblies.");
-                return false;
-            }
-
-            foreach (var loadedModule in _modLoader.LoadedModules)
-            {
-                _configurationManager.LoadCVarsFromAssembly(loadedModule);
-            }
-
-            IoCManager.Resolve<ISerializationManager>().Initialize();
-
-            // Call Init in game assemblies.
-            _modLoader.BroadcastRunLevel(ModRunLevel.PreInit);
-            _modLoader.BroadcastRunLevel(ModRunLevel.Init);
-
-            _resourceCache.PreloadTextures();
-            _userInterfaceManager.Initialize();
-            _networkManager.Initialize(false);
-            IoCManager.Resolve<INetConfigurationManager>().SetupNetworking();
-            _serializer.Initialize();
-            _inputManager.Initialize();
-            _console.Initialize();
-            _prototypeManager.Initialize();
-            _prototypeManager.LoadDirectory(new ResourcePath(@"/Prototypes/"));
-            _prototypeManager.Resync();
-            _mapManager.Initialize();
-            _entityManager.Initialize();
-            _gameStateManager.Initialize();
-            _placementManager.Initialize();
-            _viewVariablesManager.Initialize();
-            _scriptClient.Initialize();
-
-            _client.Initialize();
-            _discord.Initialize();
-            _modLoader.BroadcastRunLevel(ModRunLevel.PostInit);
-
-            if (_commandLineArgs?.Username != null)
-            {
-                _client.PlayerNameOverride = _commandLineArgs.Username;
-            }
-
-            _authManager.LoadFromEnv();
-
-            GC.Collect();
-
-            _clyde.Ready();
-
-            if ((_commandLineArgs?.Connect == true || _commandLineArgs?.Launcher == true)
-                && LaunchState.ConnectEndpoint != null)
-            {
-                _client.ConnectToServer(LaunchState.ConnectEndpoint);
-            }
-
-            return true;
+            return _clyde.InitializePreWindowing();
         }
 
         private Stream? VerifierExtraLoadHandler(string arg)
@@ -247,8 +311,10 @@ namespace Robust.Client
 
         public void Shutdown(string? reason = null)
         {
+            DebugTools.AssertNotNull(_mainLoop);
+
             // Already got shut down I assume,
-            if (!_mainLoop.Running)
+            if (!_mainLoop!.Running)
             {
                 return;
             }
@@ -277,17 +343,20 @@ namespace Robust.Client
             _modLoader.BroadcastUpdate(ModUpdateLevel.PreEngine, frameEventArgs);
             _timerManager.UpdateTimers(frameEventArgs);
             _taskManager.ProcessPendingTasks();
-            _userInterfaceManager.Update(frameEventArgs);
 
-            if (_client.RunLevel >= ClientRunLevel.Connected)
+            // GameStateManager is in full control of the simulation update in multiplayer.
+            if (_client.RunLevel == ClientRunLevel.InGame || _client.RunLevel == ClientRunLevel.Connected)
             {
-                _componentManager.CullRemovedComponents();
                 _gameStateManager.ApplyGameState();
-                _entityManager.Update(frameEventArgs.DeltaSeconds);
-                _playerManager.Update(frameEventArgs.DeltaSeconds);
             }
 
-            _stateManager.Update(frameEventArgs);
+            // In singleplayer, however, we're in full control instead.
+            else if (_client.RunLevel == ClientRunLevel.SinglePlayerGame)
+            {
+                _entityManager.TickUpdate(frameEventArgs.DeltaSeconds);
+                _lookup.Update();
+            }
+
             _modLoader.BroadcastUpdate(ModUpdateLevel.PostEngine, frameEventArgs);
         }
 
@@ -308,11 +377,6 @@ namespace Robust.Client
             _modLoader.BroadcastUpdate(ModUpdateLevel.FramePostEngine, frameEventArgs);
         }
 
-        private void Render()
-        {
-
-        }
-
         internal static void SetupLogging(ILogManager logManager, Func<ILogHandler> logHandlerFactory)
         {
             logManager.RootSawmill.AddHandler(logHandlerFactory());
@@ -389,6 +453,7 @@ namespace Robust.Client
         {
             _networkManager.Shutdown("Client shutting down");
             _midiManager.Shutdown();
+            IoCManager.Resolve<IEntityLookup>().Shutdown();
             _entityManager.Shutdown();
             _clyde.Shutdown();
         }

Robust.Client/GameControllerOptions.cs

@@ -0,0 +1,60 @@
+using Robust.Shared;
+using Robust.Shared.Utility;
+
+namespace Robust.Client
+{
+    public class GameControllerOptions
+    {
+        /// <summary>
+        ///     Whether content sandboxing will be enabled & enforced.
+        /// </summary>
+        public bool Sandboxing { get; init; } = true;
+
+        // TODO: Expose mounting methods to games using Robust as a library.
+        /// <summary>
+        ///     Lists of mount options to mount.
+        /// </summary>
+        public MountOptions MountOptions { get; init; } = new();
+
+        /// <summary>
+        ///     Name the userdata directory will have.
+        /// </summary>
+        public string UserDataDirectoryName { get; init; } = "Space Station 14";
+
+        /// <summary>
+        ///     Name of the configuration file in the user data directory.
+        /// </summary>
+        public string ConfigFileName { get; init; } = "client_config.toml";
+
+        // TODO: Define engine branding from json file in resources.
+        /// <summary>
+        ///     Default window title.
+        /// </summary>
+        public string DefaultWindowTitle { get; init; } = "Space Station 14";
+
+        /// <summary>
+        ///     Assemblies with this prefix will be loaded.
+        /// </summary>
+        public string ContentModulePrefix { get; init; } = "Content.";
+
+        /// <summary>
+        ///     Name of the content build directory, for game pack mounting purposes.
+        /// </summary>
+        public string ContentBuildDirectory { get; init; } = "Content.Client";
+
+        /// <summary>
+        ///     Directory to load all prototypes from.
+        /// </summary>
+        public ResourcePath PrototypeDirectory { get; init; } = new(@"/Prototypes/");
+
+        /// <summary>
+        ///     Whether to disable mounting the "Resources/" folder on FULL_RELEASE.
+        /// </summary>
+        public bool ResourceMountDisabled { get; init; } = false;
+
+        /// <summary>
+        ///     Whether to disable command line args server auto-connecting.
+        /// </summary>
+        public bool DisableCommandLineConnect { get; init; } = false;
+    }
+}

Robust.Client/GameObjects/ClientComponentFactory.cs

@@ -9,58 +9,30 @@ namespace Robust.Client.GameObjects
         public ClientComponentFactory()
         {
             // Required for the engine to work
-            Register<MetaDataComponent>();
-            RegisterReference<MetaDataComponent, IMetaDataComponent>();
-
-            // Required for the engine to work
-            Register<TransformComponent>();
-            RegisterReference<TransformComponent, ITransformComponent>();
-
-            Register<MapComponent>();
-            RegisterReference<MapComponent, IMapComponent>();
-
-            Register<MapGridComponent>();
-            RegisterReference<MapGridComponent, IMapGridComponent>();
-
-            Register<PhysicsComponent>();
-            RegisterReference<PhysicsComponent, IPhysBody>();
-
-            Register<CollisionWakeComponent>();
-
-            Register<ContainerManagerComponent>();
-            RegisterReference<ContainerManagerComponent, IContainerManager>();
-
             RegisterIgnore("KeyBindingInput");
 
-            Register<InputComponent>();
-
-            Register<SpriteComponent>();
-            RegisterReference<SpriteComponent, SharedSpriteComponent>();
-            RegisterReference<SpriteComponent, ISpriteComponent>();
-
-            Register<ClientOccluderComponent>();
-            RegisterReference<ClientOccluderComponent, OccluderComponent>();
-
-            Register<EyeComponent>();
-            RegisterReference<EyeComponent, SharedEyeComponent>();
-
-            Register<AppearanceComponent>();
-            RegisterReference<AppearanceComponent, SharedAppearanceComponent>();
-
-            Register<AppearanceTestComponent>();
-            Register<SnapGridComponent>();
-
-            Register<ClientUserInterfaceComponent>();
-            RegisterReference<ClientUserInterfaceComponent, SharedUserInterfaceComponent>();
-
-            Register<AnimationPlayerComponent>();
-
-            Register<TimerComponent>();
+            RegisterClass<MetaDataComponent>();
+            RegisterClass<TransformComponent>();
+            RegisterClass<MapComponent>();
+            RegisterClass<MapGridComponent>();
+            RegisterClass<PhysicsComponent>();
+            RegisterClass<CollisionWakeComponent>();
+            RegisterClass<ClientUserInterfaceComponent>();
+            RegisterClass<ContainerManagerComponent>();
+            RegisterClass<InputComponent>();
+            RegisterClass<SpriteComponent>();
+            RegisterClass<ClientOccluderComponent>();
+            RegisterClass<EyeComponent>();
+            RegisterClass<AppearanceComponent>();
+            RegisterClass<AppearanceTestComponent>();
+            RegisterClass<SnapGridComponent>();
+            RegisterClass<AnimationPlayerComponent>();
+            RegisterClass<TimerComponent>();
 
 #if DEBUG
-            Register<DebugExceptionOnAddComponent>();
-            Register<DebugExceptionInitializeComponent>();
-            Register<DebugExceptionStartupComponent>();
+            RegisterClass<DebugExceptionOnAddComponent>();
+            RegisterClass<DebugExceptionInitializeComponent>();
+            RegisterClass<DebugExceptionStartupComponent>();
 #endif
 
         }

Robust.Client/GameObjects/ClientEntityManager.cs

@@ -1,11 +1,17 @@
 using System;
 using System.Collections.Generic;
 using System.Linq;
+using JetBrains.Annotations;
+using Prometheus;
+using Robust.Client.GameStates;
 using Robust.Shared.Exceptions;
 using Robust.Shared.GameObjects;
 using Robust.Shared.IoC;
 using Robust.Shared.Log;
 using Robust.Shared.Map;
+using Robust.Shared.Network;
+using Robust.Shared.Network.Messages;
+using Robust.Shared.Timing;
 using Robust.Shared.Utility;
 
 namespace Robust.Client.GameObjects
@@ -13,303 +19,153 @@ namespace Robust.Client.GameObjects
     /// <summary>
     /// Manager for entities -- controls things like template loading and instantiation
     /// </summary>
-    public sealed class ClientEntityManager : EntityManager, IClientEntityManager
+    public sealed class ClientEntityManager : EntityManager, IClientEntityManagerInternal
     {
-        [Dependency] private readonly IMapManager _mapManager = default!;
-        [Dependency] private readonly IComponentFactory _compFactory = default!;
-#if EXCEPTION_TOLERANCE
-        [Dependency] private readonly IRuntimeLog _runtimeLog = default!;
-#endif
+        [Dependency] private readonly IClientNetManager _networkManager = default!;
+        [Dependency] private readonly IClientGameStateManager _gameStateManager = default!;
+        [Dependency] private readonly IGameTiming _gameTiming = default!;
 
-        private int _nextClientEntityUid = EntityUid.ClientUid + 1;
+        protected override int NextEntityUid { get; set; } = EntityUid.ClientUid + 1;
 
-        public override void Startup()
+        public override void Initialize()
         {
-            base.Startup();
+            SetupNetworking();
+            ReceivedComponentMessage += (_, compMsg) => DispatchComponentMessage(compMsg);
+            ReceivedSystemMessage += (_, systemMsg) => EventBus.RaiseEvent(EventSource.Network, systemMsg);
 
-            if (Started)
-            {
-                throw new InvalidOperationException("Startup() called multiple times");
-            }
-
-            EntitySystemManager.Initialize();
-            Started = true;
+            base.Initialize();
         }
 
-        public List<EntityUid> ApplyEntityStates(EntityState[]? curEntStates, IEnumerable<EntityUid>? deletions,
-            EntityState[]? nextEntStates)
+        IEntity IClientEntityManagerInternal.CreateEntity(string? prototypeName, EntityUid? uid)
         {
-            var toApply = new Dictionary<IEntity, (EntityState?, EntityState?)>();
-            var toInitialize = new List<Entity>();
-            var created = new List<EntityUid>();
-            deletions ??= new EntityUid[0];
+            return base.CreateEntity(prototypeName, uid);
+        }
 
-            if (curEntStates != null && curEntStates.Length != 0)
+        void IClientEntityManagerInternal.InitializeEntity(IEntity entity)
+        {
+            EntityManager.InitializeEntity((Entity)entity);
+        }
+
+        void IClientEntityManagerInternal.StartEntity(IEntity entity)
+        {
+            base.StartEntity((Entity)entity);
+        }
+
+        #region IEntityNetworkManager impl
+
+        public override IEntityNetworkManager EntityNetManager => this;
+
+        /// <inheritdoc />
+        public event EventHandler<NetworkComponentMessage>? ReceivedComponentMessage;
+
+        /// <inheritdoc />
+        public event EventHandler<object>? ReceivedSystemMessage;
+
+        private readonly PriorityQueue<(uint seq, MsgEntity msg)> _queue = new(new MessageTickComparer());
+        private uint _incomingMsgSequence = 0;
+
+        /// <inheritdoc />
+        public void SetupNetworking()
+        {
+            _networkManager.RegisterNetMessage<MsgEntity>(MsgEntity.NAME, HandleEntityNetworkMessage);
+        }
+
+        public override void TickUpdate(float frameTime, Histogram? histogram)
+        {
+            using (histogram?.WithLabels("EntityNet").NewTimer())
             {
-                foreach (var es in curEntStates)
+                while (_queue.Count != 0 && _queue.Peek().msg.SourceTick <= _gameStateManager.CurServerTick)
                 {
-                    //Known entities
-                    if (Entities.TryGetValue(es.Uid, out var entity))
-                    {
-                        toApply.Add(entity, (es, null));
-                    }
-                    else //Unknown entities
-                    {
-                        var metaState = (MetaDataComponentState?) es.ComponentStates
-                            ?.FirstOrDefault(c => c.NetID == NetIDs.META_DATA);
-                        if (metaState == null)
-                        {
-                            throw new InvalidOperationException($"Server sent new entity state for {es.Uid} without metadata component!");
-                        }
-                        var newEntity = CreateEntity(metaState.PrototypeId, es.Uid);
-                        toApply.Add(newEntity, (es, null));
-                        toInitialize.Add(newEntity);
-                        created.Add(newEntity.Uid);
-                    }
+                    var (_, msg) = _queue.Take();
+                    // Logger.DebugS("net.ent", "Dispatching: {0}: {1}", seq, msg);
+                    DispatchMsgEntity(msg);
                 }
             }
 
-            if (nextEntStates != null && nextEntStates.Length != 0)
-            {
-                foreach (var es in nextEntStates)
-                {
-                    if (Entities.TryGetValue(es.Uid, out var entity))
-                    {
-                        if (toApply.TryGetValue(entity, out var state))
-                        {
-                            toApply[entity] = (state.Item1, es);
-                        }
-                        else
-                        {
-                            toApply[entity] = (null, es);
-                        }
-                    }
-                }
-            }
-
-            // Make sure this is done after all entities have been instantiated.
-            foreach (var kvStates in toApply)
-            {
-                var ent = kvStates.Key;
-                var entity = (Entity) ent;
-                HandleEntityState(entity.EntityManager.ComponentManager, entity, kvStates.Value.Item1,
-                    kvStates.Value.Item2);
-            }
-
-            foreach (var kvp in toApply)
-            {
-                UpdateEntityTree(kvp.Key);
-            }
-
-            foreach (var id in deletions)
-            {
-                DeleteEntity(id);
-            }
-
-#if EXCEPTION_TOLERANCE
-            HashSet<Entity> brokenEnts = new HashSet<Entity>();
-#endif
-
-            foreach (var entity in toInitialize)
-            {
-#if EXCEPTION_TOLERANCE
-                try
-                {
-#endif
-                    InitializeEntity(entity);
-#if EXCEPTION_TOLERANCE
-                }
-                catch (Exception e)
-                {
-                    Logger.ErrorS("state", $"Server entity threw in Init: uid={entity.Uid}, proto={entity.Prototype}\n{e}");
-                    brokenEnts.Add(entity);
-                }
-#endif
-            }
-
-            foreach (var entity in toInitialize)
-            {
-#if EXCEPTION_TOLERANCE
-                if(brokenEnts.Contains(entity))
-                    continue;
-
-                try
-                {
-#endif
-                    StartEntity(entity);
-#if EXCEPTION_TOLERANCE
-                }
-                catch (Exception e)
-                {
-                    Logger.ErrorS("state", $"Server entity threw in Start: uid={entity.Uid}, proto={entity.Prototype}\n{e}");
-                    brokenEnts.Add(entity);
-                }
-#endif
-            }
-
-            foreach (var entity in toInitialize)
-            {
-#if EXCEPTION_TOLERANCE
-                if(brokenEnts.Contains(entity))
-                    continue;
-#endif
-                UpdateEntityTree(entity);
-            }
-#if EXCEPTION_TOLERANCE
-            foreach (var entity in brokenEnts)
-            {
-                entity.Delete();
-            }
-#endif
-
-            return created;
+            base.TickUpdate(frameTime, histogram);
         }
 
         /// <inheritdoc />
-        public override IEntity CreateEntityUninitialized(string? prototypeName)
+        public void SendSystemNetworkMessage(EntityEventArgs message)
         {
-            return CreateEntity(prototypeName);
+            SendSystemNetworkMessage(message, default(uint));
+        }
+
+        public void SendSystemNetworkMessage(EntityEventArgs message, uint sequence)
+        {
+            var msg = _networkManager.CreateNetMessage<MsgEntity>();
+            msg.Type = EntityMessageType.SystemMessage;
+            msg.SystemMessage = message;
+            msg.SourceTick = _gameTiming.CurTick;
+            msg.Sequence = sequence;
+
+            _networkManager.ClientSendMessage(msg);
         }
 
         /// <inheritdoc />
-        public override IEntity CreateEntityUninitialized(string? prototypeName, EntityCoordinates coordinates)
+        public void SendSystemNetworkMessage(EntityEventArgs message, INetChannel channel)
         {
-            var newEntity = CreateEntity(prototypeName, GenerateEntityUid());
-
-            if (TryGetEntity(coordinates.EntityId, out var entity))
-            {
-                newEntity.Transform.AttachParent(entity);
-                newEntity.Transform.Coordinates = coordinates;
-            }
-
-            return newEntity;
+            throw new NotSupportedException();
         }
 
         /// <inheritdoc />
-        public override IEntity CreateEntityUninitialized(string? prototypeName, MapCoordinates coordinates)
+        [Obsolete("Component Messages are deprecated, use Entity Events instead.")]
+        public void SendComponentNetworkMessage(INetChannel? channel, IEntity entity, IComponent component, ComponentMessage message)
         {
-            var newEntity = CreateEntity(prototypeName, GenerateEntityUid());
-            newEntity.Transform.AttachParent(_mapManager.GetMapEntity(coordinates.MapId));
-            newEntity.Transform.WorldPosition = coordinates.Position;
-            return newEntity;
+            if (!component.NetID.HasValue)
+                throw new ArgumentException($"Component {component.Name} does not have a NetID.", nameof(component));
+
+            var msg = _networkManager.CreateNetMessage<MsgEntity>();
+            msg.Type = EntityMessageType.ComponentMessage;
+            msg.EntityUid = entity.Uid;
+            msg.NetId = component.NetID.Value;
+            msg.ComponentMessage = message;
+            msg.SourceTick = _gameTiming.CurTick;
+
+            _networkManager.ClientSendMessage(msg);
         }
 
-        /// <inheritdoc />
-        public override IEntity SpawnEntity(string? protoName, EntityCoordinates coordinates)
+        private void HandleEntityNetworkMessage(MsgEntity message)
         {
-            var newEnt = CreateEntityUninitialized(protoName, coordinates);
-            InitializeAndStartEntity((Entity) newEnt);
-            UpdateEntityTree(newEnt);
-            return newEnt;
-        }
-
-        /// <inheritdoc />
-        public override IEntity SpawnEntity(string? protoName, MapCoordinates coordinates)
-        {
-            var entity = CreateEntityUninitialized(protoName, coordinates);
-            InitializeAndStartEntity((Entity) entity);
-            UpdateEntityTree(entity);
-            return entity;
-        }
-
-        /// <inheritdoc />
-        public override IEntity SpawnEntityNoMapInit(string? protoName, EntityCoordinates coordinates)
-        {
-            return SpawnEntity(protoName, coordinates);
-        }
-
-        protected override EntityUid GenerateEntityUid()
-        {
-            return new(_nextClientEntityUid++);
-        }
-
-        private void HandleEntityState(IComponentManager compMan, IEntity entity, EntityState? curState,
-            EntityState? nextState)
-        {
-            var compStateWork = new Dictionary<uint, (ComponentState? curState, ComponentState? nextState)>();
-            var entityUid = entity.Uid;
-
-            if (curState?.ComponentChanges != null)
+            if (message.SourceTick <= _gameStateManager.CurServerTick)
             {
-                foreach (var compChange in curState.ComponentChanges)
-                {
-                    if (compChange.Deleted)
-                    {
-                        if (compMan.TryGetComponent(entityUid, compChange.NetID, out var comp))
-                        {
-                            compMan.RemoveComponent(entityUid, comp);
-                        }
-                    }
-                    else
-                    {
-                        if (compMan.HasComponent(entityUid, compChange.NetID))
-                            continue;
-
-                        var newComp = (Component) _compFactory.GetComponent(compChange.ComponentName!);
-                        newComp.Owner = entity;
-                        compMan.AddComponent(entity, newComp, true);
-                    }
-                }
+                DispatchMsgEntity(message);
+                return;
             }
 
-            if (curState?.ComponentStates != null)
-            {
-                foreach (var compState in curState.ComponentStates)
-                {
-                    compStateWork[compState.NetID] = (compState, null);
-                }
-            }
+            // MsgEntity is sent with ReliableOrdered so Lidgren guarantees ordering of incoming messages.
+            // We still need to store a sequence input number to ensure ordering remains consistent in
+            // the priority queue.
+            _queue.Add((++_incomingMsgSequence, message));
+        }
 
-            if (nextState?.ComponentStates != null)
+        private void DispatchMsgEntity(MsgEntity message)
+        {
+            switch (message.Type)
             {
-                foreach (var compState in nextState.ComponentStates)
-                {
-                    if (compStateWork.TryGetValue(compState.NetID, out var state))
-                    {
-                        compStateWork[compState.NetID] = (state.curState, compState);
-                    }
-                    else
-                    {
-                        compStateWork[compState.NetID] = (null, compState);
-                    }
-                }
-            }
+                case EntityMessageType.ComponentMessage:
+                    ReceivedComponentMessage?.Invoke(this, new NetworkComponentMessage(message));
+                    return;
 
-            foreach (var (netId, (cur, next)) in compStateWork)
-            {
-                if (compMan.TryGetComponent(entityUid, netId, out var component))
-                {
-                    try
-                    {
-                        component.HandleComponentState(cur, next);
-                    }
-                    catch (Exception e)
-                    {
-                        var wrapper = new ComponentStateApplyException(
-                            $"Failed to apply comp state: entity={component.Owner}, comp={component.Name}", e);
-#if EXCEPTION_TOLERANCE
-                    _runtimeLog.LogException(wrapper, "Component state apply");
-#else
-                        throw wrapper;
-#endif
-                    }
-                }
-                else
-                {
-                    // The component can be null here due to interp.
-                    // Because the NEXT state will have a new component, but this one doesn't yet.
-                    // That's fine though.
-                    if (cur == null)
-                    {
-                        continue;
-                    }
-
-                    var eUid = entityUid;
-                    var eRegisteredNetUidName = _compFactory.GetRegistration(netId).Name;
-                    DebugTools.Assert(
-                        $"Component does not exist for state: entUid={eUid}, expectedNetId={netId}, expectedName={eRegisteredNetUidName}");
-                }
+                case EntityMessageType.SystemMessage:
+                    ReceivedSystemMessage?.Invoke(this, message.SystemMessage);
+                    return;
             }
         }
+
+        private sealed class MessageTickComparer : IComparer<(uint seq, MsgEntity msg)>
+        {
+            public int Compare((uint seq, MsgEntity msg) x, (uint seq, MsgEntity msg) y)
+            {
+                var cmp = y.msg.SourceTick.CompareTo(x.msg.SourceTick);
+                if (cmp != 0)
+                {
+                    return cmp;
+                }
+
+                return y.seq.CompareTo(x.seq);
+            }
+        }
+        #endregion
     }
 }

Robust.Client/GameObjects/ClientEntityNetworkManager.cs

@@ -1,128 +0,0 @@
-using System;
-using System.Collections.Generic;
-using Robust.Client.GameStates;
-using Robust.Shared.GameObjects;
-using Robust.Shared.IoC;
-using Robust.Shared.Network;
-using Robust.Shared.Network.Messages;
-using Robust.Shared.Timing;
-using Robust.Shared.Utility;
-
-namespace Robust.Client.GameObjects
-{
-    /// <summary>
-    /// The client implementation of the Entity Network Manager.
-    /// </summary>
-    public class ClientEntityNetworkManager : IEntityNetworkManager
-    {
-        [Dependency] private readonly IClientNetManager _networkManager = default!;
-        [Dependency] private readonly IClientGameStateManager _gameStateManager = default!;
-        [Dependency] private readonly IGameTiming _gameTiming = default!;
-
-        /// <inheritdoc />
-        public event EventHandler<NetworkComponentMessage>? ReceivedComponentMessage;
-
-        /// <inheritdoc />
-        public event EventHandler<object>? ReceivedSystemMessage;
-
-        private readonly PriorityQueue<(uint seq, MsgEntity msg)> _queue = new(new MessageTickComparer());
-        private uint _incomingMsgSequence = 0;
-
-        /// <inheritdoc />
-        public void SetupNetworking()
-        {
-            _networkManager.RegisterNetMessage<MsgEntity>(MsgEntity.NAME, HandleEntityNetworkMessage);
-        }
-
-        public void Update()
-        {
-            while (_queue.Count != 0 && _queue.Peek().msg.SourceTick <= _gameStateManager.CurServerTick)
-            {
-                var (_, msg) = _queue.Take();
-                // Logger.DebugS("net.ent", "Dispatching: {0}: {1}", seq, msg);
-                DispatchMsgEntity(msg);
-            }
-        }
-
-        /// <inheritdoc />
-        public void SendSystemNetworkMessage(EntityEventArgs message)
-        {
-            SendSystemNetworkMessage(message, default(uint));
-        }
-
-        public void SendSystemNetworkMessage(EntityEventArgs message, uint sequence)
-        {
-            var msg = _networkManager.CreateNetMessage<MsgEntity>();
-            msg.Type = EntityMessageType.SystemMessage;
-            msg.SystemMessage = message;
-            msg.SourceTick = _gameTiming.CurTick;
-            msg.Sequence = sequence;
-
-            _networkManager.ClientSendMessage(msg);
-        }
-
-        /// <inheritdoc />
-        public void SendSystemNetworkMessage(EntityEventArgs message, INetChannel channel)
-        {
-            throw new NotSupportedException();
-        }
-
-        /// <inheritdoc />
-        public void SendComponentNetworkMessage(INetChannel? channel, IEntity entity, IComponent component, ComponentMessage message)
-        {
-            if (!component.NetID.HasValue)
-                throw new ArgumentException($"Component {component.Name} does not have a NetID.", nameof(component));
-
-            var msg = _networkManager.CreateNetMessage<MsgEntity>();
-            msg.Type = EntityMessageType.ComponentMessage;
-            msg.EntityUid = entity.Uid;
-            msg.NetId = component.NetID.Value;
-            msg.ComponentMessage = message;
-            msg.SourceTick = _gameTiming.CurTick;
-
-            _networkManager.ClientSendMessage(msg);
-        }
-
-        private void HandleEntityNetworkMessage(MsgEntity message)
-        {
-            if (message.SourceTick <= _gameStateManager.CurServerTick)
-            {
-                DispatchMsgEntity(message);
-                return;
-            }
-
-            // MsgEntity is sent with ReliableOrdered so Lidgren guarantees ordering of incoming messages.
-            // We still need to store a sequence input number to ensure ordering remains consistent in
-            // the priority queue.
-            _queue.Add((++_incomingMsgSequence, message));
-        }
-
-        private void DispatchMsgEntity(MsgEntity message)
-        {
-            switch (message.Type)
-            {
-                case EntityMessageType.ComponentMessage:
-                    ReceivedComponentMessage?.Invoke(this, new NetworkComponentMessage(message));
-                    return;
-
-                case EntityMessageType.SystemMessage:
-                    ReceivedSystemMessage?.Invoke(this, message.SystemMessage);
-                    return;
-            }
-        }
-
-        private sealed class MessageTickComparer : IComparer<(uint seq, MsgEntity msg)>
-        {
-            public int Compare((uint seq, MsgEntity msg) x, (uint seq, MsgEntity msg) y)
-            {
-                var cmp = y.msg.SourceTick.CompareTo(x.msg.SourceTick);
-                if (cmp != 0)
-                {
-                    return cmp;
-                }
-
-                return y.seq.CompareTo(x.seq);
-            }
-        }
-    }
-}

Robust.Client/GameObjects/Components/Appearance/AppearanceComponent.cs

@@ -10,6 +10,7 @@ using YamlDotNet.RepresentationModel;
 
 namespace Robust.Client.GameObjects
 {
+    [ComponentReference(typeof(SharedAppearanceComponent))]
     public sealed class AppearanceComponent : SharedAppearanceComponent
     {
         [ViewVariables]
@@ -94,8 +95,7 @@ namespace Robust.Client.GameObjects
                 return;
             }
 
-            EntitySystem.Get<AppearanceSystem>()
-                .EnqueueAppearanceUpdate(this);
+            EntitySystem.Get<AppearanceSystem>().EnqueueUpdate(this);
             _appearanceDirty = true;
         }
 
@@ -115,21 +115,6 @@ namespace Robust.Client.GameObjects
 
             MarkDirty();
         }
-
-
-        internal class SpriteLayerToggle : AppearanceVisualizer
-        {
-            public const string NAME = "sprite_layer_toggle";
-
-            public readonly object Key;
-            public readonly int SpriteLayer;
-
-            public SpriteLayerToggle(object key, int spriteLayer)
-            {
-                Key = key;
-                SpriteLayer = spriteLayer;
-            }
-        }
     }
 
     /// <summary>

Robust.Client/GameObjects/Components/Eye/EyeComponent.cs

@@ -1,4 +1,4 @@
-using Robust.Client.Graphics;
+using Robust.Client.Graphics;
 using Robust.Shared.GameObjects;
 using Robust.Shared.IoC;
 using Robust.Shared.Map;
@@ -10,6 +10,7 @@ using Robust.Shared.ViewVariables;
 
 namespace Robust.Client.GameObjects
 {
+    [ComponentReference(typeof(SharedEyeComponent))]
     public class EyeComponent : SharedEyeComponent
     {
         [Dependency] private readonly IEyeManager _eyeManager = default!;
@@ -25,7 +26,7 @@ namespace Robust.Client.GameObjects
         [DataField("drawFov")]
         private bool _setDrawFovOnInitialize = true;
         [DataField("zoom")]
-        private Vector2 _setZoomOnInitialize = Vector2.One/2f;
+        private Vector2 _setZoomOnInitialize = Vector2.One;
         private Vector2 _offset = Vector2.Zero;
 
         public IEye? Eye => _eye;
@@ -152,6 +153,7 @@ namespace Robust.Client.GameObjects
             Zoom = state.Zoom;
             Offset = state.Offset;
             Rotation = state.Rotation;
+            VisibilityMask = state.VisibilityMask;
         }
 
         public override void OnRemove()

Robust.Client/GameObjects/Components/Light/ClientOccluderComponent.cs

@@ -1,14 +1,17 @@
 using System;
+using System.Collections.Generic;
 using Robust.Shared.GameObjects;
+using Robust.Shared.IoC;
 using Robust.Shared.Map;
 using Robust.Shared.Maths;
 using Robust.Shared.ViewVariables;
 
 namespace Robust.Client.GameObjects
 {
+    [ComponentReference(typeof(OccluderComponent))]
     internal sealed class ClientOccluderComponent : OccluderComponent
     {
-        internal SnapGridComponent? SnapGrid { get; private set; }
+        [Dependency] private readonly IMapManager _mapManager = default!;
 
         [ViewVariables] private (GridId, Vector2i) _lastPosition;
         [ViewVariables] internal OccluderDir Occluding { get; private set; }
@@ -29,39 +32,36 @@ namespace Robust.Client.GameObjects
         {
             base.Startup();
 
-            if (Owner.TryGetComponent(out SnapGridComponent? snap))
+            if (Owner.Transform.Anchored)
             {
-                SnapGrid = snap;
-                SnapGrid.OnPositionChanged += SnapGridOnPositionChanged;
-
                 SnapGridOnPositionChanged();
             }
         }
 
-        private void SnapGridOnPositionChanged()
+        public void SnapGridOnPositionChanged()
         {
             SendDirty();
-            _lastPosition = (Owner.Transform.GridID, SnapGrid!.Position);
+
+            if(!Owner.Transform.Anchored)
+                return;
+
+            var grid = _mapManager.GetGrid(Owner.Transform.GridID);
+            _lastPosition = (Owner.Transform.GridID, grid.TileIndicesFor(Owner.Transform.Coordinates));
         }
 
         protected override void Shutdown()
         {
             base.Shutdown();
 
-            if (SnapGrid != null)
-            {
-                SnapGrid.OnPositionChanged -= SnapGridOnPositionChanged;
-            }
-
             SendDirty();
         }
 
         private void SendDirty()
         {
-            if (SnapGrid != null)
+            if (Owner.Transform.Anchored)
             {
                 Owner.EntityManager.EventBus.RaiseEvent(EventSource.Local,
-                    new OccluderDirtyEvent(Owner, _lastPosition, SnapGrid.Offset));
+                    new OccluderDirtyEvent(Owner, _lastPosition));
             }
         }
 
@@ -69,16 +69,18 @@ namespace Robust.Client.GameObjects
         {
             Occluding = OccluderDir.None;
 
-            if (Deleted || SnapGrid == null)
+            if (Deleted || !Owner.Transform.Anchored)
             {
                 return;
             }
 
             void CheckDir(Direction dir, OccluderDir oclDir)
             {
-                foreach (var neighbor in SnapGrid.GetInDir(dir))
+                var grid = _mapManager.GetGrid(Owner.Transform.GridID);
+                var position = Owner.Transform.Coordinates;
+                foreach (var neighbor in grid.GetInDir(position, dir))
                 {
-                    if (neighbor.TryGetComponent(out ClientOccluderComponent? comp) && comp.Enabled)
+                    if (Owner.EntityManager.ComponentManager.TryGetComponent(neighbor, out ClientOccluderComponent? comp) && comp.Enabled)
                     {
                         Occluding |= oclDir;
                         break;

Robust.Client/GameObjects/Components/Light/PointLightComponent.cs

@@ -1,4 +1,5 @@
 using System;
+using System.Collections.Generic;
 using Robust.Client.Graphics;
 using Robust.Client.ResourceManagement;
 using Robust.Shared.Animations;
@@ -167,7 +168,7 @@ namespace Robust.Client.GameObjects
             set
             {
                 _radius = MathF.Max(value, 0.01f); // setting radius to 0 causes exceptions, so just use a value close enough to zero that it's unnoticeable.
-                Owner.EntityManager.EventBus.RaiseEvent(EventSource.Local, new PointLightRadiusChangedMessage(this));
+                Owner.EntityManager.EventBus.RaiseEvent(EventSource.Local, new PointLightRadiusChangedEvent(this));
             }
         }
 
@@ -179,6 +180,18 @@ namespace Robust.Client.GameObjects
                 Mask = null;
         }
 
+        /// <summary>
+        /// What MapId we are intersecting for RenderingTreeSystem.
+        /// </summary>
+        [ViewVariables]
+        internal MapId IntersectingMapId { get; set; } = MapId.Nullspace;
+
+        /// <summary>
+        /// What grids we're on for RenderingTreeSystem.
+        /// </summary>
+        [ViewVariables]
+        internal List<GridId> IntersectingGrids = new();
+
         void ISerializationHooks.AfterDeserialization()
         {
             if (_maskPath != null)
@@ -230,7 +243,7 @@ namespace Robust.Client.GameObjects
             if (map != MapId.Nullspace)
             {
                 Owner.EntityManager.EventBus.RaiseEvent(EventSource.Local,
-                    new RenderTreeRemoveLightMessage(this, map));
+                    new RenderTreeRemoveLightEvent(this, map));
             }
         }
 
@@ -248,11 +261,11 @@ namespace Robust.Client.GameObjects
         }
     }
 
-    public struct PointLightRadiusChangedMessage
+    public class PointLightRadiusChangedEvent : EntityEventArgs
     {
         public PointLightComponent PointLightComponent { get; }
 
-        public PointLightRadiusChangedMessage(PointLightComponent pointLightComponent)
+        public PointLightRadiusChangedEvent(PointLightComponent pointLightComponent)
         {
             PointLightComponent = pointLightComponent;
         }

Robust.Client/GameObjects/Components/Renderable/SpriteComponent.cs

@@ -1,4 +1,4 @@
-using System;
+using System;
 using System.Collections.Generic;
 using System.Diagnostics.CodeAnalysis;
 using System.Globalization;
@@ -19,6 +19,7 @@ using Robust.Shared.Reflection;
 using Robust.Shared.Serialization;
 using Robust.Shared.Serialization.Manager;
 using Robust.Shared.Serialization.Manager.Attributes;
+using Robust.Shared.Serialization.TypeSerializers.Implementations.Custom;
 using Robust.Shared.Timing;
 using Robust.Shared.Utility;
 using Robust.Shared.ViewVariables;
@@ -26,6 +27,8 @@ using DrawDepthTag = Robust.Shared.GameObjects.DrawDepth;
 
 namespace Robust.Client.GameObjects
 {
+    [ComponentReference(typeof(SharedSpriteComponent))]
+    [ComponentReference(typeof(ISpriteComponent))]
     public sealed class SpriteComponent : SharedSpriteComponent, ISpriteComponent,
         IComponentDebug, ISerializationHooks
     {
@@ -42,7 +45,7 @@ namespace Robust.Client.GameObjects
             set => _visible = value;
         }
 
-        [DataFieldWithConstant("drawdepth", typeof(DrawDepthTag))]
+        [DataField("drawdepth", customTypeSerializer: typeof(ConstantSerializer<DrawDepthTag>))]
         private int drawDepth = DrawDepthTag.Default;
 
         /// <summary>
@@ -122,6 +125,18 @@ namespace Robust.Client.GameObjects
         [DataField("directional")]
         private bool _directional = true;
 
+        /// <summary>
+        /// What MapId we are intersecting for RenderingTreeSystem.
+        /// </summary>
+        [ViewVariables]
+        internal MapId IntersectingMapId { get; set; } = MapId.Nullspace;
+
+        /// <summary>
+        /// What grids we're on for RenderingTreeSystem.
+        /// </summary>
+        [ViewVariables]
+        internal List<GridId> IntersectingGrids { get; } = new();
+
         [DataField("layerDatums")]
         private List<PrototypeLayerData> LayerDatums
         {
@@ -847,8 +862,8 @@ namespace Robust.Client.GameObjects
                 }
                 else
                 {
-                    Logger.ErrorS(LogCategory, "State '{0}' does not exist in RSI. Trace:\n{1}", stateId,
-                        Environment.StackTrace);
+                    Logger.ErrorS(LogCategory, "State '{0}' does not exist in RSI {1}. Trace:\n{2}", stateId,
+                        actualRsi.Path, Environment.StackTrace);
                     theLayer.Texture = null;
                 }
             }
@@ -1352,7 +1367,7 @@ namespace Robust.Client.GameObjects
             if (map != MapId.Nullspace)
             {
                 Owner.EntityManager.EventBus.RaiseEvent(EventSource.Local,
-                    new RenderTreeRemoveSpriteMessage(this, map));
+                    new RenderTreeRemoveSpriteEvent(this, map));
             }
         }
 
@@ -1575,9 +1590,10 @@ namespace Robust.Client.GameObjects
         {
             var builder = new StringBuilder();
             builder.AppendFormat(
-                "vis/depth/scl/rot/ofs/col/diral/dir: {0}/{1}/{2}/{3}/{4}/{5}/{6}/{7}\n",
+                "vis/depth/scl/rot/ofs/col/norot/override/dir: {0}/{1}/{2}/{3}/{4}/{5}/{6}/{8}/{7}\n",
                 Visible, DrawDepth, Scale, Rotation, Offset,
-                Color, Directional, GetDir(RSI.State.DirectionType.Dir8, Owner.Transform.WorldRotation)
+                Color, NoRotation, GetDir(RSI.State.DirectionType.Dir8, Owner.Transform.WorldRotation),
+                DirectionOverride
             );
 
             foreach (var layer in Layers)
@@ -2084,6 +2100,7 @@ namespace Robust.Client.GameObjects
             public IEntityManager EntityManager { get; } = null!;
             public string Name { get; set; } = string.Empty;
             public EntityUid Uid { get; } = EntityUid.Invalid;
+            EntityLifeStage IEntity.LifeStage { get => _lifeStage; set => _lifeStage = value; }
             public bool Initialized { get; } = false;
             public bool Initializing { get; } = false;
             public bool Deleted { get; } = true;
@@ -2100,6 +2117,7 @@ namespace Robust.Client.GameObjects
             public IMetaDataComponent MetaData { get; } = null!;
 
             private Dictionary<Type, IComponent> _components = new();
+            private EntityLifeStage _lifeStage;
 
             public T AddComponent<T>() where T : Component, new()
             {
@@ -2147,11 +2165,6 @@ namespace Robust.Client.GameObjects
                 return null!;
             }
 
-            public IComponent GetComponent(uint netID)
-            {
-                return null!;
-            }
-
             public bool TryGetComponent<T>([NotNullWhen(true)] out T? component) where T : class
             {
                 component = null;
@@ -2178,18 +2191,7 @@ namespace Robust.Client.GameObjects
                 return null;
             }
 
-            public bool TryGetComponent(uint netId, [NotNullWhen(true)]  out IComponent? component)
-            {
-                component = null;
-                return false;
-            }
-
-            public IComponent? GetComponentOrNull(uint netId)
-            {
-                return null;
-            }
-
-            public void Shutdown()
+            public void QueueDelete()
             {
             }
 
@@ -2207,10 +2209,12 @@ namespace Robust.Client.GameObjects
                 return Enumerable.Empty<T>();
             }
 
+            [Obsolete("Component Messages are deprecated, use Entity Events instead.")]
             public void SendMessage(IComponent? owner, ComponentMessage message)
             {
             }
 
+            [Obsolete("Component Messages are deprecated, use Entity Events instead.")]
             public void SendNetworkMessage(IComponent owner, ComponentMessage message, INetChannel? channel = null)
             {
             }

Robust.Client/GameObjects/Components/UserInterface/ClientUserInterfaceComponent.cs

@@ -2,14 +2,14 @@
 using System.Collections.Generic;
 using Robust.Shared.GameObjects;
 using Robust.Shared.IoC;
-using Robust.Shared.Network;
-using Robust.Shared.Players;
 using Robust.Shared.Reflection;
 using Robust.Shared.Serialization;
 using Robust.Shared.Serialization.Manager.Attributes;
+using Robust.Shared.ViewVariables;
 
 namespace Robust.Client.GameObjects
 {
+    [ComponentReference(typeof(SharedUserInterfaceComponent))]
     public class ClientUserInterfaceComponent : SharedUserInterfaceComponent, ISerializationHooks
     {
         [Dependency] private readonly IReflectionManager _reflectionManager = default!;
@@ -23,6 +23,9 @@ namespace Robust.Client.GameObjects
         [DataField("interfaces", readOnly: true)]
         private List<PrototypeData> _interfaceData = new();
 
+        [ViewVariables]
+        public IEnumerable<BoundUserInterface> Interfaces => _openInterfaces.Values;
+
         void ISerializationHooks.AfterDeserialization()
         {
             _interfaces.Clear();
@@ -33,48 +36,40 @@ namespace Robust.Client.GameObjects
             }
         }
 
-        public override void HandleNetworkMessage(ComponentMessage message, INetChannel netChannel,
-            ICommonSession? session = null)
+        internal void MessageReceived(BoundUIWrapMessage msg)
         {
-            base.HandleNetworkMessage(message, netChannel, session);
-
-            switch (message)
+            switch (msg.Message)
             {
-                case BoundInterfaceMessageWrapMessage wrapped:
-                    // Double nested switches who needs readability anyways.
-                    switch (wrapped.Message)
+                case OpenBoundInterfaceMessage _:
+                    if (_openInterfaces.ContainsKey(msg.UiKey))
                     {
-                        case OpenBoundInterfaceMessage _:
-                            if (_openInterfaces.ContainsKey(wrapped.UiKey))
-                            {
-                                return;
-                            }
+                        return;
+                    }
 
-                            OpenInterface(wrapped);
-                            break;
+                    OpenInterface(msg);
+                    break;
 
-                        case CloseBoundInterfaceMessage _:
-                            Close(wrapped.UiKey, true);
-                            break;
+                case CloseBoundInterfaceMessage _:
+                    Close(msg.UiKey, true);
+                    break;
 
-                        default:
-                            if (_openInterfaces.TryGetValue(wrapped.UiKey, out var bi))
-                            {
-                                bi.InternalReceiveMessage(wrapped.Message);
-                            }
-                            break;
+                default:
+                    if (_openInterfaces.TryGetValue(msg.UiKey, out var bi))
+                    {
+                        bi.InternalReceiveMessage(msg.Message);
                     }
 
                     break;
             }
         }
 
-        private void OpenInterface(BoundInterfaceMessageWrapMessage wrapped)
+        private void OpenInterface(BoundUIWrapMessage wrapped)
         {
             var data = _interfaces[wrapped.UiKey];
             // TODO: This type should be cached, but I'm too lazy.
             var type = _reflectionManager.LooseGetType(data.ClientType);
-            var boundInterface = (BoundUserInterface) _dynamicTypeFactory.CreateInstance(type, new[]{this, wrapped.UiKey});
+            var boundInterface =
+                (BoundUserInterface) _dynamicTypeFactory.CreateInstance(type, new[] {this, wrapped.UiKey});
             boundInterface.Open();
             _openInterfaces[wrapped.UiKey] = boundInterface;
         }
@@ -86,7 +81,7 @@ namespace Robust.Client.GameObjects
                 return;
             }
 
-            if(!remoteCall)
+            if (!remoteCall)
                 SendMessage(new CloseBoundInterfaceMessage(), uiKey);
             _openInterfaces.Remove(uiKey);
             boundUserInterface.Dispose();
@@ -94,7 +89,8 @@ namespace Robust.Client.GameObjects
 
         internal void SendMessage(BoundUserInterfaceMessage message, object uiKey)
         {
-            SendNetworkMessage(new BoundInterfaceMessageWrapMessage(message, uiKey));
+            EntitySystem.Get<UserInterfaceSystem>()
+                .Send(new BoundUIWrapMessage(Owner.Uid, message, uiKey));
         }
     }
 

Robust.Client/GameObjects/EntityManagerExt.cs

@@ -15,7 +15,7 @@ namespace Robust.Client.GameObjects
             DebugTools.AssertNotNull(localPlayer);
 
             var sequence = IoCManager.Resolve<IClientGameStateManager>().SystemMessageDispatched(msg);
-            entityManager.EntityNetManager.SendSystemNetworkMessage(msg, sequence);
+            entityManager.EntityNetManager?.SendSystemNetworkMessage(msg, sequence);
 
             var eventArgs = new EntitySessionEventArgs(localPlayer!.Session);
 

Robust.Client/GameObjects/EntitySystems/AppearanceSystem.cs

@@ -1,51 +1,33 @@
 using System.Collections.Generic;
+using JetBrains.Annotations;
 using Robust.Shared.GameObjects;
 
 namespace Robust.Client.GameObjects
 {
+    [UsedImplicitly]
     internal sealed class AppearanceSystem : EntitySystem
     {
-        private readonly Queue<AppearanceComponent> _updatesQueued = new();
+        private readonly Queue<AppearanceComponent> _queuedUpdates = new();
+
+        public void EnqueueUpdate(AppearanceComponent component)
+        {
+            _queuedUpdates.Enqueue(component);
+        }
 
         public override void FrameUpdate(float frameTime)
         {
-            while (_updatesQueued.TryDequeue(out var appearance))
+            while (_queuedUpdates.TryDequeue(out var appearance))
             {
-                UpdateComponent(appearance);
+                if (appearance.Deleted)
+                    return;
+
+                foreach (var visualizer in appearance.Visualizers)
+                {
+                    visualizer.OnChangeData(appearance);
+                }
+
                 appearance.UnmarkDirty();
             }
         }
-
-        private static void UpdateComponent(AppearanceComponent component)
-        {
-            if (component.Deleted)
-                return;
-
-            foreach (var visualizer in component.Visualizers)
-            {
-                switch (visualizer)
-                {
-                    case AppearanceComponent.SpriteLayerToggle spriteLayerToggle:
-                        UpdateSpriteLayerToggle(component, spriteLayerToggle);
-                        break;
-
-                    default:
-                        visualizer.OnChangeData(component);
-                        break;
-                }
-            }
-        }
-
-        private static void UpdateSpriteLayerToggle(AppearanceComponent component, AppearanceComponent.SpriteLayerToggle toggle)
-        {
-            component.TryGetData(toggle.Key, out bool visible);
-            var sprite = component.Owner.GetComponent<SpriteComponent>();
-            sprite.LayerSetVisible(toggle.SpriteLayer, visible);
-        }
-
-        public void EnqueueAppearanceUpdate(AppearanceComponent component)
-        {
-            _updatesQueued.Enqueue(component);
-        }
     }
 }

Robust.Client/GameObjects/EntitySystems/AudioSystem.cs

@@ -8,7 +8,6 @@ using Robust.Shared.GameObjects;
 using Robust.Shared.IoC;
 using Robust.Shared.Log;
 using Robust.Shared.Map;
-using Robust.Shared.Maths;
 using Robust.Shared.Physics;
 using Robust.Shared.Physics.Broadphase;
 using Robust.Shared.Player;
@@ -165,6 +164,12 @@ namespace Robust.Client.GameObjects
                             Logger.Warning("Interrupting positional audio, can't set position.");
                             stream.Source.StopPlaying();
                         }
+
+                        if (stream.TrackingEntity != null)
+                        {
+                            stream.Source.SetVelocity(stream.TrackingEntity.GlobalLinearVelocity());
+                        }
+
                     }
                 }
             }
@@ -188,7 +193,7 @@ namespace Robust.Client.GameObjects
         /// </summary>
         /// <param name="filename">The resource path to the OGG Vorbis file to play.</param>
         /// <param name="audioParams"></param>
-        public IPlayingAudioStream? Play(string filename, AudioParams? audioParams = null)
+        private IPlayingAudioStream? Play(string filename, AudioParams? audioParams = null)
         {
             if (_resourceCache.TryGetResource<AudioResource>(new ResourcePath(filename), out var audio))
             {
@@ -204,7 +209,7 @@ namespace Robust.Client.GameObjects
         /// </summary>
         /// <param name="stream">The audio stream to play.</param>
         /// <param name="audioParams"></param>
-        public IPlayingAudioStream Play(AudioStream stream, AudioParams? audioParams = null)
+        private IPlayingAudioStream Play(AudioStream stream, AudioParams? audioParams = null)
         {
             var source = _clyde.CreateAudioSource(stream);
             ApplyAudioParams(audioParams, source);
@@ -226,7 +231,7 @@ namespace Robust.Client.GameObjects
         /// <param name="filename">The resource path to the OGG Vorbis file to play.</param>
         /// <param name="entity">The entity "emitting" the audio.</param>
         /// <param name="audioParams"></param>
-        public IPlayingAudioStream? Play(string filename, IEntity entity, AudioParams? audioParams = null)
+        private IPlayingAudioStream? Play(string filename, IEntity entity, AudioParams? audioParams = null)
         {
             if (_resourceCache.TryGetResource<AudioResource>(new ResourcePath(filename), out var audio))
             {
@@ -243,7 +248,7 @@ namespace Robust.Client.GameObjects
         /// <param name="stream">The audio stream to play.</param>
         /// <param name="entity">The entity "emitting" the audio.</param>
         /// <param name="audioParams"></param>
-        public IPlayingAudioStream? Play(AudioStream stream, IEntity entity, AudioParams? audioParams = null)
+        private IPlayingAudioStream? Play(AudioStream stream, IEntity entity, AudioParams? audioParams = null)
         {
             var source = _clyde.CreateAudioSource(stream);
             if (!source.SetPosition(entity.Transform.WorldPosition))
@@ -272,7 +277,7 @@ namespace Robust.Client.GameObjects
         /// <param name="filename">The resource path to the OGG Vorbis file to play.</param>
         /// <param name="coordinates">The coordinates at which to play the audio.</param>
         /// <param name="audioParams"></param>
-        public IPlayingAudioStream? Play(string filename, EntityCoordinates coordinates, AudioParams? audioParams = null)
+        private IPlayingAudioStream? Play(string filename, EntityCoordinates coordinates, AudioParams? audioParams = null)
         {
             if (_resourceCache.TryGetResource<AudioResource>(new ResourcePath(filename), out var audio))
             {
@@ -289,7 +294,7 @@ namespace Robust.Client.GameObjects
         /// <param name="stream">The audio stream to play.</param>
         /// <param name="coordinates">The coordinates at which to play the audio.</param>
         /// <param name="audioParams"></param>
-        public IPlayingAudioStream? Play(AudioStream stream, EntityCoordinates coordinates,
+        private IPlayingAudioStream? Play(AudioStream stream, EntityCoordinates coordinates,
             AudioParams? audioParams = null)
         {
             var source = _clyde.CreateAudioSource(stream);

Robust.Client/GameObjects/EntitySystems/ClientOccluderSystem.cs

@@ -6,6 +6,7 @@ using Robust.Shared.GameObjects;
 using Robust.Shared.IoC;
 using Robust.Shared.Map;
 using Robust.Shared.Maths;
+using Robust.Shared.Utility;
 
 namespace Robust.Client.GameObjects
 {
@@ -20,10 +21,11 @@ namespace Robust.Client.GameObjects
     {
         [Dependency] private readonly IMapManager _mapManager = default!;
 
-        private readonly Queue<IEntity> _dirtyEntities = new();
+        private readonly Queue<EntityUid> _dirtyEntities = new();
 
         private uint _updateGeneration;
 
+        /// <inheritdoc />
         public override void Initialize()
         {
             base.Initialize();
@@ -32,6 +34,8 @@ namespace Robust.Client.GameObjects
             UpdatesAfter.Add(typeof(PhysicsSystem));
 
             SubscribeLocalEvent<OccluderDirtyEvent>(HandleDirtyEvent);
+
+            SubscribeLocalEvent<ClientOccluderComponent, SnapGridPositionChangedEvent>(HandleSnapGridMove);
         }
 
         public override void FrameUpdate(float frameTime)
@@ -47,8 +51,8 @@ namespace Robust.Client.GameObjects
 
             while (_dirtyEntities.TryDequeue(out var entity))
             {
-                if (!entity.Deleted
-                    && entity.TryGetComponent(out ClientOccluderComponent? occluder)
+                if (EntityManager.EntityExists(entity)
+                    && ComponentManager.TryGetComponent(entity, out ClientOccluderComponent? occluder)
                     && occluder.UpdateGeneration != _updateGeneration)
                 {
                     occluder.Update();
@@ -58,6 +62,11 @@ namespace Robust.Client.GameObjects
             }
         }
 
+        private static void HandleSnapGridMove(EntityUid uid, ClientOccluderComponent component, SnapGridPositionChangedEvent args)
+        {
+            component.SnapGridOnPositionChanged();
+        }
+
         private void HandleDirtyEvent(OccluderDirtyEvent ev)
         {
             var sender = ev.Sender;
@@ -65,13 +74,14 @@ namespace Robust.Client.GameObjects
                 sender.TryGetComponent(out ClientOccluderComponent? iconSmooth)
                 && iconSmooth.Running)
             {
-                var snapGrid = sender.GetComponent<SnapGridComponent>();
+                var grid1 = _mapManager.GetGrid(sender.Transform.GridID);
+                var coords = sender.Transform.Coordinates;
 
-                _dirtyEntities.Enqueue(sender);
-                AddValidEntities(snapGrid.GetInDir(Direction.North));
-                AddValidEntities(snapGrid.GetInDir(Direction.South));
-                AddValidEntities(snapGrid.GetInDir(Direction.East));
-                AddValidEntities(snapGrid.GetInDir(Direction.West));
+                _dirtyEntities.Enqueue(sender.Uid);
+                AddValidEntities(grid1.GetInDir(coords, Direction.North));
+                AddValidEntities(grid1.GetInDir(coords, Direction.South));
+                AddValidEntities(grid1.GetInDir(coords, Direction.East));
+                AddValidEntities(grid1.GetInDir(coords, Direction.West));
             }
 
             // Entity is no longer valid, update around the last position it was at.
@@ -79,28 +89,23 @@ namespace Robust.Client.GameObjects
             {
                 var pos = ev.LastPosition.Value.pos;
 
-                AddValidEntities(grid.GetSnapGridCell(pos + new Vector2i(1, 0), ev.Offset));
-                AddValidEntities(grid.GetSnapGridCell(pos + new Vector2i(-1, 0), ev.Offset));
-                AddValidEntities(grid.GetSnapGridCell(pos + new Vector2i(0, 1), ev.Offset));
-                AddValidEntities(grid.GetSnapGridCell(pos + new Vector2i(0, -1), ev.Offset));
+                AddValidEntities(grid.GetAnchoredEntities(pos + new Vector2i(1, 0)));
+                AddValidEntities(grid.GetAnchoredEntities(pos + new Vector2i(-1, 0)));
+                AddValidEntities(grid.GetAnchoredEntities(pos + new Vector2i(0, 1)));
+                AddValidEntities(grid.GetAnchoredEntities(pos + new Vector2i(0, -1)));
             }
         }
 
-        private void AddValidEntities(IEnumerable<IEntity> candidates)
+        private void AddValidEntities(IEnumerable<EntityUid> candidates)
         {
             foreach (var entity in candidates)
             {
-                if (entity.HasComponent<ClientOccluderComponent>())
+                if (ComponentManager.HasComponent<ClientOccluderComponent>(entity))
                 {
                     _dirtyEntities.Enqueue(entity);
                 }
             }
         }
-
-        private void AddValidEntities(IEnumerable<IComponent> candidates)
-        {
-            AddValidEntities(candidates.Select(c => c.Owner));
-        }
     }
 
     /// <summary>
@@ -108,15 +113,13 @@ namespace Robust.Client.GameObjects
     /// </summary>
     internal sealed class OccluderDirtyEvent : EntityEventArgs
     {
-        public OccluderDirtyEvent(IEntity sender, (GridId grid, Vector2i pos)? lastPosition, SnapGridOffset offset)
+        public OccluderDirtyEvent(IEntity sender, (GridId grid, Vector2i pos)? lastPosition)
         {
             LastPosition = lastPosition;
-            Offset = offset;
             Sender = sender;
         }
 
         public (GridId grid, Vector2i pos)? LastPosition { get; }
-        public SnapGridOffset Offset { get; }
         public IEntity Sender { get; }
     }
 }

Robust.Client/GameObjects/EntitySystems/EffectSystem.cs

@@ -67,9 +67,10 @@ namespace Robust.Client.GameObjects
             //Create effect from creation message
             var effect = new Effect(message, resourceCache, _mapManager, _entityManager);
             effect.Deathtime = gameTiming.CurTime + message.LifeTime;
-            if (effect.AttachedEntityUid != null)
+            if (effect.AttachedEntityUid != null
+                && _entityManager.TryGetEntity(effect.AttachedEntityUid.Value, out var attachedEntity))
             {
-                effect.AttachedEntity = _entityManager.GetEntity(effect.AttachedEntityUid.Value);
+                effect.AttachedEntity = attachedEntity;
             }
 
             _Effects.Add(effect);
@@ -346,11 +347,11 @@ namespace Robust.Client.GameObjects
                 _entityManager = entityManager;
             }
 
-            protected override void Draw(DrawingHandleBase handle, OverlaySpace currentSpace)
+            protected internal override void Draw(in OverlayDrawArgs args)
             {
                 var map = _owner.eyeManager.CurrentMap;
 
-                var worldHandle = (DrawingHandleWorld) handle;
+                var worldHandle = args.WorldHandle;
                 ShaderInstance? currentShader = null;
                 var player = _playerManager.LocalPlayer?.ControlledEntity;
 

Robust.Client/GameObjects/EntitySystems/InputSystem.cs

@@ -97,7 +97,7 @@ namespace Robust.Client.GameObjects
         private void DispatchInputCommand(FullInputCmdMessage message)
         {
             _stateManager.InputCommandDispatched(message);
-            EntityNetworkManager.SendSystemNetworkMessage(message, message.InputSequence);
+            EntityManager.EntityNetManager?.SendSystemNetworkMessage(message, message.InputSequence);
         }
 
         public override void Initialize()

Robust.Client/GameObjects/EntitySystems/RenderingTreeSystem.cs

@@ -1,4 +1,6 @@
 using System.Collections.Generic;
+using System.Drawing;
+using System.Linq;
 using JetBrains.Annotations;
 using Robust.Client.Physics;
 using Robust.Shared.GameObjects;
@@ -6,6 +8,7 @@ using Robust.Shared.IoC;
 using Robust.Shared.Map;
 using Robust.Shared.Maths;
 using Robust.Shared.Physics;
+using Robust.Shared.Utility;
 
 namespace Robust.Client.GameObjects
 {
@@ -19,19 +22,19 @@ namespace Robust.Client.GameObjects
 
         [Dependency] private readonly IMapManagerInternal _mapManager = default!;
 
-        private readonly Dictionary<MapId, MapTrees> _mapTrees = new();
+        private readonly Dictionary<MapId, Dictionary<GridId, MapTrees>> _gridTrees = new();
 
         private readonly List<SpriteComponent> _spriteQueue = new();
         private readonly List<PointLightComponent> _lightQueue = new();
 
-        internal DynamicTree<SpriteComponent> GetSpriteTreeForMap(MapId map)
+        internal DynamicTree<SpriteComponent> GetSpriteTreeForMap(MapId map, GridId grid)
         {
-            return _mapTrees[map].SpriteTree;
+            return _gridTrees[map][grid].SpriteTree;
         }
 
-        internal DynamicTree<PointLightComponent> GetLightTreeForMap(MapId map)
+        internal DynamicTree<PointLightComponent> GetLightTreeForMap(MapId map, GridId grid)
         {
-            return _mapTrees[map].LightTree;
+            return _gridTrees[map][grid].LightTree;
         }
 
         public override void Initialize()
@@ -44,102 +47,180 @@ namespace Robust.Client.GameObjects
 
             _mapManager.MapCreated += MapManagerOnMapCreated;
             _mapManager.MapDestroyed += MapManagerOnMapDestroyed;
+            _mapManager.OnGridCreated += MapManagerOnGridCreated;
+            _mapManager.OnGridRemoved += MapManagerOnGridRemoved;
 
-            SubscribeLocalEvent<EntMapIdChangedMessage>(EntMapIdChanged);
-            SubscribeLocalEvent<MoveEvent>(EntMoved);
-            SubscribeLocalEvent<EntParentChangedMessage>(EntParentChanged);
-            SubscribeLocalEvent<PointLightRadiusChangedMessage>(PointLightRadiusChanged);
-            SubscribeLocalEvent<RenderTreeRemoveSpriteMessage>(RemoveSprite);
-            SubscribeLocalEvent<RenderTreeRemoveLightMessage>(RemoveLight);
+            SubscribeLocalEvent<SpriteComponent, EntMapIdChangedMessage>(SpriteMapChanged);
+            SubscribeLocalEvent<SpriteComponent, MoveEvent>(SpriteMoved);
+            SubscribeLocalEvent<SpriteComponent, EntParentChangedMessage>(SpriteParentChanged);
+            SubscribeLocalEvent<SpriteComponent, RenderTreeRemoveSpriteEvent>(RemoveSprite);
+
+            SubscribeLocalEvent<PointLightComponent, EntMapIdChangedMessage>(LightMapChanged);
+            SubscribeLocalEvent<PointLightComponent, MoveEvent>(LightMoved);
+            SubscribeLocalEvent<PointLightComponent, EntParentChangedMessage>(LightParentChanged);
+            SubscribeLocalEvent<PointLightComponent, PointLightRadiusChangedEvent>(PointLightRadiusChanged);
+            SubscribeLocalEvent<PointLightComponent, RenderTreeRemoveLightEvent>(RemoveLight);
         }
 
-        // For these next 2 methods (the Remove* ones):
+        // For the RemoveX methods
         // If the Transform is removed BEFORE the Sprite/Light,
         // then the MapIdChanged code will handle and remove it (because MapId gets set to nullspace).
         // Otherwise these will still have their past MapId and that's all we need..
-        private void RemoveLight(RenderTreeRemoveLightMessage ev)
+
+        #region SpriteHandlers
+        private void SpriteMapChanged(EntityUid uid, SpriteComponent component, EntMapIdChangedMessage args)
         {
-            _mapTrees[ev.Map].LightTree.Remove(ev.Light);
+            QueueSpriteUpdate(component);
         }
 
-        private void RemoveSprite(RenderTreeRemoveSpriteMessage ev)
+        private void SpriteMoved(EntityUid uid, SpriteComponent component, MoveEvent args)
         {
-            _mapTrees[ev.Map].SpriteTree.Remove(ev.Sprite);
+            QueueSpriteUpdate(component);
         }
 
-        private void PointLightRadiusChanged(PointLightRadiusChangedMessage ev)
+        private void SpriteParentChanged(EntityUid uid, SpriteComponent component, EntParentChangedMessage args)
         {
-            QueueUpdateLight(ev.PointLightComponent);
+            QueueSpriteUpdate(component);
         }
 
-        private void EntParentChanged(EntParentChangedMessage ev)
+        private void RemoveSprite(EntityUid uid, SpriteComponent component, RenderTreeRemoveSpriteEvent args)
         {
-            UpdateEntity(ev.Entity);
+            ClearSprite(component);
         }
 
-        private void EntMoved(MoveEvent ev)
+        private void ClearSprite(SpriteComponent component)
         {
-            UpdateEntity(ev.Sender);
-        }
-
-        private void UpdateEntity(IEntity entity)
-        {
-            if (entity.TryGetComponent(out SpriteComponent? spriteComponent))
+            if (_gridTrees.TryGetValue(component.IntersectingMapId, out var gridTrees))
             {
-                if (!spriteComponent.TreeUpdateQueued)
+                foreach (var gridId in component.IntersectingGrids)
                 {
-                    spriteComponent.TreeUpdateQueued = true;
-
-                    _spriteQueue.Add(spriteComponent);
+                    if (!gridTrees.TryGetValue(gridId, out var tree)) continue;
+                    tree.SpriteTree.Remove(component);
                 }
             }
 
-            if (entity.TryGetComponent(out PointLightComponent? light))
-            {
-                QueueUpdateLight(light);
-            }
+            component.IntersectingGrids.Clear();
+        }
 
-            foreach (var child in entity.Transform.ChildEntityUids)
+        private void QueueSpriteUpdate(SpriteComponent component)
+        {
+            if (component.TreeUpdateQueued) return;
+
+            component.TreeUpdateQueued = true;
+            _spriteQueue.Add(component);
+
+            foreach (var child in component.Owner.Transform.Children)
             {
-                UpdateEntity(EntityManager.GetEntity(child));
+                QueueSpriteUpdate(child.Owner);
             }
         }
 
-        private void QueueUpdateLight(PointLightComponent light)
+        private void QueueSpriteUpdate(IEntity entity)
         {
-            if (!light.TreeUpdateQueued)
-            {
-                light.TreeUpdateQueued = true;
+            if (!entity.TryGetComponent(out SpriteComponent? spriteComponent)) return;
+            QueueSpriteUpdate(spriteComponent);
 
-                _lightQueue.Add(light);
+            foreach (var child in entity.Transform.Children)
+            {
+                QueueSpriteUpdate(child.Owner);
+            }
+        }
+        #endregion
+
+        #region LightHandlers
+        private void LightMapChanged(EntityUid uid, PointLightComponent component, EntMapIdChangedMessage args)
+        {
+            QueueLightUpdate(component);
+        }
+
+        private void LightMoved(EntityUid uid, PointLightComponent component, MoveEvent args)
+        {
+            QueueLightUpdate(component);
+        }
+
+        private void LightParentChanged(EntityUid uid, PointLightComponent component, EntParentChangedMessage args)
+        {
+            QueueLightUpdate(component);
+        }
+
+        private void PointLightRadiusChanged(EntityUid uid, PointLightComponent component, PointLightRadiusChangedEvent args)
+        {
+            QueueLightUpdate(component);
+        }
+
+        private void RemoveLight(EntityUid uid, PointLightComponent component, RenderTreeRemoveLightEvent args)
+        {
+            ClearLight(component);
+        }
+
+        private void ClearLight(PointLightComponent component)
+        {
+            if (_gridTrees.TryGetValue(component.IntersectingMapId, out var gridTrees))
+            {
+                foreach (var gridId in component.IntersectingGrids)
+                {
+                    if (!gridTrees.TryGetValue(gridId, out var tree)) continue;
+                    tree.LightTree.Remove(component);
+                }
+            }
+
+            component.IntersectingGrids.Clear();
+        }
+
+        private void QueueLightUpdate(PointLightComponent component)
+        {
+            if (component.TreeUpdateQueued) return;
+
+            component.TreeUpdateQueued = true;
+            _lightQueue.Add(component);
+
+            foreach (var child in component.Owner.Transform.Children)
+            {
+                QueueLightUpdate(child.Owner);
             }
         }
 
-        private void EntMapIdChanged(EntMapIdChangedMessage ev)
+        private void QueueLightUpdate(IEntity entity)
         {
-            // Nullspace is a valid map ID for stuff to have but we also aren't gonna bother indexing it.
-            // So that's why there's a GetValueOrDefault.
-            var oldMapTrees = _mapTrees.GetValueOrDefault(ev.OldMapId);
-            var newMapTrees = _mapTrees.GetValueOrDefault(ev.Entity.Transform.MapID);
+            if (!entity.TryGetComponent(out PointLightComponent? lightComponent)) return;
+            QueueLightUpdate(lightComponent);
 
-            if (ev.Entity.TryGetComponent(out SpriteComponent? sprite))
+            foreach (var child in entity.Transform.Children)
             {
-                oldMapTrees?.SpriteTree.Remove(sprite);
-
-                newMapTrees?.SpriteTree.AddOrUpdate(sprite);
+                QueueLightUpdate(child.Owner);
             }
+        }
+        #endregion
 
-            if (ev.Entity.TryGetComponent(out PointLightComponent? light))
-            {
-                oldMapTrees?.LightTree.Remove(light);
-
-                newMapTrees?.LightTree.AddOrUpdate(light);
-            }
+        public override void Shutdown()
+        {
+            base.Shutdown();
+            _mapManager.MapCreated -= MapManagerOnMapCreated;
+            _mapManager.MapDestroyed -= MapManagerOnMapDestroyed;
+            _mapManager.OnGridCreated -= MapManagerOnGridCreated;
+            _mapManager.OnGridRemoved -= MapManagerOnGridRemoved;
         }
 
         private void MapManagerOnMapDestroyed(object? sender, MapEventArgs e)
         {
-            _mapTrees.Remove(e.Map);
+            foreach (var (_, gridTree) in _gridTrees[e.Map])
+            {
+                foreach (var comp in gridTree.LightTree)
+                {
+                    comp.IntersectingGrids.Clear();
+                }
+
+                foreach (var comp in gridTree.SpriteTree)
+                {
+                    comp.IntersectingGrids.Clear();
+                }
+
+                // Just in case?
+                gridTree.LightTree.Clear();
+                gridTree.SpriteTree.Clear();
+            }
+
+            _gridTrees.Remove(e.Map);
         }
 
         private void MapManagerOnMapCreated(object? sender, MapEventArgs e)
@@ -149,37 +230,122 @@ namespace Robust.Client.GameObjects
                 return;
             }
 
-            _mapTrees.Add(e.Map, new MapTrees());
+            _gridTrees.Add(e.Map, new Dictionary<GridId, MapTrees>
+            {
+                {GridId.Invalid, new MapTrees()}
+            });
+        }
+
+        private void MapManagerOnGridCreated(MapId mapId, GridId gridId)
+        {
+            _gridTrees[mapId].Add(gridId, new MapTrees());
+        }
+
+        private void MapManagerOnGridRemoved(MapId mapId, GridId gridId)
+        {
+            var gridTree = _gridTrees[mapId][gridId];
+
+            foreach (var sprite in gridTree.SpriteTree)
+            {
+                sprite.IntersectingGrids.Remove(gridId);
+            }
+
+            foreach (var light in gridTree.LightTree)
+            {
+                light.IntersectingGrids.Remove(gridId);
+            }
+
+            // Clear in case
+            gridTree.LightTree.Clear();
+            gridTree.SpriteTree.Clear();
+            _gridTrees[mapId].Remove(gridId);
         }
 
         public override void FrameUpdate(float frameTime)
         {
-            foreach (var queuedUpdateSprite in _spriteQueue)
+            foreach (var sprite in _spriteQueue)
             {
-                var transform = queuedUpdateSprite.Owner.Transform;
-                var map = transform.MapID;
-                if (map == MapId.Nullspace)
-                {
-                    continue;
-                }
-                var updateMapTree = _mapTrees[map].SpriteTree;
+                var mapId = sprite.Owner.Transform.MapID;
 
-                updateMapTree.AddOrUpdate(queuedUpdateSprite);
-                queuedUpdateSprite.TreeUpdateQueued = false;
+                // If we're on a new map then clear the old one.
+                if (sprite.IntersectingMapId != mapId)
+                {
+                    ClearSprite(sprite);
+                }
+
+                sprite.IntersectingMapId = mapId;
+
+                if (mapId == MapId.Nullspace) continue;
+
+                var mapTree = _gridTrees[mapId];
+                var aabb = MapTrees.SpriteAabbFunc(sprite);
+                var intersectingGrids = _mapManager.FindGridIdsIntersecting(mapId, aabb, true).ToList();
+
+                // Remove from old
+                foreach (var gridId in sprite.IntersectingGrids)
+                {
+                    if (intersectingGrids.Contains(gridId)) continue;
+                    mapTree[gridId].SpriteTree.Remove(sprite);
+                }
+
+                // Rebuild in the update below
+                sprite.IntersectingGrids.Clear();
+
+                // Update / add to new
+                foreach (var gridId in intersectingGrids)
+                {
+                    var translated = aabb.Translated(gridId == GridId.Invalid
+                        ? Vector2.Zero
+                        : -_mapManager.GetGrid(gridId).WorldPosition);
+
+                    mapTree[gridId].SpriteTree.AddOrUpdate(sprite, translated);
+
+                    sprite.IntersectingGrids.Add(gridId);
+                }
+
+                sprite.TreeUpdateQueued = false;
             }
 
-            foreach (var queuedUpdateLight in _lightQueue)
+            foreach (var light in _lightQueue)
             {
-                var transform = queuedUpdateLight.Owner.Transform;
-                var map = transform.MapID;
-                if (map == MapId.Nullspace)
-                {
-                    continue;
-                }
-                var updateMapTree = _mapTrees[map].LightTree;
+                var mapId = light.Owner.Transform.MapID;
 
-                updateMapTree.AddOrUpdate(queuedUpdateLight);
-                queuedUpdateLight.TreeUpdateQueued = false;
+                // If we're on a new map then clear the old one.
+                if (light.IntersectingMapId != mapId)
+                {
+                    ClearLight(light);
+                }
+
+                light.IntersectingMapId = mapId;
+
+                if (mapId == MapId.Nullspace) continue;
+
+                var mapTree = _gridTrees[mapId];
+                var aabb = MapTrees.LightAabbFunc(light);
+                var intersectingGrids = _mapManager.FindGridIdsIntersecting(mapId, aabb, true).ToList();
+
+                // Remove from old
+                foreach (var gridId in intersectingGrids)
+                {
+                    if (intersectingGrids.Contains(gridId)) continue;
+                    mapTree[gridId].LightTree.Remove(light);
+                }
+
+                // Rebuild in the update below
+                light.IntersectingGrids.Clear();
+
+                // Update / add to new
+                foreach (var gridId in intersectingGrids)
+                {
+                    var translated = aabb.Translated(gridId == GridId.Invalid
+                        ? Vector2.Zero
+                        : -_mapManager.GetGrid(gridId).WorldPosition);
+
+                    mapTree[gridId].LightTree.AddOrUpdate(light, translated);
+                    light.IntersectingGrids.Add(gridId);
+                }
+
+                light.TreeUpdateQueued = false;
             }
 
             _spriteQueue.Clear();
@@ -197,14 +363,14 @@ namespace Robust.Client.GameObjects
                 LightTree = new DynamicTree<PointLightComponent>(LightAabbFunc);
             }
 
-            private static Box2 SpriteAabbFunc(in SpriteComponent value)
+            internal static Box2 SpriteAabbFunc(in SpriteComponent value)
             {
                 var worldPos = value.Owner.Transform.WorldPosition;
 
                 return new Box2(worldPos, worldPos);
             }
 
-            private static Box2 LightAabbFunc(in PointLightComponent value)
+            internal static Box2 LightAabbFunc(in PointLightComponent value)
             {
                 var worldPos = value.Owner.Transform.WorldPosition;
 
@@ -214,9 +380,9 @@ namespace Robust.Client.GameObjects
         }
     }
 
-    internal struct RenderTreeRemoveSpriteMessage
+    internal class RenderTreeRemoveSpriteEvent : EntityEventArgs
     {
-        public RenderTreeRemoveSpriteMessage(SpriteComponent sprite, MapId map)
+        public RenderTreeRemoveSpriteEvent(SpriteComponent sprite, MapId map)
         {
             Sprite = sprite;
             Map = map;
@@ -226,9 +392,9 @@ namespace Robust.Client.GameObjects
         public MapId Map { get; }
     }
 
-    internal struct RenderTreeRemoveLightMessage
+    internal class RenderTreeRemoveLightEvent : EntityEventArgs
     {
-        public RenderTreeRemoveLightMessage(PointLightComponent light, MapId map)
+        public RenderTreeRemoveLightEvent(PointLightComponent light, MapId map)
         {
             Light = light;
             Map = map;

Robust.Client/GameObjects/EntitySystems/SpriteSystem.cs

@@ -3,6 +3,7 @@ using Robust.Client.Graphics;
 using Robust.Shared.GameObjects;
 using Robust.Shared.IoC;
 using Robust.Shared.Map;
+using Robust.Shared.Maths;
 
 namespace Robust.Client.GameObjects
 {
@@ -13,12 +14,19 @@ namespace Robust.Client.GameObjects
     public class SpriteSystem : EntitySystem
     {
         [Dependency] private readonly IEyeManager _eyeManager = default!;
+        [Dependency] private readonly IMapManager _mapManager = default!;
+
+        private RenderingTreeSystem _treeSystem = default!;
+
+        public override void Initialize()
+        {
+            base.Initialize();
+            _treeSystem = Get<RenderingTreeSystem>();
+        }
 
         /// <inheritdoc />
         public override void FrameUpdate(float frameTime)
         {
-            var renderTreeSystem = EntitySystemManager.GetEntitySystem<RenderingTreeSystem>();
-
             // So we could calculate the correct size of the entities based on the contents of their sprite...
             // Or we can just assume that no entity is larger than 10x10 and get a stupid easy check.
             var pvsBounds = _eyeManager.GetWorldViewport().Enlarged(5);
@@ -29,18 +37,23 @@ namespace Robust.Client.GameObjects
                 return;
             }
 
-            var mapTree = renderTreeSystem.GetSpriteTreeForMap(currentMap);
-
-            mapTree.QueryAabb(ref frameTime, (ref float state, in SpriteComponent value) =>
+            foreach (var gridId in _mapManager.FindGridIdsIntersecting(currentMap, pvsBounds, true))
             {
-                if (value.IsInert)
-                {
-                    return true;
-                }
+                var gridBounds = gridId == GridId.Invalid ? pvsBounds : pvsBounds.Translated(-_mapManager.GetGrid(gridId).WorldPosition);
 
-                value.FrameUpdate(state);
-                return true;
-            }, pvsBounds, approx: true);
+                var mapTree = _treeSystem.GetSpriteTreeForMap(currentMap, gridId);
+
+                mapTree.QueryAabb(ref frameTime, (ref float state, in SpriteComponent value) =>
+                {
+                    if (value.IsInert)
+                    {
+                        return true;
+                    }
+
+                    value.FrameUpdate(state);
+                    return true;
+                }, gridBounds, approx: true);
+            }
         }
     }
 }

Robust.Client/GameObjects/EntitySystems/UserInterfaceSystem.cs

@@ -0,0 +1,37 @@
+using JetBrains.Annotations;
+using Robust.Shared.GameObjects;
+
+namespace Robust.Client.GameObjects
+{
+    [UsedImplicitly]
+    public sealed class UserInterfaceSystem : EntitySystem
+    {
+        public override void Initialize()
+        {
+            base.Initialize();
+
+            SubscribeNetworkEvent<BoundUIWrapMessage>(MessageReceived);
+            SubscribeLocalEvent<ClientUserInterfaceComponent, ComponentShutdown>(OnUserInterfaceShutdown);
+        }
+
+        private void OnUserInterfaceShutdown(EntityUid uid, ClientUserInterfaceComponent component, ComponentShutdown args)
+        {
+            foreach (var bui in component.Interfaces)
+            {
+                bui.Dispose();
+            }
+        }
+
+        private void MessageReceived(BoundUIWrapMessage ev)
+        {
+            var cmp = ComponentManager.GetComponent<ClientUserInterfaceComponent>(ev.Entity);
+
+            cmp.MessageReceived(ev);
+        }
+
+        internal void Send(BoundUIWrapMessage msg)
+        {
+            RaiseNetworkEvent(msg);
+        }
+    }
+}

Robust.Client/GameObjects/IClientEntityManager.cs

@@ -3,10 +3,8 @@ using Robust.Shared.GameObjects;
 
 namespace Robust.Client.GameObjects
 {
-    public interface IClientEntityManager : IEntityManager
+    public interface IClientEntityManager : IEntityManager, IEntityNetworkManager
     {
-        /// <returns>The list of new entities created.</returns>
-        List<EntityUid> ApplyEntityStates(EntityState[]? curEntStates, IEnumerable<EntityUid>? deletions,
-            EntityState[]? nextEntStates);
+
     }
 }

Robust.Client/GameObjects/IClientEntityManagerInternal.cs

@@ -0,0 +1,15 @@
+using Robust.Shared.GameObjects;
+
+namespace Robust.Client.GameObjects
+{
+    internal interface IClientEntityManagerInternal : IClientEntityManager
+    {
+        // These methods are used by the Game State Manager.
+
+        IEntity CreateEntity(string? prototypeName, EntityUid? uid = null);
+
+        void InitializeEntity(IEntity entity);
+
+        void StartEntity(IEntity entity);
+    }
+}

Robust.Client/GameObjects/PlayerMessages.cs

@@ -1,12 +1,15 @@
+using System;
 using Robust.Shared.GameObjects;
 
 namespace Robust.Client.GameObjects
 {
+    [Obsolete("Component Messages are deprecated, use Entity Events instead.")]
     public class PlayerAttachedMsg : ComponentMessage
     {
 
     }
 
+    [Obsolete("Component Messages are deprecated, use Entity Events instead.")]
     public class PlayerDetachedMsg : ComponentMessage
     {
 

Robust.Client/GameStates/ClientGameStateManager.cs

@@ -1,14 +1,18 @@
 using System;
 using System.Collections.Generic;
 using System.Diagnostics;
+using System.Linq;
 using Robust.Client.GameObjects;
 using Robust.Client.Input;
+using Robust.Client.Map;
 using Robust.Shared.GameStates;
 using Robust.Shared.IoC;
 using Robust.Shared.Network.Messages;
 using Robust.Client.Player;
+using Robust.Client.Timing;
 using Robust.Shared;
 using Robust.Shared.Configuration;
+using Robust.Shared.Exceptions;
 using Robust.Shared.GameObjects;
 using Robust.Shared.Input;
 using Robust.Shared.Log;
@@ -31,16 +35,21 @@ namespace Robust.Client.GameStates
             _pendingSystemMessages
                 = new();
 
-        [Dependency] private readonly IClientEntityManager _entities = default!;
+        [Dependency] private readonly IComponentFactory _compFactory = default!;
+        [Dependency] private readonly IClientEntityManagerInternal _entities = default!;
+        [Dependency] private readonly IEntityLookup _lookup = default!;
         [Dependency] private readonly IPlayerManager _players = default!;
         [Dependency] private readonly IClientNetManager _network = default!;
         [Dependency] private readonly IBaseClient _client = default!;
-        [Dependency] private readonly IMapManager _mapManager = default!;
-        [Dependency] private readonly IGameTiming _timing = default!;
+        [Dependency] private readonly IClientMapManager _mapManager = default!;
+        [Dependency] private readonly IClientGameTiming _timing = default!;
         [Dependency] private readonly INetConfigurationManager _config = default!;
         [Dependency] private readonly IEntitySystemManager _entitySystemManager = default!;
         [Dependency] private readonly IComponentManager _componentManager = default!;
         [Dependency] private readonly IInputManager _inputManager = default!;
+#if EXCEPTION_TOLERANCE
+        [Dependency] private readonly IRuntimeLog _runtimeLog = default!;
+#endif
 
         /// <inheritdoc />
         public int MinBufferSize => _processor.MinBufferSize;
@@ -242,65 +251,69 @@ namespace Robust.Client.GameStates
 
             if (!Predicting) return;
 
-            using var _ = _timing.StartPastPredictionArea();
-
-
-            if (_pendingInputs.Count > 0)
+            using(var _ = _timing.StartPastPredictionArea())
             {
-                Logger.DebugS(CVars.NetPredict.Name,  "CL> Predicted:");
+                if (_pendingInputs.Count > 0)
+                {
+                    Logger.DebugS(CVars.NetPredict.Name,  "CL> Predicted:");
+                }
+
+                var pendingInputEnumerator = _pendingInputs.GetEnumerator();
+                var pendingMessagesEnumerator = _pendingSystemMessages.GetEnumerator();
+                var hasPendingInput = pendingInputEnumerator.MoveNext();
+                var hasPendingMessage = pendingMessagesEnumerator.MoveNext();
+
+                var ping = _network.ServerChannel!.Ping / 1000f + PredictLagBias; // seconds.
+                var targetTick = _timing.CurTick.Value + _processor.TargetBufferSize +
+                                 (int) Math.Ceiling(_timing.TickRate * ping) + PredictTickBias;
+
+                // Logger.DebugS("net.predict", $"Predicting from {_lastProcessedTick} to {targetTick}");
+
+                for (var t = _lastProcessedTick.Value + 1; t <= targetTick; t++)
+                {
+                    var tick = new GameTick(t);
+                    _timing.CurTick = tick;
+
+                    while (hasPendingInput && pendingInputEnumerator.Current.Tick <= tick)
+                    {
+                        var inputCmd = pendingInputEnumerator.Current;
+
+                        _inputManager.NetworkBindMap.TryGetKeyFunction(inputCmd.InputFunctionId, out var boundFunc);
+
+                        Logger.DebugS(CVars.NetPredict.Name,
+                            $"    seq={inputCmd.InputSequence}, sub={inputCmd.SubTick}, dTick={tick}, func={boundFunc.FunctionName}, " +
+                            $"state={inputCmd.State}");
+
+
+                        input.PredictInputCommand(inputCmd);
+
+                        hasPendingInput = pendingInputEnumerator.MoveNext();
+                    }
+
+                    while (hasPendingMessage && pendingMessagesEnumerator.Current.sourceTick <= tick)
+                    {
+                        var msg = pendingMessagesEnumerator.Current.msg;
+
+                        _entities.EventBus.RaiseEvent(EventSource.Local, msg);
+                        _entities.EventBus.RaiseEvent(EventSource.Local, pendingMessagesEnumerator.Current.sessionMsg);
+
+                        hasPendingMessage = pendingMessagesEnumerator.MoveNext();
+                    }
+
+                    if (t != targetTick)
+                    {
+                        // Don't run EntitySystemManager.TickUpdate if this is the target tick,
+                        // because the rest of the main loop will call into it with the target tick later,
+                        // and it won't be a past prediction.
+                        _entitySystemManager.TickUpdate((float) _timing.TickPeriod.TotalSeconds);
+                        ((IBroadcastEventBusInternal) _entities.EventBus).ProcessEventQueue();
+                    }
+                }
             }
 
-            var pendingInputEnumerator = _pendingInputs.GetEnumerator();
-            var pendingMessagesEnumerator = _pendingSystemMessages.GetEnumerator();
-            var hasPendingInput = pendingInputEnumerator.MoveNext();
-            var hasPendingMessage = pendingMessagesEnumerator.MoveNext();
+            _entities.TickUpdate((float) _timing.TickPeriod.TotalSeconds);
 
-            var ping = _network.ServerChannel!.Ping / 1000f + PredictLagBias; // seconds.
-            var targetTick = _timing.CurTick.Value + _processor.TargetBufferSize +
-                             (int) Math.Ceiling(_timing.TickRate * ping) + PredictTickBias;
-
-            // Logger.DebugS("net.predict", $"Predicting from {_lastProcessedTick} to {targetTick}");
-
-            for (var t = _lastProcessedTick.Value + 1; t <= targetTick; t++)
-            {
-                var tick = new GameTick(t);
-                _timing.CurTick = tick;
-
-                while (hasPendingInput && pendingInputEnumerator.Current.Tick <= tick)
-                {
-                    var inputCmd = pendingInputEnumerator.Current;
-
-                    _inputManager.NetworkBindMap.TryGetKeyFunction(inputCmd.InputFunctionId, out var boundFunc);
-
-                    Logger.DebugS(CVars.NetPredict.Name,
-                        $"    seq={inputCmd.InputSequence}, sub={inputCmd.SubTick}, dTick={tick}, func={boundFunc.FunctionName}, " +
-                        $"state={inputCmd.State}");
-
-
-                    input.PredictInputCommand(inputCmd);
-
-                    hasPendingInput = pendingInputEnumerator.MoveNext();
-                }
-
-                while (hasPendingMessage && pendingMessagesEnumerator.Current.sourceTick <= tick)
-                {
-                    var msg = pendingMessagesEnumerator.Current.msg;
-
-                    _entities.EventBus.RaiseEvent(EventSource.Local, msg);
-                    _entities.EventBus.RaiseEvent(EventSource.Local, pendingMessagesEnumerator.Current.sessionMsg);
-
-                    hasPendingMessage = pendingMessagesEnumerator.MoveNext();
-                }
-
-                if (t != targetTick)
-                {
-                    // Don't run EntitySystemManager.Update if this is the target tick,
-                    // because the rest of the main loop will call into it with the target tick later,
-                    // and it won't be a past prediction.
-                    _entitySystemManager.Update((float) _timing.TickPeriod.TotalSeconds);
-                    ((IBroadcastEventBusInternal) _entities.EventBus).ProcessEventQueue();
-                }
-            }
+            _lookup.Update();
         }
 
         private void ResetPredictedEntities(GameTick curTick)
@@ -381,7 +394,7 @@ namespace Robust.Client.GameStates
         {
             _config.TickProcessMessages();
             _mapManager.ApplyGameStatePre(curState.MapData);
-            var createdEntities = _entities.ApplyEntityStates(curState.EntityStates, curState.EntityDeletions,
+            var createdEntities = ApplyEntityStates(curState.EntityStates, curState.EntityDeletions,
                 nextState?.EntityStates);
             _players.ApplyPlayerStates(curState.PlayerStates);
             _mapManager.ApplyGameStatePost(curState.MapData);
@@ -389,6 +402,218 @@ namespace Robust.Client.GameStates
             GameStateApplied?.Invoke(new GameStateAppliedArgs(curState));
             return createdEntities;
         }
+
+        private List<EntityUid> ApplyEntityStates(EntityState[]? curEntStates, IEnumerable<EntityUid>? deletions,
+            EntityState[]? nextEntStates)
+        {
+            var toApply = new Dictionary<IEntity, (EntityState?, EntityState?)>();
+            var toInitialize = new List<Entity>();
+            var created = new List<EntityUid>();
+            deletions ??= new EntityUid[0];
+
+            if (curEntStates != null && curEntStates.Length != 0)
+            {
+                foreach (var es in curEntStates)
+                {
+                    //Known entities
+                    if (_entities.TryGetEntity(es.Uid, out var entity))
+                    {
+                        toApply.Add(entity, (es, null));
+                    }
+                    else //Unknown entities
+                    {
+                        var metaState = (MetaDataComponentState?) es.ComponentStates
+                            ?.FirstOrDefault(c => c.NetID == NetIDs.META_DATA);
+                        if (metaState == null)
+                        {
+                            throw new InvalidOperationException($"Server sent new entity state for {es.Uid} without metadata component!");
+                        }
+                        var newEntity = (Entity)_entities.CreateEntity(metaState.PrototypeId, es.Uid);
+                        toApply.Add(newEntity, (es, null));
+                        toInitialize.Add(newEntity);
+                        created.Add(newEntity.Uid);
+                    }
+                }
+            }
+
+            if (nextEntStates != null && nextEntStates.Length != 0)
+            {
+                foreach (var es in nextEntStates)
+                {
+                    if (_entities.TryGetEntity(es.Uid, out var entity))
+                    {
+                        if (toApply.TryGetValue(entity, out var state))
+                        {
+                            toApply[entity] = (state.Item1, es);
+                        }
+                        else
+                        {
+                            toApply[entity] = (null, es);
+                        }
+                    }
+                }
+            }
+
+            // Make sure this is done after all entities have been instantiated.
+            foreach (var kvStates in toApply)
+            {
+                var ent = kvStates.Key;
+                var entity = (Entity) ent;
+                HandleEntityState(entity.EntityManager.ComponentManager, entity, kvStates.Value.Item1,
+                    kvStates.Value.Item2);
+            }
+
+            foreach (var id in deletions)
+            {
+                _entities.DeleteEntity(id);
+            }
+
+#if EXCEPTION_TOLERANCE
+            HashSet<Entity> brokenEnts = new HashSet<Entity>();
+#endif
+
+            foreach (var entity in toInitialize)
+            {
+#if EXCEPTION_TOLERANCE
+                try
+                {
+#endif
+                    _entities.InitializeEntity(entity);
+#if EXCEPTION_TOLERANCE
+                }
+                catch (Exception e)
+                {
+                    Logger.ErrorS("state", $"Server entity threw in Init: uid={entity.Uid}, proto={entity.Prototype}\n{e}");
+                    brokenEnts.Add(entity);
+                }
+#endif
+            }
+
+            foreach (var entity in toInitialize)
+            {
+#if EXCEPTION_TOLERANCE
+                if (brokenEnts.Contains(entity))
+                    continue;
+
+                try
+                {
+#endif
+                    _entities.StartEntity(entity);
+#if EXCEPTION_TOLERANCE
+                }
+                catch (Exception e)
+                {
+                    Logger.ErrorS("state", $"Server entity threw in Start: uid={entity.Uid}, proto={entity.Prototype}\n{e}");
+                    brokenEnts.Add(entity);
+                }
+#endif
+            }
+
+            foreach (var entity in toInitialize)
+            {
+#if EXCEPTION_TOLERANCE
+                if (brokenEnts.Contains(entity))
+                    continue;
+#endif
+            }
+#if EXCEPTION_TOLERANCE
+            foreach (var entity in brokenEnts)
+            {
+                entity.Delete();
+            }
+#endif
+
+            return created;
+        }
+
+        private void HandleEntityState(IComponentManager compMan, IEntity entity, EntityState? curState,
+            EntityState? nextState)
+        {
+            var compStateWork = new Dictionary<uint, (ComponentState? curState, ComponentState? nextState)>();
+            var entityUid = entity.Uid;
+
+            if (curState?.ComponentChanges != null)
+            {
+                foreach (var compChange in curState.ComponentChanges)
+                {
+                    if (compChange.Deleted)
+                    {
+                        if (compMan.TryGetComponent(entityUid, compChange.NetID, out var comp))
+                        {
+                            compMan.RemoveComponent(entityUid, comp);
+                        }
+                    }
+                    else
+                    {
+                        if (compMan.HasComponent(entityUid, compChange.NetID))
+                            continue;
+
+                        var newComp = (Component) _compFactory.GetComponent(compChange.ComponentName!);
+                        newComp.Owner = entity;
+                        compMan.AddComponent(entity, newComp, true);
+                    }
+                }
+            }
+
+            if (curState?.ComponentStates != null)
+            {
+                foreach (var compState in curState.ComponentStates)
+                {
+                    compStateWork[compState.NetID] = (compState, null);
+                }
+            }
+
+            if (nextState?.ComponentStates != null)
+            {
+                foreach (var compState in nextState.ComponentStates)
+                {
+                    if (compStateWork.TryGetValue(compState.NetID, out var state))
+                    {
+                        compStateWork[compState.NetID] = (state.curState, compState);
+                    }
+                    else
+                    {
+                        compStateWork[compState.NetID] = (null, compState);
+                    }
+                }
+            }
+
+            foreach (var (netId, (cur, next)) in compStateWork)
+            {
+                if (compMan.TryGetComponent(entityUid, netId, out var component))
+                {
+                    try
+                    {
+                        component.HandleComponentState(cur, next);
+                    }
+                    catch (Exception e)
+                    {
+                        var wrapper = new ComponentStateApplyException(
+                            $"Failed to apply comp state: entity={component.Owner}, comp={component.Name}", e);
+#if EXCEPTION_TOLERANCE
+                    _runtimeLog.LogException(wrapper, "Component state apply");
+#else
+                        throw wrapper;
+#endif
+                    }
+                }
+                else
+                {
+                    // The component can be null here due to interp.
+                    // Because the NEXT state will have a new component, but this one doesn't yet.
+                    // That's fine though.
+                    if (cur == null)
+                    {
+                        continue;
+                    }
+
+                    var eUid = entityUid;
+                    var eRegisteredNetUidName = _compFactory.GetRegistration(netId).Name;
+                    DebugTools.Assert(
+                        $"Component does not exist for state: entUid={eUid}, expectedNetId={netId}, expectedName={eRegisteredNetUidName}");
+                }
+            }
+        }
     }
 
     public class GameStateAppliedArgs : EventArgs

Robust.Client/GameStates/NetEntityOverlay.cs

@@ -1,5 +1,6 @@
 using System.Collections.Generic;
 using Robust.Client.Graphics;
+using Robust.Client.Player;
 using Robust.Client.ResourceManagement;
 using Robust.Shared.Configuration;
 using Robust.Shared.Console;
@@ -9,6 +10,7 @@ using Robust.Shared.IoC;
 using Robust.Shared.Maths;
 using Robust.Shared.Network;
 using Robust.Shared.Timing;
+using Robust.Shared.Utility;
 
 namespace Robust.Client.GameStates
 {
@@ -28,8 +30,8 @@ namespace Robust.Client.GameStates
         private const int TrafficHistorySize = 64; // Size of the traffic history bar in game ticks.
 
         /// <inheritdoc />
-        public override OverlaySpace Space => OverlaySpace.ScreenSpace;
-        
+        public override OverlaySpace Space => OverlaySpace.ScreenSpace | OverlaySpace.WorldSpace;
+
         private readonly Font _font;
         private readonly int _lineHeight;
         private readonly List<NetEntity> _netEnts = new();
@@ -43,12 +45,12 @@ namespace Robust.Client.GameStates
 
             _gameStateManager.GameStateApplied += HandleGameStateApplied;
         }
-        
+
         private void HandleGameStateApplied(GameStateAppliedArgs args)
         {
             if(_gameTiming.InPrediction) // we only care about real server states.
                 return;
-            
+
             // Shift traffic history down one
             for (var i = 0; i < _netEnts.Count; i++)
             {
@@ -75,7 +77,7 @@ namespace Robust.Client.GameStates
 
                         if (netEnt.Id != entityState.Uid)
                             continue;
-                    
+
                         //TODO: calculate size of state and record it here.
                         netEnt.Traffic[^1] = 1;
                         netEnt.LastUpdate = gameState.ToSequence;
@@ -95,15 +97,15 @@ namespace Robust.Client.GameStates
             }
 
             bool pvsEnabled = _configurationManager.GetCVar<bool>("net.pvs");
-            float pvsSize = _configurationManager.GetCVar<float>("net.maxupdaterange");
+            float pvsRange = _configurationManager.GetCVar<float>("net.maxupdaterange");
             var pvsCenter = _eyeManager.CurrentEye.Position;
-            Box2 pvsBox = Box2.CenteredAround(pvsCenter.Position, new Vector2(pvsSize*2, pvsSize*2));
+            Box2 pvsBox = Box2.CenteredAround(pvsCenter.Position, new Vector2(pvsRange*2, pvsRange*2));
 
             int timeout = _gameTiming.TickRate * 3;
             for (int i = 0; i < _netEnts.Count; i++)
             {
                 var netEnt = _netEnts[i];
-                
+
                 if(_entityManager.EntityExists(netEnt.Id))
                 {
                     //TODO: Whoever is working on PVS remake, change the InPVS detection.
@@ -124,22 +126,57 @@ namespace Robust.Client.GameStates
                 _netEnts[i] = netEnt; // copy struct back
             }
         }
-        
-        protected override void Draw(DrawingHandleBase handle, OverlaySpace currentSpace)
+
+        protected internal override void Draw(in OverlayDrawArgs args)
         {
             if (!_netManager.IsConnected)
                 return;
 
+            switch (args.Space)
+            {
+                case OverlaySpace.ScreenSpace:
+                    DrawScreen(args);
+                    break;
+                case OverlaySpace.WorldSpace:
+                    DrawWorld(args);
+                    break;
+            }
+        }
+
+        private void DrawWorld(in OverlayDrawArgs args)
+        {
+            bool pvsEnabled = _configurationManager.GetCVar<bool>("net.pvs");
+            if(!pvsEnabled)
+                return;
+
+            float pvsRange = _configurationManager.GetCVar<float>("net.maxupdaterange");
+            var pvsCenter = _eyeManager.CurrentEye.Position;
+            Box2 pvsBox = Box2.CenteredAround(pvsCenter.Position, new Vector2(pvsRange * 2, pvsRange * 2));
+
+            var worldHandle = args.WorldHandle;
+
+            worldHandle.DrawRect(pvsBox, Color.Red, false);
+        }
+
+        private void DrawScreen(in OverlayDrawArgs args)
+        {
             // remember, 0,0 is top left of ui with +X right and +Y down
-            var screenHandle = (DrawingHandleScreen)handle;
-            
+            var screenHandle = args.ScreenHandle;
+
             for (int i = 0; i < _netEnts.Count; i++)
             {
                 var netEnt = _netEnts[i];
 
+                if (!_entityManager.TryGetEntity(netEnt.Id, out var ent))
+                {
+                    _netEnts.RemoveSwap(i);
+                    i--;
+                    continue;
+                }
+
                 var xPos = 100;
                 var yPos = 10 + _lineHeight * i;
-                var name = $"({netEnt.Id}) {_entityManager.GetEntity(netEnt.Id).Prototype?.ID}";
+                var name = $"({netEnt.Id}) {ent.Prototype?.ID}";
                 var color = CalcTextColor(ref netEnt);
                 DrawString(screenHandle, _font, new Vector2(xPos + (TrafficHistorySize + 4), yPos), name, color);
                 DrawTrafficBox(screenHandle, ref netEnt, xPos, yPos);
@@ -190,9 +227,9 @@ namespace Robust.Client.GameStates
         {
             var baseLine = new Vector2(pos.X, font.GetAscent(1) + pos.Y);
 
-            foreach (var chr in str)
+            foreach (var rune in str.EnumerateRunes())
             {
-                var advance = font.DrawChar(handle, chr, baseLine, 1, textColor);
+                var advance = font.DrawChar(handle, rune, baseLine, 1, textColor);
                 baseLine += new Vector2(advance, 0);
             }
         }
@@ -225,7 +262,7 @@ namespace Robust.Client.GameStates
             {
                 if (args.Length != 1)
                 {
-                    shell.WriteError("Invalid argument amount. Expected 2 arguments.");
+                    shell.WriteError("Invalid argument amount. Expected 1 arguments.");
                     return;
                 }
 

Robust.Client/GameStates/NetGraphOverlay.cs

@@ -1,9 +1,11 @@
 using System;
 using System.Collections.Generic;
+using System.Text;
 using Robust.Client.Graphics;
 using Robust.Client.ResourceManagement;
 using Robust.Shared.Enums;
 using Robust.Shared.Console;
+using Robust.Shared.GameObjects;
 using Robust.Shared.IoC;
 using Robust.Shared.Maths;
 using Robust.Shared.Network;
@@ -36,6 +38,10 @@ namespace Robust.Client.GameStates
 
         private readonly List<(GameTick Tick, int Payload, int lag, int interp)> _history = new(HistorySize+10);
 
+        private int _totalHistoryPayload; // sum of all data point sizes in bytes
+
+        public EntityUid WatchEntId { get; set; }
+
         public NetGraphOverlay()
         {
             IoCManager.InjectDependencies(this);
@@ -60,7 +66,73 @@ namespace Robust.Client.GameStates
             // calc interp info
             var interpBuff = _gameStateManager.CurrentBufferSize - _gameStateManager.MinBufferSize;
 
+            _totalHistoryPayload += sz;
             _history.Add((toSeq, sz, lag, interpBuff));
+
+            // not watching an ent
+            if(!WatchEntId.IsValid() || WatchEntId.IsClientSide())
+                return;
+
+            string? entStateString = null;
+            string? entDelString = null;
+            var conShell = IoCManager.Resolve<IConsoleHost>().LocalShell;
+
+            var entStates = args.AppliedState.EntityStates;
+            if (entStates is not null)
+            {
+                var sb = new StringBuilder();
+                foreach (var entState in entStates)
+                {
+                    if (entState.Uid == WatchEntId)
+                    {
+                        if(entState.ComponentChanges is not null)
+                        {
+                            sb.Append($"\n  Changes:");
+                            foreach (var compChange in entState.ComponentChanges)
+                            {
+                                var del = compChange.Deleted ? 'D' : 'C';
+                                sb.Append($"\n    [{del}]{compChange.NetID}:{compChange.ComponentName}");
+                            }
+                        }
+
+                        if (entState.ComponentStates is not null)
+                        {
+                            sb.Append($"\n  States:");
+                            foreach (var compState in entState.ComponentStates)
+                            {
+                                sb.Append($"\n    {compState.NetID}:{compState.GetType().Name}");
+                            }
+                        }
+                    }
+                }
+                entStateString = sb.ToString();
+            }
+
+            var entDeletes = args.AppliedState.EntityDeletions;
+            if (entDeletes is not null)
+            {
+                var sb = new StringBuilder();
+                foreach (var entDelete in entDeletes)
+                {
+                    if (entDelete == WatchEntId)
+                    {
+                        entDelString = "\n  Deleted";
+                    }
+                }
+            }
+
+            if (!string.IsNullOrWhiteSpace(entStateString) || !string.IsNullOrWhiteSpace(entDelString))
+            {
+                var fullString = $"watchEnt: from={args.AppliedState.FromSequence}, to={args.AppliedState.ToSequence}, eid={WatchEntId}";
+                if (!string.IsNullOrWhiteSpace(entStateString))
+                    fullString += entStateString;
+
+                if (!string.IsNullOrWhiteSpace(entDelString))
+                    fullString += entDelString;
+
+                conShell.WriteLine(fullString + "\n");
+            }
+
         }
 
         /// <inheritdoc />
@@ -69,19 +141,27 @@ namespace Robust.Client.GameStates
             base.FrameUpdate(args);
 
             var over = _history.Count - HistorySize;
-            if (over > 0)
+            if (over <= 0)
+                return;
+
+            for (int i = 0; i < over; i++)
             {
-                _history.RemoveRange(0, over);
+                var point = _history[i];
+                _totalHistoryPayload -= point.Payload;
             }
+
+            _history.RemoveRange(0, over);
         }
 
-        protected override void Draw(DrawingHandleBase handle, OverlaySpace currentSpace)
+        protected internal override void Draw(in OverlayDrawArgs args)
         {
             // remember, 0,0 is top left of ui with +X right and +Y down
 
             var leftMargin = 300;
             var width = HistorySize;
             var height = 500;
+            var drawSizeThreshold = Math.Min(_totalHistoryPayload / HistorySize, 300);
+            var handle = args.ScreenHandle;
 
             // bottom payload line
             handle.DrawLine(new Vector2(leftMargin, height), new Vector2(leftMargin + width, height), Color.DarkGray.WithAlpha(0.8f));
@@ -101,6 +181,12 @@ namespace Robust.Client.GameStates
                 var yoff = height - state.Payload / BytesPerPixel;
                 handle.DrawLine(new Vector2(xOff, height), new Vector2(xOff, yoff), Color.LightGreen.WithAlpha(0.8f));
 
+                // Draw size if above average
+                if (drawSizeThreshold * 1.5 < state.Payload)
+                {
+                    DrawString(handle, _font, new Vector2(xOff, yoff - _font.GetLineHeight(1)), state.Payload.ToString());
+                }
+
                 // second tick marks
                 if (state.Tick.Value % _gameTiming.TickRate == 0)
                 {
@@ -125,6 +211,10 @@ namespace Robust.Client.GameStates
                 handle.DrawLine(new Vector2(xOff, height + LowerGraphOffset), new Vector2(xOff, height + LowerGraphOffset + state.interp * 6), interpColor.WithAlpha(0.8f));
             }
 
+            // average payload line
+            var avgyoff = height - drawSizeThreshold / BytesPerPixel;
+            handle.DrawLine(new Vector2(leftMargin, avgyoff), new Vector2(leftMargin + width, avgyoff), Color.DarkGray.WithAlpha(0.8f));
+
             // top payload warning line
             var warnYoff = height - _warningPayloadSize / BytesPerPixel;
             handle.DrawLine(new Vector2(leftMargin, warnYoff), new Vector2(leftMargin + width, warnYoff), Color.DarkGray.WithAlpha(0.8f));
@@ -134,14 +224,14 @@ namespace Robust.Client.GameStates
             handle.DrawLine(new Vector2(leftMargin, midYoff), new Vector2(leftMargin + width, midYoff), Color.DarkGray.WithAlpha(0.8f));
 
             // payload text
-            DrawString((DrawingHandleScreen)handle, _font, new Vector2(leftMargin + width, warnYoff), "56K");
-            DrawString((DrawingHandleScreen)handle, _font, new Vector2(leftMargin + width, midYoff), "33.6K");
+            DrawString(handle, _font, new Vector2(leftMargin + width, warnYoff), "56K");
+            DrawString(handle, _font, new Vector2(leftMargin + width, midYoff), "33.6K");
 
             // interp text info
             if(lastLagY != -1)
-                DrawString((DrawingHandleScreen)handle, _font, new Vector2(leftMargin + width, lastLagY), $"{lastLagMs.ToString()}ms");
+                DrawString(handle, _font, new Vector2(leftMargin + width, lastLagY), $"{lastLagMs.ToString()}ms");
 
-            DrawString((DrawingHandleScreen)handle, _font, new Vector2(leftMargin, height + LowerGraphOffset), $"{_gameStateManager.CurrentBufferSize.ToString()} states");
+            DrawString(handle, _font, new Vector2(leftMargin, height + LowerGraphOffset), $"{_gameStateManager.CurrentBufferSize.ToString()} states");
         }
 
         protected override void DisposeBehavior()
@@ -155,9 +245,9 @@ namespace Robust.Client.GameStates
         {
             var baseLine = new Vector2(pos.X, font.GetAscent(1) + pos.Y);
 
-            foreach (var chr in str)
+            foreach (var rune in str.EnumerateRunes())
             {
-                var advance = font.DrawChar(handle, chr, baseLine, 1, Color.White);
+                var advance = font.DrawChar(handle, rune, baseLine, 1, Color.White);
                 baseLine += new Vector2(advance, 0);
             }
         }
@@ -197,5 +287,36 @@ namespace Robust.Client.GameStates
                 }
             }
         }
+
+        private class NetWatchEntCommand : IConsoleCommand
+        {
+            public string Command => "net_watchent";
+            public string Help => "net_watchent <0|EntityUid>";
+            public string Description => "Dumps all network updates for an EntityId to the console.";
+
+            public void Execute(IConsoleShell shell, string argStr, string[] args)
+            {
+                if (args.Length != 1)
+                {
+                    shell.WriteError("Invalid argument amount. Expected 1 argument.");
+                    return;
+                }
+
+                if (!EntityUid.TryParse(args[0], out var eValue))
+                {
+                    shell.WriteError("Invalid argument: Needs to be 0 or an entityId.");
+                    return;
+                }
+
+                var overlayMan = IoCManager.Resolve<IOverlayManager>();
+
+                if (overlayMan.HasOverlay(typeof(NetGraphOverlay)))
+                {
+                    var netOverlay = overlayMan.GetOverlay<NetGraphOverlay>();
+
+                    netOverlay.WatchEntId = eValue;
+                }
+            }
+        }
     }
 }

Robust.Client/GameStates/NetInterpOverlay.cs

@@ -26,8 +26,9 @@ namespace Robust.Client.GameStates
             _shader = _prototypeManager.Index<ShaderPrototype>("unshaded").Instance();
         }
 
-        protected override void Draw(DrawingHandleBase handle, OverlaySpace currentSpace)
+        protected internal override void Draw(in OverlayDrawArgs args)
         {
+            var handle = args.DrawingHandle;
             handle.UseShader(_shader);
             var worldHandle = (DrawingHandleWorld) handle;
             var viewport = _eyeManager.GetWorldViewport();

Robust.Client/Graphics/ClientEye/Eye.cs

@@ -50,9 +50,9 @@ namespace Robust.Client.Graphics
         }
 
         /// <inheritdoc />
-        public void GetViewMatrix(out Matrix3 viewMatrix)
+        public void GetViewMatrix(out Matrix3 viewMatrix, Vector2 renderScale)
         {
-            var scaleMat = Matrix3.CreateScale(_scale.X, _scale.Y);
+            var scaleMat = Matrix3.CreateScale(_scale.X * renderScale.X, _scale.Y * renderScale.Y);
             var rotMat = Matrix3.CreateRotation(_rotation);
             var transMat = Matrix3.CreateTranslation(-_coords.Position);
 
@@ -60,9 +60,9 @@ namespace Robust.Client.Graphics
         }
 
         /// <inheritdoc />
-        public void GetViewMatrixInv(out Matrix3 viewMatrixInv)
+        public void GetViewMatrixInv(out Matrix3 viewMatrixInv, Vector2 renderScale)
         {
-            GetViewMatrix(out var viewMatrix);
+            GetViewMatrix(out var viewMatrix, renderScale);
             viewMatrixInv = Matrix3.Invert(viewMatrix);
         }
     }

Robust.Client/Graphics/ClientEye/EyeManager.cs

@@ -1,4 +1,6 @@
-using Robust.Shared.GameObjects;
+using Robust.Client.UserInterface;
+using Robust.Client.UserInterface.CustomControls;
+using Robust.Shared.GameObjects;
 using Robust.Shared.IoC;
 using Robust.Shared.Map;
 using Robust.Shared.Maths;
@@ -19,6 +21,7 @@ namespace Robust.Client.Graphics
 
         [Dependency] private readonly IClyde _displayManager = default!;
         [Dependency] private readonly IEntityManager _entityManager = default!;
+        [Dependency] private readonly IUserInterfaceManager _uiManager = default!;
 
         // We default to this when we get set to a null eye.
         private readonly FixedEye _defaultEye = new();
@@ -32,11 +35,18 @@ namespace Robust.Client.Graphics
             set => _currentEye = value;
         }
 
+        public IViewportControl MainViewport { get; set; } = default!;
+
         public void ClearCurrentEye()
         {
             _currentEye = _defaultEye;
         }
 
+        void IEyeManager.Initialize()
+        {
+            MainViewport = _uiManager.MainViewport;
+        }
+
         /// <inheritdoc />
         public MapId CurrentMap => CurrentEye.Position.MapId;
 
@@ -49,7 +59,7 @@ namespace Robust.Client.Graphics
             var topRight = ScreenToMap(new Vector2(vpSize.X, 0));
             var bottomRight = ScreenToMap(vpSize);
             var bottomLeft = ScreenToMap(new Vector2(0, vpSize.Y));
-            
+
             var left = MathHelper.Min(topLeft.X, topRight.X, bottomRight.X, bottomLeft.X);
             var bottom = MathHelper.Min(topLeft.Y, topRight.Y, bottomRight.Y, bottomLeft.Y);
             var right = MathHelper.Max(topLeft.X, topRight.X, bottomRight.X, bottomLeft.X);
@@ -61,16 +71,7 @@ namespace Robust.Client.Graphics
         /// <inheritdoc />
         public Vector2 WorldToScreen(Vector2 point)
         {
-            var newPoint = point;
-
-            CurrentEye.GetViewMatrix(out var viewMatrix);
-            newPoint = viewMatrix * newPoint;
-
-            // (inlined version of UiProjMatrix)
-            newPoint *= new Vector2(1, -1) * PixelsPerMeter;
-            newPoint += _displayManager.ScreenSize / 2f;
-
-            return newPoint;
+            return MainViewport.WorldToScreen(point);
         }
 
         /// <inheritdoc />
@@ -103,29 +104,23 @@ namespace Robust.Client.Graphics
 
         public ScreenCoordinates MapToScreen(MapCoordinates point)
         {
-            return new(WorldToScreen(point.Position));
+            return new(WorldToScreen(point.Position), MainViewport.Window?.Id ?? default);
         }
 
         /// <inheritdoc />
         public MapCoordinates ScreenToMap(ScreenCoordinates point)
         {
-            return ScreenToMap(point.Position);
+            var (pos, window) = point;
+            if (window != MainViewport.Window?.Id)
+                return default;
+
+            return MainViewport.ScreenToMap(pos);
         }
 
         /// <inheritdoc />
         public MapCoordinates ScreenToMap(Vector2 point)
         {
-            var newPoint = point;
-
-            // (inlined version of UiProjMatrix^-1)
-            newPoint -= _displayManager.ScreenSize / 2f;
-            newPoint *= new Vector2(1, -1) / PixelsPerMeter;
-
-            // view matrix
-            CurrentEye.GetViewMatrixInv(out var viewMatrixInv);
-            newPoint = viewMatrixInv * newPoint;
-
-            return new MapCoordinates(newPoint, CurrentMap);
+            return MainViewport.ScreenToMap(point);
         }
     }
 }

Robust.Client/Graphics/ClientEye/IEye.cs

@@ -41,13 +41,15 @@ namespace Robust.Client.Graphics
         /// world space to camera space.
         /// </summary>
         /// <param name="viewMatrix">View matrix for this camera.</param>
-        void GetViewMatrix(out Matrix3 viewMatrix);
+        /// <param name="renderScale"></param>
+        void GetViewMatrix(out Matrix3 viewMatrix, Vector2 renderScale);
 
         /// <summary>
         /// Returns the inverted view matrix for this eye, used to convert a point from
         /// camera space to world space.
         /// </summary>
         /// <param name="viewMatrixInv">Inverted view matrix for this camera.</param>
-        void GetViewMatrixInv(out Matrix3 viewMatrixInv);
+        /// <param name="renderScale"></param>
+        void GetViewMatrixInv(out Matrix3 viewMatrixInv, Vector2 renderScale);
     }
 }

Robust.Client/Graphics/ClientEye/IEyeManager.cs

@@ -1,4 +1,5 @@
-using Robust.Shared.Map;
+using Robust.Client.UserInterface.CustomControls;
+using Robust.Shared.Map;
 using Robust.Shared.Maths;
 
 namespace Robust.Client.Graphics
@@ -17,6 +18,8 @@ namespace Robust.Client.Graphics
         /// </remarks>
         IEye CurrentEye { get; set; }
 
+        IViewportControl MainViewport { get; set; }
+
         /// <summary>
         /// The ID of the map on which the current eye is "placed".
         /// </summary>
@@ -72,5 +75,6 @@ namespace Robust.Client.Graphics
         MapCoordinates ScreenToMap(Vector2 point);
 
         void ClearCurrentEye();
+        void Initialize();
     }
 }

Robust.Client/Graphics/Clyde/Audio/Clyde.Audio.cs

@@ -53,7 +53,7 @@ namespace Robust.Client.Graphics.Clyde
 
             IsEfxSupported = HasAlDeviceExtension("ALC_EXT_EFX");
 
-            _configurationManager.OnValueChanged(CVars.AudioMasterVolume, SetMasterVolume, true);
+            _cfg.OnValueChanged(CVars.AudioMasterVolume, SetMasterVolume, true);
         }
 
         private void _audioCreateContext()
@@ -81,7 +81,7 @@ namespace Robust.Client.Graphics.Clyde
 
         private void _audioOpenDevice()
         {
-            var preferredDevice = _configurationManager.GetCVar(CVars.AudioDevice);
+            var preferredDevice = _cfg.GetCVar(CVars.AudioDevice);
 
             // Open device.
             if (!string.IsNullOrEmpty(preferredDevice))
@@ -183,6 +183,32 @@ namespace Robust.Client.Graphics.Clyde
             if (handles.filterHandle != 0) EFX.DeleteFilter(handles.filterHandle);
         }
 
+        public AudioStream LoadAudioRaw(short[] samples, int channels, int sampleRate)
+        {
+            var buffer = AL.GenBuffer();
+
+            unsafe
+            {
+                fixed (short* ptr = samples)
+                {
+                    AL.BufferData(
+                        buffer,
+                        channels == 1 ? ALFormat.Mono16 : ALFormat.Stereo16,
+                        (IntPtr) ptr,
+                        samples.Length * 2,
+                        sampleRate);
+                }
+            }
+
+            _checkAlError();
+
+            var handle = new ClydeHandle(_audioSampleBuffers.Count);
+            _audioSampleBuffers.Add(new LoadedAudioSample(buffer));
+            // ReSharper disable once PossibleLossOfFraction
+            var length = TimeSpan.FromSeconds(samples.Length / channels / (double) sampleRate);
+            return new AudioStream(handle, length, channels);
+        }
+
         public void SetMasterVolume(float newVolume)
         {
             AL.Listener(ALListenerf.Gain, _baseGain * newVolume);
@@ -439,6 +465,21 @@ namespace Robust.Client.Graphics.Clyde
                 _checkAlError();
             }
 
+            public void SetVolumeDirect(float decibels)
+            {
+                _checkDisposed();
+                var priorOcclusion = 1f;
+                if (!IsEfxSupported)
+                {
+                    AL.GetSource(SourceHandle, ALSourcef.Gain, out var priorGain);
+                    priorOcclusion = priorGain / _gain;
+                }
+
+                _gain = decibels;
+                AL.Source(SourceHandle, ALSourcef.Gain, _gain * priorOcclusion);
+                _checkAlError();
+            }
+
             public void SetOcclusion(float blocks)
             {
                 _checkDisposed();
@@ -482,7 +523,7 @@ namespace Robust.Client.Graphics.Clyde
 
                 var (x, y) = position;
 
-                if (!ValidatePosition(x, y))
+                if (!AreFinite(x, y))
                 {
                     return false;
                 }
@@ -503,7 +544,7 @@ namespace Robust.Client.Graphics.Clyde
                 return true;
             }
 
-            private static bool ValidatePosition(float x, float y)
+            private static bool AreFinite(float x, float y)
             {
                 if (float.IsFinite(x) && float.IsFinite(y))
                 {
@@ -513,6 +554,22 @@ namespace Robust.Client.Graphics.Clyde
                 return false;
             }
 
+            public void SetVelocity(Vector2 velocity)
+            {
+                _checkDisposed();
+
+                var (x, y) = velocity;
+
+                if (!AreFinite(x, y))
+                {
+                    return;
+                }
+
+                AL.Source(SourceHandle, ALSource3f.Velocity, x, y, 0);
+
+                _checkAlError();
+            }
+
             public void SetPitch(float pitch)
             {
                 _checkDisposed();
@@ -667,7 +724,6 @@ namespace Robust.Client.Graphics.Clyde
                 _checkAlError();
             }
 
-
             private void SetOcclusionEfx(float gain, float cutoff)
             {
                 if (FilterHandle == 0)
@@ -694,7 +750,7 @@ namespace Robust.Client.Graphics.Clyde
 
                 var (x, y) = position;
 
-                if (!ValidatePosition(x, y))
+                if (!AreFinite(x, y))
                 {
                     return false;
                 }
@@ -706,7 +762,7 @@ namespace Robust.Client.Graphics.Clyde
                 return true;
             }
 
-            private static bool ValidatePosition(float x, float y)
+            private static bool AreFinite(float x, float y)
             {
                 if (float.IsFinite(x) && float.IsFinite(y))
                 {
@@ -716,6 +772,37 @@ namespace Robust.Client.Graphics.Clyde
                 return false;
             }
 
+            public void SetVelocity(Vector2 velocity)
+            {
+                _checkDisposed();
+
+                var (x, y) = velocity;
+
+                if (!AreFinite(x, y))
+                {
+                    return;
+                }
+
+                AL.Source(SourceHandle!.Value, ALSource3f.Velocity, x, y, 0);
+
+                _checkAlError();
+            }
+
+            public void SetVolumeDirect(float masterVolumeDecay)
+            {
+                _checkDisposed();
+                var priorOcclusion = 1f;
+                if (!IsEfxSupported)
+                {
+                    AL.GetSource(SourceHandle!.Value, ALSourcef.Gain, out var priorGain);
+                    priorOcclusion = priorGain / _gain;
+                }
+
+                _gain = masterVolumeDecay;
+                AL.Source(SourceHandle!.Value, ALSourcef.Gain, _gain * priorOcclusion);
+                _checkAlError();
+            }
+
             public void SetPitch(float pitch)
             {
                 _checkDisposed();
@@ -739,7 +826,7 @@ namespace Robust.Client.Graphics.Clyde
             {
                 if (SourceHandle == null) return;
 
-                if (!disposing || Thread.CurrentThread != _master._mainThread)
+                if (!disposing || Thread.CurrentThread != _master._gameThread)
                 {
                     // We can't run this code inside another thread so tell Clyde to clear it up later.
                     _master.DeleteBufferedSourceOnMainThread(SourceHandle.Value, FilterHandle);

Robust.Client/Graphics/Clyde/Clyde.Cursor.cs

@@ -1,143 +0,0 @@
-using System;
-using System.Collections.Concurrent;
-using System.Collections.Generic;
-using OpenToolkit.GraphicsLibraryFramework;
-using Robust.Client.Utility;
-using Robust.Shared.Maths;
-using SixLabors.ImageSharp;
-using SixLabors.ImageSharp.PixelFormats;
-using GlfwImage = OpenToolkit.GraphicsLibraryFramework.Image;
-
-namespace Robust.Client.Graphics.Clyde
-{
-    internal sealed partial class Clyde
-    {
-        // These are actually Cursor* but we can't do that because no pointer generic arguments.
-        // Need a queue to dispose cursors since the GLFW methods aren't allowed from non-main thread (finalizers).
-        // And they also aren't re-entrant.
-        private readonly ConcurrentQueue<IntPtr> _cursorDisposeQueue = new();
-
-        private readonly Dictionary<StandardCursorShape, CursorImpl> _standardCursors =
-            new();
-
-        // Keep current active cursor around so it doesn't get garbage collected.
-        private CursorImpl? _currentCursor;
-
-        public ICursor GetStandardCursor(StandardCursorShape shape)
-        {
-            return _standardCursors[shape];
-        }
-
-        public unsafe ICursor CreateCursor(Image<Rgba32> image, Vector2i hotSpot)
-        {
-            fixed (Rgba32* pixPtr = image.GetPixelSpan())
-            {
-                var gImg = new GlfwImage(image.Width, image.Height, (byte*) pixPtr);
-                var (hotX, hotY) = hotSpot;
-                var ptr = GLFW.CreateCursor(gImg, hotX, hotY);
-
-                return new CursorImpl(this, ptr, false);
-            }
-        }
-
-        public unsafe void SetCursor(ICursor? cursor)
-        {
-            if (_currentCursor == cursor)
-            {
-                // Nothing has to be done!
-                return;
-            }
-
-            if (cursor == null)
-            {
-                _currentCursor = null;
-                GLFW.SetCursor(_glfwWindow, null);
-                return;
-            }
-
-            if (!(cursor is CursorImpl impl) || impl.Owner != this)
-            {
-                throw new ArgumentException("Cursor is not created by this clyde instance.");
-            }
-
-            if (impl.Cursor == null)
-            {
-                throw new ObjectDisposedException(nameof(cursor));
-            }
-
-            _currentCursor = impl;
-            GLFW.SetCursor(_glfwWindow, impl.Cursor);
-        }
-
-        private unsafe void FlushCursorDispose()
-        {
-            while (_cursorDisposeQueue.TryDequeue(out var cursor))
-            {
-                var ptr = (Cursor*) cursor;
-
-                if (_currentCursor != null && ptr == _currentCursor.Cursor)
-                {
-                    // Currently active cursor getting disposed.
-                    _currentCursor = null;
-                }
-
-                GLFW.DestroyCursor(ptr);
-            }
-        }
-
-        private void InitCursors()
-        {
-            unsafe void AddStandardCursor(StandardCursorShape standardShape, CursorShape shape)
-            {
-                var ptr = GLFW.CreateStandardCursor(shape);
-
-                var impl = new CursorImpl(this, ptr, true);
-
-                _standardCursors.Add(standardShape, impl);
-            }
-
-            AddStandardCursor(StandardCursorShape.Arrow, CursorShape.Arrow);
-            AddStandardCursor(StandardCursorShape.IBeam, CursorShape.IBeam);
-            AddStandardCursor(StandardCursorShape.Crosshair, CursorShape.Crosshair);
-            AddStandardCursor(StandardCursorShape.Hand, CursorShape.Hand);
-            AddStandardCursor(StandardCursorShape.HResize, CursorShape.HResize);
-            AddStandardCursor(StandardCursorShape.VResize, CursorShape.VResize);
-        }
-
-        private sealed class CursorImpl : ICursor
-        {
-            private readonly bool _standard;
-            public Clyde Owner { get; }
-            public unsafe Cursor* Cursor { get; private set; }
-
-            public unsafe CursorImpl(Clyde clyde, Cursor* pointer, bool standard)
-            {
-                _standard = standard;
-                Owner = clyde;
-                Cursor = pointer;
-            }
-
-            ~CursorImpl()
-            {
-                DisposeImpl();
-            }
-
-            private unsafe void DisposeImpl()
-            {
-                Owner._cursorDisposeQueue.Enqueue((IntPtr) Cursor);
-                Cursor = null;
-            }
-
-            public void Dispose()
-            {
-                if (_standard)
-                {
-                    throw new InvalidOperationException("Can't dispose standard cursor shape.");
-                }
-
-                GC.SuppressFinalize(this);
-                DisposeImpl();
-            }
-        }
-    }
-}

Robust.Client/Graphics/Clyde/Clyde.Events.cs

@@ -0,0 +1,172 @@
+// Makes switching easier.
+#if EXCEPTION_TOLERANCE
+#define EXCEPTION_TOLERANCE_LOCAL
+using System;
+using Robust.Shared.Log;
+#endif
+
+using System.Collections.Generic;
+using OpenToolkit.Graphics.OpenGL4;
+using Robust.Client.Input;
+using Robust.Shared.Maths;
+
+namespace Robust.Client.Graphics.Clyde
+{
+    internal sealed partial class Clyde
+    {
+        // To avoid re-entrancy bollocks we need ANOTHER queue here to actually dispatch our raw input events.
+        // Yes, on top of the two queues inside the GLFW impl.
+        // Because the GLFW-impl queue has to get flushed to avoid deadlocks on window creation
+        // which is ALSO where key events get raised from in a re-entrant fashion. Yay.
+        private readonly Queue<DEventBase> _eventDispatchQueue = new();
+
+        private void DispatchEvents()
+        {
+            while (_eventDispatchQueue.TryDequeue(out var ev))
+            {
+#if EXCEPTION_TOLERANCE_LOCAL
+                try
+#endif
+                {
+                    DispatchSingleEvent(ev);
+                }
+#if EXCEPTION_TOLERANCE_LOCAL
+                catch (Exception e)
+                {
+                    Logger.ErrorS("clyde.win", $"Error dispatching window event {ev.GetType().Name}:\n{e}");
+                }
+#endif
+            }
+        }
+
+        private void DispatchSingleEvent(DEventBase ev)
+        {
+            switch (ev)
+            {
+                case DEventKeyDown(var args):
+                    KeyDown?.Invoke(args);
+                    break;
+                case DEventKeyUp(var args):
+                    KeyUp?.Invoke(args);
+                    break;
+                case DEventMouseMove(var args):
+                    MouseMove?.Invoke(args);
+                    break;
+                case DEventMouseEnterLeave(var args):
+                    MouseEnterLeave?.Invoke(args);
+                    break;
+                case DEventScroll(var args):
+                    MouseWheel?.Invoke(args);
+                    break;
+                case DEventText(var args):
+                    TextEntered?.Invoke(args);
+                    break;
+                case DEventWindowClosed(var reg, var args):
+                    reg.Closed?.Invoke(args);
+                    CloseWindow?.Invoke(args);
+
+                    if (reg.DisposeOnClose && !reg.IsMainWindow)
+                        DoDestroyWindow(reg);
+                    break;
+                case DEventWindowContentScaleChanged(var args):
+                    OnWindowScaleChanged?.Invoke(args);
+                    break;
+                case DEventWindowFocus(var args):
+                    OnWindowFocused?.Invoke(args);
+                    break;
+                case DEventWindowResized(var args):
+                    OnWindowResized?.Invoke(args);
+                    break;
+            }
+        }
+
+        private void SendKeyUp(KeyEventArgs ev)
+        {
+            _eventDispatchQueue.Enqueue(new DEventKeyUp(ev));
+        }
+
+        private void SendKeyDown(KeyEventArgs ev)
+        {
+            _eventDispatchQueue.Enqueue(new DEventKeyDown(ev));
+        }
+
+        private void SendScroll(MouseWheelEventArgs ev)
+        {
+            _eventDispatchQueue.Enqueue(new DEventScroll(ev));
+        }
+
+        private void SendCloseWindow(WindowReg windowReg, WindowClosedEventArgs ev)
+        {
+            _eventDispatchQueue.Enqueue(new DEventWindowClosed(windowReg, ev));
+        }
+
+        private void SendWindowResized(WindowReg reg, Vector2i oldSize)
+        {
+            if (reg.IsMainWindow)
+            {
+                UpdateMainWindowLoadedRtSize();
+                GL.Viewport(0, 0, reg.FramebufferSize.X, reg.FramebufferSize.Y);
+                CheckGlError();
+            }
+            else
+            {
+                reg.RenderTexture!.Dispose();
+                CreateWindowRenderTexture(reg);
+            }
+
+            var eventArgs = new WindowResizedEventArgs(
+                oldSize,
+                reg.FramebufferSize,
+                reg.Handle);
+
+            _eventDispatchQueue.Enqueue(new DEventWindowResized(eventArgs));
+        }
+
+        private void SendWindowContentScaleChanged(WindowContentScaleEventArgs ev)
+        {
+            _eventDispatchQueue.Enqueue(new DEventWindowContentScaleChanged(ev));
+        }
+
+        private void SendWindowFocus(WindowFocusedEventArgs ev)
+        {
+            _eventDispatchQueue.Enqueue(new DEventWindowFocus(ev));
+        }
+
+        private void SendText(TextEventArgs ev)
+        {
+            _eventDispatchQueue.Enqueue(new DEventText(ev));
+        }
+
+        private void SendMouseMove(MouseMoveEventArgs ev)
+        {
+            _eventDispatchQueue.Enqueue(new DEventMouseMove(ev));
+        }
+
+        private void SendMouseEnterLeave(MouseEnterLeaveEventArgs ev)
+        {
+            _eventDispatchQueue.Enqueue(new DEventMouseEnterLeave(ev));
+        }
+
+        // D stands for Dispatch
+        private abstract record DEventBase;
+
+        private sealed record DEventKeyUp(KeyEventArgs Args) : DEventBase;
+
+        private sealed record DEventKeyDown(KeyEventArgs Args) : DEventBase;
+
+        private sealed record DEventScroll(MouseWheelEventArgs Args) : DEventBase;
+
+        private sealed record DEventWindowClosed(WindowReg Reg, WindowClosedEventArgs Args) : DEventBase;
+
+        private sealed record DEventWindowResized(WindowResizedEventArgs Args) : DEventBase;
+
+        private sealed record DEventWindowContentScaleChanged(WindowContentScaleEventArgs Args) : DEventBase;
+
+        private sealed record DEventWindowFocus(WindowFocusedEventArgs Args) : DEventBase;
+
+        private sealed record DEventText(TextEventArgs Args) : DEventBase;
+
+        private sealed record DEventMouseMove(MouseMoveEventArgs Args) : DEventBase;
+        private sealed record DEventMouseEnterLeave(MouseEnterLeaveEventArgs Args) : DEventBase;
+    }
+}

Robust.Client/Graphics/Clyde/Clyde.GLFeatures.cs

@@ -1,4 +1,4 @@
-using System.Collections.Generic;
+using System.Collections.Generic;
 using System.Diagnostics.CodeAnalysis;
 using OpenToolkit.Graphics.OpenGL4;
 using Robust.Shared.Log;
@@ -57,7 +57,7 @@ namespace Robust.Client.Graphics.Clyde
         {
             var extensions = GetGLExtensions();
 
-            Logger.DebugS("clyde.ogl", "OpenGL capabilities:");
+            _sawmillOgl.Debug("OpenGL capabilities:");
 
             if (!_isGLES)
             {
@@ -81,7 +81,7 @@ namespace Robust.Client.Graphics.Clyde
                 {
                     // We're ES <3.2, KHR_debug is extension and needs KHR suffixes.
                     _isGLKhrDebugESExtension = true;
-                    Logger.DebugS("clyde.ogl", "  khr_debug is ES extension!");
+                    _sawmillOgl.Debug("  khr_debug is ES extension!");
                 }
 
                 CheckGLCap(ref _hasGLVertexArrayObject, "vertex_array_object", (3, 0));
@@ -104,7 +104,7 @@ namespace Robust.Client.Graphics.Clyde
             // This is 3.2 or extensions
             _hasGLFloatFramebuffers = !_isGLES;
 
-            Logger.DebugS("clyde.ogl", $"  GLES: {_isGLES}");
+            _sawmillOgl.Debug($"  GLES: {_isGLES}");
 
             void CheckGLCap(ref bool cap, string capName, (int major, int minor)? versionMin = null,
                 params string[] exts)
@@ -115,15 +115,15 @@ namespace Robust.Client.Graphics.Clyde
 
                 var prev = cap;
                 var cVarName = $"display.ogl_block_{capName}";
-                var block = _configurationManager.GetCVar<bool>(cVarName);
+                var block = _cfg.GetCVar<bool>(cVarName);
 
                 if (block)
                 {
                     cap = false;
-                    Logger.DebugS("clyde.ogl", $"  {cVarName} SET, BLOCKING {capName} (was: {prev})");
+                    _sawmillOgl.Debug($"  {cVarName} SET, BLOCKING {capName} (was: {prev})");
                 }
 
-                Logger.DebugS("clyde.ogl", $"  {capName}: {cap}");
+                _sawmillOgl.Debug($"  {capName}: {cap}");
             }
         }
 
@@ -146,7 +146,7 @@ namespace Robust.Client.Graphics.Clyde
 
             foreach (var cvar in cvars)
             {
-                _configurationManager.RegisterCVar($"display.ogl_block_{cvar}", false);
+                _cfg.RegisterCVar($"display.ogl_block_{cvar}", false);
             }
         }
 
@@ -168,14 +168,14 @@ namespace Robust.Client.Graphics.Clyde
                     extensionsText += extension;
                     extensions.Add(extension);
                 }
-                Logger.DebugS("clyde.ogl", "OpenGL Extensions: {0}", extensionsText);
+                _sawmillOgl.Debug("OpenGL Extensions: {0}", extensionsText);
                 return extensions;
             }
             else
             {
                 // GLES uses the (old?) API
                 var extensions = GL.GetString(StringName.Extensions);
-                Logger.DebugS("clyde.ogl", "OpenGL Extensions: {0}", extensions);
+                _sawmillOgl.Debug("OpenGL Extensions: {0}", extensions);
                 return new HashSet<string>(extensions.Split(' '));
             }
         }

Robust.Client/Graphics/Clyde/Clyde.GridRendering.cs

@@ -208,12 +208,12 @@ namespace Robust.Client.Graphics.Clyde
             _setChunkDirty(grid, chunk);
         }
 
-        private void _updateOnGridCreated(GridId gridId)
+        private void _updateOnGridCreated(MapId mapId, GridId gridId)
         {
             _mapChunkData.Add(gridId, new Dictionary<Vector2i, MapChunkData>());
         }
 
-        private void _updateOnGridRemoved(GridId gridId)
+        private void _updateOnGridRemoved(MapId mapId, GridId gridId)
         {
             var data = _mapChunkData[gridId];
             foreach (var chunkDatum in data.Values)

Robust.Client/Graphics/Clyde/Clyde.HLR.cs

@@ -8,6 +8,7 @@ using Robust.Shared.Map;
 using Robust.Shared.Maths;
 using Robust.Shared.Utility;
 using OpenToolkit.Graphics.OpenGL4;
+using Robust.Client.UserInterface.CustomControls;
 using Robust.Shared.Enums;
 
 namespace Robust.Client.Graphics.Clyde
@@ -24,18 +25,28 @@ namespace Robust.Client.Graphics.Clyde
                 =
                 new();
 
-        public void Render()
+        public unsafe void Render()
         {
             CheckTransferringScreenshots();
 
+            var allMinimized = true;
+            foreach (var windowReg in _windowing!.AllWindows)
+            {
+                if (!windowReg.IsMinimized)
+                {
+                    allMinimized = false;
+                    break;
+                }
+            }
+
             var size = ScreenSize;
-            if (size.X == 0 || size.Y == 0 || _isMinimized)
+            if (size.X == 0 || size.Y == 0 || allMinimized)
             {
                 ClearFramebuffer(Color.Black);
 
                 // We have to keep running swapbuffers here
                 // or else the user's PC will turn into a heater!!
-                SwapBuffers();
+                SwapMainBuffers();
                 return;
             }
 
@@ -51,7 +62,7 @@ namespace Robust.Client.Graphics.Clyde
             ClearFramebuffer(Color.Black);
 
             // Update shared UBOs.
-            _updateUniformConstants(_framebufferSize);
+            _updateUniformConstants(_windowing.MainWindow!.FramebufferSize);
 
             {
                 CalcScreenMatrices(ScreenSize, out var proj, out var view);
@@ -63,103 +74,133 @@ namespace Robust.Client.Graphics.Clyde
             {
                 DrawSplash(_renderHandle);
                 FlushRenderQueue();
-                SwapBuffers();
+                SwapMainBuffers();
                 return;
             }
 
-            RenderOverlays(OverlaySpace.ScreenSpaceBelowWorld);
-
-            _mainViewport.Eye = _eyeManager.CurrentEye;
-            RenderViewport(_mainViewport); //Worldspace overlays are rendered here.
+            foreach (var weak in _viewports.Values)
             {
-                var handle = _renderHandle.DrawingHandleScreen;
-                var tex = _mainViewport.RenderTarget.Texture;
-
-                handle.DrawTexture(tex, (0, 0));
-                FlushRenderQueue();
+                if (weak.TryGetTarget(out var viewport) && viewport.AutomaticRender)
+                    RenderViewport(viewport);
             }
 
-            TakeScreenshot(ScreenshotType.BeforeUI);
-
-            RenderOverlays(OverlaySpace.ScreenSpace);
-
             using (DebugGroup("UI"))
             {
                 _userInterfaceManager.Render(_renderHandle);
                 FlushRenderQueue();
             }
 
-            TakeScreenshot(ScreenshotType.AfterUI);
+            TakeScreenshot(ScreenshotType.Final);
+
+            BlitSecondaryWindows();
 
             // And finally, swap those buffers!
-            SwapBuffers();
+            SwapMainBuffers();
         }
 
-        private void RenderOverlays(OverlaySpace space)
+        private void RenderOverlays(Viewport vp, OverlaySpace space, in Box2 worldBox)
         {
             using (DebugGroup($"Overlays: {space}"))
             {
-                var list = new List<Overlay>();
-
-                foreach (var overlay in _overlayManager.AllOverlays)
+                var list = GetOverlaysForSpace(space);
+                foreach (var overlay in list)
                 {
-                    if ((overlay.Space & space) != 0)
+                    if (overlay.RequestScreenTexture)
                     {
-                        list.Add(overlay);
-                    }
-                }
-                FlushRenderQueue();
-                list.Sort(OverlayComparer.Instance);
-                foreach (var overlay in list) {
-                    if (overlay.RequestScreenTexture) {
                         FlushRenderQueue();
-                        UpdateOverlayScreenTexture(space, _mainViewport.RenderTarget);
+                        UpdateOverlayScreenTexture(space, vp.RenderTarget);
                     }
-                    if (overlay.OverwriteTargetFrameBuffer()) {
+
+                    if (overlay.OverwriteTargetFrameBuffer())
+                    {
                         ClearFramebuffer(default);
                     }
-                    overlay.ClydeRender(_renderHandle, space);
-                    FlushRenderQueue();
+
+                    overlay.ClydeRender(_renderHandle, space, null, vp, new UIBox2i((0, 0), vp.Size), worldBox);
                 }
             }
         }
 
+        private void RenderOverlaysDirect(
+            Viewport vp,
+            IViewportControl vpControl,
+            DrawingHandleBase handle,
+            OverlaySpace space,
+            in UIBox2i bounds)
+        {
+            var list = GetOverlaysForSpace(space);
+
+            var worldBounds = CalcWorldBounds(vp);
+            var args = new OverlayDrawArgs(space, vpControl, vp, handle, bounds, worldBounds);
+
+            foreach (var overlay in list)
+            {
+                overlay.Draw(args);
+            }
+        }
+
+        private List<Overlay> GetOverlaysForSpace(OverlaySpace space)
+        {
+            var list = new List<Overlay>();
+
+            foreach (var overlay in _overlayManager.AllOverlays)
+            {
+                if ((overlay.Space & space) != 0)
+                {
+                    list.Add(overlay);
+                }
+            }
+
+            list.Sort(OverlayComparer.Instance);
+
+            return list;
+        }
+
         private ClydeTexture? ScreenBufferTexture;
         private GLHandle screenBufferHandle;
         private Vector2 lastFrameSize;
+
         /// <summary>
         ///    Sends SCREEN_TEXTURE to all overlays in the given OverlaySpace that request it.
         /// </summary>
-        private bool UpdateOverlayScreenTexture(OverlaySpace space, RenderTexture texture) {
+        private bool UpdateOverlayScreenTexture(OverlaySpace space, RenderTexture texture)
+        {
             //This currently does NOT consider viewports and just grabs the current screen framebuffer. This will need to be improved upon in the future.
             List<Overlay> oTargets = new List<Overlay>();
-            foreach (var overlay in _overlayManager.AllOverlays) {
-                if (overlay.RequestScreenTexture && overlay.Space == space) {
+            foreach (var overlay in _overlayManager.AllOverlays)
+            {
+                if (overlay.RequestScreenTexture && overlay.Space == space)
+                {
                     oTargets.Add(overlay);
                 }
             }
-            if (oTargets.Count > 0 && ScreenBufferTexture != null) {
-                if (lastFrameSize != _framebufferSize) { 
+
+            if (oTargets.Count > 0 && ScreenBufferTexture != null)
+            {
+                if (lastFrameSize != texture.Size)
+                {
                     GL.BindTexture(TextureTarget.Texture2D, screenBufferHandle.Handle);
-                    GL.TexImage2D(TextureTarget.Texture2D, 0, PixelInternalFormat.Srgb8Alpha8, _framebufferSize.X, _framebufferSize.Y, 0,
+                    GL.TexImage2D(TextureTarget.Texture2D, 0,
+                        _hasGLSrgb ? PixelInternalFormat.Srgb8Alpha8 : PixelInternalFormat.Rgba8, texture.Size.X,
+                        texture.Size.Y, 0,
                         PixelFormat.Rgba, PixelType.UnsignedByte, IntPtr.Zero);
                 }
-                lastFrameSize = _framebufferSize;
+
+                lastFrameSize = texture.Size;
                 CopyRenderTextureToTexture(texture, ScreenBufferTexture);
-                foreach (Overlay overlay in oTargets) {
+                foreach (Overlay overlay in oTargets)
+                {
                     overlay.ScreenTexture = ScreenBufferTexture;
                 }
+
                 oTargets.Clear();
                 return true;
             }
+
             return false;
         }
 
 
-
-
-
-
         private void DrawEntities(Viewport viewport, Box2 worldBounds)
         {
             if (_eyeManager.CurrentMap == MapId.Nullspace || !_mapManager.HasMapEntity(_eyeManager.CurrentMap))
@@ -167,7 +208,7 @@ namespace Robust.Client.Graphics.Clyde
                 return;
             }
 
-            RenderOverlays(OverlaySpace.WorldSpaceBelowEntities);
+            RenderOverlays(viewport, OverlaySpace.WorldSpaceBelowEntities, worldBounds);
 
             var screenSize = viewport.Size;
 
@@ -218,7 +259,13 @@ namespace Robust.Client.Graphics.Clyde
                             flushed = true;
                         }
 
-                        overlay.ClydeRender(_renderHandle, OverlaySpace.WorldSpace);
+                        overlay.ClydeRender(
+                            _renderHandle,
+                            OverlaySpace.WorldSpace,
+                            null,
+                            viewport,
+                            new UIBox2i((0, 0), viewport.Size),
+                            worldBounds);
                         overlayIndex = j;
                         continue;
                     }
@@ -237,13 +284,13 @@ namespace Robust.Client.Graphics.Clyde
                     var spriteRT = spriteBB.TopRight;
 
                     // finally we can calculate screen bounding in pixels
-                    var screenLB = _eyeManager.WorldToScreen(spriteLB);
-                    var screenRT = _eyeManager.WorldToScreen(spriteRT);
+                    var screenLB = viewport.WorldToLocal(spriteLB);
+                    var screenRT = viewport.WorldToLocal(spriteRT);
 
                     // we need to scale RT a for effects like emission or highlight
                     // scale can be passed with PostShader as variable in future
                     var postShadeScale = 1.25f;
-                    var screenSpriteSize = (Vector2i)((screenRT - screenLB) * postShadeScale).Rounded();
+                    var screenSpriteSize = (Vector2i) ((screenRT - screenLB) * postShadeScale).Rounded();
                     screenSpriteSize.Y = -screenSpriteSize.Y;
 
                     // I'm not 100% sure why it works, but without it post-shader
@@ -268,8 +315,8 @@ namespace Robust.Client.Graphics.Clyde
                         // which is necessary for light application,
                         // but it's ACTUALLY drawing into the center of the render target.
                         var spritePos = spriteBB.Center;
-                        var screenPos = _eyeManager.WorldToScreen(spritePos);
-                        var (roundedX, roundedY) = roundedPos = (Vector2i)screenPos;
+                        var screenPos = viewport.WorldToLocal(spritePos);
+                        var (roundedX, roundedY) = roundedPos = (Vector2i) screenPos;
                         var flippedPos = new Vector2i(roundedX, screenSize.Y - roundedY);
                         flippedPos -= entityPostRenderTarget.Size / 2;
                         _renderHandle.Viewport(Box2i.FromDimensions(-flippedPos, screenSize));
@@ -303,6 +350,9 @@ namespace Robust.Client.Graphics.Clyde
 
                     _renderHandle.SetProjView(oldProj, oldView);
                     _renderHandle.UseShader(null);
+
+                    // TODO: cache this properly across frames.
+                    entityPostRenderTarget.DisposeDeferred();
                 }
             }
 
@@ -318,29 +368,44 @@ namespace Robust.Client.Graphics.Clyde
         {
             var spriteSystem = _entitySystemManager.GetEntitySystem<RenderingTreeSystem>();
 
-            var tree = spriteSystem.GetSpriteTreeForMap(map);
-
-            tree.QueryAabb(ref list, ((
-                ref RefList<(SpriteComponent sprite, Matrix3 matrix, Angle worldRot, float yWorldPos)> state,
-                in SpriteComponent value) =>
+            foreach (var gridId in _mapManager.FindGridIdsIntersecting(map, worldBounds, true))
             {
-                if (value.ContainerOccluded || !value.Visible)
+                Box2 gridBounds;
+
+                if (gridId == GridId.Invalid)
                 {
-                    return true;
+                    gridBounds = worldBounds;
+                }
+                else
+                {
+                    gridBounds = worldBounds.Translated(-_mapManager.GetGrid(gridId).WorldPosition);
                 }
 
-                var entity = value.Owner;
-                var transform = entity.Transform;
+                var tree = spriteSystem.GetSpriteTreeForMap(map, gridId);
 
-                ref var entry = ref state.AllocAdd();
-                entry.sprite = value;
-                entry.worldRot = transform.WorldRotation;
-                entry.matrix = transform.WorldMatrix;
-                var worldPos = entry.matrix.Transform(transform.LocalPosition);
-                entry.yWorldPos = worldPos.Y;
-                return true;
+                tree.QueryAabb(ref list, ((
+                    ref RefList<(SpriteComponent sprite, Matrix3 matrix, Angle worldRot, float yWorldPos)> state,
+                    in SpriteComponent value) =>
+                {
+                    // TODO: Probably value in storing this as its own DynamicTree
+                    if (value.ContainerOccluded || !value.Visible)
+                    {
+                        return true;
+                    }
 
-            }), worldBounds, approx: true);
+                    var entity = value.Owner;
+                    var transform = entity.Transform;
+
+                    ref var entry = ref state.AllocAdd();
+                    entry.sprite = value;
+                    entry.worldRot = transform.WorldRotation;
+                    entry.matrix = transform.WorldMatrix;
+                    var worldPos = entry.matrix.Transform(transform.LocalPosition);
+                    entry.yWorldPos = worldPos.Y;
+                    return true;
+
+                }), gridBounds, approx: true);
+            }
         }
 
         private void DrawSplash(IRenderHandle handle)
@@ -350,13 +415,8 @@ namespace Robust.Client.Graphics.Clyde
             handle.DrawingHandleScreen.DrawTexture(texture, (ScreenSize - texture.Size) / 2);
         }
 
-        private void RenderViewport(Viewport viewport)
+        private void RenderInRenderTarget(RenderTargetBase rt, Action a)
         {
-            if (viewport.Eye == null)
-            {
-                return;
-            }
-
             // TODO: for the love of god all this state pushing/popping needs to be cleaned up.
 
             var oldTransform = _currentMatrixModel;
@@ -365,28 +425,54 @@ namespace Robust.Client.Graphics.Clyde
             // Have to flush the render queue so that all commands finish rendering to the previous framebuffer.
             FlushRenderQueue();
 
-            var eye = viewport.Eye;
-
-            var oldVp = _currentViewport;
-            _currentViewport = viewport;
-
             var state = PushRenderStateFull();
 
             {
-                // Actual code that isn't just pushing/popping renderer state so we can return safely.
-
-                var rt = _currentViewport.RenderTarget;
                 BindRenderTargetFull(RtToLoaded(rt));
                 ClearFramebuffer(default);
                 SetViewportImmediate(Box2i.FromDimensions(Vector2i.Zero, rt.Size));
-                _updateUniformConstants(viewport.Size);
+                _updateUniformConstants(rt.Size);
+                CalcScreenMatrices(rt.Size, out var proj, out var view);
+                SetProjViewFull(proj, view);
 
-                CalcWorldMatrices(rt.Size, eye, out var proj, out var view);
+                // Smugleaf moment
+                a();
+
+                FlushRenderQueue();
+            }
+
+            FenceRenderTarget(rt);
+
+            PopRenderStateFull(state);
+            _updateUniformConstants(_currentRenderTarget.Size);
+
+            SetScissorFull(oldScissor);
+            _currentMatrixModel = oldTransform;
+        }
+
+        private void RenderViewport(Viewport viewport)
+        {
+            if (viewport.Eye == null || viewport.Eye.Position.MapId == MapId.Nullspace)
+            {
+                return;
+            }
+
+            RenderInRenderTarget(viewport.RenderTarget, () =>
+            {
+                using var _ = DebugGroup($"Viewport: {viewport.Name}");
+
+                var oldVp = _currentViewport;
+
+                _currentViewport = viewport;
+                var eye = viewport.Eye;
+
+                // Actual code that isn't just pushing/popping renderer state so we can return safely.
+
+                CalcWorldMatrices(viewport.RenderTarget.Size, viewport.RenderScale, eye, out var proj, out var view);
                 SetProjViewFull(proj, view);
 
                 // Calculate world-space AABB for camera, to cull off-screen things.
-                var worldBounds = Box2.CenteredAround(eye.Position.Position,
-                    _framebufferSize / (float) EyeManager.PixelsPerMeter * eye.Zoom);
+                var worldBounds = CalcWorldBounds(viewport);
 
                 if (_eyeManager.CurrentMap != MapId.Nullspace)
                 {
@@ -395,6 +481,9 @@ namespace Robust.Client.Graphics.Clyde
                         DrawLightsAndFov(viewport, worldBounds, eye);
                     }
 
+                    RenderOverlays(viewport, OverlaySpace.WorldSpaceBelowWorld, worldBounds);
+                    FlushRenderQueue();
+
                     using (DebugGroup("Grids"))
                     {
                         _drawGrids(worldBounds);
@@ -406,18 +495,11 @@ namespace Robust.Client.Graphics.Clyde
                         DrawEntities(viewport, worldBounds);
                     }
 
-                    RenderOverlays(OverlaySpace.WorldSpaceBelowFOV);
+                    RenderOverlays(viewport, OverlaySpace.WorldSpaceBelowFOV, worldBounds);
 
                     if (_lightManager.Enabled && _lightManager.DrawHardFov && eye.DrawFov)
                     {
-                        GL.Clear(ClearBufferMask.StencilBufferBit);
-                        GL.Enable(EnableCap.StencilTest);
-                        GL.StencilOp(OpenToolkit.Graphics.OpenGL4.StencilOp.Keep, OpenToolkit.Graphics.OpenGL4.StencilOp.Keep, OpenToolkit.Graphics.OpenGL4.StencilOp.Replace);
-                        GL.StencilFunc(StencilFunction.Always, 1, 0xFF);
-                        GL.StencilMask(0xFF);
                         ApplyFovToBuffer(viewport, eye);
-                        GL.StencilMask(0x00);
-                        GL.Disable(EnableCap.StencilTest);
                     }
                 }
 
@@ -433,7 +515,7 @@ namespace Robust.Client.Graphics.Clyde
                     // So there are distortions from incorrect projection.
                     _renderHandle.UseShader(_fovDebugShaderInstance);
                     _renderHandle.DrawingHandleScreen.SetTransform(Matrix3.Identity);
-                    var pos = UIBox2.FromDimensions(ScreenSize / 2 - (200, 200), (400, 400));
+                    var pos = UIBox2.FromDimensions(viewport.Size / 2 - (200, 200), (400, 400));
                     _renderHandle.DrawingHandleScreen.DrawTextureRect(FovTexture, pos);
                 }
 
@@ -443,24 +525,25 @@ namespace Robust.Client.Graphics.Clyde
                     _renderHandle.DrawingHandleScreen.SetTransform(Matrix3.Identity);
                     _renderHandle.DrawingHandleScreen.DrawTextureRect(
                         viewport.WallBleedIntermediateRenderTarget2.Texture,
-                        UIBox2.FromDimensions(Vector2.Zero, ScreenSize), new Color(1, 1, 1, 0.5f));
+                        UIBox2.FromDimensions(Vector2.Zero, viewport.Size), new Color(1, 1, 1, 0.5f));
                 }
 
+                RenderOverlays(viewport, OverlaySpace.WorldSpace, worldBounds);
+                FlushRenderQueue();
 
-                RenderOverlays(OverlaySpace.WorldSpace);
+                _currentViewport = oldVp;
+            });
+        }
 
-                GL.StencilFunc(StencilFunction.Notequal, 1, 0xFF);
-                GL.Disable(EnableCap.DepthTest);
-                RenderOverlays(OverlaySpace.WorldSpaceFOVStencil);
-                GL.Disable(EnableCap.StencilTest);
-            }
+        private static Box2 CalcWorldBounds(Viewport viewport)
+        {
+            var eye = viewport.Eye;
+            if (eye == null)
+                return default;
 
-            PopRenderStateFull(state);
-            _updateUniformConstants(oldVp?.Size ?? _framebufferSize);
-
-            SetScissorFull(oldScissor);
-            _currentMatrixModel = oldTransform;
-            _currentViewport = oldVp;
+            // TODO: This seems completely unfit by lacking things like rotation handling.
+            return Box2.CenteredAround(eye.Position.Position,
+                viewport.Size / viewport.RenderScale / EyeManager.PixelsPerMeter * eye.Zoom);
         }
 
         private sealed class OverlayComparer : IComparer<Overlay>

Robust.Client/Graphics/Clyde/Clyde.Helpers.cs

@@ -47,7 +47,7 @@ namespace Robust.Client.Graphics.Clyde
 
             GL.BindTexture(TextureTarget.Texture2D, _loadedTextures[target.TextureId].OpenGLObject.Handle);
             CheckGlError();
-            GL.CopyTexSubImage2D(TextureTarget.Texture2D, 0, 0, 0, 0, 0, _framebufferSize.X, _framebufferSize.Y);
+            GL.CopyTexSubImage2D(TextureTarget.Texture2D, 0, 0, 0, 0, 0, source.Size.X, source.Size.Y);
             CheckGlError();
 
             if (pause && store != null) {
@@ -160,12 +160,12 @@ namespace Robust.Client.Graphics.Clyde
         }
 
         [MethodImpl(MethodImplOptions.NoInlining)]
-        private static void CheckGlErrorInternal(string? path, int line)
+        private void CheckGlErrorInternal(string? path, int line)
         {
             var err = GL.GetError();
             if (err != ErrorCode.NoError)
             {
-                Logger.ErrorS("clyde.ogl", $"OpenGL error: {err} at {path}:{line}\n{Environment.StackTrace}");
+                _sawmillOgl.Error($"OpenGL error: {err} at {path}:{line}\n{Environment.StackTrace}");
             }
         }
 
@@ -276,7 +276,7 @@ namespace Robust.Client.Graphics.Clyde
 
         private void LoadGLProc<T>(string name, out T field) where T : Delegate
         {
-            var proc = _graphicsContext.GetProcAddress(name);
+            var proc = _windowing!.GraphicsBindingContext.GetProcAddress(name);
             if (proc == IntPtr.Zero || proc == new IntPtr(1) || proc == new IntPtr(2))
             {
                 throw new InvalidOperationException($"Unable to load GL function '{name}'!");

Robust.Client/Graphics/Clyde/Clyde.LightRendering.cs

@@ -10,6 +10,7 @@ using Robust.Shared.Map;
 using Robust.Shared.Maths;
 using static Robust.Client.GameObjects.ClientOccluderComponent;
 using OGLTextureWrapMode = OpenToolkit.Graphics.OpenGL.TextureWrapMode;
+using TKStencilOp = OpenToolkit.Graphics.OpenGL4.StencilOp;
 
 namespace Robust.Client.Graphics.Clyde
 {
@@ -195,7 +196,6 @@ namespace Robust.Client.Graphics.Clyde
                 }
             }
 
-
             _lightSoftShaderHandle = LoadShaderHandle("/Shaders/Internal/light-soft.swsl");
             _lightHardShaderHandle = LoadShaderHandle("/Shaders/Internal/light-hard.swsl");
             _fovShaderHandle = LoadShaderHandle("/Shaders/Internal/fov.swsl");
@@ -361,16 +361,23 @@ namespace Robust.Client.Graphics.Clyde
                 FinalizeDepthDraw();
             }
 
-            BindRenderTargetImmediate(RtToLoaded(viewport.LightRenderTarget));
-            CheckGlError();
-            GLClearColor(_lightManager.AmbientLightColor);
-            GL.Clear(ClearBufferMask.ColorBufferBit);
-            CheckGlError();
+            GL.Enable(EnableCap.StencilTest);
+            _isStencilling = true;
 
             var (lightW, lightH) = GetLightMapSize(viewport.Size);
             GL.Viewport(0, 0, lightW, lightH);
             CheckGlError();
 
+            BindRenderTargetImmediate(RtToLoaded(viewport.LightRenderTarget));
+            CheckGlError();
+            GLClearColor(_lightManager.AmbientLightColor);
+            GL.ClearStencil(0xFF);
+            GL.StencilMask(0xFF);
+            GL.Clear(ClearBufferMask.ColorBufferBit | ClearBufferMask.StencilBufferBit);
+            CheckGlError();
+
+            ApplyLightingFovToBuffer(viewport, eye);
+
             var lightShader = _loadedShaders[_enableSoftShadows ? _lightSoftShaderHandle : _lightHardShaderHandle].Program;
             lightShader.Use();
 
@@ -382,6 +389,11 @@ namespace Robust.Client.Graphics.Clyde
             GL.BlendFunc(BlendingFactor.SrcAlpha, BlendingFactor.One);
             CheckGlError();
 
+            GL.StencilFunc(StencilFunction.Equal, 0xFF, 0xFF);
+            CheckGlError();
+            GL.StencilOp(TKStencilOp.Keep, TKStencilOp.Keep, TKStencilOp.Keep);
+            CheckGlError();
+
             var lastRange = float.NaN;
             var lastPower = float.NaN;
             var lastColor = new Color(float.NaN, float.NaN, float.NaN, float.NaN);
@@ -463,11 +475,11 @@ namespace Robust.Client.Graphics.Clyde
             }
 
             ResetBlendFunc();
+            GL.Disable(EnableCap.StencilTest);
+            _isStencilling = false;
 
             CheckGlError();
 
-            ApplyLightingFovToBuffer(viewport, eye);
-
             BlurOntoWalls(viewport, eye);
 
             MergeWallLayer(viewport);
@@ -485,40 +497,55 @@ namespace Robust.Client.Graphics.Clyde
             GetLightsToRender(MapId map, in Box2 worldBounds)
         {
             var renderingTreeSystem = _entitySystemManager.GetEntitySystem<RenderingTreeSystem>();
-            var lightTree = renderingTreeSystem.GetLightTreeForMap(map);
-
             var state = (this, worldBounds, count: 0);
 
-            lightTree.QueryAabb(ref state, (ref (Clyde clyde, Box2 worldBounds, int count) state, in PointLightComponent light) =>
+            foreach (var gridId in _mapManager.FindGridIdsIntersecting(map, worldBounds, true))
             {
-                var transform = light.Owner.Transform;
+                Box2 gridBounds;
 
-                if (state.count >= LightsToRenderListSize)
+                if (gridId == GridId.Invalid)
                 {
-                    // There are too many lights to fit in the static memory.
-                    return false;
+                    gridBounds = worldBounds;
+                }
+                else
+                {
+                    gridBounds = worldBounds.Translated(-_mapManager.GetGrid(gridId).WorldPosition);
                 }
 
-                if (!light.Enabled || light.ContainerOccluded)
+                var lightTree = renderingTreeSystem.GetLightTreeForMap(map, gridId);
+
+                lightTree.QueryAabb(ref state, (ref (Clyde clyde, Box2 worldBounds, int count) state, in PointLightComponent light) =>
                 {
+                    var transform = light.Owner.Transform;
+
+                    if (state.count >= LightsToRenderListSize)
+                    {
+                        // There are too many lights to fit in the static memory.
+                        return false;
+                    }
+
+                    // TODO: Don't insert into trees for these, same as sprites.
+                    if (!light.Enabled || light.ContainerOccluded)
+                    {
+                        return true;
+                    }
+
+                    var lightPos = transform.WorldMatrix.Transform(light.Offset);
+
+                    var circle = new Circle(lightPos, light.Radius);
+
+                    // If the light doesn't touch anywhere the camera can see, it doesn't matter.
+                    if (!circle.Intersects(state.worldBounds))
+                    {
+                        return true;
+                    }
+
+                    float distanceSquared = (state.worldBounds.Center - lightPos).LengthSquared;
+                    state.clyde._lightsToRenderList[state.count++] = (light, lightPos, distanceSquared);
+
                     return true;
-                }
-
-                var lightPos = transform.WorldMatrix.Transform(light.Offset);
-
-                var circle = new Circle(lightPos, light.Radius);
-
-                // If the light doesn't touch anywhere the camera can see, it doesn't matter.
-                if (!circle.Intersects(state.worldBounds))
-                {
-                    return true;
-                }
-
-                float distanceSquared = (state.worldBounds.Center - lightPos).LengthSquared;
-                state.clyde._lightsToRenderList[state.count++] = (light, lightPos, distanceSquared);
-
-                return true;
-            }, worldBounds);
+                }, gridBounds);
+            }
 
             if (state.count > _maxLightsPerScene)
             {
@@ -577,7 +604,7 @@ namespace Robust.Client.Graphics.Clyde
 
             // Have to scale the blurring radius based on viewport size and camera zoom.
             const float refCameraHeight = 14;
-            var cameraSize = eye.Zoom.Y * viewport.Size.Y / EyeManager.PixelsPerMeter;
+            var cameraSize = eye.Zoom.Y * viewport.Size.Y * (1 / viewport.RenderScale.Y) / EyeManager.PixelsPerMeter;
             // 7e-3f is just a magic factor that makes it look ok.
             var factor = 7e-3f * (refCameraHeight / cameraSize);
 
@@ -645,6 +672,12 @@ namespace Robust.Client.Graphics.Clyde
 
         private void ApplyFovToBuffer(Viewport viewport, IEye eye)
         {
+            GL.Clear(ClearBufferMask.StencilBufferBit);
+            GL.Enable(EnableCap.StencilTest);
+            GL.StencilOp(OpenToolkit.Graphics.OpenGL4.StencilOp.Keep, OpenToolkit.Graphics.OpenGL4.StencilOp.Keep, OpenToolkit.Graphics.OpenGL4.StencilOp.Replace);
+            GL.StencilFunc(StencilFunction.Always, 1, 0xFF);
+            GL.StencilMask(0xFF);
+
             // Applies FOV to the final framebuffer.
 
             var fovShader = _loadedShaders[_fovShaderHandle].Program;
@@ -658,6 +691,10 @@ namespace Robust.Client.Graphics.Clyde
             fovShader.SetUniformMaybe("center", eye.Position.Position);
 
             DrawBlit(viewport, fovShader);
+
+            GL.StencilMask(0x00);
+            GL.Disable(EnableCap.StencilTest);
+            _isStencilling = false;
         }
 
         private void ApplyLightingFovToBuffer(Viewport viewport, IEye eye)
@@ -690,6 +727,13 @@ namespace Robust.Client.Graphics.Clyde
             fovShader.SetUniformTextureMaybe(UniIMainTexture, TextureUnit.Texture0);
             fovShader.SetUniformMaybe("center", eye.Position.Position);
 
+            GL.StencilMask(0xFF);
+            CheckGlError();
+            GL.StencilFunc(StencilFunction.Always, 0, 0);
+            CheckGlError();
+            GL.StencilOp(TKStencilOp.Keep, TKStencilOp.Keep, TKStencilOp.Replace);
+            CheckGlError();
+
             DrawBlit(viewport, fovShader);
 
             if (_hasGLSamplerObjects)
@@ -939,7 +983,8 @@ namespace Robust.Client.Graphics.Clyde
             viewport.WallMaskRenderTarget = CreateRenderTarget(viewport.Size, RenderTargetColorFormat.R8,
                 name: $"{viewport.Name}-{nameof(viewport.WallMaskRenderTarget)}");
 
-            viewport.LightRenderTarget = CreateRenderTarget(lightMapSize, lightMapColorFormat,
+            viewport.LightRenderTarget = CreateRenderTarget(lightMapSize,
+                new RenderTargetFormatParameters(lightMapColorFormat, hasDepthStencil: true),
                 lightMapSampleParameters,
                 $"{viewport.Name}-{nameof(viewport.LightRenderTarget)}");
 
@@ -977,13 +1022,13 @@ namespace Robust.Client.Graphics.Clyde
             return (w, h);
         }
 
-        protected override void LightmapDividerChanged(int newValue)
+        private void LightmapDividerChanged(int newValue)
         {
             _lightmapDivider = newValue;
             RegenAllLightRts();
         }
 
-        protected override void MaxLightsPerSceneChanged(int newValue)
+        private void MaxLightsPerSceneChanged(int newValue)
         {
             _maxLightsPerScene = newValue;
 
@@ -1002,7 +1047,7 @@ namespace Robust.Client.Graphics.Clyde
                 nameof(_shadowRenderTarget));
         }
 
-        protected override void SoftShadowsChanged(bool newValue)
+        private void SoftShadowsChanged(bool newValue)
         {
             _enableSoftShadows = newValue;
         }

Robust.Client/Graphics/Clyde/Clyde.RenderHandle.cs

@@ -112,6 +112,11 @@ namespace Robust.Client.Graphics.Clyde
                 return clydeTexture;
             }
 
+            public void RenderInRenderTarget(IRenderTarget target, Action a)
+            {
+                _clyde.RenderInRenderTarget((RenderTargetBase) target, a);
+            }
+
             public void SetScissor(UIBox2i? scissorBox)
             {
                 _clyde.DrawSetScissor(scissorBox);

Robust.Client/Graphics/Clyde/Clyde.RenderTargets.cs

@@ -6,6 +6,7 @@ using OpenToolkit.Graphics.OpenGL4;
 using Robust.Shared.Maths;
 using Robust.Shared.Utility;
 using Robust.Shared.Log;
+using SixLabors.ImageSharp.PixelFormats;
 
 // ReSharper disable once IdentifierTypo
 using RTCF = Robust.Client.Graphics.RenderTargetColorFormat;
@@ -23,9 +24,8 @@ namespace Robust.Client.Graphics.Clyde
         private readonly ConcurrentQueue<ClydeHandle> _renderTargetDisposeQueue
             = new();
 
-        IRenderWindow IClyde.MainWindowRenderTarget => _mainWindowRenderTarget;
         // Initialized in Clyde's constructor
-        private readonly RenderWindow _mainWindowRenderTarget;
+        private readonly RenderMainWindow _mainMainWindowRenderMainTarget;
 
         // This is always kept up-to-date, except in CreateRenderTarget (because it restores the old value)
         // It is used for SRGB emulation.
@@ -97,7 +97,7 @@ namespace Robust.Client.Graphics.Clyde
                         case RTCF.RG32F:
                         case RTCF.R11FG11FB10F:
                         case RTCF.Rgba16F:
-                            Logger.WarningS("clyde.ogl", "The framebuffer {0} [{1}] is trying to be floating-point when that's not supported. Forcing Rgba8.", name == null ? "[unnamed]" : name, size);
+                            _sawmillOgl.Warning("The framebuffer {0} [{1}] is trying to be floating-point when that's not supported. Forcing Rgba8.", name == null ? "[unnamed]" : name, size);
                             colorFormat = RTCF.Rgba8;
                             break;
                     }
@@ -191,7 +191,8 @@ namespace Robust.Client.Graphics.Clyde
                 FramebufferHandle = fbo,
                 Size = size,
                 TextureHandle = textureObject.TextureId,
-                MemoryPressure = pressure
+                MemoryPressure = pressure,
+                ColorFormat = format.ColorFormat
             };
 
             //GC.AddMemoryPressure(pressure);
@@ -266,10 +267,10 @@ namespace Robust.Client.Graphics.Clyde
             }
         }
 
-        private void UpdateWindowLoadedRtSize()
+        private void UpdateMainWindowLoadedRtSize()
         {
-            var loadedRt = RtToLoaded(_mainWindowRenderTarget);
-            loadedRt.Size = _framebufferSize;
+            var loadedRt = RtToLoaded(_mainMainWindowRenderMainTarget);
+            loadedRt.Size = _windowing!.MainWindow!.FramebufferSize;
         }
 
         private sealed class LoadedRenderTarget
@@ -278,6 +279,8 @@ namespace Robust.Client.Graphics.Clyde
             public Vector2i Size;
             public bool IsSrgb;
 
+            public RTCF ColorFormat;
+
             // Remaining properties only apply if the render target is NOT a window.
             // Handle to the framebuffer object.
             public GLHandle FramebufferHandle;
@@ -295,6 +298,9 @@ namespace Robust.Client.Graphics.Clyde
             protected readonly Clyde Clyde;
             private bool _disposed;
 
+            public bool MakeGLFence;
+            public nint LastGLSync;
+
             protected RenderTargetBase(Clyde clyde, ClydeHandle handle)
             {
                 Clyde = clyde;
@@ -302,6 +308,12 @@ namespace Robust.Client.Graphics.Clyde
             }
 
             public abstract Vector2i Size { get; }
+
+            public void CopyPixelsToMemory<T>(CopyPixelsDelegate<T> callback, UIBox2i? subRegion = null) where T : unmanaged, IPixel<T>
+            {
+                Clyde.CopyRenderTargetPixels(Handle, subRegion, callback);
+            }
+
             public ClydeHandle Handle { get; }
 
             protected virtual void Dispose(bool disposing)
@@ -320,6 +332,23 @@ namespace Robust.Client.Graphics.Clyde
                 GC.SuppressFinalize(this);
             }
 
+            public void DisposeDeferred()
+            {
+                if (_disposed)
+                {
+                    return;
+                }
+
+                _disposed = true;
+                DisposeDeferredImpl();
+                GC.SuppressFinalize(this);
+            }
+
+            protected virtual void DisposeDeferredImpl()
+            {
+
+            }
+
             ~RenderTargetBase()
             {
                 Dispose(false);
@@ -347,16 +376,21 @@ namespace Robust.Client.Graphics.Clyde
                 }
                 else
                 {
-                    Clyde._renderTargetDisposeQueue.Enqueue(Handle);
+                    DisposeDeferredImpl();
                 }
             }
+
+            protected override void DisposeDeferredImpl()
+            {
+                Clyde._renderTargetDisposeQueue.Enqueue(Handle);
+            }
         }
 
-        private sealed class RenderWindow : RenderTargetBase, IRenderWindow
+        private sealed class RenderMainWindow : RenderTargetBase
         {
-            public override Vector2i Size => Clyde._framebufferSize;
+            public override Vector2i Size => Clyde._windowing!.MainWindow!.FramebufferSize;
 
-            public RenderWindow(Clyde clyde, ClydeHandle handle) : base(clyde, handle)
+            public RenderMainWindow(Clyde clyde, ClydeHandle handle) : base(clyde, handle)
             {
             }
         }

Robust.Client/Graphics/Clyde/Clyde.Rendering.cs

@@ -1,17 +1,14 @@
 using System;
 using System.Collections.Generic;
 using System.Diagnostics.CodeAnalysis;
-using System.Linq;
 using System.Runtime.CompilerServices;
 using System.Runtime.InteropServices;
 using OpenToolkit.Graphics.OpenGL4;
 using Robust.Client.GameObjects;
 using Robust.Client.Utility;
-using Robust.Shared.Log;
+using Robust.Shared;
 using Robust.Shared.Maths;
 using Robust.Shared.Utility;
-using SixLabors.ImageSharp;
-using SixLabors.ImageSharp.PixelFormats;
 using Color = Robust.Shared.Maths.Color;
 using TKStencilOp = OpenToolkit.Graphics.OpenGL4.StencilOp;
 
@@ -120,9 +117,10 @@ namespace Robust.Client.Graphics.Clyde
             view = Matrix3.Identity;
         }
 
-        private static void CalcWorldMatrices(in Vector2i screenSize, IEye eye, out Matrix3 proj, out Matrix3 view)
+        private static void CalcWorldMatrices(in Vector2i screenSize, in Vector2 renderScale, IEye eye,
+            out Matrix3 proj, out Matrix3 view)
         {
-            eye.GetViewMatrix(out view);
+            eye.GetViewMatrix(out view, renderScale);
 
             CalcWorldProjMatrix(screenSize, out proj);
         }
@@ -266,8 +264,15 @@ namespace Robust.Client.Graphics.Clyde
 
         private void _drawQuad(Vector2 a, Vector2 b, in Matrix3 modelMatrix, GLShaderProgram program)
         {
-            BindVertexArray(QuadVAO.Handle);
+            DrawQuadWithVao(QuadVAO, a, b, modelMatrix, program);
+        }
+
+        private void DrawQuadWithVao(GLHandle vao, Vector2 a, Vector2 b, in Matrix3 modelMatrix,
+            GLShaderProgram program)
+        {
+            BindVertexArray(vao.Handle);
             CheckGlError();
+
             var rectTransform = Matrix3.Identity;
             (rectTransform.R0C0, rectTransform.R1C1) = b - a;
             (rectTransform.R0C2, rectTransform.R1C2) = a;
@@ -283,6 +288,16 @@ namespace Robust.Client.Graphics.Clyde
         ///     Flushes the render handle, processing and re-pooling all the command lists.
         /// </summary>
         private void FlushRenderQueue()
+        {
+            FlushBatchQueue();
+
+            // Reset renderer state.
+            _currentMatrixModel = Matrix3.Identity;
+            _queuedShader = _defaultShader.Handle;
+            SetScissorFull(null);
+        }
+
+        private void FlushBatchQueue()
         {
             // Finish any batches that may have been WiP.
             BreakBatch();
@@ -308,11 +323,6 @@ namespace Robust.Client.Graphics.Clyde
 
             ProcessRenderCommands();
             _queuedRenderCommands.Clear();
-
-            // Reset renderer state.
-            _currentMatrixModel = Matrix3.Identity;
-            _queuedShader = _defaultShader.Handle;
-            SetScissorFull(null);
         }
 
         private void SetScissorFull(UIBox2i? state)
@@ -418,8 +428,8 @@ namespace Robust.Client.Graphics.Clyde
                         //It's important to start at Texture6 here since DrawCommandBatch uses Texture0 and Texture1 immediately after calling this
                         //function! If passing in textures as uniforms ever stops working it might be since someone made it use all the way up to Texture6 too.
                         //Might change this in the future?
-                        TextureUnit cTarget = TextureUnit.Texture6+textureUnitVal;
-                        SetTexture(cTarget, ((ClydeTexture)clydeTexture).TextureId);
+                        TextureUnit cTarget = TextureUnit.Texture6 + textureUnitVal;
+                        SetTexture(cTarget, ((ClydeTexture) clydeTexture).TextureId);
                         program.SetUniformTexture(name, cTarget);
                         textureUnitVal++;
                         break;
@@ -500,6 +510,7 @@ namespace Robust.Client.Graphics.Clyde
         private void DrawTexture(ClydeHandle texture, Vector2 bl, Vector2 br, Vector2 tl, Vector2 tr, in Color modulate,
             in Box2 texCoords)
         {
+            EnsureBatchSpaceAvailable(4, GetQuadBatchIndexCount());
             EnsureBatchState(texture, in modulate, true, GetQuadBatchPrimitiveType(), _queuedShader);
 
             bl = _currentMatrixModel.Transform(bl);
@@ -525,6 +536,8 @@ namespace Robust.Client.Graphics.Clyde
             FinishBatch();
             _batchMetaData = null;
 
+            EnsureBatchSpaceAvailable(vertices.Length, indices.Length);
+
             vertices.CopyTo(BatchVertexData.AsSpan(BatchVertexIndex));
 
             // We are weaving this into the batch buffers for performance (and simplicity).
@@ -566,6 +579,8 @@ namespace Robust.Client.Graphics.Clyde
             FinishBatch();
             _batchMetaData = null;
 
+            EnsureBatchSpaceAvailable(vertices.Length, 0);
+
             vertices.CopyTo(BatchVertexData.AsSpan(BatchVertexIndex));
 
             ref var command = ref AllocRenderCommand(RenderCommandType.DrawBatch);
@@ -601,6 +616,7 @@ namespace Robust.Client.Graphics.Clyde
 
         private void DrawLine(Vector2 a, Vector2 b, Color color)
         {
+            EnsureBatchSpaceAvailable(2, 0);
             EnsureBatchState(_stockTextureWhite.TextureId, color, false, BatchPrimitiveType.LineList, _queuedShader);
 
             a = _currentMatrixModel.Transform(a);
@@ -615,6 +631,14 @@ namespace Robust.Client.Graphics.Clyde
             _debugStats.LastClydeDrawCalls += 1;
         }
 
+        private void EnsureBatchSpaceAvailable(int vtx, int idx)
+        {
+            if (BatchVertexIndex + vtx >= BatchVertexData.Length || BatchIndexIndex + idx > BatchIndexData.Length)
+            {
+                FlushBatchQueue();
+            }
+        }
+
         private void DrawSetScissor(UIBox2i? scissorBox)
         {
             BreakBatch();
@@ -773,116 +797,6 @@ namespace Robust.Client.Graphics.Clyde
             _batchMetaData = null;
         }
 
-        private unsafe void TakeScreenshot(ScreenshotType type)
-        {
-            if (_queuedScreenshots.Count == 0 || _queuedScreenshots.All(p => p.type != type))
-            {
-                return;
-            }
-
-            var delegates = _queuedScreenshots.Where(p => p.type == type).ToList();
-
-            _queuedScreenshots.RemoveAll(p => p.type == type);
-
-            GL.PixelStore(PixelStoreParameter.PackAlignment, 1);
-            CheckGlError();
-
-            var bufferLength = ScreenSize.X * ScreenSize.Y;
-            if (!(_hasGLFenceSync && HasGLAnyMapBuffer && _hasGLPixelBufferObjects))
-            {
-                Logger.DebugS("clyde.ogl", "Necessary features for async screenshots not available, falling back to blocking path.");
-
-                // We need these 3 features to be able to do asynchronous screenshots, if we don't have them,
-                // we'll have to fall back to a crappy synchronous stalling method of glReadPixels().
-
-                var buffer = new Rgba32[bufferLength];
-                fixed (Rgba32* ptr = buffer)
-                {
-                    var bufSize = sizeof(Rgba32) * bufferLength;
-                    GL.ReadnPixels(0, 0, ScreenSize.X, ScreenSize.Y, PixelFormat.Rgba, PixelType.UnsignedByte, bufSize,
-                        (IntPtr) ptr);
-                    CheckGlError();
-                }
-
-                var (w, h) = ScreenSize;
-
-                var image = new Image<Rgb24>(w, h);
-                var imageSpan = image.GetPixelSpan();
-
-                FlipCopyScreenshot(buffer, imageSpan, w, h);
-
-                RunCallback(image);
-                return;
-            }
-
-            GL.GenBuffers(1, out uint pbo);
-            CheckGlError();
-            GL.BindBuffer(BufferTarget.PixelPackBuffer, pbo);
-            CheckGlError();
-            GL.BufferData(BufferTarget.PixelPackBuffer, bufferLength * sizeof(Rgba32), IntPtr.Zero,
-                BufferUsageHint.StreamRead);
-            CheckGlError();
-            GL.ReadPixels(0, 0, ScreenSize.X, ScreenSize.Y, PixelFormat.Rgba, PixelType.UnsignedByte, IntPtr.Zero);
-            CheckGlError();
-            var fence = GL.FenceSync(SyncCondition.SyncGpuCommandsComplete, WaitSyncFlags.None);
-            CheckGlError();
-
-            GL.BindBuffer(BufferTarget.PixelPackBuffer, 0);
-            CheckGlError();
-
-            _transferringScreenshots.Add((pbo, fence, ScreenSize, RunCallback));
-
-            void RunCallback(Image<Rgb24> image) => delegates.ForEach(p => p.callback(image));
-        }
-
-        private unsafe void CheckTransferringScreenshots()
-        {
-            if (_transferringScreenshots.Count == 0)
-            {
-                return;
-            }
-
-            foreach (var screenshot in _transferringScreenshots.ToList())
-            {
-                var (pbo, fence, (width, height), callback) = screenshot;
-
-                int status;
-                GL.GetSync(fence, SyncParameterName.SyncStatus, sizeof(int), null, &status);
-                CheckGlError();
-
-                if (status == (int) All.Signaled)
-                {
-                    var bufLen = width * height;
-                    var bufSize = sizeof(Rgba32) * bufLen;
-
-                    GL.BindBuffer(BufferTarget.PixelPackBuffer, pbo);
-                    CheckGlError();
-                    var ptr = MapFullBuffer(BufferTarget.PixelPackBuffer, bufSize, BufferAccess.ReadOnly,
-                        BufferAccessMask.MapReadBit);
-
-                    var packSpan = new ReadOnlySpan<Rgba32>((void*) ptr, width * height);
-
-                    var image = new Image<Rgb24>(width, height);
-                    var imageSpan = image.GetPixelSpan();
-
-                    FlipCopyScreenshot(packSpan, imageSpan, width, height);
-
-                    UnmapBuffer(BufferTarget.PixelPackBuffer);
-                    GL.BindBuffer(BufferTarget.PixelPackBuffer, 0);
-                    CheckGlError();
-                    GL.DeleteBuffer(pbo);
-                    CheckGlError();
-                    GL.DeleteSync(fence);
-                    CheckGlError();
-
-                    _transferringScreenshots.Remove(screenshot);
-
-                    // TODO: Don't do unnecessary copy here.
-                    callback(image);
-                }
-            }
-        }
-
         private FullStoredRendererState PushRenderStateFull()
         {
             return new FullStoredRendererState(_currentMatrixProj, _currentMatrixView, _currentRenderTarget);
@@ -913,7 +827,7 @@ namespace Robust.Client.Graphics.Clyde
             _lightingReady = false;
             _currentMatrixModel = Matrix3.Identity;
             SetScissorFull(null);
-            BindRenderTargetFull(_mainWindowRenderTarget);
+            BindRenderTargetFull(_mainMainWindowRenderMainTarget);
             _batchMetaData = null;
             _queuedShader = _defaultShader.Handle;
         }
@@ -927,6 +841,109 @@ namespace Robust.Client.Graphics.Clyde
                 BlendingFactorDest.OneMinusSrcAlpha);
         }
 
+        private void BlitSecondaryWindows()
+        {
+            // Only got main window.
+            if (_windowing!.AllWindows.Count == 1)
+                return;
+
+            if (!_hasGLFenceSync && _cfg.GetCVar(CVars.DisplayForceSyncWindows))
+            {
+                GL.Finish();
+            }
+
+            if (EffectiveThreadWindowBlit)
+            {
+                foreach (var window in _windowing.AllWindows)
+                {
+                    if (window.IsMainWindow)
+                        continue;
+
+                    window.BlitDoneEvent!.Reset();
+                    window.BlitStartEvent!.Set();
+                    window.BlitDoneEvent.Wait();
+                }
+            }
+            else
+            {
+                foreach (var window in _windowing.AllWindows)
+                {
+                    if (window.IsMainWindow)
+                        continue;
+
+                    _windowing.GLMakeContextCurrent(window);
+                    BlitThreadDoSecondaryWindowBlit(window);
+                }
+
+                _windowing.GLMakeContextCurrent(_windowing.MainWindow!);
+            }
+        }
+
+        private void BlitThreadDoSecondaryWindowBlit(WindowReg window)
+        {
+            var rt = window.RenderTexture!;
+
+            if (_hasGLFenceSync)
+            {
+                // 0xFFFFFFFFFFFFFFFFUL is GL_TIMEOUT_IGNORED
+                var sync = rt!.LastGLSync;
+                GL.WaitSync(sync, WaitSyncFlags.None, unchecked((long) 0xFFFFFFFFFFFFFFFFUL));
+                CheckGlError();
+            }
+
+            GL.Viewport(0, 0, window.FramebufferSize.X, window.FramebufferSize.Y);
+            CheckGlError();
+
+            SetTexture(TextureUnit.Texture0, window.RenderTexture!.Texture);
+
+            GL.DrawArrays(PrimitiveType.TriangleStrip, 0, 4);
+            CheckGlError();
+
+            window.BlitDoneEvent?.Set();
+            _windowing!.WindowSwapBuffers(window);
+        }
+
+        private void BlitThreadInit(WindowReg reg)
+        {
+            _windowing!.GLMakeContextCurrent(reg);
+            _windowing.GLSwapInterval(0);
+
+            if (!_isGLES)
+                GL.Enable(EnableCap.FramebufferSrgb);
+
+            var vao = GL.GenVertexArray();
+            GL.BindVertexArray(vao);
+            GL.BindBuffer(BufferTarget.ArrayBuffer, WindowVBO.ObjectHandle);
+            // Vertex Coords
+            GL.VertexAttribPointer(0, 2, VertexAttribPointerType.Float, false, Vertex2D.SizeOf, 0);
+            GL.EnableVertexAttribArray(0);
+            // Texture Coords.
+            GL.VertexAttribPointer(1, 2, VertexAttribPointerType.Float, false, Vertex2D.SizeOf, 2 * sizeof(float));
+            GL.EnableVertexAttribArray(1);
+
+            var program = _compileProgram(_winBlitShaderVert, _winBlitShaderFrag, new (string, uint)[]
+            {
+                ("aPos", 0),
+                ("tCoord", 1),
+            }, includeLib: false);
+
+            GL.UseProgram(program.Handle);
+            var loc = GL.GetUniformLocation(program.Handle, "tex");
+            SetTexture(TextureUnit.Texture0, reg.RenderTexture!.Texture);
+            GL.Uniform1(loc, 0);
+        }
+
+        private void FenceRenderTarget(RenderTargetBase rt)
+        {
+            if (!_hasGLFenceSync || !rt.MakeGLFence)
+                return;
+
+            if (rt.LastGLSync != 0)
+                GL.DeleteSync(rt.LastGLSync);
+
+            rt.LastGLSync = GL.FenceSync(SyncCondition.SyncGpuCommandsComplete, WaitSyncFlags.None);
+        }
+
         [StructLayout(LayoutKind.Explicit)]
         private struct RenderCommand
         {

Robust.Client/Graphics/Clyde/Clyde.Screenshots.cs

@@ -0,0 +1,223 @@
+using System;
+using System.Collections.Generic;
+using OpenToolkit.Graphics.OpenGL4;
+using Robust.Client.Utility;
+using Robust.Shared.Log;
+using Robust.Shared.Maths;
+using Robust.Shared.Utility;
+using SixLabors.ImageSharp;
+using SixLabors.ImageSharp.PixelFormats;
+using PF = OpenToolkit.Graphics.OpenGL4.PixelFormat;
+using PT = OpenToolkit.Graphics.OpenGL4.PixelType;
+
+namespace Robust.Client.Graphics.Clyde
+{
+    // Contains primary screenshot and pixel-copying logic.
+
+    internal sealed partial class Clyde
+    {
+        // Full-framebuffer screenshots undergo the following sequence of events:
+        // 1. Screenshots are queued by content or whatever.
+        // 2. When the rendering code reaches the screenshot type,
+        //    we instruct the GPU driver to copy the framebuffer and asynchronously transfer it to host memory.
+        // 3. Transfer finished asynchronously, we invoke the callback.
+        //
+        // On RAW GLES2, we cannot do this asynchronously due to lacking GL features,
+        // and the game will stutter as a result. This is sadly unavoidable.
+        //
+        // For CopyPixels on render targets, the copy and transfer is started immediately when the function is called.
+
+        private readonly List<QueuedScreenshot> _queuedScreenshots = new();
+        private readonly List<TransferringPixelCopy> _transferringPixelCopies = new();
+
+        public void Screenshot(ScreenshotType type, CopyPixelsDelegate<Rgb24> callback, UIBox2i? subRegion = null)
+        {
+            _queuedScreenshots.Add(new QueuedScreenshot(type, callback, subRegion));
+        }
+
+        private void TakeScreenshot(ScreenshotType type)
+        {
+            if (_queuedScreenshots.Count == 0)
+            {
+                return;
+            }
+
+            GL.PixelStore(PixelStoreParameter.PackAlignment, 1);
+            CheckGlError();
+
+            for (var i = 0; i < _queuedScreenshots.Count; i++)
+            {
+                var (qType, callback, subRegion) = _queuedScreenshots[i];
+                if (qType != type)
+                    continue;
+
+                DoCopyPixels(ScreenSize, subRegion, callback);
+                _queuedScreenshots.RemoveSwap(i--);
+            }
+        }
+
+        private void CopyRenderTargetPixels<T>(
+            ClydeHandle renderTarget,
+            UIBox2i? subRegion,
+            CopyPixelsDelegate<T> callback)
+            where T : unmanaged, IPixel<T>
+        {
+            var loaded = _renderTargets[renderTarget];
+
+            var original = GL.GetInteger(GetPName.ReadFramebufferBinding);
+
+            GL.BindFramebuffer(FramebufferTarget.ReadFramebuffer, loaded.FramebufferHandle.Handle);
+
+            DoCopyPixels(loaded.Size, subRegion, callback);
+
+            GL.BindFramebuffer(FramebufferTarget.ReadFramebuffer, original);
+        }
+
+        private unsafe void DoCopyPixels<T>(
+            Vector2i fbSize,
+            UIBox2i? subRegion,
+            CopyPixelsDelegate<T> callback)
+            where T : unmanaged, IPixel<T>
+        {
+            var (pf, pt) = default(T) switch
+            {
+                Rgba32 => (PF.Rgba, PT.UnsignedByte),
+                Rgb24 => (PF.Rgb, PT.UnsignedByte),
+                _ => throw new ArgumentException("Unsupported pixel type.")
+            };
+
+            var size = ClydeBase.ClampSubRegion(fbSize, subRegion);
+
+            var bufferLength = size.X * size.Y;
+            if (!(_hasGLFenceSync && HasGLAnyMapBuffer && _hasGLPixelBufferObjects))
+            {
+                _sawmillOgl.Debug("clyde.ogl",
+                    "Necessary features for async screenshots not available, falling back to blocking path.");
+
+                // We need these 3 features to be able to do asynchronous screenshots, if we don't have them,
+                // we'll have to fall back to a crappy synchronous stalling method of glReadnPixels().
+
+                var buffer = new T[bufferLength];
+                fixed (T* ptr = buffer)
+                {
+                    var bufSize = sizeof(T) * bufferLength;
+                    GL.ReadnPixels(
+                        0, 0,
+                        size.X, size.Y,
+                        pf, pt,
+                        bufSize,
+                        (nint) ptr);
+
+                    CheckGlError();
+                }
+
+                var image = new Image<T>(size.X, size.Y);
+                var imageSpan = image.GetPixelSpan();
+
+                FlipCopy(buffer, imageSpan, size.X, size.Y);
+
+                callback(image);
+                return;
+            }
+
+            GL.GenBuffers(1, out uint pbo);
+            CheckGlError();
+
+            GL.BindBuffer(BufferTarget.PixelPackBuffer, pbo);
+            CheckGlError();
+
+            GL.BufferData(
+                BufferTarget.PixelPackBuffer,
+                bufferLength * sizeof(Rgba32), IntPtr.Zero,
+                BufferUsageHint.StreamRead);
+            CheckGlError();
+
+            GL.ReadPixels(0, 0, size.X, size.Y, pf, pt, IntPtr.Zero);
+            CheckGlError();
+
+            var fence = GL.FenceSync(SyncCondition.SyncGpuCommandsComplete, WaitSyncFlags.None);
+            CheckGlError();
+
+            GL.BindBuffer(BufferTarget.PixelPackBuffer, 0);
+            CheckGlError();
+
+            var transferring = new TransferringPixelCopy(pbo, fence, size, FinishPixelTransfer<T>, callback);
+            _transferringPixelCopies.Add(transferring);
+        }
+
+        private unsafe void CheckTransferringScreenshots()
+        {
+            if (_transferringPixelCopies.Count == 0)
+            {
+                return;
+            }
+
+            for (var i = 0; i < _transferringPixelCopies.Count; i++)
+            {
+                var transferring = _transferringPixelCopies[i];
+
+                // Check if transfer done (sync signalled)
+                int status;
+                GL.GetSync(transferring.Sync, SyncParameterName.SyncStatus, sizeof(int), null, &status);
+                CheckGlError();
+
+                if (status != (int) All.Signaled)
+                    continue;
+
+                transferring.TransferContinue(transferring);
+                _transferringPixelCopies.RemoveSwap(i--);
+            }
+        }
+
+        private unsafe void FinishPixelTransfer<T>(TransferringPixelCopy transferring) where T : unmanaged, IPixel<T>
+        {
+            var (pbo, fence, (width, height), _, callback) = transferring;
+
+            var bufLen = width * height;
+            var bufSize = sizeof(T) * bufLen;
+
+            GL.BindBuffer(BufferTarget.PixelPackBuffer, pbo);
+            CheckGlError();
+
+            var ptr = MapFullBuffer(
+                BufferTarget.PixelPackBuffer,
+                bufSize,
+                BufferAccess.ReadOnly,
+                BufferAccessMask.MapReadBit);
+
+            var packSpan = new ReadOnlySpan<T>(ptr, width * height);
+
+            var image = new Image<T>(width, height);
+            var imageSpan = image.GetPixelSpan();
+
+            FlipCopy(packSpan, imageSpan, width, height);
+
+            UnmapBuffer(BufferTarget.PixelPackBuffer);
+
+            GL.BindBuffer(BufferTarget.PixelPackBuffer, 0);
+            CheckGlError();
+
+            GL.DeleteBuffer(pbo);
+            CheckGlError();
+
+            GL.DeleteSync(fence);
+            CheckGlError();
+
+            var castCallback = (CopyPixelsDelegate<T>) callback;
+            castCallback(image);
+        }
+
+        private sealed record QueuedScreenshot(
+            ScreenshotType Type,
+            CopyPixelsDelegate<Rgb24> Callback,
+            UIBox2i? SubRegion);
+
+        private sealed record TransferringPixelCopy(
+            uint Pbo,
+            nint Sync,
+            Vector2i Size,
+            // Funny callback dance to handle the generics.
+            Action<TransferringPixelCopy> TransferContinue,
+            Delegate Callback);
+    }
+}

Robust.Client/Graphics/Clyde/Clyde.Shaders.cs

@@ -23,6 +23,9 @@ namespace Robust.Client.Graphics.Clyde
         private string _shaderWrapCodeRawFrag = default!;
         private string _shaderWrapCodeRawVert = default!;
 
+        private string _winBlitShaderVert = default!;
+        private string _winBlitShaderFrag = default!;
+
         private readonly Dictionary<ClydeHandle, LoadedShader> _loadedShaders =
             new();
 
@@ -117,6 +120,9 @@ namespace Robust.Client.Graphics.Clyde
             _shaderWrapCodeRawVert = ReadEmbeddedShader("base-raw.vert");
             _shaderWrapCodeRawFrag = ReadEmbeddedShader("base-raw.frag");
 
+            _winBlitShaderVert = ReadEmbeddedShader("winblit.vert");
+            _winBlitShaderFrag = ReadEmbeddedShader("winblit.frag");
+
             var defaultLoadedShader = _resourceCache
                 .GetResource<ShaderSourceResource>("/Shaders/Internal/default-sprite.swsl").ClydeHandle;
 
@@ -135,7 +141,7 @@ namespace Robust.Client.Graphics.Clyde
         }
 
         private GLShaderProgram _compileProgram(string vertexSource, string fragmentSource,
-            (string, uint)[] attribLocations, string? name = null)
+            (string, uint)[] attribLocations, string? name = null, bool includeLib=true)
         {
             GLShader? vertexShader = null;
             GLShader? fragmentShader = null;
@@ -172,8 +178,9 @@ namespace Robust.Client.Graphics.Clyde
                 versionHeader += "#define HAS_UNIFORM_BUFFERS\n";
             }
 
-            vertexSource = versionHeader + "#define VERTEX_SHADER\n" + _shaderLibrary + vertexSource;
-            fragmentSource = versionHeader + "#define FRAGMENT_SHADER\n" + _shaderLibrary + fragmentSource;
+            var lib = includeLib ? _shaderLibrary : "";
+            vertexSource = versionHeader + "#define VERTEX_SHADER\n" + lib + vertexSource;
+            fragmentSource = versionHeader + "#define FRAGMENT_SHADER\n" + lib + fragmentSource;
 
             try
             {

Robust.Client/Graphics/Clyde/Clyde.Textures.cs

@@ -26,10 +26,10 @@ namespace Robust.Client.Graphics.Clyde
 
         private readonly ConcurrentQueue<ClydeHandle> _textureDisposeQueue = new();
 
-        public Texture LoadTextureFromPNGStream(Stream stream, string? name = null,
+        public OwnedTexture LoadTextureFromPNGStream(Stream stream, string? name = null,
             TextureLoadParameters? loadParams = null)
         {
-            DebugTools.Assert(_mainThread == Thread.CurrentThread);
+            DebugTools.Assert(_gameThread == Thread.CurrentThread);
 
             // Load using Rgba32.
             using var image = Image.Load<Rgba32>(stream);
@@ -37,10 +37,10 @@ namespace Robust.Client.Graphics.Clyde
             return LoadTextureFromImage(image, name, loadParams);
         }
 
-        public Texture LoadTextureFromImage<T>(Image<T> image, string? name = null,
+        public OwnedTexture LoadTextureFromImage<T>(Image<T> image, string? name = null,
             TextureLoadParameters? loadParams = null) where T : unmanaged, IPixel<T>
         {
-            DebugTools.Assert(_mainThread == Thread.CurrentThread);
+            DebugTools.Assert(_gameThread == Thread.CurrentThread);
 
             var actualParams = loadParams ?? TextureLoadParameters.Default;
             var pixelType = typeof(T);
@@ -324,11 +324,13 @@ namespace Robust.Client.Graphics.Clyde
                 if (typeof(T) == typeof(A8))
                 {
                     SetSubImage(texture, dstTl, ApplyA8Swizzle((Image<A8>) (object) srcImage), srcBox);
+                    return;
                 }
 
                 if (typeof(T) == typeof(L8))
                 {
                     SetSubImage(texture, dstTl, ApplyL8Swizzle((Image<L8>) (object) srcImage), srcBox);
+                    return;
                 }
             }
 
@@ -450,24 +452,6 @@ namespace Robust.Client.Graphics.Clyde
             }
         }
 
-        private static void FlipCopyScreenshot(ReadOnlySpan<Rgba32> srcSpan, Span<Rgb24> dstSpan, int w, int h)
-        {
-            var dr = h - 1;
-            for (var r = 0; r < h; r++, dr--)
-            {
-                var si = r * w;
-                var di = dr * w;
-                var srcRow = srcSpan[si..(si + w)];
-                var dstRow = dstSpan[di..(di + w)];
-
-                for (var x = 0; x < w; x++)
-                {
-                    var src = srcRow[x];
-                    dstRow[x] = new Rgb24(src.R, src.G, src.B);
-                }
-            }
-        }
-
         private static Image<Rgba32> ApplyA8Swizzle(Image<A8> source)
         {
             var newImage = new Image<Rgba32>(source.Width, source.Height);

Robust.Client/Graphics/Clyde/Clyde.Viewport.cs

@@ -1,5 +1,8 @@
 using System;
 using System.Collections.Generic;
+using Robust.Client.UserInterface.CustomControls;
+using Robust.Shared.Enums;
+using Robust.Shared.Map;
 using Robust.Shared.Maths;
 
 namespace Robust.Client.Graphics.Clyde
@@ -10,7 +13,7 @@ namespace Robust.Client.Graphics.Clyde
         private readonly Dictionary<ClydeHandle, WeakReference<Viewport>> _viewports =
             new();
 
-        private Viewport CreateViewport(Vector2i size, string? name = null)
+        private Viewport CreateViewport(Vector2i size, TextureSampleParameters? sampleParameters = default, string? name = null)
         {
             var handle = AllocRid();
             var viewport = new Viewport(handle, name, this)
@@ -18,6 +21,7 @@ namespace Robust.Client.Graphics.Clyde
                 Size = size,
                 RenderTarget = CreateRenderTarget(size,
                     new RenderTargetFormatParameters(RenderTargetColorFormat.Rgba8Srgb, true),
+                    sampleParameters: sampleParameters,
                     name: $"{name}-MainRenderTarget")
             };
 
@@ -28,9 +32,9 @@ namespace Robust.Client.Graphics.Clyde
             return viewport;
         }
 
-        IClydeViewport IClyde.CreateViewport(Vector2i size, string? name)
+        IClydeViewport IClyde.CreateViewport(Vector2i size, TextureSampleParameters? sampleParameters, string? name)
         {
-            return CreateViewport(size, name);
+            return CreateViewport(size, sampleParameters, name);
         }
 
         private static Vector2 ScreenToMap(Vector2 point, Viewport vp)
@@ -45,7 +49,7 @@ namespace Robust.Client.Graphics.Clyde
             point *= new Vector2(1, -1) / EyeManager.PixelsPerMeter;
 
             // view matrix
-            vp.Eye.GetViewMatrixInv(out var viewMatrixInv);
+            vp.Eye.GetViewMatrixInv(out var viewMatrixInv, vp.RenderScale);
             point = viewMatrixInv * point;
 
             return point;
@@ -106,12 +110,66 @@ namespace Robust.Client.Graphics.Clyde
             }
 
             public Vector2i Size { get; set; }
+            public Vector2 RenderScale { get; set; } = Vector2.One;
+            public bool AutomaticRender { get; set; }
 
             void IClydeViewport.Render()
             {
                 _clyde.RenderViewport(this);
             }
 
+            public MapCoordinates LocalToWorld(Vector2 point)
+            {
+                if (Eye == null)
+                    return default;
+
+                var newPoint = point;
+
+                // (inlined version of UiProjMatrix^-1)
+                newPoint -= Size / 2f;
+                newPoint *= new Vector2(1, -1) / EyeManager.PixelsPerMeter;
+
+                // view matrix
+                Eye.GetViewMatrixInv(out var viewMatrixInv, RenderScale);
+                newPoint = viewMatrixInv * newPoint;
+
+                return new MapCoordinates(newPoint, Eye.Position.MapId);
+            }
+
+            public Vector2 WorldToLocal(Vector2 point)
+            {
+                if (Eye == null)
+                    return default;
+
+                var eye = (IEye) Eye;
+                var newPoint = point;
+
+                eye.GetViewMatrix(out var viewMatrix, RenderScale);
+                newPoint = viewMatrix * newPoint;
+
+                // (inlined version of UiProjMatrix)
+                newPoint *= new Vector2(1, -1) * EyeManager.PixelsPerMeter;
+                newPoint += Size / 2f;
+
+                return newPoint;
+            }
+
+            public void RenderScreenOverlaysBelow(
+                DrawingHandleScreen handle,
+                IViewportControl control,
+                in UIBox2i viewportBounds)
+            {
+                _clyde.RenderOverlaysDirect(this, control, handle, OverlaySpace.ScreenSpaceBelowWorld, viewportBounds);
+            }
+
+            public void RenderScreenOverlaysAbove(
+                DrawingHandleScreen handle,
+                IViewportControl control,
+                in UIBox2i viewportBounds)
+            {
+                _clyde.RenderOverlaysDirect(this, control, handle, OverlaySpace.ScreenSpace, viewportBounds);
+            }
+
             public void Dispose()
             {
                 RenderTarget.Dispose();

Robust.Client/Graphics/Clyde/Clyde.cs

@@ -1,21 +1,19 @@
 using System;
-using System.Collections.Generic;
 using System.Diagnostics;
 using System.Globalization;
 using System.Runtime.InteropServices;
+using System.Threading;
 using OpenToolkit.Graphics.OpenGL4;
 using Robust.Client.Map;
 using Robust.Client.ResourceManagement;
 using Robust.Client.UserInterface;
 using Robust.Shared;
+using Robust.Shared.Configuration;
 using Robust.Shared.GameObjects;
 using Robust.Shared.IoC;
 using Robust.Shared.Log;
 using Robust.Shared.Map;
-using Robust.Shared.Maths;
 using Robust.Shared.Timing;
-using SixLabors.ImageSharp;
-using SixLabors.ImageSharp.PixelFormats;
 using DependencyAttribute = Robust.Shared.IoC.DependencyAttribute;
 
 namespace Robust.Client.Graphics.Clyde
@@ -23,7 +21,7 @@ namespace Robust.Client.Graphics.Clyde
     /// <summary>
     ///     Responsible for most things rendering on OpenGL mode.
     /// </summary>
-    internal sealed partial class Clyde : ClydeBase, IClydeInternal, IClydeAudio, IPostInjectInit
+    internal sealed partial class Clyde : IClydeInternal, IClydeAudio, IPostInjectInit
     {
         [Dependency] private readonly IClydeTileDefinitionManager _tileDefinitionManager = default!;
         [Dependency] private readonly IEyeManager _eyeManager = default!;
@@ -35,6 +33,7 @@ namespace Robust.Client.Graphics.Clyde
         [Dependency] private readonly IUserInterfaceManagerInternal _userInterfaceManager = default!;
         [Dependency] private readonly IEntitySystemManager _entitySystemManager = default!;
         [Dependency] private readonly IGameTiming _gameTiming = default!;
+        [Dependency] private readonly IConfigurationManager _cfg = default!;
 
         private GLUniformBuffer<ProjViewMatrices> ProjViewUBO = default!;
         private GLUniformBuffer<UniformConstants> UniformConstantsUBO = default!;
@@ -47,7 +46,9 @@ namespace Robust.Client.Graphics.Clyde
         private GLBuffer QuadVBO = default!;
         private GLHandle QuadVAO;
 
-        private Viewport _mainViewport = default!;
+        // VBO to blit to the window
+        // VAO is per-window and not stored (not necessary!)
+        private GLBuffer WindowVBO = default!;
 
         private bool _drawingSplash = true;
 
@@ -59,18 +60,15 @@ namespace Robust.Client.Graphics.Clyde
 
         private bool _checkGLErrors;
 
-        private readonly List<(ScreenshotType type, Action<Image<Rgb24>> callback)> _queuedScreenshots
-            = new();
+        private Thread? _gameThread;
 
-        private readonly List<(uint pbo, IntPtr sync, Vector2i size, Action<Image<Rgb24>> callback)>
-            _transferringScreenshots
-                = new();
+        private ISawmill _sawmillOgl = default!;
 
         public Clyde()
         {
             // Init main window render target.
             var windowRid = AllocRid();
-            var window = new RenderWindow(this, windowRid);
+            var window = new RenderMainWindow(this, windowRid);
             var loadedData = new LoadedRenderTarget
             {
                 IsWindow = true,
@@ -78,33 +76,54 @@ namespace Robust.Client.Graphics.Clyde
             };
             _renderTargets.Add(windowRid, loadedData);
 
-            _mainWindowRenderTarget = window;
+            _mainMainWindowRenderMainTarget = window;
             _currentRenderTarget = RtToLoaded(window);
             _currentBoundRenderTarget = _currentRenderTarget;
         }
 
-        public override bool Initialize()
+        public bool InitializePreWindowing()
         {
-            base.Initialize();
+            _sawmillOgl = Logger.GetSawmill("clyde.ogl");
 
-            _configurationManager.OnValueChanged(CVars.DisplayOGLCheckErrors, b => _checkGLErrors = b, true);
+            _cfg.OnValueChanged(CVars.DisplayOGLCheckErrors, b => _checkGLErrors = b, true);
+            _cfg.OnValueChanged(CVars.DisplayVSync, VSyncChanged, true);
+            _cfg.OnValueChanged(CVars.DisplayWindowMode, WindowModeChanged, true);
+            _cfg.OnValueChanged(CVars.DisplayLightMapDivider, LightmapDividerChanged, true);
+            _cfg.OnValueChanged(CVars.DisplayMaxLightsPerScene, MaxLightsPerSceneChanged, true);
+            _cfg.OnValueChanged(CVars.DisplaySoftShadows, SoftShadowsChanged, true);
+            // I can't be bothered to tear down and set these threads up in a cvar change handler.
+            _threadWindowBlit = _cfg.GetCVar(CVars.DisplayThreadWindowBlit);
 
-            if (!InitWindowing())
-            {
+            return InitWindowing();
+        }
+
+        public bool InitializePostWindowing()
+        {
+            _gameThread = Thread.CurrentThread;
+            if (!InitMainWindowAndRenderer())
                 return false;
-            }
 
             _initializeAudio();
-            ReloadConfig();
-
             return true;
         }
 
+        public bool SeparateWindowThread => true;
+
+        public void EnterWindowLoop()
+        {
+            _windowing!.EnterWindowLoop();
+        }
+
+        public void TerminateWindowLoop()
+        {
+            _windowing!.TerminateWindowLoop();
+        }
+
         public void FrameProcess(FrameEventArgs eventArgs)
         {
             _updateAudio();
 
-            FlushCursorDispose();
+            _windowing?.FlushDispose();
             FlushShaderInstanceDispose();
             FlushRenderTargetDispose();
             FlushTextureDispose();
@@ -121,21 +140,6 @@ namespace Robust.Client.Graphics.Clyde
         public IClydeDebugInfo DebugInfo { get; private set; } = default!;
         public IClydeDebugStats DebugStats => _debugStats;
 
-        protected override void ReadConfig()
-        {
-            base.ReadConfig();
-            _lightmapDivider = _configurationManager.GetCVar(CVars.DisplayLightMapDivider);
-            _maxLightsPerScene = _configurationManager.GetCVar(CVars.DisplayMaxLightsPerScene);
-            _enableSoftShadows = _configurationManager.GetCVar(CVars.DisplaySoftShadows);
-        }
-
-        protected override void ReloadConfig()
-        {
-            base.ReloadConfig();
-
-            RegenAllLightRts();
-        }
-
         public void PostInject()
         {
             _mapManager.TileChanged += _updateTileMapOnUpdate;
@@ -148,15 +152,6 @@ namespace Robust.Client.Graphics.Clyde
             RegisterBlockCVars();
         }
 
-        public override event Action<WindowResizedEventArgs>? OnWindowResized;
-
-        public override event Action<WindowFocusedEventArgs>? OnWindowFocused;
-
-        public void Screenshot(ScreenshotType type, Action<Image<Rgb24>> callback)
-        {
-            _queuedScreenshots.Add((type, callback));
-        }
-
         private void InitOpenGL()
         {
             var vendor = GL.GetString(StringName.Vendor);
@@ -165,16 +160,16 @@ namespace Robust.Client.Graphics.Clyde
             var major = GL.GetInteger(GetPName.MajorVersion);
             var minor = GL.GetInteger(GetPName.MinorVersion);
 
-            Logger.DebugS("clyde.ogl", "OpenGL Vendor: {0}", vendor);
-            Logger.DebugS("clyde.ogl", "OpenGL Renderer: {0}", renderer);
-            Logger.DebugS("clyde.ogl", "OpenGL Version: {0}", version);
+            _sawmillOgl.Debug("OpenGL Vendor: {0}", vendor);
+            _sawmillOgl.Debug("OpenGL Renderer: {0}", renderer);
+            _sawmillOgl.Debug("OpenGL Version: {0}", version);
 
             var overrideVersion = ParseGLOverrideVersion();
 
             if (overrideVersion != null)
             {
                 (major, minor) = overrideVersion.Value;
-                Logger.DebugS("clyde.ogl", "OVERRIDING detected GL version to: {0}.{1}", major, minor);
+                _sawmillOgl.Debug("OVERRIDING detected GL version to: {0}.{1}", major, minor);
             }
 
             DetectOpenGLFeatures(major, minor);
@@ -201,7 +196,7 @@ namespace Robust.Client.Graphics.Clyde
             }
             if (!HasGLAnyVertexArrayObjects)
             {
-                Logger.WarningS("clyde.ogl", "NO VERTEX ARRAY OBJECTS! Things will probably go terribly, terribly wrong (no fallback path yet)");
+                _sawmillOgl.Warning("NO VERTEX ARRAY OBJECTS! Things will probably go terribly, terribly wrong (no fallback path yet)");
             }
 
             ResetBlendFunc();
@@ -211,23 +206,23 @@ namespace Robust.Client.Graphics.Clyde
             // Primitive Restart's presence or lack thereof changes the amount of required memory.
             InitRenderingBatchBuffers();
 
-            Logger.DebugS("clyde.ogl", "Loading stock textures...");
+            _sawmillOgl.Debug("Loading stock textures...");
 
             LoadStockTextures();
 
-            Logger.DebugS("clyde.ogl", "Loading stock shaders...");
+            _sawmillOgl.Debug("Loading stock shaders...");
 
             LoadStockShaders();
 
-            Logger.DebugS("clyde.ogl", "Creating various GL objects...");
+            _sawmillOgl.Debug("Creating various GL objects...");
 
             CreateMiscGLObjects();
 
-            Logger.DebugS("clyde.ogl", "Setting up RenderHandle...");
+            _sawmillOgl.Debug("Setting up RenderHandle...");
 
             _renderHandle = new RenderHandle(this);
 
-            Logger.DebugS("clyde.ogl", "Setting viewport and rendering splash...");
+            _sawmillOgl.Debug("Setting viewport and rendering splash...");
 
             GL.Viewport(0, 0, ScreenSize.X, ScreenSize.Y);
             CheckGlError();
@@ -238,7 +233,7 @@ namespace Robust.Client.Graphics.Clyde
 
         private (int major, int minor)? ParseGLOverrideVersion()
         {
-            var overrideGLVersion = _configurationManager.GetCVar(CVars.DisplayOGLOverrideVersion);
+            var overrideGLVersion = _cfg.GetCVar(CVars.DisplayOGLOverrideVersion);
             if (string.IsNullOrEmpty(overrideGLVersion))
             {
                 return null;
@@ -247,14 +242,14 @@ namespace Robust.Client.Graphics.Clyde
             var split = overrideGLVersion.Split(".");
             if (split.Length != 2)
             {
-                Logger.WarningS("clyde.ogl", "display.ogl_override_version is in invalid format");
+                _sawmillOgl.Warning("display.ogl_override_version is in invalid format");
                 return null;
             }
 
             if (!int.TryParse(split[0], NumberStyles.Integer, CultureInfo.InvariantCulture, out var major)
                 || !int.TryParse(split[1], NumberStyles.Integer, CultureInfo.InvariantCulture, out var minor))
             {
-                Logger.WarningS("clyde.ogl", "display.ogl_override_version is in invalid format");
+                _sawmillOgl.Warning("display.ogl_override_version is in invalid format");
                 return null;
             }
 
@@ -277,15 +272,27 @@ namespace Robust.Client.Graphics.Clyde
                     quadVertices,
                     nameof(QuadVBO));
 
-                QuadVAO = new GLHandle(GenVertexArray());
-                BindVertexArray(QuadVAO.Handle);
-                ObjectLabelMaybe(ObjectLabelIdentifier.VertexArray, QuadVAO, nameof(QuadVAO));
-                // Vertex Coords
-                GL.VertexAttribPointer(0, 2, VertexAttribPointerType.Float, false, Vertex2D.SizeOf, 0);
-                GL.EnableVertexAttribArray(0);
-                // Texture Coords.
-                GL.VertexAttribPointer(1, 2, VertexAttribPointerType.Float, false, Vertex2D.SizeOf, 2 * sizeof(float));
-                GL.EnableVertexAttribArray(1);
+                QuadVAO = MakeQuadVao();
+
+                CheckGlError();
+            }
+
+            // Window VBO
+            {
+                Span<Vertex2D> winVertices = stackalloc[]
+                {
+                    new Vertex2D(-1, 1, 0, 1),
+                    new Vertex2D(-1, -1, 0, 0),
+                    new Vertex2D(1, 1, 1, 1),
+                    new Vertex2D(1, -1, 1, 0),
+                };
+
+                WindowVBO = new GLBuffer<Vertex2D>(
+                    this,
+                    BufferTarget.ArrayBuffer,
+                    BufferUsageHint.StaticDraw,
+                    winVertices,
+                    nameof(WindowVBO));
 
                 CheckGlError();
             }
@@ -314,23 +321,26 @@ namespace Robust.Client.Graphics.Clyde
             ProjViewUBO = new GLUniformBuffer<ProjViewMatrices>(this, BindingIndexProjView, nameof(ProjViewUBO));
             UniformConstantsUBO = new GLUniformBuffer<UniformConstants>(this, BindingIndexUniformConstants, nameof(UniformConstantsUBO));
 
-            CreateMainViewport();
-
             screenBufferHandle = new GLHandle(GL.GenTexture());
             GL.BindTexture(TextureTarget.Texture2D, screenBufferHandle.Handle);
             ApplySampleParameters(TextureSampleParameters.Default);
-            ScreenBufferTexture = GenTexture(screenBufferHandle, _framebufferSize, true, null, TexturePixelType.Rgba32);
+            ScreenBufferTexture = GenTexture(screenBufferHandle, _windowing!.MainWindow!.FramebufferSize, true, null, TexturePixelType.Rgba32);
         }
 
-        private void CreateMainViewport()
+        private GLHandle MakeQuadVao()
         {
-            var (w, h) = _framebufferSize;
+            var vao = new GLHandle(GenVertexArray());
+            BindVertexArray(vao.Handle);
+            ObjectLabelMaybe(ObjectLabelIdentifier.VertexArray, vao, nameof(QuadVAO));
+            GL.BindBuffer(BufferTarget.ArrayBuffer, QuadVBO.ObjectHandle);
+            // Vertex Coords
+            GL.VertexAttribPointer(0, 2, VertexAttribPointerType.Float, false, Vertex2D.SizeOf, 0);
+            GL.EnableVertexAttribArray(0);
+            // Texture Coords.
+            GL.VertexAttribPointer(1, 2, VertexAttribPointerType.Float, false, Vertex2D.SizeOf, 2 * sizeof(float));
+            GL.EnableVertexAttribArray(1);
 
-            // Ensure viewport size is always even to avoid artifacts.
-            if (w % 2 == 1) w += 1;
-            if (h % 2 == 1) h += 1;
-
-            _mainViewport = CreateViewport((w, h), nameof(_mainViewport));
+            return vao;
         }
 
         [Conditional("DEBUG")]
@@ -338,7 +348,7 @@ namespace Robust.Client.Graphics.Clyde
         {
             if (!_hasGLKhrDebug)
             {
-                Logger.DebugS("clyde.ogl", "KHR_debug not present, OpenGL debug logging not enabled.");
+                _sawmillOgl.Debug("KHR_debug not present, OpenGL debug logging not enabled.");
                 return;
             }
 

Robust.Client/Graphics/Clyde/ClydeHeadless.cs

@@ -1,8 +1,12 @@
 using System;
+using System.Collections.Generic;
 using System.IO;
+using System.Threading.Tasks;
 using JetBrains.Annotations;
 using Robust.Client.Audio;
 using Robust.Client.Input;
+using Robust.Client.UserInterface.CustomControls;
+using Robust.Shared.Map;
 using Robust.Shared.Maths;
 using Robust.Shared.Timing;
 using SixLabors.ImageSharp;
@@ -15,13 +19,16 @@ namespace Robust.Client.Graphics.Clyde
     ///     Hey look, it's Clyde's evil twin brother!
     /// </summary>
     [UsedImplicitly]
-    internal sealed class ClydeHeadless : ClydeBase, IClydeInternal, IClydeAudio
+    internal sealed class ClydeHeadless : IClydeInternal, IClydeAudio
     {
         // Would it make sense to report a fake resolution like 720p here so code doesn't break? idk.
-        public IRenderWindow MainWindowRenderTarget { get; }
-        public override Vector2i ScreenSize { get; } = (1280, 720);
+        public IClydeWindow MainWindow { get; }
+        public Vector2i ScreenSize => (1280, 720);
+        public IEnumerable<IClydeWindow> AllWindows => _windows;
         public Vector2 DefaultWindowScale => (1, 1);
-        public override bool IsFocused => true;
+        public bool IsFocused => true;
+        private readonly List<IClydeWindow> _windows = new();
+        private int _nextWindowId = 2;
 
         public ShaderInstance InstanceShader(ClydeHandle handle)
         {
@@ -30,13 +37,26 @@ namespace Robust.Client.Graphics.Clyde
 
         public ClydeHeadless()
         {
-            MainWindowRenderTarget = new DummyRenderWindow(this);
+            var mainRt = new DummyRenderWindow(this);
+            var window = new DummyWindow(mainRt) {Id = new WindowId(1)};
+
+            _windows.Add(window);
+            MainWindow = window;
         }
 
-        public Vector2 MouseScreenPosition => ScreenSize / 2;
+        public ScreenCoordinates MouseScreenPosition => default;
         public IClydeDebugInfo DebugInfo { get; } = new DummyDebugInfo();
         public IClydeDebugStats DebugStats { get; } = new DummyDebugStats();
 
+        public event Action<TextEventArgs>? TextEntered { add { } remove { } }
+        public event Action<MouseMoveEventArgs>? MouseMove { add { } remove { } }
+        public event Action<MouseEnterLeaveEventArgs>? MouseEnterLeave { add { } remove { } }
+        public event Action<KeyEventArgs>? KeyUp { add { } remove { } }
+        public event Action<KeyEventArgs>? KeyDown { add { } remove { } }
+        public event Action<MouseWheelEventArgs>? MouseWheel { add { } remove { } }
+        public event Action<WindowClosedEventArgs>? CloseWindow { add { } remove { } }
+        public event Action<WindowDestroyedEventArgs>? DestroyWindow { add { } remove { } }
+
         public Texture GetStockTexture(ClydeStockTexture stockTexture)
         {
             return new DummyTexture((1, 1));
@@ -45,8 +65,6 @@ namespace Robust.Client.Graphics.Clyde
         public ClydeDebugLayers DebugLayers { get; set; }
 
         public string GetKeyName(Keyboard.Key key) => string.Empty;
-        public string GetKeyNameScanCode(int scanCode) => string.Empty;
-        public int GetKeyScanCode(Keyboard.Key key) => default;
 
         public void Shutdown()
         {
@@ -58,7 +76,12 @@ namespace Robust.Client.Graphics.Clyde
             return null;
         }
 
-        public override void SetWindowTitle(string title)
+        public void SetWindowTitle(string title)
+        {
+            // Nada.
+        }
+
+        public void SetWindowMonitor(IClydeMonitor monitor)
         {
             // Nada.
         }
@@ -68,19 +91,19 @@ namespace Robust.Client.Graphics.Clyde
             // Nada.
         }
 
-        public override bool Initialize()
-        {
-            base.Initialize();
-            return true;
-        }
-
-        public override event Action<WindowResizedEventArgs> OnWindowResized
+        public event Action<WindowResizedEventArgs> OnWindowResized
         {
             add { }
             remove { }
         }
 
-        public override event Action<WindowFocusedEventArgs> OnWindowFocused
+        public event Action<WindowFocusedEventArgs> OnWindowFocused
+        {
+            add { }
+            remove { }
+        }
+
+        public event Action<WindowContentScaleEventArgs> OnWindowScaleChanged
         {
             add { }
             remove { }
@@ -101,7 +124,29 @@ namespace Robust.Client.Graphics.Clyde
             // Nada.
         }
 
-        public Texture LoadTextureFromPNGStream(Stream stream, string? name = null,
+        public bool SeparateWindowThread => false;
+
+        public bool InitializePreWindowing()
+        {
+            return true;
+        }
+
+        public void TerminateWindowLoop()
+        {
+            throw new InvalidOperationException("ClydeHeadless does not use windowing threads");
+        }
+
+        public void EnterWindowLoop()
+        {
+            throw new InvalidOperationException("ClydeHeadless does not use windowing threads");
+        }
+
+        public bool InitializePostWindowing()
+        {
+            return true;
+        }
+
+        public OwnedTexture LoadTextureFromPNGStream(Stream stream, string? name = null,
             TextureLoadParameters? loadParams = null)
         {
             using (var image = Image.Load<Rgba32>(stream))
@@ -110,7 +155,7 @@ namespace Robust.Client.Graphics.Clyde
             }
         }
 
-        public Texture LoadTextureFromImage<T>(Image<T> image, string? name = null,
+        public OwnedTexture LoadTextureFromImage<T>(Image<T> image, string? name = null,
             TextureLoadParameters? loadParams = null) where T : unmanaged, IPixel<T>
         {
             return new DummyTexture((image.Width, image.Height));
@@ -146,14 +191,34 @@ namespace Robust.Client.Graphics.Clyde
             // Nada.
         }
 
-        public void Screenshot(ScreenshotType type, Action<Image<Rgb24>> callback)
+        public void Screenshot(ScreenshotType type, CopyPixelsDelegate<Rgb24> callback, UIBox2i? subRegion = null)
         {
-            callback(new Image<Rgb24>(ScreenSize.X, ScreenSize.Y));
+            // Immediately call callback with an empty buffer.
+            var (x, y) = ClydeBase.ClampSubRegion(ScreenSize, subRegion);
+            callback(new Image<Rgb24>(x, y));
         }
 
-        public IClydeViewport CreateViewport(Vector2i size, string? name = null)
+        public IClydeViewport CreateViewport(Vector2i size, TextureSampleParameters? sampleParameters,
+            string? name = null)
         {
-            return new Viewport();
+            return new Viewport(size);
+        }
+
+        public IEnumerable<IClydeMonitor> EnumerateMonitors()
+        {
+            // TODO: Actually return something.
+            yield break;
+        }
+
+        public Task<IClydeWindow> CreateWindow(WindowCreateParameters parameters)
+        {
+            var window = new DummyWindow(CreateRenderTarget((123, 123), default))
+            {
+                Id = new WindowId(_nextWindowId++)
+            };
+            _windows.Add(window);
+
+            return Task.FromResult<IClydeWindow>(window);
         }
 
         public ClydeHandle LoadShader(ParsedShader shader, string? name = null)
@@ -183,6 +248,11 @@ namespace Robust.Client.Graphics.Clyde
             return new(default, default, 1, name);
         }
 
+        public AudioStream LoadAudioRaw(short[] samples, int channels, int sampleRate)
+        {
+            throw new NotImplementedException();
+        }
+
         public IClydeAudioSource CreateAudioSource(AudioStream stream)
         {
             return DummyAudioSource.Instance;
@@ -193,9 +263,9 @@ namespace Robust.Client.Graphics.Clyde
             return DummyBufferedAudioSource.Instance;
         }
 
-        public string GetText()
+        public Task<string> GetText()
         {
-            return string.Empty;
+            return Task.FromResult(string.Empty);
         }
 
         public void SetText(string text)
@@ -267,6 +337,16 @@ namespace Robust.Client.Graphics.Clyde
             {
                 // Nada.
             }
+
+            public void SetVelocity(Vector2 velocity)
+            {
+                // Nada.
+            }
+
+            public void SetVolumeDirect(float masterVolumeDecay)
+            {
+                // Nada.
+            }
         }
 
         private sealed class DummyBufferedAudioSource : DummyAudioSource, IClydeBufferedAudioSource
@@ -402,18 +482,21 @@ namespace Robust.Client.Graphics.Clyde
             }
 
             public Vector2i Size { get; }
-            public Texture Texture { get; }
 
-            public void Delete()
+            public void CopyPixelsToMemory<T>(CopyPixelsDelegate<T> callback, UIBox2i? subRegion) where T : unmanaged, IPixel<T>
             {
+                var (x, y) = ClydeBase.ClampSubRegion(Size, subRegion);
+                callback(new Image<T>(x, y));
             }
 
+            public Texture Texture { get; }
+
             public void Dispose()
             {
             }
         }
 
-        private sealed class DummyRenderWindow : IRenderWindow
+        private sealed class DummyRenderWindow : IRenderTarget
         {
             private readonly ClydeHeadless _clyde;
 
@@ -424,6 +507,12 @@ namespace Robust.Client.Graphics.Clyde
 
             public Vector2i Size => _clyde.ScreenSize;
 
+            public void CopyPixelsToMemory<T>(CopyPixelsDelegate<T> callback, UIBox2i? subRegion) where T : unmanaged, IPixel<T>
+            {
+                var (x, y) = ClydeBase.ClampSubRegion(Size, subRegion);
+                callback(new Image<T>(x, y));
+            }
+
             public void Dispose()
             {
             }
@@ -449,6 +538,11 @@ namespace Robust.Client.Graphics.Clyde
 
         private sealed class Viewport : IClydeViewport
         {
+            public Viewport(Vector2i size)
+            {
+                Size = size;
+            }
+
             public void Dispose()
             {
             }
@@ -458,9 +552,67 @@ namespace Robust.Client.Graphics.Clyde
 
             public IEye? Eye { get; set; }
             public Vector2i Size { get; }
+            public Vector2 RenderScale { get; set; }
+            public bool AutomaticRender { get; set; }
 
             public void Render()
             {
+                // Nada
+            }
+
+            public MapCoordinates LocalToWorld(Vector2 point)
+            {
+                return default;
+            }
+
+            public Vector2 WorldToLocal(Vector2 point)
+            {
+                return default;
+            }
+
+            public void RenderScreenOverlaysBelow(
+                DrawingHandleScreen handle,
+                IViewportControl control,
+                in UIBox2i viewportBounds)
+            {
+                // Nada
+            }
+
+            public void RenderScreenOverlaysAbove(
+                DrawingHandleScreen handle,
+                IViewportControl control,
+                in UIBox2i viewportBounds)
+            {
+                // Nada
+            }
+        }
+
+        private sealed class DummyWindow : IClydeWindow
+        {
+            public DummyWindow(IRenderTarget renderTarget)
+            {
+                RenderTarget = renderTarget;
+            }
+
+            public Vector2i Size { get; } = default;
+            public bool IsDisposed { get; private set; }
+            public WindowId Id { get; set; }
+            public IRenderTarget RenderTarget { get; }
+            public string Title { get; set; } = "";
+            public bool IsFocused => false;
+            public bool IsMinimized => false;
+            public bool IsVisible { get; set; } = true;
+            public Vector2 ContentScale => Vector2.One;
+            public bool DisposeOnClose { get; set; }
+            public event Action<WindowClosedEventArgs>? Closed { add { } remove { } }
+
+            public void MaximizeOnMonitor(IClydeMonitor monitor)
+            {
+            }
+
+            public void Dispose()
+            {
+                IsDisposed = true;
             }
         }
     }

Robust.Client/Graphics/Clyde/GLObjects/Clyde.ShaderProgram.cs

@@ -18,7 +18,7 @@ namespace Robust.Client.Graphics.Clyde
         {
             private readonly sbyte?[] _uniformIntCache = new sbyte?[UniCount];
             private readonly Dictionary<string, int> _uniformCache = new();
-            private uint _handle = 0;
+            public uint Handle = 0;
             private GLShader? _fragmentShader;
             private GLShader? _vertexShader;
             public string? Name { get; }
@@ -49,22 +49,22 @@ namespace Robust.Client.Graphics.Clyde
             public void Link((string, uint)[] attribLocations)
             {
                 ClearCaches();
-                _handle = (uint) GL.CreateProgram();
+                Handle = (uint) GL.CreateProgram();
                 _clyde.CheckGlError();
                 if (Name != null)
                 {
-                    _clyde.ObjectLabelMaybe(ObjectLabelIdentifier.Program, _handle, Name);
+                    _clyde.ObjectLabelMaybe(ObjectLabelIdentifier.Program, Handle, Name);
                 }
 
                 if (_vertexShader != null)
                 {
-                    GL.AttachShader(_handle, _vertexShader.ObjectHandle);
+                    GL.AttachShader(Handle, _vertexShader.ObjectHandle);
                     _clyde.CheckGlError();
                 }
 
                 if (_fragmentShader != null)
                 {
-                    GL.AttachShader(_handle, _fragmentShader.ObjectHandle);
+                    GL.AttachShader(Handle, _fragmentShader.ObjectHandle);
                     _clyde.CheckGlError();
                 }
 
@@ -74,45 +74,50 @@ namespace Robust.Client.Graphics.Clyde
                     // So we have to manually do it here.
                     // Ugh.
 
-                    GL.BindAttribLocation(_handle, loc, varName);
+                    GL.BindAttribLocation(Handle, loc, varName);
                     _clyde.CheckGlError();
                 }
 
-                GL.LinkProgram(_handle);
+                GL.LinkProgram(Handle);
                 _clyde.CheckGlError();
 
-                GL.GetProgram(_handle, GetProgramParameterName.LinkStatus, out var compiled);
+                GL.GetProgram(Handle, GetProgramParameterName.LinkStatus, out var compiled);
                 _clyde.CheckGlError();
                 if (compiled != 1)
                 {
-                    throw new ShaderCompilationException(GL.GetProgramInfoLog((int) _handle));
+                    throw new ShaderCompilationException(GL.GetProgramInfoLog((int) Handle));
                 }
             }
 
             public void Use()
             {
-                DebugTools.Assert(_handle != 0);
-
                 if (_clyde._currentProgram == this)
                 {
                     return;
                 }
 
+                ForceUse();
+            }
+
+            public void ForceUse()
+            {
+                DebugTools.Assert(Handle != 0);
+
                 _clyde._currentProgram = this;
-                GL.UseProgram(_handle);
+                GL.UseProgram(Handle);
                 _clyde.CheckGlError();
             }
 
             public void Delete()
             {
-                if (_handle == 0)
+                if (Handle == 0)
                 {
                     return;
                 }
 
-                GL.DeleteProgram(_handle);
+                GL.DeleteProgram(Handle);
                 _clyde.CheckGlError();
-                _handle = 0;
+                Handle = 0;
             }
 
             public int GetUniform(string name)
@@ -137,14 +142,14 @@ namespace Robust.Client.Graphics.Clyde
 
             public bool TryGetUniform(string name, out int index)
             {
-                DebugTools.Assert(_handle != 0);
+                DebugTools.Assert(Handle != 0);
 
                 if (_uniformCache.TryGetValue(name, out index))
                 {
                     return index != -1;
                 }
 
-                index = GL.GetUniformLocation(_handle, name);
+                index = GL.GetUniformLocation(Handle, name);
                 _clyde.CheckGlError();
                 _uniformCache.Add(name, index);
                 return index != -1;
@@ -152,7 +157,7 @@ namespace Robust.Client.Graphics.Clyde
 
             public bool TryGetUniform(int id, out int index)
             {
-                DebugTools.Assert(_handle != 0);
+                DebugTools.Assert(Handle != 0);
                 DebugTools.Assert(id < UniCount);
 
                 var value = _uniformIntCache[id];
@@ -192,7 +197,7 @@ namespace Robust.Client.Graphics.Clyde
                         throw new ArgumentOutOfRangeException();
                 }
 
-                index = GL.GetUniformLocation(_handle, name);
+                index = GL.GetUniformLocation(Handle, name);
                 _clyde.CheckGlError();
                 _uniformIntCache[id] = (sbyte)index;
                 return index != -1;
@@ -203,9 +208,9 @@ namespace Robust.Client.Graphics.Clyde
 
             public void BindBlock(string blockName, uint blockBinding)
             {
-                var index = (uint) GL.GetUniformBlockIndex(_handle, blockName);
+                var index = (uint) GL.GetUniformBlockIndex(Handle, blockName);
                 _clyde.CheckGlError();
-                GL.UniformBlockBinding(_handle, index, blockBinding);
+                GL.UniformBlockBinding(Handle, index, blockBinding);
                 _clyde.CheckGlError();
             }
 

Robust.Client/Graphics/Clyde/GLObjects/Clyde.UniformBuffer.cs

@@ -23,6 +23,7 @@ namespace Robust.Client.Graphics.Clyde
         private class GLUniformBuffer<T> where T : unmanaged, IAppliableUniformSet
         {
             private readonly Clyde _clyde;
+            private readonly int _index;
 
             /// <summary>
             ///     GPU Buffer (only used when uniform buffers are available)
@@ -37,13 +38,23 @@ namespace Robust.Client.Graphics.Clyde
             public GLUniformBuffer(Clyde clyde, int index, string? name = null)
             {
                 _clyde = clyde;
+                _index = index;
                 if (_clyde._hasGLUniformBuffers)
                 {
                     _implUBO = new GLBuffer(_clyde, BufferTarget.UniformBuffer, BufferUsageHint.StreamDraw, name);
                     unsafe {
                         _implUBO.Reallocate(sizeof(T));
                     }
-                    GL.BindBufferBase(BufferRangeTarget.UniformBuffer, index, (int) _implUBO.ObjectHandle);
+
+                    Rebind();
+                }
+            }
+
+            public void Rebind()
+            {
+                if (_implUBO != null)
+                {
+                    GL.BindBufferBase(BufferRangeTarget.UniformBuffer, _index, (int) _implUBO!.ObjectHandle);
                 }
             }
 

Robust.Client/Graphics/Clyde/Shaders/base-default.frag

@@ -4,7 +4,6 @@ varying highp vec2 Pos;
 uniform sampler2D lightMap;
 uniform highp vec4 modulate;
 
-#line 1000
 // [SHADER_HEADER_CODE]
 
 void main()
@@ -13,7 +12,6 @@ void main()
 
     lowp vec4 COLOR;
 
-    #line 10000
     // [SHADER_CODE]
 
     lowp vec3 lightSample = texture2D(lightMap, Pos).rgb;

Robust.Client/Graphics/Clyde/Shaders/winblit.frag

@@ -0,0 +1,16 @@
+#ifndef HAS_VARYING_ATTRIBUTE
+#define texture2D texture
+#define varying in
+#define attribute in
+#define gl_FragColor colourOutput
+out highp vec4 colourOutput;
+#endif
+
+varying highp vec2 UV;
+
+uniform sampler2D tex;
+
+void main()
+{
+    gl_FragColor = texture2D(tex, UV);
+}

Robust.Client/Graphics/Clyde/Shaders/winblit.vert

@@ -0,0 +1,20 @@
+#ifndef HAS_VARYING_ATTRIBUTE
+#define texture2D texture
+#define varying out
+#define attribute in
+#endif
+
+
+// Vertex position.
+/*layout (location = 0)*/ attribute vec2 aPos;
+// Texture coordinates.
+/*layout (location = 1)*/ attribute vec2 tCoord;
+
+varying vec2 UV;
+
+void main()
+{
+    UV = tCoord;
+
+    gl_Position = vec4(aPos, 0.0, 1.0);
+}

Robust.Client/Graphics/Clyde/Shaders/z-library.glsl

@@ -89,9 +89,10 @@ uniform highp vec2 TEXTURE_PIXEL_SIZE;
 // -- srgb emulation --
 
 #ifdef HAS_SRGB
-highp vec4 zTexture(highp vec2 uv)
+
+highp vec4 zTextureSpec(sampler2D tex, highp vec2 uv)
 {
-    return texture2D(TEXTURE, uv);
+    return texture2D(tex, uv);
 }
 
 highp vec4 zAdjustResult(highp vec4 col)
@@ -101,9 +102,9 @@ highp vec4 zAdjustResult(highp vec4 col)
 #else
 uniform lowp vec2 SRGB_EMU_CONFIG;
 
-highp vec4 zTexture(highp vec2 uv)
+highp vec4 zTextureSpec(sampler2D tex, highp vec2 uv)
 {
-    highp vec4 col = texture2D(TEXTURE, uv);
+    highp vec4 col = texture2D(tex, uv);
     if (SRGB_EMU_CONFIG.x > 0.5)
     {
         return zFromSrgb(col);
@@ -121,5 +122,10 @@ highp vec4 zAdjustResult(highp vec4 col)
 }
 #endif
 
+highp vec4 zTexture(highp vec2 uv)
+{
+    return zTextureSpec(TEXTURE, uv);
+}
+
 // -- Utilities End --
 

Robust.Client/Graphics/Clyde/Windowing/Glfw.Cursors.cs

@@ -0,0 +1,173 @@
+using System;
+using System.Collections.Generic;
+using System.Threading;
+using OpenToolkit.GraphicsLibraryFramework;
+using Robust.Client.Utility;
+using Robust.Shared.Maths;
+using Robust.Shared.Utility;
+using SixLabors.ImageSharp;
+using SixLabors.ImageSharp.PixelFormats;
+using GlfwImage = OpenToolkit.GraphicsLibraryFramework.Image;
+
+namespace Robust.Client.Graphics.Clyde
+{
+    internal partial class Clyde
+    {
+        private sealed unsafe partial class GlfwWindowingImpl
+        {
+            private readonly Dictionary<ClydeHandle, WinThreadCursorReg> _winThreadCursors = new();
+            private readonly Dictionary<StandardCursorShape, CursorImpl> _standardCursors = new();
+
+            public ICursor CursorGetStandard(StandardCursorShape shape)
+            {
+                return _standardCursors[shape];
+            }
+
+            public ICursor CursorCreate(Image<Rgba32> image, Vector2i hotSpot)
+            {
+                var cloneImg = new Image<Rgba32>(image.Width, image.Height);
+                image.GetPixelSpan().CopyTo(cloneImg.GetPixelSpan());
+
+                var id = _clyde.AllocRid();
+                SendCmd(new CmdCursorCreate(cloneImg, hotSpot, id));
+
+                return new CursorImpl(this, id, false);
+            }
+
+            private void WinThreadCursorCreate(CmdCursorCreate cmd)
+            {
+                var (img, (hotX, hotY), id) = cmd;
+
+                fixed (Rgba32* pixPtr = img.GetPixelSpan())
+                {
+                    var gImg = new GlfwImage(img.Width, img.Height, (byte*) pixPtr);
+                    var ptr = GLFW.CreateCursor(gImg, hotX, hotY);
+
+                    _winThreadCursors.Add(id, new WinThreadCursorReg {Ptr = ptr});
+                }
+
+                img.Dispose();
+            }
+
+            public void CursorSet(WindowReg window, ICursor? cursor)
+            {
+                CheckWindowDisposed(window);
+
+                var reg = (GlfwWindowReg) window;
+
+                if (reg.Cursor == cursor)
+                {
+                    // Nothing has to be done!
+                    return;
+                }
+
+                if (cursor == null)
+                {
+                    reg.Cursor = null;
+                    SendCmd(new CmdWinCursorSet((nint) reg.GlfwWindow, default));
+                    return;
+                }
+
+                var impl = (CursorImpl) cursor;
+                DebugTools.Assert(impl.Owner == this);
+
+                if (impl.Id == default)
+                {
+                    throw new ObjectDisposedException(nameof(cursor));
+                }
+
+                reg.Cursor = impl;
+                SendCmd(new CmdWinCursorSet((nint) reg.GlfwWindow, impl.Id));
+            }
+
+            private void WinThreadWinCursorSet(CmdWinCursorSet cmd)
+            {
+                var window = (Window*) cmd.Window;
+                Cursor* ptr = null;
+                if (cmd.Cursor != default)
+                    ptr = _winThreadCursors[cmd.Cursor].Ptr;
+
+                if (_win32Experience)
+                {
+                    // Based on a true story.
+                    Thread.Sleep(15);
+                }
+
+                GLFW.SetCursor(window, ptr);
+            }
+
+            private void WinThreadCursorDestroy(CmdCursorDestroy cmd)
+            {
+                var cursorReg = _winThreadCursors[cmd.Cursor];
+
+                GLFW.DestroyCursor(cursorReg.Ptr);
+
+                _winThreadCursors.Remove(cmd.Cursor);
+            }
+
+            private void InitCursors()
+            {
+                // Gets ran on window thread don't worry about it.
+
+                void AddStandardCursor(StandardCursorShape standardShape, CursorShape shape)
+                {
+                    var id = _clyde.AllocRid();
+                    var ptr = GLFW.CreateStandardCursor(shape);
+
+                    var impl = new CursorImpl(this, id, true);
+
+                    _standardCursors.Add(standardShape, impl);
+                    _winThreadCursors.Add(id, new WinThreadCursorReg {Ptr = ptr});
+                }
+
+                AddStandardCursor(StandardCursorShape.Arrow, CursorShape.Arrow);
+                AddStandardCursor(StandardCursorShape.IBeam, CursorShape.IBeam);
+                AddStandardCursor(StandardCursorShape.Crosshair, CursorShape.Crosshair);
+                AddStandardCursor(StandardCursorShape.Hand, CursorShape.Hand);
+                AddStandardCursor(StandardCursorShape.HResize, CursorShape.HResize);
+                AddStandardCursor(StandardCursorShape.VResize, CursorShape.VResize);
+            }
+
+            private sealed class CursorImpl : ICursor
+            {
+                private readonly bool _standard;
+                public GlfwWindowingImpl Owner { get; }
+                public ClydeHandle Id { get; private set; }
+
+                public CursorImpl(GlfwWindowingImpl clyde, ClydeHandle id, bool standard)
+                {
+                    _standard = standard;
+                    Owner = clyde;
+                    Id = id;
+                }
+
+                ~CursorImpl()
+                {
+                    DisposeImpl();
+                }
+
+                private void DisposeImpl()
+                {
+                    Owner.SendCmd(new CmdCursorDestroy(Id));
+                    Id = default;
+                }
+
+                public void Dispose()
+                {
+                    if (_standard)
+                    {
+                        throw new InvalidOperationException("Can't dispose standard cursor shape.");
+                    }
+
+                    GC.SuppressFinalize(this);
+                    DisposeImpl();
+                }
+            }
+
+            public sealed class WinThreadCursorReg
+            {
+                public Cursor* Ptr;
+            }
+        }
+    }
+}

Robust.Client/Graphics/Clyde/Windowing/Glfw.Events.cs

@@ -0,0 +1,256 @@
+using System;
+using OpenToolkit.GraphicsLibraryFramework;
+using Robust.Client.Input;
+using Robust.Shared.Map;
+
+namespace Robust.Client.Graphics.Clyde
+{
+    partial class Clyde
+    {
+        private partial class GlfwWindowingImpl
+        {
+            public void ProcessEvents(bool single=false)
+            {
+                while (_eventReader.TryRead(out var ev))
+                {
+                    try
+                    {
+                        ProcessEvent(ev);
+                    }
+                    catch (Exception e)
+                    {
+                        _sawmill.Error(
+                            "clyde.win",
+                            $"Caught exception in windowing event ({ev.GetType()}):\n{e}");
+                    }
+
+                    if (single)
+                        break;
+                }
+            }
+
+            // Block waiting on the windowing -> game thread channel.
+            // I swear to god do not use this unless you know what you are doing.
+            private void WaitEvents()
+            {
+                _eventReader.WaitToReadAsync().AsTask().Wait();
+            }
+
+            private void ProcessEvent(EventBase evb)
+            {
+                switch (evb)
+                {
+                    case EventMouseButton mb:
+                        ProcessEventMouseButton(mb);
+                        break;
+                    case EventCursorPos cp:
+                        ProcessEventCursorPos(cp);
+                        break;
+                    case EventCursorEnter ev:
+                        ProcessEventCursorEnter(ev);
+                        break;
+                    case EventScroll s:
+                        ProcessEventScroll(s);
+                        break;
+                    case EventKey k:
+                        ProcessEventKey(k);
+                        break;
+                    case EventChar c:
+                        ProcessEventChar(c);
+                        break;
+                    case EventMonitorSetup ms:
+                        ProcessSetupMonitor(ms);
+                        break;
+                    case EventMonitorDestroy md:
+                        ProcessEventDestroyMonitor(md);
+                        break;
+                    case EventWindowCreate wCreate:
+                        FinishWindowCreate(wCreate);
+                        break;
+                    case EventWindowClose wc:
+                        ProcessEventWindowClose(wc);
+                        break;
+                    case EventWindowFocus wf:
+                        ProcessEventWindowFocus(wf);
+                        break;
+                    case EventWindowSize ws:
+                        ProcessEventWindowSize(ws);
+                        break;
+                    case EventWindowPos wp:
+                        ProcessEventWindowPos(wp);
+                        break;
+                    case EventWindowIconify wi:
+                        ProcessEventWindowIconify(wi);
+                        break;
+                    case EventWindowContentScale cs:
+                        ProcessEventWindowContentScale(cs);
+                        break;
+                    default:
+                        _sawmill.Error($"Unknown GLFW event type: {evb.GetType()}");
+                        break;
+                }
+            }
+
+            private void ProcessEventChar(EventChar ev)
+            {
+                _clyde.SendText(new TextEventArgs(ev.CodePoint));
+            }
+
+            private void ProcessEventCursorPos(EventCursorPos ev)
+            {
+                var windowReg = FindWindow(ev.Window);
+                if (windowReg == null)
+                    return;
+
+                var newPos = ((float) ev.XPos, (float) ev.YPos) * windowReg.PixelRatio;
+                var delta = newPos - windowReg.LastMousePos;
+                windowReg.LastMousePos = newPos;
+
+                _clyde._currentHoveredWindow = windowReg;
+
+                _clyde.SendMouseMove(new MouseMoveEventArgs(delta, new ScreenCoordinates(newPos, windowReg.Id)));
+            }
+
+            private void ProcessEventCursorEnter(EventCursorEnter ev)
+            {
+                var windowReg = FindWindow(ev.Window);
+                if (windowReg == null)
+                    return;
+
+                if (ev.Entered)
+                {
+                    _clyde._currentHoveredWindow = windowReg;
+                }
+                else if (_clyde._currentHoveredWindow == windowReg)
+                {
+                    _clyde._currentHoveredWindow = null;
+                }
+
+                _clyde.SendMouseEnterLeave(new MouseEnterLeaveEventArgs(windowReg.Handle, ev.Entered));
+            }
+
+            private void ProcessEventKey(EventKey ev)
+            {
+                EmitKeyEvent(ConvertGlfwKey(ev.Key), ev.Action, ev.Mods);
+            }
+
+            private void EmitKeyEvent(Keyboard.Key key, InputAction action, KeyModifiers mods)
+            {
+                var shift = (mods & KeyModifiers.Shift) != 0;
+                var alt = (mods & KeyModifiers.Alt) != 0;
+                var control = (mods & KeyModifiers.Control) != 0;
+                var system = (mods & KeyModifiers.Super) != 0;
+
+                var ev = new KeyEventArgs(
+                    key,
+                    action == InputAction.Repeat,
+                    alt, control, shift, system);
+
+                switch (action)
+                {
+                    case InputAction.Release:
+                        _clyde.SendKeyUp(ev);
+                        break;
+                    case InputAction.Press:
+                    case InputAction.Repeat:
+                        _clyde.SendKeyDown(ev);
+                        break;
+                    default:
+                        throw new ArgumentOutOfRangeException(nameof(action), action, null);
+                }
+            }
+
+            private void ProcessEventMouseButton(EventMouseButton ev)
+            {
+                EmitKeyEvent(Mouse.MouseButtonToKey(ConvertGlfwButton(ev.Button)), ev.Action, ev.Mods);
+            }
+
+            private void ProcessEventScroll(EventScroll ev)
+            {
+                var windowReg = FindWindow(ev.Window);
+                if (windowReg == null)
+                    return;
+
+                var eventArgs = new MouseWheelEventArgs(
+                    ((float) ev.XOffset, (float) ev.YOffset),
+                    new ScreenCoordinates(windowReg.LastMousePos, windowReg.Id));
+                _clyde.SendScroll(eventArgs);
+            }
+
+            private void ProcessEventWindowClose(EventWindowClose ev)
+            {
+                var windowReg = FindWindow(ev.Window);
+                if (windowReg == null)
+                    return;
+
+                _clyde.SendCloseWindow(windowReg, new WindowClosedEventArgs(windowReg.Handle));
+            }
+
+            private void ProcessEventWindowSize(EventWindowSize ev)
+            {
+                var window = ev.Window;
+                var width = ev.Width;
+                var height = ev.Height;
+                var fbW = ev.FramebufferWidth;
+                var fbH = ev.FramebufferHeight;
+
+                var windowReg = FindWindow(window);
+                if (windowReg == null)
+                    return;
+
+                var oldSize = windowReg.FramebufferSize;
+                windowReg.FramebufferSize = (fbW, fbH);
+                windowReg.WindowSize = (width, height);
+
+                if (fbW == 0 || fbH == 0 || width == 0 || height == 0)
+                    return;
+
+                windowReg.PixelRatio = windowReg.FramebufferSize / windowReg.WindowSize;
+
+                _clyde.SendWindowResized(windowReg, oldSize);
+            }
+
+            private void ProcessEventWindowPos(EventWindowPos ev)
+            {
+                var window = ev.Window;
+                var x = ev.X;
+                var y = ev.Y;
+
+                var windowReg = FindWindow(window);
+                if (windowReg == null)
+                    return;
+
+                windowReg.WindowPos = (x, y);
+            }
+
+            private void ProcessEventWindowContentScale(EventWindowContentScale ev)
+            {
+                var windowReg = FindWindow(ev.Window);
+                if (windowReg == null)
+                    return;
+
+                windowReg.WindowScale = (ev.XScale, ev.YScale);
+                _clyde.SendWindowContentScaleChanged(new WindowContentScaleEventArgs(windowReg.Handle));
+            }
+
+            private void ProcessEventWindowIconify(EventWindowIconify ev)
+            {
+                var windowReg = FindWindow(ev.Window);
+                if (windowReg == null)
+                    return;
+
+                windowReg.IsMinimized = ev.Iconified;
+            }
+
+            private void ProcessEventWindowFocus(EventWindowFocus ev)
+            {
+                var windowReg = FindWindow(ev.Window);
+                if (windowReg == null)
+                    return;
+
+                windowReg.IsFocused = ev.Focused;
+                _clyde.SendWindowFocus(new WindowFocusedEventArgs(ev.Focused, windowReg.Handle));
+            }
+        }
+    }
+}

Robust.Client/Graphics/Clyde/Windowing/Glfw.Keys.cs

@@ -0,0 +1,225 @@
+using System.Collections.Generic;
+using System.Runtime.InteropServices;
+using System.Threading;
+using OpenToolkit.GraphicsLibraryFramework;
+using Robust.Client.Input;
+using Robust.Shared.Localization;
+using GlfwKey = OpenToolkit.GraphicsLibraryFramework.Keys;
+using GlfwButton = OpenToolkit.GraphicsLibraryFramework.MouseButton;
+using static Robust.Client.Input.Mouse;
+using static Robust.Client.Input.Keyboard;
+
+namespace Robust.Client.Graphics.Clyde
+{
+    internal partial class Clyde
+    {
+        private sealed partial class GlfwWindowingImpl
+        {
+            // TODO: to avoid having to ask the windowing thread, key names are cached.
+            // This means they don't update correctly if the user switches keyboard mode. RIP.
+
+            private readonly Dictionary<Key, string> _printableKeyNameMap = new();
+
+            private void InitKeyMap()
+            {
+                // From GLFW's source code: this is the actual list of "printable" keys
+                // that GetKeyName returns something for.
+                CacheKey(Keys.KeyPadEqual);
+                for (var k = Keys.KeyPad0; k <= Keys.KeyPadAdd; k++)
+                {
+                    CacheKey(k);
+                }
+
+                for (var k = Keys.Apostrophe; k <= Keys.World2; k++)
+                {
+                    CacheKey(k);
+                }
+
+                void CacheKey(GlfwKey key)
+                {
+                    var rKey = ConvertGlfwKey(key);
+                    if (rKey == Key.Unknown)
+                        return;
+
+                    var name = GLFW.GetKeyName(key, 0);
+                    _printableKeyNameMap.Add(rKey, name);
+                }
+            }
+
+            public string KeyGetName(Keyboard.Key key)
+            {
+                if (_printableKeyNameMap.TryGetValue(key, out var name))
+                {
+                    var textInfo = Thread.CurrentThread.CurrentCulture.TextInfo;
+                    return textInfo.ToTitleCase(name);
+                }
+
+                name = Keyboard.GetSpecialKeyName(key, _loc);
+                if (name != null)
+                {
+                    return Loc.GetString(name);
+                }
+
+                return Loc.GetString("<unknown key>");
+            }
+
+            public static Button ConvertGlfwButton(GlfwButton button)
+            {
+                return MouseButtonMap[button];
+            }
+
+            private static readonly Dictionary<GlfwButton, Button> MouseButtonMap = new()
+            {
+                {GlfwButton.Left, Button.Left},
+                {GlfwButton.Middle, Button.Middle},
+                {GlfwButton.Right, Button.Right},
+                {GlfwButton.Button4, Button.Button4},
+                {GlfwButton.Button5, Button.Button5},
+                {GlfwButton.Button6, Button.Button6},
+                {GlfwButton.Button7, Button.Button7},
+                {GlfwButton.Button8, Button.Button8},
+            };
+
+            private static readonly Dictionary<GlfwKey, Key> KeyMap;
+            private static readonly Dictionary<Key, GlfwKey> KeyMapReverse;
+
+
+            internal static Key ConvertGlfwKey(GlfwKey key)
+            {
+                if (KeyMap.TryGetValue(key, out var result))
+                {
+                    return result;
+                }
+
+                return Key.Unknown;
+            }
+
+            internal static GlfwKey ConvertGlfwKeyReverse(Key key)
+            {
+                if (KeyMapReverse.TryGetValue(key, out var result))
+                {
+                    return result;
+                }
+
+                return GlfwKey.Unknown;
+            }
+
+            static GlfwWindowingImpl()
+            {
+                KeyMap = new Dictionary<GlfwKey, Key>
+                {
+                    {GlfwKey.A, Key.A},
+                    {GlfwKey.B, Key.B},
+                    {GlfwKey.C, Key.C},
+                    {GlfwKey.D, Key.D},
+                    {GlfwKey.E, Key.E},
+                    {GlfwKey.F, Key.F},
+                    {GlfwKey.G, Key.G},
+                    {GlfwKey.H, Key.H},
+                    {GlfwKey.I, Key.I},
+                    {GlfwKey.J, Key.J},
+                    {GlfwKey.K, Key.K},
+                    {GlfwKey.L, Key.L},
+                    {GlfwKey.M, Key.M},
+                    {GlfwKey.N, Key.N},
+                    {GlfwKey.O, Key.O},
+                    {GlfwKey.P, Key.P},
+                    {GlfwKey.Q, Key.Q},
+                    {GlfwKey.R, Key.R},
+                    {GlfwKey.S, Key.S},
+                    {GlfwKey.T, Key.T},
+                    {GlfwKey.U, Key.U},
+                    {GlfwKey.V, Key.V},
+                    {GlfwKey.W, Key.W},
+                    {GlfwKey.X, Key.X},
+                    {GlfwKey.Y, Key.Y},
+                    {GlfwKey.Z, Key.Z},
+                    {GlfwKey.D0, Key.Num0},
+                    {GlfwKey.D1, Key.Num1},
+                    {GlfwKey.D2, Key.Num2},
+                    {GlfwKey.D3, Key.Num3},
+                    {GlfwKey.D4, Key.Num4},
+                    {GlfwKey.D5, Key.Num5},
+                    {GlfwKey.D6, Key.Num6},
+                    {GlfwKey.D7, Key.Num7},
+                    {GlfwKey.D8, Key.Num8},
+                    {GlfwKey.D9, Key.Num9},
+                    {GlfwKey.KeyPad0, Key.NumpadNum0},
+                    {GlfwKey.KeyPad1, Key.NumpadNum1},
+                    {GlfwKey.KeyPad2, Key.NumpadNum2},
+                    {GlfwKey.KeyPad3, Key.NumpadNum3},
+                    {GlfwKey.KeyPad4, Key.NumpadNum4},
+                    {GlfwKey.KeyPad5, Key.NumpadNum5},
+                    {GlfwKey.KeyPad6, Key.NumpadNum6},
+                    {GlfwKey.KeyPad7, Key.NumpadNum7},
+                    {GlfwKey.KeyPad8, Key.NumpadNum8},
+                    {GlfwKey.KeyPad9, Key.NumpadNum9},
+                    {GlfwKey.Escape, Key.Escape},
+                    {GlfwKey.LeftControl, Key.Control},
+                    {GlfwKey.RightControl, Key.Control},
+                    {GlfwKey.RightShift, Key.Shift},
+                    {GlfwKey.LeftShift, Key.Shift},
+                    {GlfwKey.LeftAlt, Key.Alt},
+                    {GlfwKey.RightAlt, Key.Alt},
+                    {GlfwKey.LeftSuper, Key.LSystem},
+                    {GlfwKey.RightSuper, Key.RSystem},
+                    {GlfwKey.Menu, Key.Menu},
+                    {GlfwKey.LeftBracket, Key.LBracket},
+                    {GlfwKey.RightBracket, Key.RBracket},
+                    {GlfwKey.Semicolon, Key.SemiColon},
+                    {GlfwKey.Comma, Key.Comma},
+                    {GlfwKey.Period, Key.Period},
+                    {GlfwKey.Apostrophe, Key.Apostrophe},
+                    {GlfwKey.Slash, Key.Slash},
+                    {GlfwKey.Backslash, Key.BackSlash},
+                    {GlfwKey.GraveAccent, Key.Tilde},
+                    {GlfwKey.Equal, Key.Equal},
+                    {GlfwKey.Space, Key.Space},
+                    {GlfwKey.Enter, Key.Return},
+                    {GlfwKey.KeyPadEnter, Key.NumpadEnter},
+                    {GlfwKey.Backspace, Key.BackSpace},
+                    {GlfwKey.Tab, Key.Tab},
+                    {GlfwKey.PageUp, Key.PageUp},
+                    {GlfwKey.PageDown, Key.PageDown},
+                    {GlfwKey.End, Key.End},
+                    {GlfwKey.Home, Key.Home},
+                    {GlfwKey.Insert, Key.Insert},
+                    {GlfwKey.Delete, Key.Delete},
+                    {GlfwKey.Minus, Key.Minus},
+                    {GlfwKey.KeyPadAdd, Key.NumpadAdd},
+                    {GlfwKey.KeyPadSubtract, Key.NumpadSubtract},
+                    {GlfwKey.KeyPadDivide, Key.NumpadDivide},
+                    {GlfwKey.KeyPadMultiply, Key.NumpadMultiply},
+                    {GlfwKey.KeyPadDecimal, Key.NumpadDecimal},
+                    {GlfwKey.Left, Key.Left},
+                    {GlfwKey.Right, Key.Right},
+                    {GlfwKey.Up, Key.Up},
+                    {GlfwKey.Down, Key.Down},
+                    {GlfwKey.F1, Key.F1},
+                    {GlfwKey.F2, Key.F2},
+                    {GlfwKey.F3, Key.F3},
+                    {GlfwKey.F4, Key.F4},
+                    {GlfwKey.F5, Key.F5},
+                    {GlfwKey.F6, Key.F6},
+                    {GlfwKey.F7, Key.F7},
+                    {GlfwKey.F8, Key.F8},
+                    {GlfwKey.F9, Key.F9},
+                    {GlfwKey.F10, Key.F10},
+                    {GlfwKey.F11, Key.F11},
+                    {GlfwKey.F12, Key.F12},
+                    {GlfwKey.F13, Key.F13},
+                    {GlfwKey.F14, Key.F14},
+                    {GlfwKey.F15, Key.F15},
+                    {GlfwKey.Pause, Key.Pause},
+                };
+
+                KeyMapReverse = new Dictionary<Key, GlfwKey>();
+
+                foreach (var (key, value) in KeyMap)
+                {
+                    KeyMapReverse[value] = key;
+                }
+            }
+        }
+    }
+}

Robust.Client/Graphics/Clyde/Windowing/Glfw.Monitors.cs

@@ -0,0 +1,133 @@
+using System.Collections.Generic;
+using System.Runtime.CompilerServices;
+using OpenToolkit.GraphicsLibraryFramework;
+using Robust.Shared.Utility;
+using GlfwVideoMode = OpenToolkit.GraphicsLibraryFramework.VideoMode;
+
+namespace Robust.Client.Graphics.Clyde
+{
+    internal partial class Clyde
+    {
+        private sealed unsafe partial class GlfwWindowingImpl
+        {
+            // TODO: GLFW doesn't have any events for complex monitor config changes,
+            // so we need some way to reload stuff if e.g. the primary monitor changes.
+            // Still better than SDL2 though which doesn't acknowledge monitor changes at all.
+
+            // Monitors are created at GLFW's will,
+            // so we need to make SURE monitors keep existing while operating on them.
+            // because, you know, async. Don't want a use-after-free.
+            private readonly Dictionary<int, WinThreadMonitorReg> _winThreadMonitors = new();
+
+            // Can't use ClydeHandle because it's 64 bit.
+            private int _nextMonitorId = 1;
+            private int _primaryMonitorId;
+            private readonly Dictionary<int, GlfwMonitorReg> _monitors = new();
+
+            private void InitMonitors()
+            {
+                var monitors = GLFW.GetMonitorsRaw(out var count);
+
+                for (var i = 0; i < count; i++)
+                {
+                    WinThreadSetupMonitor(monitors[i]);
+                }
+
+                var primaryMonitor = GLFW.GetPrimaryMonitor();
+                var up = GLFW.GetMonitorUserPointer(primaryMonitor);
+                _primaryMonitorId = (int) up;
+
+                ProcessEvents();
+            }
+
+            [MethodImpl(MethodImplOptions.NoInlining)]
+            private void WinThreadSetupMonitor(Monitor* monitor)
+            {
+                var id = _nextMonitorId++;
+
+                DebugTools.Assert(GLFW.GetMonitorUserPointer(monitor) == null,
+                    "GLFW window already has user pointer??");
+
+                var name = GLFW.GetMonitorName(monitor);
+                var videoMode = GLFW.GetVideoMode(monitor);
+                var modesPtr = GLFW.GetVideoModesRaw(monitor, out var modeCount);
+                var modes = new VideoMode[modeCount];
+                for (var i = 0; i < modes.Length; i++)
+                {
+                    modes[i] = ConvertVideoMode(modesPtr[i]);
+                }
+
+                GLFW.SetMonitorUserPointer(monitor, (void*) id);
+
+                _winThreadMonitors.Add(id, new WinThreadMonitorReg {Ptr = monitor});
+
+                SendEvent(new EventMonitorSetup(id, name, ConvertVideoMode(*videoMode), modes));
+            }
+
+            private static VideoMode ConvertVideoMode(in GlfwVideoMode mode)
+            {
+                return new()
+                {
+                    Width = (ushort) mode.Width,
+                    Height = (ushort) mode.Height,
+                    RedBits = (byte) mode.RedBits,
+                    RefreshRate = (ushort) mode.RefreshRate,
+                    GreenBits = (byte) mode.GreenBits,
+                    BlueBits = (byte) mode.BlueBits,
+                };
+            }
+
+            private void ProcessSetupMonitor(EventMonitorSetup ev)
+            {
+                var impl = new MonitorHandle(
+                    ev.Id,
+                    ev.Name,
+                    (ev.CurrentMode.Width, ev.CurrentMode.Height),
+                    ev.CurrentMode.RefreshRate,
+                    ev.AllModes);
+
+                _clyde._monitorHandles.Add(impl);
+                _monitors[ev.Id] = new GlfwMonitorReg
+                {
+                    Id = ev.Id,
+                    Handle = impl
+                };
+            }
+
+            private void WinThreadDestroyMonitor(Monitor* monitor)
+            {
+                var ptr = (int) GLFW.GetMonitorUserPointer(monitor);
+
+                if (ptr == 0)
+                {
+                    var name = GLFW.GetMonitorName(monitor);
+                    _sawmill.Warning($"Monitor '{name}' had no user pointer set??");
+                    return;
+                }
+
+                _winThreadMonitors.Remove(ptr);
+
+                GLFW.SetMonitorUserPointer(monitor, null);
+
+                SendEvent(new EventMonitorDestroy(ptr));
+            }
+
+            private void ProcessEventDestroyMonitor(EventMonitorDestroy ev)
+            {
+                var reg = _monitors[ev.Id];
+                _monitors.Remove(ev.Id);
+                _clyde._monitorHandles.Remove(reg.Handle);
+            }
+
+            private sealed class GlfwMonitorReg : MonitorReg
+            {
+                public int Id;
+            }
+
+            private sealed class WinThreadMonitorReg
+            {
+                public Monitor* Ptr;
+            }
+        }
+    }
+}

Robust.Client/Graphics/Clyde/Windowing/Glfw.RawEvents.cs

@@ -0,0 +1,223 @@
+using System.Threading.Tasks;
+using OpenToolkit.GraphicsLibraryFramework;
+
+namespace Robust.Client.Graphics.Clyde
+{
+    partial class Clyde
+    {
+        private unsafe partial class GlfwWindowingImpl
+        {
+            // Keep delegates around to prevent GC issues.
+            private GLFWCallbacks.ErrorCallback? _errorCallback;
+            private GLFWCallbacks.MonitorCallback? _monitorCallback;
+            private GLFWCallbacks.CharCallback? _charCallback;
+            private GLFWCallbacks.CursorPosCallback? _cursorPosCallback;
+            private GLFWCallbacks.CursorEnterCallback? _cursorEnterCallback;
+            private GLFWCallbacks.KeyCallback? _keyCallback;
+            private GLFWCallbacks.MouseButtonCallback? _mouseButtonCallback;
+            private GLFWCallbacks.ScrollCallback? _scrollCallback;
+            private GLFWCallbacks.WindowCloseCallback? _windowCloseCallback;
+            private GLFWCallbacks.WindowPosCallback? _windowPosCallback;
+            private GLFWCallbacks.WindowSizeCallback? _windowSizeCallback;
+            private GLFWCallbacks.WindowContentScaleCallback? _windowContentScaleCallback;
+            private GLFWCallbacks.WindowIconifyCallback? _windowIconifyCallback;
+            private GLFWCallbacks.WindowFocusCallback? _windowFocusCallback;
+
+            private void StoreCallbacks()
+            {
+                _errorCallback = OnGlfwError;
+                _monitorCallback = OnGlfwMonitor;
+                _charCallback = OnGlfwChar;
+                _cursorPosCallback = OnGlfwCursorPos;
+                _cursorEnterCallback = OnGlfwCursorEnter;
+                _keyCallback = OnGlfwKey;
+                _mouseButtonCallback = OnGlfwMouseButton;
+                _scrollCallback = OnGlfwScroll;
+                _windowCloseCallback = OnGlfwWindowClose;
+                _windowSizeCallback = OnGlfwWindowSize;
+                _windowPosCallback = OnGlfwWindowPos;
+                _windowContentScaleCallback = OnGlfwWindowContentScale;
+                _windowIconifyCallback = OnGlfwWindowIconify;
+                _windowFocusCallback = OnGlfwWindowFocus;
+            }
+
+            private void SetupGlobalCallbacks()
+            {
+                GLFW.SetMonitorCallback(_monitorCallback);
+            }
+
+            private void OnGlfwMonitor(Monitor* monitor, ConnectedState state)
+            {
+                if (state == ConnectedState.Connected)
+                    WinThreadSetupMonitor(monitor);
+                else
+                    WinThreadDestroyMonitor(monitor);
+            }
+
+            private void OnGlfwChar(Window* window, uint codepoint)
+            {
+                SendEvent(new EventChar((nint) window, codepoint));
+            }
+
+            private void OnGlfwCursorPos(Window* window, double x, double y)
+            {
+                // System.Console.WriteLine($"{(nint)window:X16}: {x},{y}");
+                SendEvent(new EventCursorPos((nint) window, x, y));
+            }
+
+            private void OnGlfwCursorEnter(Window* window, bool entered)
+            {
+                // System.Console.WriteLine($"{(nint)window:X16}: {entered}");
+                SendEvent(new EventCursorEnter((nint) window, entered));
+            }
+
+            private void OnGlfwKey(Window* window, Keys key, int scanCode, InputAction action, KeyModifiers mods)
+            {
+                SendEvent(new EventKey((nint) window, key, scanCode, action, mods));
+            }
+
+            private void OnGlfwMouseButton(Window* window, MouseButton button, InputAction action, KeyModifiers mods)
+            {
+                SendEvent(new EventMouseButton((nint) window, button, action, mods));
+            }
+
+            private void OnGlfwScroll(Window* window, double offsetX, double offsetY)
+            {
+                SendEvent(new EventScroll((nint) window, offsetX, offsetY));
+            }
+
+            private void OnGlfwWindowClose(Window* window)
+            {
+                SendEvent(new EventWindowClose((nint) window));
+            }
+
+            private void OnGlfwWindowSize(Window* window, int width, int height)
+            {
+                GLFW.GetFramebufferSize(window, out var fbW, out var fbH);
+                SendEvent(new EventWindowSize((nint) window, width, height, fbW, fbH));
+            }
+
+            private void OnGlfwWindowPos(Window* window, int x, int y)
+            {
+                SendEvent(new EventWindowPos((nint) window, x, y));
+            }
+
+            private void OnGlfwWindowContentScale(Window* window, float xScale, float yScale)
+            {
+                SendEvent(new EventWindowContentScale((nint) window, xScale, yScale));
+            }
+
+            private void OnGlfwWindowIconify(Window* window, bool iconified)
+            {
+                SendEvent(new EventWindowIconify((nint) window, iconified));
+            }
+
+            private void OnGlfwWindowFocus(Window* window, bool focused)
+            {
+                SendEvent(new EventWindowFocus((nint) window, focused));
+            }
+
+            // NOTE: events do not correspond 1:1 to GLFW events
+            // This is because they need to pack all the data required
+            // for the game-thread event handling.
+
+            private abstract record EventBase;
+
+            private record EventMouseButton(
+                nint Window,
+                MouseButton Button,
+                InputAction Action,
+                KeyModifiers Mods
+            ) : EventBase;
+
+            private record EventCursorPos(
+                nint Window,
+                double XPos,
+                double YPos
+            ) : EventBase;
+
+            private record EventCursorEnter(
+                nint Window,
+                bool Entered
+            ) : EventBase;
+
+            private record EventScroll(
+                nint Window,
+                double XOffset,
+                double YOffset
+            ) : EventBase;
+
+            private record EventKey(
+                nint Window,
+                Keys Key,
+                int ScanCode,
+                InputAction Action,
+                KeyModifiers Mods
+            ) : EventBase;
+
+            private record EventChar
+            (
+                nint Window,
+                uint CodePoint
+            ) : EventBase;
+
+            private record EventWindowClose
+            (
+                nint Window
+            ) : EventBase;
+
+            private record EventWindowCreate(
+                GlfwWindowCreateResult Result,
+                TaskCompletionSource<GlfwWindowCreateResult> Tcs
+            ) : EventBase;
+
+            private record EventWindowSize
+            (
+                nint Window,
+                int Width,
+                int Height,
+                int FramebufferWidth,
+                int FramebufferHeight
+            ) : EventBase;
+
+            private record EventWindowPos
+            (
+                nint Window,
+                int X,
+                int Y
+            ) : EventBase;
+
+            private record EventWindowContentScale
+            (
+                nint Window,
+                float XScale,
+                float YScale
+            ) : EventBase;
+
+            private record EventWindowIconify
+            (
+                nint Window,
+                bool Iconified
+            ) : EventBase;
+
+            private record EventWindowFocus
+            (
+                nint Window,
+                bool Focused
+            ) : EventBase;
+
+            private record EventMonitorSetup
+            (
+                int Id,
+                string Name,
+                VideoMode CurrentMode,
+                VideoMode[] AllModes
+            ) : EventBase;
+
+            private record EventMonitorDestroy
+            (
+                int Id
+            ) : EventBase;
+        }
+    }
+}

Robust.Client/Graphics/Clyde/Windowing/Glfw.WindowThread.cs

@@ -0,0 +1,250 @@
+using System.Runtime.InteropServices;
+using System.Threading.Channels;
+using System.Threading.Tasks;
+using OpenToolkit.GraphicsLibraryFramework;
+using Robust.Shared;
+using Robust.Shared.Maths;
+using SixLabors.ImageSharp;
+using SixLabors.ImageSharp.PixelFormats;
+
+namespace Robust.Client.Graphics.Clyde
+{
+    internal partial class Clyde
+    {
+        private sealed partial class GlfwWindowingImpl
+        {
+            // glfwPostEmptyEvent is broken on macOS and crashes when not called from the main thread
+            // (despite what the docs claim, and yes this makes it useless).
+            // Because of this, we just forego it and use glfwWaitEventsTimeout on macOS instead.
+            private static readonly bool IsMacOS = RuntimeInformation.IsOSPlatform(OSPlatform.OSX);
+
+            private bool _windowingRunning;
+            private ChannelWriter<CmdBase> _cmdWriter = default!;
+            private ChannelReader<CmdBase> _cmdReader = default!;
+
+            private ChannelReader<EventBase> _eventReader = default!;
+            private ChannelWriter<EventBase> _eventWriter = default!;
+
+            //
+            // Let it be forever recorded that I started work on windowing thread separation
+            // because win32 SetCursor was taking 15ms spinwaiting inside the kernel.
+            //
+
+            //
+            // To avoid stutters and solve some other problems like smooth window resizing,
+            // we (by default) use a separate thread for windowing.
+            //
+            // Types like WindowReg are considered to be part of the "game" thread
+            // and should **NOT** be directly updated/accessed from the windowing thread.
+            //
+            // Got that?
+            //
+
+            //
+            // The windowing -> game channel is bounded so that the OS properly detects the game as locked
+            // up when it actually locks up. The other way around is not bounded to avoid deadlocks.
+            // This also means that all operations like clipboard reading, window creation, etc....
+            // have to be asynchronous.
+            //
+
+            public void EnterWindowLoop()
+            {
+                _windowingRunning = true;
+
+                while (_windowingRunning)
+                {
+                    if (IsMacOS)
+                        GLFW.WaitEventsTimeout(0.008);
+                    else
+                        GLFW.WaitEvents();
+
+                    while (_cmdReader.TryRead(out var cmd))
+                    {
+                        ProcessGlfwCmd(cmd);
+                    }
+                }
+            }
+
+            private void ProcessGlfwCmd(CmdBase cmdb)
+            {
+                switch (cmdb)
+                {
+                    case CmdTerminate:
+                        _windowingRunning = false;
+                        break;
+
+                    case CmdWinSetTitle cmd:
+                        WinThreadWinSetTitle(cmd);
+                        break;
+
+                    case CmdWinSetMonitor cmd:
+                        WinThreadWinSetMonitor(cmd);
+                        break;
+
+                    case CmdWinSetVisible cmd:
+                        WinThreadWinSetVisible(cmd);
+                        break;
+
+                    case CmdWinRequestAttention cmd:
+                        WinThreadWinRequestAttention(cmd);
+                        break;
+
+                    case CmdWinSetFullscreen cmd:
+                        WinThreadWinSetFullscreen(cmd);
+                        break;
+
+                    case CmdWinCreate cmd:
+                        WinThreadWinCreate(cmd);
+                        break;
+
+                    case CmdWinDestroy cmd:
+                        WinThreadWinDestroy(cmd);
+                        break;
+
+                    case CmdSetClipboard cmd:
+                        WinThreadSetClipboard(cmd);
+                        break;
+
+                    case CmdGetClipboard cmd:
+                        WinThreadGetClipboard(cmd);
+                        break;
+
+                    case CmdCursorCreate cmd:
+                        WinThreadCursorCreate(cmd);
+                        break;
+
+                    case CmdCursorDestroy cmd:
+                        WinThreadCursorDestroy(cmd);
+                        break;
+
+                    case CmdWinCursorSet cmd:
+                        WinThreadWinCursorSet(cmd);
+                        break;
+                }
+            }
+
+            public void TerminateWindowLoop()
+            {
+                SendCmd(new CmdTerminate());
+            }
+
+            private void InitChannels()
+            {
+                var cmdChannel = Channel.CreateUnbounded<CmdBase>(new UnboundedChannelOptions
+                {
+                    SingleReader = true,
+                    // Finalizers can write to this in some cases.
+                    SingleWriter = false
+                });
+
+                _cmdReader = cmdChannel.Reader;
+                _cmdWriter = cmdChannel.Writer;
+
+                var bufferSize = _cfg.GetCVar(CVars.DisplayInputBufferSize);
+                var eventChannel = Channel.CreateBounded<EventBase>(new BoundedChannelOptions(bufferSize)
+                {
+                    FullMode = BoundedChannelFullMode.Wait,
+                    SingleReader = true,
+                    SingleWriter = true
+                });
+
+                _eventReader = eventChannel.Reader;
+                _eventWriter = eventChannel.Writer;
+            }
+
+            private void SendCmd(CmdBase cmd)
+            {
+                _cmdWriter.TryWrite(cmd);
+
+                // Post empty event to unstuck WaitEvents if necessary.
+                if (!IsMacOS)
+                    GLFW.PostEmptyEvent();
+            }
+
+            private void SendEvent(EventBase ev)
+            {
+                var task = _eventWriter.WriteAsync(ev);
+
+                if (!task.IsCompletedSuccessfully)
+                {
+                    task.AsTask().Wait();
+                }
+            }
+
+            private abstract record CmdBase;
+
+            private sealed record CmdTerminate : CmdBase;
+
+            private sealed record CmdWinSetTitle(
+                nint Window,
+                string Title
+            ) : CmdBase;
+
+            private sealed record CmdWinSetMonitor(
+                nint Window,
+                int MonitorId,
+                int X, int Y,
+                int W, int H,
+                int RefreshRate
+            ) : CmdBase;
+
+            private sealed record CmdWinMaximize(
+                nint Window
+            ) : CmdBase;
+
+            private sealed record CmdWinSetFullscreen(
+                nint Window
+            ) : CmdBase;
+
+            private sealed record CmdWinSetVisible(
+                nint Window,
+                bool Visible
+            ) : CmdBase;
+
+            private sealed record CmdWinRequestAttention(
+                nint Window
+            ) : CmdBase;
+
+            private sealed record CmdWinCreate(
+                Renderer Renderer,
+                WindowCreateParameters Parameters,
+                nint ShareWindow,
+                TaskCompletionSource<GlfwWindowCreateResult> Tcs
+            ) : CmdBase;
+
+            private sealed record CmdWinDestroy(
+                nint Window
+            ) : CmdBase;
+
+            private sealed record GlfwWindowCreateResult(
+                GlfwWindowReg? Reg,
+                (string Desc, ErrorCode Code)? Error
+            );
+
+            private sealed record CmdSetClipboard(
+                nint Window,
+                string Text
+            ) : CmdBase;
+
+            private sealed record CmdGetClipboard(
+                nint Window,
+                TaskCompletionSource<string> Tcs
+            ) : CmdBase;
+
+            private sealed record CmdWinCursorSet(
+                nint Window,
+                ClydeHandle Cursor
+            ) : CmdBase;
+
+            private sealed record CmdCursorCreate(
+                Image<Rgba32> Bytes,
+                Vector2i Hotspot,
+                ClydeHandle Cursor
+            ) : CmdBase;
+
+            private sealed record CmdCursorDestroy(
+                ClydeHandle Cursor
+            ) : CmdBase;
+        }
+    }
+}

Robust.Client/Graphics/Clyde/Windowing/Glfw.Windows.cs

@@ -0,0 +1,687 @@
+using System;
+using System.Collections.Generic;
+using System.Diagnostics.CodeAnalysis;
+using System.Linq;
+using System.Runtime.InteropServices;
+using System.Threading.Tasks;
+using OpenToolkit;
+using OpenToolkit.Graphics.OpenGL4;
+using OpenToolkit.GraphicsLibraryFramework;
+using Robust.Client.Input;
+using Robust.Client.Utility;
+using Robust.Shared;
+using Robust.Shared.Map;
+using Robust.Shared.Maths;
+using Robust.Shared.Utility;
+using SixLabors.ImageSharp.PixelFormats;
+using GlfwImage = OpenToolkit.GraphicsLibraryFramework.Image;
+using Monitor = OpenToolkit.GraphicsLibraryFramework.Monitor;
+
+namespace Robust.Client.Graphics.Clyde
+{
+    internal partial class Clyde
+    {
+        // Wait for it.
+        private sealed partial class GlfwWindowingImpl
+        {
+            private readonly List<GlfwWindowReg> _windows = new();
+
+            public IReadOnlyList<WindowReg> AllWindows => _windows;
+            public IBindingsContext GraphicsBindingContext => _mainGraphicsContext;
+
+            public WindowReg? MainWindow => _mainWindow;
+            private GlfwWindowReg? _mainWindow;
+            private GlfwBindingsContext _mainGraphicsContext = default!;
+            private int _nextWindowId = 1;
+
+            public async Task<WindowHandle> WindowCreate(WindowCreateParameters parameters)
+            {
+                // tfw await not allowed in unsafe contexts
+
+                // GL APIs don't take kindly to making a new window without unbinding the main context. Great.
+                // Leaving code for async path in, in case it works on like GLX.
+                var unbindContextAndBlock = true;
+
+                DebugTools.AssertNotNull(_mainWindow);
+
+                Task<GlfwWindowCreateResult> task;
+                unsafe
+                {
+                    if (unbindContextAndBlock)
+                        GLFW.MakeContextCurrent(null);
+
+                    task = SharedWindowCreate(
+                        _clyde._chosenRenderer,
+                        parameters,
+                        _mainWindow!.GlfwWindow);
+                }
+
+                if (unbindContextAndBlock)
+                {
+                    unsafe
+                    {
+                        // Block the main thread (to avoid stuff like texture uploads being problematic).
+                        WaitWindowCreate(task);
+
+                        if (unbindContextAndBlock)
+                            GLFW.MakeContextCurrent(_mainWindow.GlfwWindow);
+                    }
+                }
+                else
+                {
+                    await task;
+                }
+
+                var (reg, error) = await task;
+
+                if (reg == null)
+                {
+                    var (desc, errCode) = error!.Value;
+                    throw new GlfwException($"{errCode}: {desc}");
+                }
+
+                _clyde.CreateWindowRenderTexture(reg);
+                _clyde.InitWindowBlitThread(reg);
+
+                unsafe
+                {
+                    GLFW.MakeContextCurrent(_mainWindow.GlfwWindow);
+                }
+
+                return reg.Handle;
+            }
+        }
+
+        // Yes, you read that right.
+        private sealed unsafe partial class GlfwWindowingImpl
+        {
+            public bool TryInitMainWindow(Renderer renderer, [NotNullWhen(false)] out string? error)
+            {
+                var width = _cfg.GetCVar(CVars.DisplayWidth);
+                var height = _cfg.GetCVar(CVars.DisplayHeight);
+                var prevWidth = width;
+                var prevHeight = height;
+
+                IClydeMonitor? monitor = null;
+                var fullscreen = false;
+
+                if (_clyde._windowMode == WindowMode.Fullscreen)
+                {
+                    monitor = _monitors[_primaryMonitorId].Handle;
+                    width = monitor.Size.X;
+                    height = monitor.Size.Y;
+                    fullscreen = true;
+                }
+
+                var parameters = new WindowCreateParameters
+                {
+                    Width = width,
+                    Height = height,
+                    Monitor = monitor,
+                    Fullscreen = fullscreen
+                };
+
+                var windowTask = SharedWindowCreate(renderer, parameters, null);
+                WaitWindowCreate(windowTask);
+
+                var (reg, err) = windowTask.Result;
+                if (reg == null)
+                {
+                    var (desc, code) = err!.Value;
+                    error = $"[{code}] {desc}";
+
+                    return false;
+                }
+
+                DebugTools.Assert(reg.Id == WindowId.Main);
+
+                _mainWindow = reg;
+                reg.IsMainWindow = true;
+
+                if (fullscreen)
+                {
+                    reg.PrevWindowSize = (prevWidth, prevHeight);
+                    reg.PrevWindowPos = (50, 50);
+                }
+
+                UpdateVSync();
+
+                error = null;
+                return true;
+            }
+
+            private void WaitWindowCreate(Task<GlfwWindowCreateResult> windowTask)
+            {
+                while (!windowTask.IsCompleted)
+                {
+                    // Keep processing events until the window task gives either an error or success.
+                    WaitEvents();
+                    ProcessEvents(single: true);
+                }
+            }
+
+            private Task<GlfwWindowCreateResult> SharedWindowCreate(
+                Renderer renderer,
+                WindowCreateParameters parameters,
+                Window* share)
+            {
+                // Yes we ping-pong this TCS through the window thread and back, deal with it.
+                var tcs = new TaskCompletionSource<GlfwWindowCreateResult>();
+                SendCmd(new CmdWinCreate(
+                    renderer,
+                    parameters,
+                    (nint) share,
+                    tcs));
+
+                return tcs.Task;
+            }
+
+            private void FinishWindowCreate(EventWindowCreate ev)
+            {
+                var (res, tcs) = ev;
+                var reg = res.Reg;
+
+                if (reg != null)
+                {
+                    _windows.Add(reg);
+                    _clyde._windowHandles.Add(reg.Handle);
+                }
+
+                tcs.TrySetResult(res);
+            }
+
+            private void WinThreadWinCreate(CmdWinCreate cmd)
+            {
+                var (renderer, parameters, share, tcs) = cmd;
+
+                var window = CreateGlfwWindowForRenderer(renderer, parameters, (Window*) share);
+
+                if (window == null)
+                {
+                    var err = GLFW.GetError(out var desc);
+
+                    SendEvent(new EventWindowCreate(new GlfwWindowCreateResult(null, (desc, err)), tcs));
+                    return;
+                }
+
+                // We can't invoke the TCS directly from the windowing thread because:
+                // * it'd hit the synchronization context,
+                //   which would make (blocking) main window init more annoying.
+                // * it'd not be synchronized to other incoming window events correctly which might be icky.
+                // So we send the TCS back to the game thread
+                // which processes events in the correct order and has better control of stuff during init.
+                var reg = WinThreadSetupWindow(window);
+
+                SendEvent(new EventWindowCreate(new GlfwWindowCreateResult(reg, null), tcs));
+            }
+
+            private void WinThreadWinDestroy(CmdWinDestroy cmd)
+            {
+                GLFW.DestroyWindow((Window*) cmd.Window);
+            }
+
+            public void WindowSetTitle(WindowReg window, string title)
+            {
+                CheckWindowDisposed(window);
+
+                if (title == null)
+                {
+                    throw new ArgumentNullException(nameof(title));
+                }
+
+                var reg = (GlfwWindowReg) window;
+
+                SendCmd(new CmdWinSetTitle((nint) reg.GlfwWindow, title));
+            }
+
+            private void WinThreadWinSetTitle(CmdWinSetTitle cmd)
+            {
+                GLFW.SetWindowTitle((Window*) cmd.Window, cmd.Title);
+            }
+
+            public void WindowSetMonitor(WindowReg window, IClydeMonitor monitor)
+            {
+                CheckWindowDisposed(window);
+
+                var winReg = (GlfwWindowReg) window;
+
+                var monitorImpl = (MonitorHandle) monitor;
+
+                SendCmd(new CmdWinSetMonitor(
+                    (nint) winReg.GlfwWindow,
+                    monitorImpl.Id,
+                    0, 0,
+                    monitorImpl.Size.X, monitorImpl.Size.Y,
+                    monitorImpl.RefreshRate));
+            }
+
+            private void WinThreadWinSetMonitor(CmdWinSetMonitor cmd)
+            {
+                Monitor* monitorPtr;
+                if (cmd.MonitorId == 0)
+                {
+                    monitorPtr = null;
+                }
+                else if (_winThreadMonitors.TryGetValue(cmd.MonitorId, out var monitorReg))
+                {
+                    monitorPtr = monitorReg.Ptr;
+                }
+                else
+                {
+                    return;
+                }
+
+                GLFW.SetWindowMonitor(
+                    (Window*) cmd.Window,
+                    monitorPtr,
+                    cmd.X, cmd.Y,
+                    cmd.W, cmd.H,
+                    cmd.RefreshRate
+                );
+            }
+
+            public void WindowSetVisible(WindowReg window, bool visible)
+            {
+                var reg = (GlfwWindowReg) window;
+                reg.IsVisible = visible;
+
+                SendCmd(new CmdWinSetVisible((nint) reg.GlfwWindow, visible));
+            }
+
+            private void WinThreadWinSetVisible(CmdWinSetVisible cmd)
+            {
+                var win = (Window*) cmd.Window;
+
+                if (cmd.Visible)
+                {
+                    GLFW.ShowWindow(win);
+                }
+                else
+                {
+                    GLFW.HideWindow(win);
+                }
+            }
+
+            public void WindowRequestAttention(WindowReg window)
+            {
+                CheckWindowDisposed(window);
+
+                var reg = (GlfwWindowReg) window;
+
+                SendCmd(new CmdWinRequestAttention((nint) reg.GlfwWindow));
+            }
+
+            private void WinThreadWinRequestAttention(CmdWinRequestAttention cmd)
+            {
+                var win = (Window*) cmd.Window;
+
+                GLFW.RequestWindowAttention(win);
+            }
+
+            public void WindowSwapBuffers(WindowReg window)
+            {
+                CheckWindowDisposed(window);
+
+                var reg = (GlfwWindowReg) window;
+
+                GLFW.SwapBuffers(reg.GlfwWindow);
+            }
+
+            public void UpdateVSync()
+            {
+                if (_mainWindow == null)
+                    return;
+
+                GLFW.MakeContextCurrent(_mainWindow!.GlfwWindow);
+                GLFW.SwapInterval(_clyde._vSync ? 1 : 0);
+            }
+
+            public void UpdateMainWindowMode()
+            {
+                if (_mainWindow == null)
+                {
+                    return;
+                }
+
+                var win = _mainWindow;
+                if (_clyde._windowMode == WindowMode.Fullscreen)
+                {
+                    _mainWindow.PrevWindowSize = win.WindowSize;
+                    _mainWindow.PrevWindowPos = win.PrevWindowPos;
+
+                    SendCmd(new CmdWinSetFullscreen((nint) _mainWindow.GlfwWindow));
+                }
+                else
+                {
+                    SendCmd(new CmdWinSetMonitor(
+                        (nint) _mainWindow.GlfwWindow,
+                        0,
+                        _mainWindow.PrevWindowPos.X, _mainWindow.PrevWindowPos.Y,
+                        _mainWindow.PrevWindowSize.X, _mainWindow.PrevWindowSize.Y,
+                        0
+                    ));
+                }
+            }
+
+            private void WinThreadWinSetFullscreen(CmdWinSetFullscreen cmd)
+            {
+                var ptr = (Window*) cmd.Window;
+                GLFW.GetWindowSize(ptr, out var w, out var h);
+                GLFW.GetWindowPos(ptr, out var x, out var y);
+
+                var monitor = MonitorForWindow(ptr);
+                var mode = GLFW.GetVideoMode(monitor);
+
+                GLFW.SetWindowMonitor(
+                    ptr,
+                    monitor,
+                    0, 0,
+                    mode->Width, mode->Height,
+                    mode->RefreshRate);
+            }
+
+            // glfwGetWindowMonitor only works for fullscreen windows.
+            // Picks the monitor with the top-left corner of the window.
+            private Monitor* MonitorForWindow(Window* window)
+            {
+                GLFW.GetWindowPos(window, out var winPosX, out var winPosY);
+                var monitors = GLFW.GetMonitorsRaw(out var count);
+                for (var i = 0; i < count; i++)
+                {
+                    var monitor = monitors[i];
+                    GLFW.GetMonitorPos(monitor, out var monPosX, out var monPosY);
+                    var videoMode = GLFW.GetVideoMode(monitor);
+
+                    var box = Box2i.FromDimensions(monPosX, monPosY, videoMode->Width, videoMode->Height);
+                    if (box.Contains(winPosX, winPosY))
+                        return monitor;
+                }
+
+                // Fallback
+                return GLFW.GetPrimaryMonitor();
+            }
+
+            public uint? WindowGetX11Id(WindowReg window)
+            {
+                CheckWindowDisposed(window);
+
+                var reg = (GlfwWindowReg) window;
+                try
+                {
+                    return GLFW.GetX11Window(reg.GlfwWindow);
+                }
+                catch (EntryPointNotFoundException)
+                {
+                    return null;
+                }
+            }
+
+            public void WindowDestroy(WindowReg window)
+            {
+                var reg = (GlfwWindowReg) window;
+                if (reg.IsDisposed)
+                    return;
+
+                reg.IsDisposed = true;
+
+                SendCmd(new CmdWinDestroy((nint) reg.GlfwWindow));
+
+                _windows.Remove(reg);
+                _clyde._windowHandles.Remove(reg.Handle);
+
+                _clyde.DestroyWindow?.Invoke(new WindowDestroyedEventArgs(window.Handle));
+            }
+
+            private Window* CreateGlfwWindowForRenderer(
+                Renderer r,
+                WindowCreateParameters parameters,
+                Window* contextShare)
+            {
+#if DEBUG
+                GLFW.WindowHint(WindowHintBool.OpenGLDebugContext, true);
+#endif
+                GLFW.WindowHint(WindowHintString.X11ClassName, "SS14");
+                GLFW.WindowHint(WindowHintString.X11InstanceName, "SS14");
+
+                if (r == Renderer.OpenGL33)
+                {
+                    GLFW.WindowHint(WindowHintInt.ContextVersionMajor, 3);
+                    GLFW.WindowHint(WindowHintInt.ContextVersionMinor, 3);
+                    GLFW.WindowHint(WindowHintBool.OpenGLForwardCompat, true);
+                    GLFW.WindowHint(WindowHintClientApi.ClientApi, ClientApi.OpenGlApi);
+                    GLFW.WindowHint(WindowHintContextApi.ContextCreationApi, ContextApi.NativeContextApi);
+                    GLFW.WindowHint(WindowHintOpenGlProfile.OpenGlProfile, OpenGlProfile.Core);
+                    GLFW.WindowHint(WindowHintBool.SrgbCapable, true);
+                }
+                else if (r == Renderer.OpenGL31)
+                {
+                    GLFW.WindowHint(WindowHintInt.ContextVersionMajor, 3);
+                    GLFW.WindowHint(WindowHintInt.ContextVersionMinor, 1);
+                    GLFW.WindowHint(WindowHintBool.OpenGLForwardCompat, false);
+                    GLFW.WindowHint(WindowHintClientApi.ClientApi, ClientApi.OpenGlApi);
+                    GLFW.WindowHint(WindowHintContextApi.ContextCreationApi, ContextApi.NativeContextApi);
+                    GLFW.WindowHint(WindowHintOpenGlProfile.OpenGlProfile, OpenGlProfile.Any);
+                    GLFW.WindowHint(WindowHintBool.SrgbCapable, true);
+                }
+                else if (r == Renderer.OpenGLES2)
+                {
+                    GLFW.WindowHint(WindowHintInt.ContextVersionMajor, 2);
+                    GLFW.WindowHint(WindowHintInt.ContextVersionMinor, 0);
+                    GLFW.WindowHint(WindowHintBool.OpenGLForwardCompat, true);
+                    GLFW.WindowHint(WindowHintClientApi.ClientApi, ClientApi.OpenGlEsApi);
+                    // GLES2 is initialized through EGL to allow ANGLE usage.
+                    // (It may be an idea to make this a configuration cvar)
+                    GLFW.WindowHint(WindowHintContextApi.ContextCreationApi, ContextApi.EglContextApi);
+                    GLFW.WindowHint(WindowHintOpenGlProfile.OpenGlProfile, OpenGlProfile.Any);
+                    GLFW.WindowHint(WindowHintBool.SrgbCapable, false);
+                }
+
+
+                Monitor* monitor = null;
+                if (parameters.Monitor != null &&
+                    _winThreadMonitors.TryGetValue(parameters.Monitor.Id, out var monitorReg))
+                {
+                    monitor = monitorReg.Ptr;
+                }
+
+                GLFW.WindowHint(WindowHintBool.Visible, false);
+
+                var window = GLFW.CreateWindow(
+                    parameters.Width, parameters.Height,
+                    parameters.Title,
+                    parameters.Fullscreen ? monitor : null,
+                    contextShare);
+
+                // Check if window failed to create.
+                if (window == null)
+                    return null;
+
+                if (parameters.Maximized)
+                {
+                    GLFW.GetMonitorPos(monitor, out var x, out var y);
+                    GLFW.SetWindowPos(window, x, y);
+                    GLFW.MaximizeWindow(window);
+                }
+
+                if (parameters.Visible)
+                {
+                    GLFW.ShowWindow(window);
+                }
+
+
+
+                return window;
+            }
+
+            private GlfwWindowReg WinThreadSetupWindow(Window* window)
+            {
+                var reg = new GlfwWindowReg
+                {
+                    GlfwWindow = window,
+                    Id = new WindowId(_nextWindowId++)
+                };
+                var handle = new WindowHandle(_clyde, reg);
+                reg.Handle = handle;
+
+                LoadWindowIcon(window);
+
+                GLFW.SetCharCallback(window, _charCallback);
+                GLFW.SetKeyCallback(window, _keyCallback);
+                GLFW.SetWindowCloseCallback(window, _windowCloseCallback);
+                GLFW.SetCursorPosCallback(window, _cursorPosCallback);
+                GLFW.SetCursorEnterCallback(window, _cursorEnterCallback);
+                GLFW.SetWindowSizeCallback(window, _windowSizeCallback);
+                GLFW.SetWindowPosCallback(window, _windowPosCallback);
+                GLFW.SetScrollCallback(window, _scrollCallback);
+                GLFW.SetMouseButtonCallback(window, _mouseButtonCallback);
+                GLFW.SetWindowContentScaleCallback(window, _windowContentScaleCallback);
+                GLFW.SetWindowIconifyCallback(window, _windowIconifyCallback);
+                GLFW.SetWindowFocusCallback(window, _windowFocusCallback);
+
+                GLFW.GetFramebufferSize(window, out var fbW, out var fbH);
+                reg.FramebufferSize = (fbW, fbH);
+
+                GLFW.GetWindowContentScale(window, out var scaleX, out var scaleY);
+                reg.WindowScale = (scaleX, scaleY);
+
+                GLFW.GetWindowSize(window, out var w, out var h);
+                reg.PrevWindowSize = reg.WindowSize = (w, h);
+
+                GLFW.GetWindowPos(window, out var x, out var y);
+                reg.PrevWindowPos = (x, y);
+
+                reg.PixelRatio = reg.FramebufferSize / reg.WindowSize;
+
+                return reg;
+            }
+
+            private WindowReg? FindWindow(nint window) => FindWindow((Window*) window);
+
+            private WindowReg? FindWindow(Window* window)
+            {
+                foreach (var windowReg in _windows)
+                {
+                    if (windowReg.GlfwWindow == window)
+                    {
+                        return windowReg;
+                    }
+                }
+
+                return null;
+            }
+
+
+            public int KeyGetScanCode(Keyboard.Key key)
+            {
+                return GLFW.GetKeyScancode(ConvertGlfwKeyReverse(key));
+            }
+
+            public string KeyGetNameScanCode(int scanCode)
+            {
+                return GLFW.GetKeyName(Keys.Unknown, scanCode);
+            }
+
+            public Task<string> ClipboardGetText()
+            {
+                var tcs = new TaskCompletionSource<string>();
+                SendCmd(new CmdGetClipboard((nint) _mainWindow!.GlfwWindow, tcs));
+                return tcs.Task;
+            }
+
+            private void WinThreadGetClipboard(CmdGetClipboard cmd)
+            {
+                var clipboard = GLFW.GetClipboardString((Window*) cmd.Window);
+                // Don't have to care about synchronization I don't think so just fire this immediately.
+                cmd.Tcs.TrySetResult(clipboard);
+            }
+
+            public void ClipboardSetText(string text)
+            {
+                SendCmd(new CmdSetClipboard((nint) _mainWindow!.GlfwWindow, text));
+            }
+
+            private void WinThreadSetClipboard(CmdSetClipboard cmd)
+            {
+                GLFW.SetClipboardString((Window*) cmd.Window, cmd.Text);
+            }
+
+            public void LoadWindowIcon(Window* window)
+            {
+                var icons = _clyde.LoadWindowIcons().ToArray();
+
+                // Turn each image into a byte[] so we can actually pin their contents.
+                // Wish I knew a clean way to do this without allocations.
+                var images = icons
+                    .Select(i => (MemoryMarshal.Cast<Rgba32, byte>(i.GetPixelSpan()).ToArray(), i.Width, i.Height))
+                    .ToList();
+
+                // ReSharper disable once SuggestVarOrType_Elsewhere
+                Span<GCHandle> handles = stackalloc GCHandle[images.Count];
+                Span<GlfwImage> glfwImages = stackalloc GlfwImage[images.Count];
+
+                for (var i = 0; i < images.Count; i++)
+                {
+                    var image = images[i];
+                    handles[i] = GCHandle.Alloc(image.Item1, GCHandleType.Pinned);
+                    var addrOfPinnedObject = (byte*) handles[i].AddrOfPinnedObject();
+                    glfwImages[i] = new GlfwImage(image.Width, image.Height, addrOfPinnedObject);
+                }
+
+                GLFW.SetWindowIcon(window, glfwImages);
+
+                foreach (var handle in handles)
+                {
+                    handle.Free();
+                }
+            }
+
+            public void GLInitMainContext(bool gles)
+            {
+                _mainGraphicsContext = new GlfwBindingsContext();
+                GL.LoadBindings(_mainGraphicsContext);
+
+                if (gles)
+                {
+                    // On GLES we use some OES and KHR functions so make sure to initialize them.
+                    OpenToolkit.Graphics.ES20.GL.LoadBindings(_mainGraphicsContext);
+                }
+            }
+
+            public void GLMakeContextCurrent(WindowReg window)
+            {
+                CheckWindowDisposed(window);
+
+                var reg = (GlfwWindowReg) window;
+
+                GLFW.MakeContextCurrent(reg.GlfwWindow);
+            }
+
+            public void GLSwapInterval(int interval)
+            {
+                GLFW.SwapInterval(interval);
+            }
+
+            private void CheckWindowDisposed(WindowReg reg)
+            {
+                if (reg.IsDisposed)
+                    throw new ObjectDisposedException("Window disposed");
+            }
+
+            private sealed class GlfwWindowReg : WindowReg
+            {
+                public Window* GlfwWindow;
+
+                // Kept around to avoid it being GCd.
+                public CursorImpl? Cursor;
+            }
+
+            private class GlfwBindingsContext : IBindingsContext
+            {
+                public IntPtr GetProcAddress(string procName)
+                {
+                    return GLFW.GetProcAddress(procName);
+                }
+            }
+        }
+    }
+}

Robust.Client/Graphics/Clyde/Windowing/Glfw.cs

@@ -0,0 +1,119 @@
+using System;
+using System.Runtime.Serialization;
+using OpenToolkit.GraphicsLibraryFramework;
+using Robust.Shared;
+using Robust.Shared.Configuration;
+using Robust.Shared.IoC;
+using Robust.Shared.Localization;
+using Robust.Shared.Log;
+
+namespace Robust.Client.Graphics.Clyde
+{
+    internal partial class Clyde
+    {
+        private sealed partial class GlfwWindowingImpl : IWindowingImpl
+        {
+            [Dependency] private readonly ILogManager _logManager = default!;
+            [Dependency] private readonly IConfigurationManager _cfg = default!;
+            [Dependency] private readonly ILocalizationManager _loc = default!;
+
+            private readonly Clyde _clyde;
+
+            private readonly ISawmill _sawmill;
+            private readonly ISawmill _sawmillGlfw;
+
+            private bool _glfwInitialized;
+            private bool _win32Experience;
+
+            public GlfwWindowingImpl(Clyde clyde)
+            {
+                _clyde = clyde;
+                IoCManager.InjectDependencies(this);
+
+                _sawmill = _logManager.GetSawmill("clyde.win");
+                _sawmillGlfw = _logManager.GetSawmill("clyde.win.glfw");
+            }
+
+            public bool Init()
+            {
+#if DEBUG
+                _cfg.OnValueChanged(CVars.DisplayWin32Experience, b => _win32Experience = b, true);
+#endif
+
+                InitChannels();
+
+                if (!InitGlfw())
+                {
+                    return false;
+                }
+
+                SetupGlobalCallbacks();
+                InitMonitors();
+                InitCursors();
+                InitKeyMap();
+
+                return true;
+            }
+
+            public void Shutdown()
+            {
+                if (_glfwInitialized)
+                {
+                    _sawmill.Debug("Terminating GLFW.");
+                    GLFW.Terminate();
+                }
+            }
+
+            public void FlushDispose()
+            {
+                // Not currently used
+            }
+
+            private bool InitGlfw()
+            {
+                StoreCallbacks();
+
+                GLFW.SetErrorCallback(_errorCallback);
+                if (!GLFW.Init())
+                {
+                    var err = GLFW.GetError(out var desc);
+                    _sawmill.Fatal($"Failed to initialize GLFW! [{err}] {desc}");
+                    return false;
+                }
+
+                _glfwInitialized = true;
+                var version = GLFW.GetVersionString();
+                _sawmill.Debug("GLFW initialized, version: {0}.", version);
+
+                return true;
+            }
+
+            private void OnGlfwError(ErrorCode code, string description)
+            {
+                _sawmillGlfw.Error("GLFW Error: [{0}] {1}", code, description);
+            }
+
+            [Serializable]
+            public class GlfwException : Exception
+            {
+                public GlfwException()
+                {
+                }
+
+                public GlfwException(string message) : base(message)
+                {
+                }
+
+                public GlfwException(string message, Exception inner) : base(message, inner)
+                {
+                }
+
+                protected GlfwException(
+                    SerializationInfo info,
+                    StreamingContext context) : base(info, context)
+                {
+                }
+            }
+        }
+    }
+}