Adds ServerOptions, improve GameControllerOptions, fix engine integration tests (#1844)

* Adds ServerOptions, improve GameControllerOptions, fix engine integration tests

* Do component auto-registration in engine integration tests by default

* Fix integration tests on content, register components ONLY if not contentstarted or options are null

* Add integration test for engine integration tests working correctly

* Move cvar overrides out of content and into engine.

.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 }}
 

.github/workflows/test-content.yml

@@ -38,4 +38,4 @@ jobs:
     - name: Content.Tests
       run: dotnet test --no-build Content.Tests/Content.Tests.csproj -v n
     - name: Content.IntegrationTests
-      run: dotnet test --no-build Content.IntegrationTests/Content.IntegrationTests.csproj -v n
+      run: COMPlus_gcServer=1 dotnet test --no-build Content.IntegrationTests/Content.IntegrationTests.csproj -v n

.gitmodules

@@ -13,3 +13,6 @@
 [submodule "ManagedHttpListener"]
 	path = ManagedHttpListener
 	url = https://github.com/space-wizards/ManagedHttpListener.git
+[submodule "Linguini"]
+	path = Linguini
+	url = https://github.com/space-wizards/Linguini

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/GLFWNative.cs

@@ -23,12 +23,12 @@ namespace OpenToolkit.GraphicsLibraryFramework
                     return IntPtr.Zero;
                 }
 
-                if (RuntimeInformation.IsOSPlatform(OSPlatform.Linux))
+                if (OperatingSystem.IsLinux())
                 {
                     return NativeLibrary.Load("libglfw.so.3", assembly, path);
                 }
 
-                if (RuntimeInformation.IsOSPlatform(OSPlatform.OSX))
+                if (OperatingSystem.IsMacOS())
                 {
                     return NativeLibrary.Load("libglfw.3.dylib", assembly, path);
                 }

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/EngineCredits/Libraries.yml

@@ -23,6 +23,48 @@
     OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION
     WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.
 
+- name: Box2D
+  license:
+    MIT License
+
+    Copyright (c) 2019 Erin Catto
+
+    Permission is hereby granted, free of charge, to any person obtaining a copy
+    of this software and associated documentation files (the "Software"), to deal
+    in the Software without restriction, including without limitation the rights
+    to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
+    copies of the Software, and to permit persons to whom the Software is 
+    furnished to do so, subject to the following conditions:
+
+    The above copyright notice and this permission notice shall be included in all
+    copies or substantial portions of the Software.
+
+    THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+    IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+    FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
+    AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+    LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
+    OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
+    SOFTWARE.
+
+- name: Bullet Physics SDK
+  license:
+    The files in this repository are licensed under the zlib license, except for the files under 'Extras' and examples/ThirdPartyLibs.
+
+    Bullet Continuous Collision Detection and Physics Library
+    http://bulletphysics.org
+
+    This software is provided 'as-is', without any express or implied warranty.
+    In no event will the authors be held liable for any damages arising from the use of this software.
+    Permission is granted to anyone to use this software for any purpose,
+    including commercial applications, and to alter it and redistribute it freely,
+    subject to the following restrictions:
+
+    1. The origin of this software must not be misrepresented; you must not claim that you wrote the original software. 
+    If you use this software in a product, an acknowledgment in the product documentation would be appreciated but is not required.
+    2. Altered source versions must be plainly marked as such, and must not be misrepresented as being the original software.
+    3. This notice may not be removed or altered from any source distribution. 
+
 - name: Castle Core
   license: |
     Copyright 2004-2016 Castle Project - http://www.castleproject.org/
@@ -317,6 +359,43 @@
     See the License for the specific language governing permissions and
     limitations under the License.
 
+- name: Farseer Physics Engine
+  license:
+    Microsoft Permissive License (Ms-PL)
+
+    This license governs use of the accompanying software.
+    If you use the software, you accept this license.
+    If you do not accept the license, do not use the software.
+
+    1. Definitions
+    The terms "reproduce," "reproduction," "derivative works," and "distribution" have the same meaning here as under U.S. copyright law.
+    A "contribution" is the original software, or any additions or changes to the software.
+    A "contributor" is any person that distributes its contribution under this license.
+    "Licensed patents" are a contributor's patent claims that read directly on its contribution.
+
+    2. Grant of Rights
+    (A) Copyright Grant- Subject to the terms of this license, including the license conditions and limitations in section 3, 
+    each contributor grants you a non-exclusive, worldwide, royalty-free copyright license to reproduce its contribution, 
+    prepare derivative works of its contribution, and distribute its contribution or any derivative works that you create.
+    (B) Patent Grant- Subject to the terms of this license, including the license conditions and limitations in section 3, 
+    each contributor grants you a non-exclusive, worldwide, royalty-free license under its licensed patents to 
+    make, have made, use, sell, offer for sale, import, and/or otherwise dispose of its contribution in the software or 
+    derivative works of the contribution in the software.
+
+    3. Conditions and Limitations
+    (A) No Trademark License- This license does not grant you rights to use any contributors' name, logo, or trademarks.
+    (B) If you bring a patent claim against any contributor over patents that you claim are infringed by the software, 
+    your patent license from such contributor to the software ends automatically.
+    (C) If you distribute any portion of the software, you must retain all copyright, patent, trademark, 
+    and attribution notices that are present in the software.
+    (D) If you distribute any portion of the software in source code form, you may do so only under this license by 
+    including a complete copy of this license with your distribution. If you distribute any portion of the software in 
+    compiled or object code form, you may only do so under a license that complies with this license.
+    (E) The software is licensed "as-is." You bear the risk of using it. The contributors give no express warranties, 
+    guarantees or conditions. You may have additional consumer rights under your local laws which this license cannot change. 
+    To the extent permitted under your local laws, the contributors exclude the implied warranties of 
+    merchantability, fitness for a particular purpose and non-infringement.
+
 - name: Mono.Cecil
   license: |
     Copyright (c) 2008 - 2015 Jb Evain

Resources/Locale/en-US/custom-controls.ftl

@@ -0,0 +1,7 @@
+## EntitySpawnWindow
+
+entity-spawn-window-title = Entity Spawn Panel
+entity-spawn-window-search-bar-placeholder = search
+entity-spawn-window-clear-button = Clear
+entity-spawn-window-erase-button-text = Erase Mode
+entity-spawn-window-override-menu-tooltip = Override placement

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/Locale/en-US/tab-container.ftl

@@ -0,0 +1 @@
+tab-container-not-tab-title-provided = No title

Resources/Locale/en-US/view-variables.ftl

@@ -0,0 +1,11 @@
+## ViewVariablesInstanceEntity
+
+view-variable-instance-entity-server-components-add-component-button-placeholder = Add Component
+view-variable-instance-entity-client-variables-tab-title = Client Variables
+view-variable-instance-entity-client-components-tab-title = Client Components
+view-variable-instance-entity-server-variables-tab-title = Server Variables
+view-variable-instance-entity-server-components-tab-title = Server Components
+view-variable-instance-entity-client-components-search-bar-placeholder = Search
+view-variable-instance-entity-server-components-search-bar-placeholder = Search
+view-variable-instance-entity-add-window-server-components = Add Component [S]
+view-variable-instance-entity-add-window-client-components = Add Component [C]

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

@@ -1,5 +1,6 @@
 using System;
 using System.Collections.Generic;
+using System.IO;
 using System.Linq;
 using System.Text;
 using Microsoft.CodeAnalysis;
@@ -147,9 +148,10 @@ namespace {nameSpace}
             foreach (var typeSymbol in symbols)
             {
                 var xamlFileName = $"{typeSymbol.Name}.xaml";
-                var relevantXamlFile = context.AdditionalFiles.FirstOrDefault(t => t.Path.EndsWith(xamlFileName));
+                var xamlFileNameSep = $"{Path.DirectorySeparatorChar}{xamlFileName}";
+                var relevantXamlFiles = context.AdditionalFiles.Where(t => t.Path.EndsWith(xamlFileNameSep)).ToArray();
 
-                if (relevantXamlFile == null)
+                if (relevantXamlFiles.Length == 0)
                 {
                     context.ReportDiagnostic(
                         Diagnostic.Create(
@@ -165,13 +167,28 @@ namespace {nameSpace}
                     continue;
                 }
 
-                var txt = relevantXamlFile.GetText()?.ToString();
-                if (txt == null)
+                if (relevantXamlFiles.Length > 1)
                 {
                     context.ReportDiagnostic(
                         Diagnostic.Create(
                             new DiagnosticDescriptor(
                                 "RXN0002",
+                                $"Found multiple candidate XAML files for {typeSymbol}",
+                                $"Multiple files exist with name {xamlFileName}",
+                                "Usage",
+                                DiagnosticSeverity.Error,
+                                true),
+                            typeSymbol.Locations[0]));
+                    continue;
+                }
+
+                var txt = relevantXamlFiles[0].GetText()?.ToString();
+                if (txt == null)
+                {
+                    context.ReportDiagnostic(
+                        Diagnostic.Create(
+                            new DiagnosticDescriptor(
+                                "RXN0004",
                                 $"Unexpected empty Xaml-File was found at {xamlFileName}",
                                 "Expected Content due to a Class with the same name being annotated with [GenerateTypedNameReferences].",
                                 "Usage",
@@ -192,7 +209,7 @@ namespace {nameSpace}
                     context.ReportDiagnostic(
                         Diagnostic.Create(
                             new DiagnosticDescriptor(
-                                "AXN0003",
+                                "RXN0003",
                                 "Unhandled exception occured while generating typed Name references.",
                                 $"Unhandled exception occured while generating typed Name references: {e}",
                                 "Usage",
@@ -247,7 +264,6 @@ namespace {nameSpace}
                                 DiagnosticSeverity.Error,
                                 true),
                             Location.None));
-                    return null;
                 }
             }
 

Robust.Client/Audio/Midi/MidiManager.cs

@@ -6,6 +6,8 @@ using System.Threading;
 using NFluidsynth;
 using Robust.Client.Graphics;
 using Robust.Client.ResourceManagement;
+using Robust.Shared;
+using Robust.Shared.Configuration;
 using Robust.Shared.ContentPack;
 using Robust.Shared.GameObjects;
 using Robust.Shared.IoC;
@@ -15,6 +17,7 @@ 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 +36,6 @@ 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 +43,11 @@ 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>
@@ -73,9 +63,11 @@ namespace Robust.Client.Audio.Midi
         [Dependency] private readonly IEyeManager _eyeManager = default!;
         [Dependency] private readonly IResourceManagerInternal _resourceManager = default!;
         [Dependency] private readonly IEntityManager _entityManager = default!;
+        [Dependency] private readonly IConfigurationManager _cfgMan = default!;
 
         private SharedBroadPhaseSystem _broadPhaseSystem = default!;
 
+        [ViewVariables]
         public bool IsAvailable
         {
             get
@@ -86,12 +78,29 @@ 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;
+
+                _cfgMan.SetCVar(CVars.MidiVolume, value);
+                _volumeDirty = true;
+            }
+        }
 
         private static readonly string[] LinuxSoundfonts =
         {
@@ -118,12 +127,19 @@ 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()
         {
             if (FluidsynthInitialized || _failedInitialize) return;
 
+            _cfgMan.OnValueChanged(CVars.MidiVolume, value =>
+            {
+                _volume = value;
+                _volumeDirty = true;
+            }, true);
+
             _midiSawmill = Logger.GetSawmill("midi");
             _sawmill = Logger.GetSawmill("midi.fluidsynth");
             _loggerDelegate = LoggerDelegate;
@@ -176,18 +192,6 @@ 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)
@@ -221,7 +225,7 @@ namespace Robust.Client.Audio.Midi
                 // Since the last loaded soundfont takes priority, we load the fallback soundfont before the soundfont.
                 renderer.LoadSoundfont(FallbackSoundfont);
 
-                if (RuntimeInformation.IsOSPlatform(OSPlatform.Linux))
+                if (OperatingSystem.IsLinux())
                 {
                     foreach (var filepath in LinuxSoundfonts)
                     {
@@ -239,19 +243,21 @@ namespace Robust.Client.Audio.Midi
                         break;
                     }
                 }
-                else if (RuntimeInformation.IsOSPlatform(OSPlatform.OSX))
+                else if (OperatingSystem.IsMacOS())
                 {
                     if (File.Exists(OsxSoundfont) && SoundFont.IsSoundFont(OsxSoundfont))
                         renderer.LoadSoundfont(OsxSoundfont, true);
                 }
-                else if (RuntimeInformation.IsOSPlatform(OSPlatform.Windows))
+                else if (OperatingSystem.IsWindows())
                 {
                     if (File.Exists(WindowsSoundfont) && SoundFont.IsSoundFont(WindowsSoundfont))
                         renderer.LoadSoundfont(WindowsSoundfont, true);
                 }
 
                 lock (_renderers)
+                {
                     _renderers.Add(renderer);
+                }
 
                 return renderer;
             }
@@ -269,69 +275,79 @@ 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 +358,7 @@ namespace Robust.Client.Audio.Midi
             while (_alive)
             {
                 lock (_renderers)
+                {
                     for (var i = 0; i < _renderers.Count; i++)
                     {
                         var renderer = _renderers[i];
@@ -349,10 +366,11 @@ namespace Robust.Client.Audio.Midi
                             renderer.Render();
                         else
                         {
-                            ((IMidiRenderer)renderer).InternalDispose();
+                            renderer.InternalDispose();
                             _renderers.Remove(renderer);
                         }
                     }
+                }
 
                 Thread.Sleep(1);
             }
@@ -363,9 +381,13 @@ 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 +442,7 @@ 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 +466,7 @@ namespace Robust.Client.Audio.Midi
                 {
                     return -1;
                 }
+
                 return 0;
             }
 
@@ -464,10 +488,12 @@ 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

@@ -7,7 +7,9 @@ using Robust.Shared.GameObjects;
 using Robust.Shared.IoC;
 using Robust.Shared.Log;
 using Robust.Shared.Map;
+using Robust.Shared.Maths;
 using Robust.Shared.Utility;
+using Robust.Shared.ViewVariables;
 using MidiEvent = NFluidsynth.MidiEvent;
 
 namespace Robust.Client.Audio.Midi
@@ -21,6 +23,17 @@ 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 +123,11 @@ 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 +177,7 @@ 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!;
@@ -186,10 +204,16 @@ namespace Robust.Client.Audio.Midi
         private const int SampleRate = 44100;
         private const int Buffers = SampleRate / 2205;
         private readonly object _playerStateLock = new();
+        private bool _debugEvents = false;
         private SequencerClientId _synthRegister;
+        private SequencerClientId _debugRegister;
         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 +227,7 @@ namespace Robust.Client.Audio.Midi
             }
         }
 
+        [ViewVariables(VVAccess.ReadWrite)]
         public byte MidiBank
         {
             get => _midiBank;
@@ -216,6 +241,7 @@ namespace Robust.Client.Audio.Midi
             }
         }
 
+        [ViewVariables(VVAccess.ReadWrite)]
         public uint MidiSoundfont
         {
             get => _midiSoundfont;
@@ -229,10 +255,16 @@ 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 +275,19 @@ 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 +299,11 @@ 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)
         {
@@ -276,6 +316,7 @@ namespace Robust.Client.Audio.Midi
             _soundFontLoader = soundFontLoader;
             _synth = new Synth(_settings);
             _sequencer = new Sequencer(false);
+            _debugRegister = _sequencer.RegisterClient("honk", DumpSequencerEvent);
             _synthRegister = _sequencer.RegisterFluidsynth(_synth);
 
             _synth.AddSoundFontLoader(soundFontLoader);
@@ -285,6 +326,27 @@ namespace Robust.Client.Audio.Midi
             Source.StartPlaying();
         }
 
+        private void DumpSequencerEvent(uint time, SequencerEvent @event)
+        {
+            // ReSharper disable once UseStringInterpolation
+            _midiSawmill.Debug(string.Format(
+                "{0:D8}: {1} chan:{2:D2} key:{3:D5} bank:{4:D2} ctrl:{5:D5} dur:{6:D5} pitch:{7:D5} prog:{8:D3} val:{9:D5} vel:{10:D5}",
+                time,
+                @event.Type.ToString().PadLeft(22),
+                @event.Channel,
+                @event.Key,
+                @event.Bank,
+                @event.Control,
+                @event.Duration,
+                @event.Pitch,
+                @event.Program,
+                @event.Value,
+                @event.Velocity));
+
+            @event.Dest = _synthRegister;
+            _sequencer.SendNow(@event);
+        }
+
         public bool OpenInput()
         {
             if (Disposed)
@@ -294,7 +356,11 @@ 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 +398,13 @@ 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 +428,8 @@ namespace Robust.Client.Audio.Midi
 
         public void StopAllNotes()
         {
-            _synth.AllNotesOff(-1);
+            lock(_playerStateLock)
+                _synth.AllNotesOff(-1);
         }
 
         public void LoadSoundfont(string filename, bool resetPresets = false)
@@ -372,13 +444,15 @@ 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;
 
-            // SSE needs this.
-            DebugTools.Assert(length % 4 == 0, "Sample length must be multiple of 4");
-
             var buffersProcessed = Source.GetNumberOfBuffersProcessed();
             if(buffersProcessed == Buffers) _midiSawmill.Warning("MIDI buffer overflow!");
             if (buffersProcessed == 0) return;
@@ -393,36 +467,16 @@ namespace Robust.Client.Audio.Midi
                 Source.GetBuffersProcessed(buffers);
 
                 lock (_playerStateLock)
+                {
+                    // _sequencer.Process(10);
                     _synth?.WriteSampleFloat(length * buffers.Length, audio, 0, Mono ? 1 : 2,
                         audio, Mono ? length * buffers.Length : 1, Mono ? 1 : 2);
-
+                }
                 if (Mono) // Turn audio to mono
                 {
                     var l = length * buffers.Length;
 
-                    if (Sse.IsSupported)
-                    {
-                        fixed (float* ptr = audio)
-                        {
-                            for (var j = 0; j < l; j += 4)
-                            {
-                                var k = j + l;
-
-                                var jV = Sse.LoadVector128(ptr + j);
-                                var kV = Sse.LoadVector128(ptr + k);
-
-                                Sse.Store(j + ptr, Sse.Add(jV, kV));
-                            }
-                        }
-                    }
-                    else
-                    {
-                        for (var j = 0; j < l; j++)
-                        {
-                            var k = j + l;
-                            audio[j] = ((audio[k] + audio[j]));
-                        }
-                    }
+                    NumericsHelpers.Add(audio[..l], audio[l..]);
                 }
 
                 for (var i = 0; i < buffers.Length; i++)
@@ -452,6 +506,7 @@ 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 +517,7 @@ namespace Robust.Client.Audio.Midi
             var timestamp = SequencerTick;
             var midiEv = (Shared.Audio.Midi.MidiEvent) midiEvent;
             midiEv.Tick = timestamp;
+            midiEvent.Dispose();
             SendMidiEvent(midiEv);
             return 0;
         }
@@ -478,16 +534,16 @@ namespace Robust.Client.Audio.Midi
                 lock(_playerStateLock)
                     switch (midiEvent.Type)
                     {
-                        // Note On 0x80
-                        case 144:
-                            _synth.NoteOn(midiEvent.Channel, midiEvent.Key, midiEvent.Velocity);
-                            break;
-
-                        // Note Off - 0x90
+                        // Note Off - 0x80
                         case 128:
                             _synth.NoteOff(midiEvent.Channel, midiEvent.Key);
                             break;
 
+                        // Note On 0x90
+                        case 144:
+                            _synth.NoteOn(midiEvent.Channel, midiEvent.Key, midiEvent.Velocity);
+                            break;
+
                         // After Touch - 0xA
                         case 160:
                             _synth.KeyPressure(midiEvent.Channel, midiEvent.Key, midiEvent.Value);
@@ -522,6 +578,12 @@ namespace Robust.Client.Audio.Midi
                         case 81:
                         // System Messages - 0xF0
                         case 240:
+                            switch (midiEvent.Control)
+                            {
+                                case 11:
+                                    _synth.AllNotesOff(midiEvent.Channel);
+                                    break;
+                            }
                             return;
 
                         default:
@@ -543,7 +605,7 @@ namespace Robust.Client.Audio.Midi
             if (Disposed) return;
 
             var seqEv = (SequencerEvent) midiEvent;
-            seqEv.Dest = _synthRegister;
+            seqEv.Dest = _debugEvents ? _debugRegister : _synthRegister;
             _sequencer.SendAt(seqEv, time, absolute);
         }
 
@@ -566,10 +628,15 @@ namespace Robust.Client.Audio.Midi
         void IMidiRenderer.InternalDispose()
         {
             Source?.Dispose();
+            _driver?.Dispose();
+
+            // Do NOT dispose of the sequencer after the synth or it'll cause a segfault for some fucking reason.
+            _sequencer?.UnregisterClient(_debugRegister);
+            _sequencer?.UnregisterClient(_synthRegister);
+            _sequencer?.Dispose();
+            
             _synth?.Dispose();
             _player?.Dispose();
-            _driver?.Dispose();
-            _sequencer?.Dispose();
         }
     }
 }

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/CommandLineArgs.cs

@@ -17,6 +17,7 @@ namespace Robust.Client
         public bool Launcher { get; }
         public string? Username { get; }
         public IReadOnlyCollection<(string key, string value)> CVars { get; }
+        public IReadOnlyCollection<(string key, string value)> LogLevels { get; }
 
         // Manual parser because C# has no good command line parsing libraries. Also dependencies bad.
         // Also I don't like spending 100ms parsing command line args. Do you?
@@ -31,6 +32,7 @@ namespace Robust.Client
             var launcher = false;
             string? username = null;
             var cvars = new List<(string, string)>();
+            var logLevels = new List<(string, string)>();
             var mountOptions = new MountOptions();
 
             using var enumerator = args.GetEnumerator();
@@ -124,6 +126,26 @@ namespace Robust.Client
 
                     mountOptions.DirMounts.Add(enumerator.Current);
                 }
+                else if (arg == "--loglevel")
+                {
+                    if (!enumerator.MoveNext())
+                    {
+                        C.WriteLine("Missing loglevel sawmill.");
+                        return false;
+                    }
+
+                    var loglevel = enumerator.Current;
+                    DebugTools.AssertNotNull(loglevel);
+                    var pos = loglevel.IndexOf('=');
+
+                    if (pos == -1)
+                    {
+                        C.WriteLine("Expected = in loglevel.");
+                        return false;
+                    }
+
+                    logLevels.Add((loglevel[..pos], loglevel[(pos + 1)..]));
+                }
                 else if (arg == "--help")
                 {
                     PrintHelp();
@@ -142,6 +164,7 @@ namespace Robust.Client
                 launcher,
                 username,
                 cvars,
+                logLevels,
                 connectAddress,
                 ss14Address,
                 mountOptions);
@@ -162,6 +185,7 @@ Options:
   --launcher          Run in launcher mode (no main menu, auto connect).
   --username          Override username.
   --cvar              Specifies an additional cvar overriding the config file. Syntax is <key>=<value>
+  --loglevel          Specifies an additional sawmill log level overriding the default values. Syntax is <key>=<value>
   --mount-dir         Resource directory to mount.
   --mount-zip         Resource zip to mount.
   --help              Display this help text and exit.
@@ -175,6 +199,7 @@ Options:
             bool launcher,
             string? username,
             IReadOnlyCollection<(string key, string value)> cVars,
+            IReadOnlyCollection<(string key, string value)> logLevels,
             string connectAddress, string? ss14Address,
             MountOptions mountOptions)
         {
@@ -184,6 +209,7 @@ Options:
             Launcher = launcher;
             Username = username;
             CVars = cVars;
+            LogLevels = logLevels;
             ConnectAddress = connectAddress;
             Ss14Address = ss14Address;
             MountOptions = mountOptions;

Robust.Client/Console/ClientConsoleHost.cs

@@ -36,7 +36,7 @@ namespace Robust.Client.Console
             Message = message;
         }
     }
-    
+
     /// <inheritdoc cref="IClientConsoleHost" />
     internal class ClientConsoleHost : ConsoleHost, IClientConsoleHost
     {
@@ -45,9 +45,9 @@ namespace Robust.Client.Console
         /// <inheritdoc />
         public void Initialize()
         {
-            NetManager.RegisterNetMessage<MsgConCmdReg>(MsgConCmdReg.NAME, HandleConCmdReg);
-            NetManager.RegisterNetMessage<MsgConCmdAck>(MsgConCmdAck.NAME, HandleConCmdAck);
-            NetManager.RegisterNetMessage<MsgConCmd>(MsgConCmd.NAME, ProcessCommand);
+            NetManager.RegisterNetMessage<MsgConCmdReg>(HandleConCmdReg);
+            NetManager.RegisterNetMessage<MsgConCmdAck>(HandleConCmdAck);
+            NetManager.RegisterNetMessage<MsgConCmd>(ProcessCommand);
 
             Reset();
             LogManager.RootSawmill.AddHandler(new DebugConsoleLogHandler(this));

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/LightBBCommand.cs

@@ -0,0 +1,19 @@
+#if DEBUG
+using Robust.Client.GameObjects;
+using Robust.Shared.Console;
+using Robust.Shared.GameObjects;
+
+namespace Robust.Client.Console.Commands
+{
+    internal sealed class LightDebugCommand : IConsoleCommand
+    {
+        public string Command => "lightbb";
+        public string Description => "Toggles whether to show light bounding boxes";
+        public string Help => $"{Command}";
+        public void Execute(IConsoleShell shell, string argStr, string[] args)
+        {
+            EntitySystem.Get<DebugLightTreeSystem>().Enabled ^= true;
+        }
+    }
+}
+#endif

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/Commands/Scripting.cs

@@ -1,6 +1,5 @@
 using Robust.Shared.Console;
 using Robust.Shared.IoC;
-using Robust.Shared.Localization;
 
 namespace Robust.Client.Console.Commands
 {
@@ -41,7 +40,7 @@ namespace Robust.Client.Console.Commands
             var mgr = IoCManager.Resolve<IScriptClient>();
             if (!mgr.CanScript)
             {
-                shell.WriteError(Loc.GetString("You do not have server side scripting permission."));
+                shell.WriteError("You do not have server side scripting permission.");
                 return;
             }
 

Robust.Client/Console/ScriptClient.cs

@@ -17,11 +17,11 @@ namespace Robust.Client.Console
 
         public void Initialize()
         {
-            _netManager.RegisterNetMessage<MsgScriptStop>(MsgScriptStop.NAME);
-            _netManager.RegisterNetMessage<MsgScriptEval>(MsgScriptEval.NAME);
-            _netManager.RegisterNetMessage<MsgScriptStart>(MsgScriptStart.NAME);
-            _netManager.RegisterNetMessage<MsgScriptResponse>(MsgScriptResponse.NAME, ReceiveScriptResponse);
-            _netManager.RegisterNetMessage<MsgScriptStartAck>(MsgScriptStartAck.NAME, ReceiveScriptStartAckResponse);
+            _netManager.RegisterNetMessage<MsgScriptStop>();
+            _netManager.RegisterNetMessage<MsgScriptEval>();
+            _netManager.RegisterNetMessage<MsgScriptStart>();
+            _netManager.RegisterNetMessage<MsgScriptResponse>(ReceiveScriptResponse);
+            _netManager.RegisterNetMessage<MsgScriptStartAck>(ReceiveScriptStartAckResponse);
         }
 
         private void ReceiveScriptStartAckResponse(MsgScriptStartAck message)
@@ -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/Console/ScriptConsoleClient.cs

@@ -1,5 +1,4 @@
 #if CLIENT_SCRIPTING
-using System;
 using System.Collections.Generic;
 using System.Diagnostics.CodeAnalysis;
 using System.Linq;
@@ -14,7 +13,6 @@ using Microsoft.CodeAnalysis.Text;
 using Robust.Client.UserInterface.CustomControls;
 using Robust.Client.ViewVariables;
 using Robust.Shared.IoC;
-using Robust.Shared.Localization;
 using Robust.Shared.Maths;
 using Robust.Shared.Reflection;
 using Robust.Shared.Scripting;
@@ -43,14 +41,14 @@ namespace Robust.Client.Console
 
         public ScriptConsoleClient()
         {
-            Title = Loc.GetString("Robust C# Interactive (CLIENT)");
+            Title = "Robust C# Interactive (CLIENT)";
             ScriptInstanceShared.InitDummy();
 
             _globals = new ScriptGlobalsImpl(this);
 
             IoCManager.InjectDependencies(this);
 
-            OutputPanel.AddText(Loc.GetString(@"Robust C# interactive console (CLIENT)."));
+            OutputPanel.AddText("Robust C# interactive console (CLIENT).");
             OutputPanel.AddText(">");
         }
 

Robust.Client/Console/WatchWindow.cs

@@ -8,8 +8,6 @@ using Robust.Client.UserInterface;
 using Robust.Client.UserInterface.Controls;
 using Robust.Client.UserInterface.CustomControls;
 using Robust.Shared.IoC;
-using Robust.Shared.Localization;
-using Robust.Shared.Maths;
 using Robust.Shared.Reflection;
 using Robust.Shared.Scripting;
 using Robust.Shared.Timing;
@@ -31,7 +29,7 @@ namespace Robust.Client.Console
 
             ScriptInstanceShared.InitDummy();
 
-            Title = Loc.GetString("Watch Window");
+            Title = "Watch Window";
 
             var mainVBox = new VBoxContainer
             {
@@ -49,11 +47,11 @@ namespace Robust.Client.Console
                             (_addWatchEdit = new HistoryLineEdit
                             {
                                 HorizontalExpand = true,
-                                PlaceHolder = Loc.GetString("Add watch (C# interactive)")
+                                PlaceHolder = "Add watch (C# interactive)"
                             }),
                             (_addWatchButton = new Button
                             {
-                                Text = Loc.GetString("Add")
+                                Text = "Add"
                             })
                         }
                     }
@@ -118,7 +116,7 @@ namespace Robust.Client.Console
                         }),
                         (delButton = new Button
                         {
-                            Text = Loc.GetString("Remove")
+                            Text = "Remove"
                         }),
                     }
                 });
@@ -178,7 +176,7 @@ namespace Robust.Client.Console
                             ClipText = true,
                             HorizontalExpand = true
                         },
-                        (delButton = new Button {Text = Loc.GetString("Remove")})
+                        (delButton = new Button {Text = "Remove"})
                     }
                 });
 

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);
+            GameController.Start(args, new GameControllerOptions(), true);
 #endif
         }
+
+        public static void StartLibrary(string[] args, GameControllerOptions options)
+        {
+            GameController.Start(args, options, true, null);
+        }
     }
 }

Robust.Client/Debugging/DebugDrawing.cs

@@ -1,15 +1,18 @@
-using System;
+using System;
 using System.Collections.Generic;
 using Robust.Client.Graphics;
 using Robust.Client.Input;
 using Robust.Client.ResourceManagement;
+using Robust.Shared.Enums;
 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
@@ -18,11 +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 IEntityLookup _lookup = default!;
+        [Dependency] private readonly IMapManager _mapManager = default!;
         [Dependency] private readonly IInputManager _inputManager = default!;
 
         private bool _debugColliders;
@@ -41,14 +43,14 @@ namespace Robust.Client.Debugging
 
                 _debugColliders = value;
 
-                if (value)
+                if (value && !_overlayManager.HasOverlay<PhysicsOverlay>())
                 {
-                    _overlayManager.AddOverlay(new PhysicsOverlay(_componentManager, _eyeManager,
-                        _prototypeManager, _inputManager, _physicsManager));
+                    _overlayManager.AddOverlay(new PhysicsOverlay(_eyeManager,
+                        _prototypeManager, _inputManager, _mapManager));
                 }
                 else
                 {
-                    _overlayManager.RemoveOverlay(nameof(PhysicsOverlay));
+                    _overlayManager.RemoveOverlay<PhysicsOverlay>();
                 }
             }
         }
@@ -66,23 +68,22 @@ namespace Robust.Client.Debugging
 
                 _debugPositions = value;
 
-                if (value)
+                if (value && !_overlayManager.HasOverlay<EntityPositionOverlay>())
                 {
-                    _overlayManager.AddOverlay(new EntityPositionOverlay(_entityManager, _eyeManager));
+                    _overlayManager.AddOverlay(new EntityPositionOverlay(_lookup, _eyeManager));
                 }
                 else
                 {
-                    _overlayManager.RemoveOverlay(nameof(EntityPositionOverlay));
+                    _overlayManager.RemoveOverlay<EntityPositionOverlay>();
                 }
             }
         }
 
         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;
@@ -91,13 +92,12 @@ namespace Robust.Client.Debugging
             private Vector2 _hoverStartScreen = Vector2.Zero;
             private List<IPhysBody> _hoverBodies = new();
 
-            public PhysicsOverlay(IComponentManager compMan, IEyeManager eyeMan, IPrototypeManager protoMan, IInputManager inputManager, IPhysicsManager physicsManager)
-                : base(nameof(PhysicsOverlay))
+
+            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>();
@@ -105,22 +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;
@@ -129,54 +130,63 @@ namespace Robust.Client.Debugging
                 {
                     if (body != _hoverBodies[0])
                     {
-                        DrawString(screenHandle, _font, drawPos + new Vector2(0, row * lineHeight), "------");
+                        screenHandle.DrawString(_font, drawPos + new Vector2(0, row * lineHeight), "------");
                         row++;
                     }
 
-                    DrawString(screenHandle, _font, drawPos + new Vector2(0, row * lineHeight), $"Ent: {body.Entity}");
+                    screenHandle.DrawString(_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)}");
+                    screenHandle.DrawString(_font, drawPos + new Vector2(0, row * lineHeight), $"Layer: {Convert.ToString(body.CollisionLayer, 2)}");
                     row++;
-                    DrawString(screenHandle, _font, drawPos + new Vector2(0, row * lineHeight), $"Mask: {Convert.ToString(body.CollisionMask, 2)}");
+                    screenHandle.DrawString(_font, drawPos + new Vector2(0, row * lineHeight), $"Mask: {Convert.ToString(body.CollisionMask, 2)}");
                     row++;
-                    DrawString(screenHandle, _font, drawPos + new Vector2(0, row * lineHeight), $"Enabled: {body.CanCollide}, Hard: {body.Hard}, Anchored: {(body).BodyType == BodyType.Static}");
+                    screenHandle.DrawString(_font, drawPos + new Vector2(0, row * lineHeight), $"Enabled: {body.CanCollide}, Hard: {body.Hard}, Anchored: {(body).BodyType == BodyType.Static}");
                     row++;
                 }
 
             }
 
-            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();
                     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))
@@ -189,17 +199,6 @@ namespace Robust.Client.Debugging
                 }
             }
 
-            private static void DrawString(DrawingHandleScreen handle, Font font, Vector2 pos, string str)
-            {
-                var baseLine = new Vector2(pos.X, font.GetAscent(1) + pos.Y);
-
-                foreach (var chr in str)
-                {
-                    var advance = font.DrawChar(handle, chr, baseLine, 1, Color.White);
-                    baseLine += new Vector2(advance, 0);
-                }
-            }
-
             private class PhysDrawingAdapter : DebugDrawingHandle
             {
                 private readonly DrawingHandleWorld _handle;
@@ -260,34 +259,33 @@ namespace Robust.Client.Debugging
 
         private sealed class EntityPositionOverlay : Overlay
         {
-            private readonly IEntityManager _entityManager;
+            private readonly IEntityLookup _lookup;
             private readonly IEyeManager _eyeManager;
 
             public override OverlaySpace Space => OverlaySpace.WorldSpace;
 
-            public EntityPositionOverlay(IEntityManager entityManager, IEyeManager eyeManager) : base(nameof(EntityPositionOverlay))
+            public EntityPositionOverlay(IEntityLookup lookup, IEyeManager eyeManager)
             {
-                _entityManager = entityManager;
+                _lookup = lookup;
                 _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;
-                foreach (var entity in _entityManager.GetEntities())
+                var worldHandle = (DrawingHandleWorld) args.DrawingHandle;
+                var viewport = _eyeManager.GetWorldViewport();
+
+                foreach (var entity in _lookup.GetEntitiesIntersecting(_eyeManager.CurrentMap, viewport))
                 {
                     var transform = entity.Transform;
-                    if (transform.MapID != _eyeManager.CurrentMap ||
-                        !_eyeManager.GetWorldViewport().Contains(transform.WorldPosition))
-                    {
-                        continue;
-                    }
 
                     var center = transform.WorldPosition;
-                    var xLine = transform.WorldRotation.RotateVec(Vector2.UnitX);
-                    var yLine = transform.WorldRotation.RotateVec(Vector2.UnitY);
+                    var worldRotation = transform.WorldRotation;
+
+                    var xLine = worldRotation.RotateVec(Vector2.UnitX);
+                    var yLine = worldRotation.RotateVec(Vector2.UnitY);
 
                     worldHandle.DrawLine(center, center + xLine * stubLength, Color.Red);
                     worldHandle.DrawLine(center, center + yLine * stubLength, Color.Green);

Robust.Client/Debugging/DebugDrawingManager.cs

@@ -1,11 +1,12 @@
-using Robust.Shared.IoC;
-using Robust.Shared.Network.Messages;
 using System;
 using System.Collections.Generic;
 using Robust.Client.Graphics;
+using Robust.Shared.Enums;
+using Robust.Shared.IoC;
 using Robust.Shared.Maths;
-using Robust.Shared.Timing;
 using Robust.Shared.Network;
+using Robust.Shared.Network.Messages;
+using Robust.Shared.Timing;
 
 namespace Robust.Client.Debugging
 {
@@ -38,13 +39,13 @@ namespace Robust.Client.Debugging
 
                 _debugDrawRays = value;
 
-                if (value)
+                if (value && !_overlayManager.HasOverlay<DebugDrawRayOverlay>())
                 {
                     _overlayManager.AddOverlay(new DebugDrawRayOverlay(this));
                 }
                 else
                 {
-                    _overlayManager.RemoveOverlay(nameof(DebugDrawRayOverlay));
+                    _overlayManager.RemoveOverlay<DebugDrawRayOverlay>();
                 }
             }
         }
@@ -53,7 +54,7 @@ namespace Robust.Client.Debugging
 
         public void Initialize()
         {
-            _net.RegisterNetMessage<MsgRay>(MsgRay.NAME, HandleDrawRay);
+            _net.RegisterNetMessage<MsgRay>(HandleDrawRay);
         }
 
         private void HandleDrawRay(MsgRay msg)
@@ -81,13 +82,14 @@ namespace Robust.Client.Debugging
             private readonly DebugDrawingManager _owner;
             public override OverlaySpace Space => OverlaySpace.WorldSpace;
 
-            public DebugDrawRayOverlay(DebugDrawingManager owner) : base(nameof(DebugDrawRayOverlay))
+            public DebugDrawRayOverlay(DebugDrawingManager owner)
             {
                 _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

@@ -24,6 +24,7 @@
 
 using System;
 using Robust.Client.Graphics;
+using Robust.Shared.Enums;
 using Robust.Shared.GameObjects;
 using Robust.Shared.IoC;
 using Robust.Shared.Maths;
@@ -55,7 +56,7 @@ namespace Robust.Client.Debugging
                     IoCManager.Resolve<IOverlayManager>().AddOverlay(new PhysicsDebugOverlay(this));
 
                 if (value == PhysicsDebugFlags.None)
-                    IoCManager.Resolve<IOverlayManager>().RemoveOverlay(nameof(PhysicsDebugOverlay));
+                    IoCManager.Resolve<IOverlayManager>().RemoveOverlay(typeof(PhysicsDebugOverlay));
 
                 _flags = value;
             }
@@ -119,16 +120,16 @@ namespace Robust.Client.Debugging
 
         public override OverlaySpace Space => OverlaySpace.WorldSpace;
 
-        public PhysicsDebugOverlay(DebugPhysicsSystem system) : base(nameof(PhysicsDebugOverlay))
+        public PhysicsDebugOverlay(DebugPhysicsSystem system)
         {
             _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.Loader.cs

@@ -11,7 +11,7 @@ namespace Robust.Client
         {
             public void Main(IMainArgs args)
             {
-                Start(args.Args, contentStart: false, args);
+                Start(args.Args, new GameControllerOptions(), contentStart: false, args);
             }
         }
     }

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);
+            Start(args, new GameControllerOptions());
         }
 
-        public static void Start(string[] args, bool contentStart = false, IMainArgs? loaderArgs=null)
+        public static void Start(string[] args, GameControllerOptions options, bool contentStart = false, IMainArgs? loaderArgs=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 +48,16 @@ namespace Robust.Client
 
             InitIoC(mode);
 
-            var gc = (GameController) IoCManager.Resolve<IGameController>();
+            var gc = IoCManager.Resolve<GameController>();
             gc.SetCommandLineArgs(args);
             gc._loaderArgs = loaderArgs;
 
             // 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, options);
         }
 
         public void OverrideMainLoop(IGameLoop gameLoop)
@@ -66,52 +65,68 @@ namespace Robust.Client
             _mainLoop = gameLoop;
         }
 
-        public void MainLoop(DisplayMode mode)
+        public void Run(DisplayMode mode, GameControllerOptions options, Func<ILogHandler>? logHandlerFactory = null)
         {
-            if (_mainLoop == null)
+            if (!StartupSystemSplash(options, 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!;
@@ -59,92 +61,39 @@ 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;
-
         public void SetCommandLineArgs(CommandLineArgs args)
         {
             _commandLineArgs = args;
         }
 
-        public bool Startup(Func<ILogHandler>? logHandlerFactory = null)
+        internal bool StartupContinue(DisplayMode displayMode)
         {
-            ReadInitialLaunchState();
-
-            SetupLogging(_logManager, logHandlerFactory ?? (() => new ConsoleLogHandler()));
+            _clyde.InitializePostWindowing();
+            _clyde.SetWindowTitle(Options.DefaultWindowTitle);
 
             _taskManager.Initialize();
-
-            // Figure out user data directory.
-            var userDataDir = GetUserDataDir();
-
-            _configurationManager.Initialize(false);
-
-            // MUST load cvars before loading from config file so the cfg manager is aware of secure cvars.
-            // So SECURE CVars are blacklisted from config.
-            _configurationManager.LoadCVarsFromAssembly(typeof(GameController).Assembly); // Client
-            _configurationManager.LoadCVarsFromAssembly(typeof(IConfigurationManager).Assembly); // Shared
-
-            if (LoadConfigAndUserData)
-            {
-                var configFile = Path.Combine(userDataDir, "client_config.toml");
-                if (File.Exists(configFile))
-                {
-                    // Load config from user data if available.
-                    _configurationManager.LoadFromFile(configFile);
-                }
-                else
-                {
-                    // Else we just use code-defined defaults and let it save to file when the user changes things.
-                    _configurationManager.SetSaveFile(configFile);
-                }
-            }
-
-            _configurationManager.OverrideConVars(EnvironmentVariables.GetEnvironmentCVars());
-
-            if (_commandLineArgs != null)
-            {
-                _configurationManager.OverrideConVars(_commandLineArgs.CVars);
-            }
-
-            _resourceCache.Initialize(LoadConfigAndUserData ? userDataDir : null);
-
-            ProgramShared.DoMounts(_resourceCache, _commandLineArgs?.MountOptions, "Content.Client", _loaderArgs != null);
-            if (_loaderArgs != null)
-            {
-                _stringSerializer.EnableCaching = false;
-                _resourceCache.MountLoaderApi(_loaderArgs.FileApi, "Resources/");
-                _modLoader.VerifierExtraLoadHandler = VerifierExtraLoadHandler;
-            }
-
-            // Bring display up as soon as resources are mounted.
-            if (!_clyde.Initialize())
-            {
-                return false;
-            }
-
-            _clyde.SetWindowTitle("Space Station 14");
-
-            _fontManager.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(!_disableAssemblyLoadContext);
-            _modLoader.SetEnableSandboxing(true);
+            _modLoader.SetUseLoadContext(!ContentStart);
+            _modLoader.SetEnableSandboxing(Options.Sandboxing);
 
-            if (!_modLoader.TryLoadModulesFrom(new ResourcePath("/Assemblies/"), "Content."))
+            if (!_modLoader.TryLoadModulesFrom(Options.AssemblyDirectory, Options.ContentModulePrefix))
             {
                 Logger.Fatal("Errors while loading content assemblies.");
                 return false;
@@ -161,14 +110,16 @@ namespace Robust.Client
             _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(new ResourcePath(@"/Prototypes/"));
+            _prototypeManager.LoadDirectory(Options.PrototypeDirectory);
             _prototypeManager.Resync();
             _mapManager.Initialize();
             _entityManager.Initialize();
@@ -188,9 +139,53 @@ namespace Robust.Client
 
             _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 ((_commandLineArgs?.Connect == true || _commandLineArgs?.Launcher == true)
+            if (!Options.DisableCommandLineConnect &&
+                (_commandLineArgs?.Connect == true || _commandLineArgs?.Launcher == true)
                 && LaunchState.ConnectEndpoint != null)
             {
                 _client.ConnectToServer(LaunchState.ConnectEndpoint);
@@ -199,6 +194,101 @@ namespace Robust.Client
             return true;
         }
 
+        internal bool StartupSystemSplash(GameControllerOptions options, Func<ILogHandler>? logHandlerFactory)
+        {
+            Options = options;
+            ReadInitialLaunchState();
+
+            SetupLogging(_logManager, logHandlerFactory ?? (() => new ConsoleLogHandler()));
+
+            if (_commandLineArgs != null)
+            {
+                foreach (var (sawmill, level) in _commandLineArgs.LogLevels)
+                {
+                    LogLevel? logLevel;
+                    if (level == "null")
+                        logLevel = null;
+                    else
+                    {
+                        if (!Enum.TryParse<LogLevel>(level, out var result))
+                        {
+                            System.Console.WriteLine($"LogLevel {level} does not exist!");
+                            continue;
+                        }
+                        logLevel = result;
+                    }
+                    _logManager.GetSawmill(sawmill).Level = logLevel;
+                }
+            }
+
+            ProgramShared.PrintRuntimeInfo(_logManager.RootSawmill);
+
+            // Figure out user data directory.
+            var userDataDir = GetUserDataDir();
+
+            _configurationManager.Initialize(false);
+
+            // MUST load cvars before loading from config file so the cfg manager is aware of secure cvars.
+            // So SECURE CVars are blacklisted from config.
+            _configurationManager.LoadCVarsFromAssembly(typeof(GameController).Assembly); // Client
+            _configurationManager.LoadCVarsFromAssembly(typeof(IConfigurationManager).Assembly); // Shared
+
+            if (Options.LoadConfigAndUserData)
+            {
+                var configFile = Path.Combine(userDataDir, Options.ConfigFileName);
+                if (File.Exists(configFile))
+                {
+                    // Load config from user data if available.
+                    _configurationManager.LoadFromFile(configFile);
+                }
+                else
+                {
+                    // Else we just use code-defined defaults and let it save to file when the user changes things.
+                    _configurationManager.SetSaveFile(configFile);
+                }
+            }
+
+            _configurationManager.OverrideConVars(EnvironmentVariables.GetEnvironmentCVars());
+
+            if (_commandLineArgs != null)
+            {
+                _configurationManager.OverrideConVars(_commandLineArgs.CVars);
+            }
+
+            ProfileOptSetup.Setup(_configurationManager);
+
+            _resourceCache.Initialize(Options.LoadConfigAndUserData ? userDataDir : null);
+
+            var mountOptions = _commandLineArgs != null
+                ? MountOptions.Merge(_commandLineArgs.MountOptions, Options.MountOptions) : Options.MountOptions;
+
+            ProgramShared.DoMounts(_resourceCache, mountOptions, Options.ContentBuildDirectory, Options.AssemblyDirectory,
+                Options.LoadContentResources, _loaderArgs != null && !Options.ResourceMountDisabled, ContentStart);
+
+            if (_loaderArgs != null)
+            {
+                _stringSerializer.EnableCaching = false;
+                _resourceCache.MountLoaderApi(_loaderArgs.FileApi, "Resources/");
+                _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.
+            return _clyde.InitializePreWindowing();
+        }
+
         private Stream? VerifierExtraLoadHandler(string arg)
         {
             DebugTools.AssertNotNull(_loaderArgs);
@@ -242,8 +332,10 @@ 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;
             }
@@ -272,17 +364,20 @@ 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);
         }
 
@@ -303,11 +398,6 @@ namespace Robust.Client
             _modLoader.BroadcastUpdate(ModUpdateLevel.FramePostEngine, frameEventArgs);
         }
 
-        private void Render()
-        {
-
-        }
-
         internal static void SetupLogging(ILogManager logManager, Func<ILogHandler> logHandlerFactory)
         {
             logManager.RootSawmill.AddHandler(logHandlerFactory());
@@ -380,10 +470,11 @@ namespace Robust.Client
             Clyde,
         }
 
-        private void Cleanup()
+        internal void Cleanup()
         {
             _networkManager.Shutdown("Client shutting down");
             _midiManager.Shutdown();
+            IoCManager.Resolve<IEntityLookup>().Shutdown();
             _entityManager.Shutdown();
             _clyde.Shutdown();
         }

Robust.Client/GameControllerOptions.cs

@@ -0,0 +1,75 @@
+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 assemblies from.
+        /// </summary>
+        public ResourcePath AssemblyDirectory { get; init; } = new(@"/Assemblies/");
+
+        /// <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 mount content resources when not on FULL_RELEASE.
+        /// </summary>
+        public bool LoadContentResources { get; init; } = true;
+
+        /// <summary>
+        ///     Whether to load config and user data.
+        /// </summary>
+        public bool LoadConfigAndUserData { get; init; } = true;
+
+        /// <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 +1,13 @@
 using System;
 using System.Collections.Generic;
-using System.Linq;
-using Robust.Shared.Exceptions;
+using Prometheus;
+using Robust.Client.GameStates;
+using Robust.Client.Player;
 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 +15,158 @@ 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 IPlayerManager _playerManager = default!;
+        [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>(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:
+                    var msg = message.SystemMessage;
+                    var sessionType = typeof(EntitySessionMessage<>).MakeGenericType(msg.GetType());
+                    var sessionMsg = Activator.CreateInstance(sessionType, new EntitySessionEventArgs(_playerManager.LocalPlayer!.Session), msg)!;
+                    ReceivedSystemMessage?.Invoke(this, msg);
+                    ReceivedSystemMessage?.Invoke(this, sessionMsg);
+                    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(EntitySystemMessage message)
-        {
-            SendSystemNetworkMessage(message, default(uint));
-        }
-
-        public void SendSystemNetworkMessage(EntitySystemMessage 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(EntitySystemMessage 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;
         }
 
@@ -104,7 +104,7 @@ namespace Robust.Client.GameObjects
             _appearanceDirty = false;
         }
 
-        public override void Initialize()
+        protected override void Initialize()
         {
             base.Initialize();
 
@@ -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;
@@ -115,7 +116,7 @@ namespace Robust.Client.GameObjects
         public MapCoordinates? Position => _eye?.Position;
 
         /// <inheritdoc />
-        public override void Initialize()
+        protected override void Initialize()
         {
             base.Initialize();
 
@@ -152,9 +153,10 @@ namespace Robust.Client.GameObjects
             Zoom = state.Zoom;
             Offset = state.Offset;
             Rotation = state.Rotation;
+            VisibilityMask = state.VisibilityMask;
         }
 
-        public override void OnRemove()
+        protected override void OnRemove()
         {
             base.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();
+                AnchorStateChanged();
             }
         }
 
-        private void SnapGridOnPositionChanged()
+        public void AnchorStateChanged()
         {
             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

@@ -1,9 +1,12 @@
-using System;
+using System;
+using System.Collections.Generic;
 using Robust.Client.Graphics;
 using Robust.Client.ResourceManagement;
 using Robust.Shared.Animations;
+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.Serialization;
@@ -43,11 +46,29 @@ namespace Robust.Client.GameObjects
         public bool Enabled
         {
             get => _enabled;
-            set => _enabled = value;
+            set
+            {
+                if (_enabled == value) return;
+
+                _enabled = value;
+                Owner.EntityManager.EventBus.RaiseLocalEvent(Owner.Uid, new PointLightUpdateEvent());
+            }
         }
 
         [ViewVariables(VVAccess.ReadWrite)]
-        public bool ContainerOccluded { get; set; }
+        public bool ContainerOccluded
+        {
+            get => _containerOccluded;
+            set
+            {
+                if (_containerOccluded == value) return;
+
+                _containerOccluded = value;
+                Owner.EntityManager.EventBus.RaiseLocalEvent(Owner.Uid, new PointLightUpdateEvent());
+            }
+        }
+
+        private bool _containerOccluded;
 
         /// <summary>
         ///     Determines if the light mask should automatically rotate with the entity. (like a flashlight)
@@ -116,30 +137,13 @@ namespace Robust.Client.GameObjects
         public bool VisibleNested
         {
             get => _visibleNested;
-            set
-            {
-                if (_visibleNested == value) return;
-                _visibleNested = value;
-                if (value)
-                {
-                    if (Owner.Transform.Parent == null) return;
-
-                    _lightOnParent = true;
-                }
-                else
-                {
-                    if (!_lightOnParent) return;
-
-                    _lightOnParent = false;
-                }
-            }
+            set => _visibleNested = value;
         }
 
         [DataField("radius")]
         private float _radius = 5f;
         [DataField("nestedvisible")]
         private bool _visibleNested = true;
-        private bool _lightOnParent;
         [DataField("color")]
         private Color _color = Color.White;
         [DataField("offset")]
@@ -166,8 +170,10 @@ namespace Robust.Client.GameObjects
             get => _radius;
             set
             {
+                if (MathHelper.CloseTo(value, _radius)) return;
+
                 _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 +185,9 @@ namespace Robust.Client.GameObjects
                 Mask = null;
         }
 
+        [ViewVariables]
+        internal RenderingTreeComponent? RenderTree { get; set; }
+
         void ISerializationHooks.AfterDeserialization()
         {
             if (_maskPath != null)
@@ -187,42 +196,13 @@ namespace Robust.Client.GameObjects
             }
         }
 
-        public override void Initialize()
+        protected override void Initialize()
         {
             base.Initialize();
             UpdateMask();
         }
 
-        /// <inheritdoc />
-        public override void HandleMessage(ComponentMessage message, IComponent? component)
-        {
-            base.HandleMessage(message, component);
-
-            if (message is ParentChangedMessage msg)
-            {
-                HandleTransformParentChanged(msg);
-            }
-        }
-
-        private void HandleTransformParentChanged(ParentChangedMessage obj)
-        {
-            // TODO: this does not work for things nested multiply layers deep.
-            if (!VisibleNested)
-            {
-                return;
-            }
-
-            if (obj.NewParent != null && obj.NewParent.IsValid())
-            {
-                _lightOnParent = true;
-            }
-            else
-            {
-                _lightOnParent = false;
-            }
-        }
-
-        public override void OnRemove()
+        protected override void OnRemove()
         {
             base.OnRemove();
 
@@ -230,7 +210,7 @@ namespace Robust.Client.GameObjects
             if (map != MapId.Nullspace)
             {
                 Owner.EntityManager.EventBus.RaiseEvent(EventSource.Local,
-                    new RenderTreeRemoveLightMessage(this, map));
+                    new RenderTreeRemoveLightEvent(this, map));
             }
         }
 
@@ -248,13 +228,18 @@ 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;
         }
     }
+
+    internal sealed class PointLightUpdateEvent : EntityEventArgs
+    {
+
+    }
 }

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
     {
@@ -36,13 +39,19 @@ namespace Robust.Client.GameObjects
         private bool _visible = true;
 
         [ViewVariables(VVAccess.ReadWrite)]
-        public bool Visible
+        public override bool Visible
         {
             get => _visible;
-            set => _visible = value;
+            set
+            {
+                if (_visible == value) return;
+                _visible = value;
+
+                Owner.EntityManager.EventBus.RaiseLocalEvent(Owner.Uid, new SpriteUpdateEvent());
+            }
         }
 
-        [DataFieldWithConstant("drawdepth", typeof(DrawDepthTag))]
+        [DataField("drawdepth", customTypeSerializer: typeof(ConstantSerializer<DrawDepthTag>))]
         private int drawDepth = DrawDepthTag.Default;
 
         /// <summary>
@@ -122,6 +131,9 @@ namespace Robust.Client.GameObjects
         [DataField("directional")]
         private bool _directional = true;
 
+        [ViewVariables]
+        internal RenderingTreeComponent? RenderTree { get; set; } = null;
+
         [DataField("layerDatums")]
         private List<PrototypeLayerData> LayerDatums
         {
@@ -137,7 +149,7 @@ namespace Robust.Client.GameObjects
             }
             set
             {
-                if(value == null) return;
+                if (value == null) return;
 
                 Layers.Clear();
                 foreach (var layerDatum in value)
@@ -147,11 +159,12 @@ namespace Robust.Client.GameObjects
                     if (!string.IsNullOrWhiteSpace(layerDatum.RsiPath))
                     {
                         var path = TextureRoot / layerDatum.RsiPath;
-                        try
+
+                        if (IoCManager.Resolve<IResourceCache>().TryGetResource(path, out RSIResource? resource))
                         {
-                            layer.RSI = IoCManager.Resolve<IResourceCache>().GetResource<RSIResource>(path).RSI;
+                            layer.RSI = resource.RSI;
                         }
-                        catch
+                        else
                         {
                             Logger.ErrorS(LogCategory, "Unable to load layer RSI '{0}'.", path);
                         }
@@ -250,7 +263,7 @@ namespace Robust.Client.GameObjects
                 }
 
                 _layerMapShared = true;
-                UpdateIsInert();
+                QueueUpdateIsInert();
             }
         }
 
@@ -293,17 +306,30 @@ namespace Robust.Client.GameObjects
         }
 
         [DataField("sprite", readOnly: true)] private string? rsi;
-        [DataField("layers", readOnly: true)] private List<PrototypeLayerData> layerDatums = new ();
+        [DataField("layers", readOnly: true)] private List<PrototypeLayerData> layerDatums = new();
 
         [DataField("state", readOnly: true)] private string? state;
         [DataField("texture", readOnly: true)] private string? texture;
 
         [ViewVariables(VVAccess.ReadWrite)]
-        public bool ContainerOccluded { get; set; }
+        public bool ContainerOccluded
+        {
+            get => _containerOccluded;
+            set
+            {
+                if (_containerOccluded == value) return;
+                _containerOccluded = value;
+                Owner.EntityManager.EventBus.RaiseLocalEvent(Owner.Uid, new SpriteUpdateEvent());
+            }
+        }
+
+        private bool _containerOccluded;
 
         [ViewVariables(VVAccess.ReadWrite)]
         public bool TreeUpdateQueued { get; set; }
 
+        [ViewVariables(VVAccess.ReadWrite)] private bool _inertUpdateQueued;
+
         [ViewVariables(VVAccess.ReadWrite)]
         public ShaderInstance? PostShader { get; set; }
 
@@ -333,13 +359,13 @@ namespace Robust.Client.GameObjects
                 if (!string.IsNullOrWhiteSpace(rsi))
                 {
                     var rsiPath = TextureRoot / rsi;
-                    try
+                    if(IoCManager.Resolve<IResourceCache>().TryGetResource(rsiPath, out RSIResource? resource))
                     {
-                        BaseRSI = IoCManager.Resolve<IResourceCache>().GetResource<RSIResource>(rsiPath).RSI;
+                        BaseRSI = resource.RSI;
                     }
-                    catch (Exception e)
+                    else
                     {
-                        Logger.ErrorS(SpriteComponent.LogCategory, "Unable to load RSI '{0}'. Trace:\n{1}", rsiPath, e);
+                        Logger.ErrorS(LogCategory, "Unable to load RSI '{0}'. Trace:\n{1}", rsiPath);
                     }
                 }
             }
@@ -467,7 +493,7 @@ namespace Robust.Client.GameObjects
 
         public int AddBlankLayer(int? newIndex = null)
         {
-            var layer = new Layer(this) {Visible = false};
+            var layer = new Layer(this) { Visible = false };
             return AddLayer(layer, newIndex);
         }
 
@@ -496,13 +522,13 @@ namespace Robust.Client.GameObjects
 
         public int AddLayer(Texture? texture, int? newIndex = null)
         {
-            var layer = new Layer(this) {Texture = texture};
+            var layer = new Layer(this) { Texture = texture };
             return AddLayer(layer, newIndex);
         }
 
         public int AddLayer(RSI.StateId stateId, int? newIndex = null)
         {
-            var layer = new Layer(this) {State = stateId};
+            var layer = new Layer(this) { State = stateId };
             if (BaseRSI != null && BaseRSI.TryGetState(stateId, out var state))
             {
                 layer.AnimationTimeLeft = state.GetDelay(0);
@@ -548,7 +574,7 @@ namespace Robust.Client.GameObjects
 
         public int AddLayer(RSI.StateId stateId, RSI? rsi, int? newIndex = null)
         {
-            var layer = new Layer(this) {State = stateId, RSI = rsi};
+            var layer = new Layer(this) { State = stateId, RSI = rsi };
             if (rsi != null && rsi.TryGetState(stateId, out var state))
             {
                 layer.AnimationTimeLeft = state.GetDelay(0);
@@ -604,7 +630,7 @@ namespace Robust.Client.GameObjects
                 index = Layers.Count - 1;
             }
 
-            UpdateIsInert();
+            QueueUpdateIsInert();
             return index;
         }
 
@@ -631,7 +657,7 @@ namespace Robust.Client.GameObjects
                 }
             }
 
-            UpdateIsInert();
+            QueueUpdateIsInert();
         }
 
         public void RemoveLayer(object layerKey)
@@ -847,8 +873,8 @@ 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;
                 }
             }
@@ -1273,8 +1299,8 @@ namespace Robust.Client.GameObjects
 
             var layerColor = color * layer.Color;
 
-            var position = -(Vector2) texture.Size / (2f * EyeManager.PixelsPerMeter) + layer.Offset;
-            var textureSize = texture.Size / (float) EyeManager.PixelsPerMeter;
+            var position = -(Vector2)texture.Size / (2f * EyeManager.PixelsPerMeter) + layer.Offset;
+            var textureSize = texture.Size / (float)EyeManager.PixelsPerMeter;
             var quad = Box2.FromDimensions(position, textureSize);
 
             // TODO: Implement layer-specific rotation and scale.
@@ -1294,7 +1320,7 @@ namespace Robust.Client.GameObjects
         public static Angle CalcRectWorldAngle(Angle worldAngle, int numDirections)
         {
             var theta = worldAngle.Theta;
-            var segSize = (MathF.PI*2) / (numDirections * 2);
+            var segSize = (MathF.PI * 2) / (numDirections * 2);
             var segments = (int)(theta / segSize);
             var odd = segments % 2;
             var result = theta - (segments * segSize) - (odd * segSize);
@@ -1344,18 +1370,6 @@ namespace Robust.Client.GameObjects
             return texture;
         }
 
-        public override void OnRemove()
-        {
-            base.OnRemove();
-
-            var map = Owner.Transform.MapID;
-            if (map != MapId.Nullspace)
-            {
-                Owner.EntityManager.EventBus.RaiseEvent(EventSource.Local,
-                    new RenderTreeRemoveSpriteMessage(this, map));
-            }
-        }
-
         public void FrameUpdate(float delta)
         {
             foreach (var t in Layers)
@@ -1406,7 +1420,7 @@ namespace Robust.Client.GameObjects
             if (curState == null)
                 return;
 
-            var thestate = (SpriteComponentState) curState;
+            var thestate = (SpriteComponentState)curState;
 
             Visible = thestate.Visible;
             DrawDepth = thestate.DrawDepth;
@@ -1494,8 +1508,20 @@ namespace Robust.Client.GameObjects
             };
         }
 
-        private void UpdateIsInert()
+        private void QueueUpdateIsInert()
         {
+            if (_inertUpdateQueued)
+                return;
+
+            _inertUpdateQueued = true;
+            // Yes that null check is valid because of that stupid fucking dummy IEntity.
+            // Who thought that was a good idea.
+            Owner?.EntityManager?.EventBus?.RaiseEvent(EventSource.Local, new SpriteUpdateInertEvent {Sprite = this});
+        }
+
+        internal void DoUpdateIsInert()
+        {
+            _inertUpdateQueued = false;
             IsInert = true;
 
             foreach (var layer in Layers)
@@ -1575,9 +1601,10 @@ 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)
@@ -1844,14 +1871,14 @@ namespace Robust.Client.GameObjects
             {
                 AutoAnimated = value;
 
-                _parent.UpdateIsInert();
+                _parent.QueueUpdateIsInert();
             }
 
             public void SetVisible(bool value)
             {
                 Visible = value;
 
-                _parent.UpdateIsInert();
+                _parent.QueueUpdateIsInert();
             }
 
             public void SetRsi(RSI? rsi)
@@ -1883,7 +1910,7 @@ namespace Robust.Client.GameObjects
                     }
                 }
 
-                _parent.UpdateIsInert();
+                _parent.QueueUpdateIsInert();
             }
 
             public void SetState(RSI.StateId stateId)
@@ -1915,7 +1942,7 @@ namespace Robust.Client.GameObjects
                 AnimationTime = 0;
                 AnimationTimeLeft = state.GetDelay(0);
 
-                _parent.UpdateIsInert();
+                _parent.QueueUpdateIsInert();
             }
 
             public void SetTexture(Texture? texture)
@@ -1923,7 +1950,7 @@ namespace Robust.Client.GameObjects
                 State = default;
                 Texture = texture;
 
-                _parent.UpdateIsInert();
+                _parent.QueueUpdateIsInert();
             }
 
             public void SetOffset(Vector2 offset)
@@ -1975,13 +2002,13 @@ namespace Robust.Client.GameObjects
             switch (layerProp)
             {
                 case "texture":
-                    LayerSetTexture(index, (string) value);
+                    LayerSetTexture(index, (string)value);
                     return;
                 case "state":
-                    LayerSetState(index, (string) value);
+                    LayerSetState(index, (string)value);
                     return;
                 case "color":
-                    LayerSetColor(index, (Color) value);
+                    LayerSetColor(index, (Color)value);
                     return;
                 default:
                     throw new ArgumentException($"Unknown layer property '{layerProp}'");
@@ -2026,7 +2053,7 @@ namespace Robust.Client.GameObjects
                 yield break;
             }
 
-            var dummy = new DummyIconEntity {Prototype = prototype};
+            var dummy = new DummyIconEntity { Prototype = prototype };
             var spriteComponent = dummy.AddComponent<SpriteComponent>();
 
             if (prototype.Components.TryGetValue("Appearance", out _))
@@ -2070,7 +2097,7 @@ namespace Robust.Client.GameObjects
                 return GetFallbackState(resourceCache);
             }
 
-            var dummy = new DummyIconEntity {Prototype = prototype};
+            var dummy = new DummyIconEntity { Prototype = prototype };
             var spriteComponent = dummy.AddComponent<SpriteComponent>();
             dummy.Delete();
 
@@ -2084,6 +2111,7 @@ 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;
@@ -2100,12 +2128,13 @@ 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()
             {
                 var typeFactory = IoCManager.Resolve<IDynamicTypeFactoryInternal>();
                 var serializationManager = IoCManager.Resolve<ISerializationManager>();
-                var comp = (T) typeFactory.CreateInstanceUnchecked(typeof(T));
+                var comp = (T)typeFactory.CreateInstanceUnchecked(typeof(T));
                 _components[typeof(T)] = comp;
                 comp.Owner = this;
 
@@ -2139,7 +2168,7 @@ namespace Robust.Client.GameObjects
 
             public T GetComponent<T>()
             {
-                return (T) _components[typeof(T)];
+                return (T)_components[typeof(T)];
             }
 
             public IComponent GetComponent(Type type)
@@ -2147,16 +2176,11 @@ 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;
                 if (!_components.TryGetValue(typeof(T), out var value)) return false;
-                component = (T) value;
+                component = (T)value;
                 return true;
             }
 
@@ -2178,18 +2202,7 @@ 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 +2220,12 @@ 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)
             {
             }
@@ -2221,4 +2236,14 @@ namespace Robust.Client.GameObjects
         }
         #endregion
     }
+
+    internal sealed class SpriteUpdateEvent : EntityEventArgs
+    {
+
+    }
+
+    internal struct SpriteUpdateInertEvent
+    {
+        public SpriteComponent Sprite;
+    }
 }

Robust.Client/GameObjects/Components/RenderingTreeComponent.cs

@@ -0,0 +1,43 @@
+using Robust.Shared.GameObjects;
+using Robust.Shared.Maths;
+using Robust.Shared.Physics;
+
+namespace Robust.Client.GameObjects
+{
+    [RegisterComponent]
+    public sealed class RenderingTreeComponent : Component
+    {
+        public override string Name => "RenderingTree";
+
+        internal DynamicTree<SpriteComponent> SpriteTree { get; private set; } = new(SpriteAabbFunc);
+        internal DynamicTree<PointLightComponent> LightTree { get; private set; } = new(LightAabbFunc);
+
+        private static Box2 SpriteAabbFunc(in SpriteComponent value)
+        {
+            var worldPos = value.Owner.Transform.WorldPosition;
+            return new Box2(worldPos, worldPos);
+        }
+
+        private static Box2 LightAabbFunc(in PointLightComponent value)
+        {
+            var worldPos = value.Owner.Transform.WorldPosition;
+
+            var boxSize = value.Radius * 2;
+            return Box2.CenteredAround(worldPos, (boxSize, boxSize));
+        }
+
+        internal static Box2 SpriteAabbFunc(SpriteComponent value, Vector2? worldPos = null)
+        {
+            worldPos ??= value.Owner.Transform.WorldPosition;
+
+            return new Box2(worldPos.Value, worldPos.Value);
+        }
+
+        internal static Box2 LightAabbFunc(PointLightComponent value, Vector2? worldPos = null)
+        {
+            worldPos ??= value.Owner.Transform.WorldPosition;
+            var boxSize = value.Radius * 2;
+            return Box2.CenteredAround(worldPos.Value, (boxSize, boxSize));
+        }
+    }
+}

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

@@ -9,13 +9,13 @@ namespace Robust.Client.GameObjects
     public static class EntityManagerExt
     {
         public static void RaisePredictiveEvent<T>(this IEntityManager entityManager, T msg)
-            where T : EntitySystemMessage
+            where T : EntityEventArgs
         {
             var localPlayer = IoCManager.Resolve<IPlayerManager>().LocalPlayer;
             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))
             {
@@ -243,13 +248,13 @@ 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))
             {
                 source.Dispose();
-                Logger.Warning("Can't play positional audio, can't set position.");
+                Logger.Warning($"Can't play positional audio \"{stream.Name}\", can't set position.");
                 return null;
             }
 
@@ -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))
             {
@@ -289,14 +294,14 @@ 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);
             if (!source.SetPosition(coordinates.ToMapPos(EntityManager)))
             {
                 source.Dispose();
-                Logger.Warning("Can't play positional audio, can't set position.");
+                Logger.Warning("Can't play positional audio \"{stream.Name}\", can't set position.");
                 return null;
             }
 

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, AnchorStateChangedEvent>(HandleAnchorChanged);
         }
 
         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 HandleAnchorChanged(EntityUid uid, ClientOccluderComponent component, AnchorStateChangedEvent args)
+        {
+            component.AnchorStateChanged();
+        }
+
         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.
@@ -79,44 +89,37 @@ 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>
     ///     Event raised by a <see cref="ClientOccluderComponent"/> when it needs to be recalculated.
     /// </summary>
-    internal sealed class OccluderDirtyEvent : EntitySystemMessage
+    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/DebugGridTileLookupSystem.cs

@@ -0,0 +1,134 @@
+#if DEBUG
+using System;
+using System.Text;
+using Robust.Client.Graphics;
+using Robust.Client.Input;
+using Robust.Client.UserInterface;
+using Robust.Client.UserInterface.Controls;
+using Robust.Shared.Console;
+using Robust.Shared.GameObjects;
+using Robust.Shared.IoC;
+using Robust.Shared.Map;
+using Robust.Shared.Maths;
+
+namespace Robust.Client.GameObjects
+{
+    internal sealed class DebugGridTileLookupSystem : EntitySystem
+    {
+        [Dependency] private readonly IEyeManager _eyeManager = default!;
+        [Dependency] private readonly IInputManager _inputManager = default!;
+        [Dependency] private readonly IMapManager _mapManager = default!;
+
+        public bool Enabled
+        {
+            get => _enabled;
+            set
+            {
+                if (_enabled == value) return;
+                _enabled = value;
+
+                if (_enabled)
+                {
+                    _label.Visible = true;
+                    LastTile = default;
+                }
+                else
+                {
+                    _label.Text = null;
+                    _label.Visible = false;
+                }
+            }
+        }
+
+        private bool _enabled;
+
+        private (GridId Grid, Vector2i Indices) LastTile;
+
+        // Label and shit that follows cursor
+        private Label _label = new()
+        {
+            Visible = false,
+        };
+
+        public override void Initialize()
+        {
+            base.Initialize();
+            SubscribeNetworkEvent<SendGridTileLookupMessage>(HandleSentEntities);
+            IoCManager.Resolve<IUserInterfaceManager>().StateRoot.AddChild(_label);
+        }
+
+        public override void Shutdown()
+        {
+            base.Shutdown();
+            UnsubscribeNetworkEvent<SendGridTileLookupMessage>();
+            IoCManager.Resolve<IUserInterfaceManager>().StateRoot.RemoveChild(_label);
+        }
+
+        private void RequestEntities(GridId gridId, Vector2i indices)
+        {
+            if (gridId == GridId.Invalid) return;
+            RaiseNetworkEvent(new RequestGridTileLookupMessage(gridId, indices));
+        }
+
+        private void HandleSentEntities(SendGridTileLookupMessage message)
+        {
+            if (!Enabled) return;
+            var text = new StringBuilder();
+            text.AppendLine($"GridId: {LastTile.Grid}, Tile: {LastTile.Indices}");
+
+            for (var i = 0; i < message.Entities.Count; i++)
+            {
+                var uid = message.Entities[i];
+
+                if (!EntityManager.TryGetEntity(uid, out var entity)) continue;
+
+                text.AppendLine(entity.ToString());
+            }
+
+            _label.Text = text.ToString();
+        }
+
+        public override void FrameUpdate(float frameTime)
+        {
+            base.FrameUpdate(frameTime);
+            if (!Enabled) return;
+
+            var mousePos = _inputManager.MouseScreenPosition;
+            var worldPos = _eyeManager.ScreenToMap(mousePos);
+
+            GridId gridId;
+            Vector2i tile;
+
+            if (_mapManager.TryFindGridAt(worldPos, out var grid))
+            {
+                gridId = grid.Index;
+                tile = grid.WorldToTile(worldPos.Position);
+            }
+            else
+            {
+                gridId = GridId.Invalid;
+                tile = new Vector2i((int) MathF.Floor(worldPos.Position.X), (int) MathF.Floor(worldPos.Position.Y));
+            }
+
+            LayoutContainer.SetPosition(_label, mousePos.Position);
+
+            if ((gridId, tile).Equals(LastTile)) return;
+
+            _label.Text = null;
+            LastTile = (gridId, tile);
+            RequestEntities(gridId, tile);
+        }
+    }
+
+    internal sealed class RequestTileEntities : IConsoleCommand
+    {
+        public string Command => "tilelookup";
+        public string Description => "Used for debugging GridTileLookupSystem";
+        public string Help => $"{Command}";
+        public void Execute(IConsoleShell shell, string argStr, string[] args)
+        {
+            EntitySystem.Get<DebugGridTileLookupSystem>().Enabled ^= true;
+        }
+    }
+}
+#endif

Robust.Client/GameObjects/EntitySystems/DebugLightTreeSystem.cs

@@ -0,0 +1,84 @@
+#if DEBUG
+using Robust.Client.Graphics;
+using Robust.Shared.Enums;
+using Robust.Shared.GameObjects;
+using Robust.Shared.IoC;
+using Robust.Shared.Map;
+using Robust.Shared.Maths;
+
+namespace Robust.Client.GameObjects
+{
+    internal sealed class DebugLightTreeSystem : EntitySystem
+    {
+        private DebugLightOverlay? _lightOverlay;
+
+        public bool Enabled
+        {
+            get => _enabled;
+            set
+            {
+                if (_enabled == value) return;
+
+                _enabled = value;
+                var overlayManager = IoCManager.Resolve<IOverlayManager>();
+
+                if (_enabled)
+                {
+                    _lightOverlay = new DebugLightOverlay(
+                        IoCManager.Resolve<IEntityLookup>(),
+                        IoCManager.Resolve<IEyeManager>(),
+                        IoCManager.Resolve<IMapManager>(),
+                        Get<RenderingTreeSystem>());
+
+                    overlayManager.AddOverlay(_lightOverlay);
+                }
+                else
+                {
+                    overlayManager.RemoveOverlay(_lightOverlay!);
+                    _lightOverlay = null;
+                }
+            }
+        }
+
+        private bool _enabled;
+
+        private sealed class DebugLightOverlay : Overlay
+        {
+            private IEntityLookup _lookup;
+            private IEyeManager _eyeManager;
+            private IMapManager _mapManager;
+
+            private RenderingTreeSystem _tree;
+
+            public override OverlaySpace Space => OverlaySpace.WorldSpace;
+
+            public DebugLightOverlay(IEntityLookup lookup, IEyeManager eyeManager, IMapManager mapManager, RenderingTreeSystem tree)
+            {
+                _lookup = lookup;
+                _eyeManager = eyeManager;
+                _mapManager = mapManager;
+                _tree = tree;
+            }
+
+            protected internal override void Draw(in OverlayDrawArgs args)
+            {
+                var map = _eyeManager.CurrentMap;
+                if (map == MapId.Nullspace) return;
+
+                var viewport = _eyeManager.GetWorldViewport();
+
+                foreach (var tree in _tree.GetLightTrees(map, viewport))
+                {
+                    foreach (var light in tree)
+                    {
+                        var aabb = _lookup.GetWorldAabbFromEntity(light.Owner);
+                        if (!aabb.Intersects(viewport)) continue;
+
+                        args.WorldHandle.DrawRect(aabb, Color.Green.WithAlpha(0.1f));
+                    }
+                }
+            }
+        }
+    }
+}
+#endif

Robust.Client/GameObjects/EntitySystems/EffectSystem.cs

@@ -11,6 +11,7 @@ using Robust.Shared.Log;
 using Robust.Shared.Prototypes;
 using Robust.Shared.Timing;
 using Robust.Shared.Utility;
+using Robust.Shared.Enums;
 
 namespace Robust.Client.GameObjects
 {
@@ -42,7 +43,7 @@ namespace Robust.Client.GameObjects
         {
             base.Shutdown();
 
-            overlayManager.RemoveOverlay("EffectSystem");
+            overlayManager.RemoveOverlay(typeof(EffectOverlay));
         }
 
         public void CreateEffect(EffectSystemMessage message)
@@ -66,9 +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);
@@ -329,7 +331,6 @@ namespace Robust.Client.GameObjects
         {
             private readonly IPlayerManager _playerManager;
 
-            public override bool AlwaysDirty => true;
             public override OverlaySpace Space => OverlaySpace.WorldSpace;
 
             private readonly ShaderInstance _unshadedShader;
@@ -337,8 +338,7 @@ namespace Robust.Client.GameObjects
             private readonly IMapManager _mapManager;
             private readonly IEntityManager _entityManager;
 
-            public EffectOverlay(EffectSystem owner, IPrototypeManager protoMan, IMapManager mapMan, IPlayerManager playerMan, IEntityManager entityManager) : base(
-                "EffectSystem")
+            public EffectOverlay(EffectSystem owner, IPrototypeManager protoMan, IMapManager mapMan, IPlayerManager playerMan, IEntityManager entityManager)
             {
                 _owner = owner;
                 _unshadedShader = protoMan.Index<ShaderPrototype>("unshaded").Instance();
@@ -347,11 +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()
@@ -157,7 +157,7 @@ namespace Robust.Client.GameObjects
     /// <summary>
     ///     Entity system message that is raised when the player changes attached entities.
     /// </summary>
-    public class PlayerAttachSysMessage : EntitySystemMessage
+    public class PlayerAttachSysMessage : EntityEventArgs
     {
         /// <summary>
         ///     New entity the player is attached to.
@@ -173,4 +173,24 @@ namespace Robust.Client.GameObjects
             AttachedEntity = attachedEntity;
         }
     }
+
+    public class PlayerAttachedEvent : EntityEventArgs
+    {
+        public PlayerAttachedEvent(IEntity entity)
+        {
+            Entity = entity;
+        }
+
+        public IEntity Entity { get; }
+    }
+
+    public class PlayerDetachedEvent : EntityEventArgs
+    {
+        public PlayerDetachedEvent(IEntity entity)
+        {
+            Entity = entity;
+        }
+
+        public IEntity Entity { get; }
+    }
 }

Robust.Client/GameObjects/EntitySystems/RenderingTreeSystem.cs

@@ -1,11 +1,17 @@
 using System.Collections.Generic;
+using System.Drawing;
+using System.Linq;
 using JetBrains.Annotations;
 using Robust.Client.Physics;
+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.Physics;
+using Robust.Shared.Utility;
 
 namespace Robust.Client.GameObjects
 {
@@ -15,23 +21,58 @@ namespace Robust.Client.GameObjects
     [UsedImplicitly]
     public sealed class RenderingTreeSystem : EntitySystem
     {
+        internal const string LoggerSawmill = "rendertree";
+
         // Nullspace is not indexed. Keep that in mind.
 
-        [Dependency] private readonly IMapManagerInternal _mapManager = default!;
-
-        private readonly Dictionary<MapId, MapTrees> _mapTrees = new();
+        [Dependency] private readonly IMapManager _mapManager = default!;
 
         private readonly List<SpriteComponent> _spriteQueue = new();
         private readonly List<PointLightComponent> _lightQueue = new();
 
-        internal DynamicTree<SpriteComponent> GetSpriteTreeForMap(MapId map)
+        private HashSet<EntityUid> _checkedChildren = new();
+
+        /// <summary>
+        /// <see cref="CVars.MaxLightRadius"/>
+        /// </summary>
+        public float MaxLightRadius { get; private set; }
+
+        internal IEnumerable<RenderingTreeComponent> GetRenderTrees(MapId mapId, Box2 worldAABB)
         {
-            return _mapTrees[map].SpriteTree;
+            if (mapId == MapId.Nullspace) yield break;
+
+            var enclosed = false;
+
+            foreach (var grid in _mapManager.FindGridsIntersecting(mapId, worldAABB))
+            {
+                yield return EntityManager.GetEntity(grid.GridEntityId).GetComponent<RenderingTreeComponent>();
+
+                // if we're enclosed then we know no other grids relevant + don't need the map's rendertree
+                if (grid.WorldBounds.Encloses(in worldAABB))
+                {
+                    enclosed = true;
+                    break;
+                }
+            }
+
+            if (!enclosed)
+                yield return _mapManager.GetMapEntity(mapId).GetComponent<RenderingTreeComponent>();
         }
 
-        internal DynamicTree<PointLightComponent> GetLightTreeForMap(MapId map)
+        internal IEnumerable<DynamicTree<SpriteComponent>> GetSpriteTrees(MapId mapId, Box2 worldAABB)
         {
-            return _mapTrees[map].LightTree;
+            foreach (var comp in GetRenderTrees(mapId, worldAABB))
+            {
+                yield return comp.SpriteTree;
+            }
+        }
+
+        internal IEnumerable<DynamicTree<PointLightComponent>> GetLightTrees(MapId mapId, Box2 worldAABB)
+        {
+            foreach (var comp in GetRenderTrees(mapId, worldAABB))
+            {
+                yield return comp.LightTree;
+            }
         }
 
         public override void Initialize()
@@ -43,103 +84,164 @@ namespace Robust.Client.GameObjects
             UpdatesAfter.Add(typeof(PhysicsSystem));
 
             _mapManager.MapCreated += MapManagerOnMapCreated;
-            _mapManager.MapDestroyed += MapManagerOnMapDestroyed;
+            _mapManager.OnGridCreated += MapManagerOnGridCreated;
 
-            SubscribeLocalEvent<EntMapIdChangedMessage>(EntMapIdChanged);
-            SubscribeLocalEvent<MoveEvent>(EntMoved);
-            SubscribeLocalEvent<EntParentChangedMessage>(EntParentChanged);
-            SubscribeLocalEvent<PointLightRadiusChangedMessage>(PointLightRadiusChanged);
-            SubscribeLocalEvent<RenderTreeRemoveSpriteMessage>(RemoveSprite);
-            SubscribeLocalEvent<RenderTreeRemoveLightMessage>(RemoveLight);
+            // Due to how recursion works, this must be done.
+            SubscribeLocalEvent<MoveEvent>(AnythingMoved);
+
+            SubscribeLocalEvent<SpriteComponent, EntMapIdChangedMessage>(SpriteMapChanged);
+            SubscribeLocalEvent<SpriteComponent, EntParentChangedMessage>(SpriteParentChanged);
+            SubscribeLocalEvent<SpriteComponent, ComponentRemove>(RemoveSprite);
+            SubscribeLocalEvent<SpriteComponent, SpriteUpdateEvent>(HandleSpriteUpdate);
+
+            SubscribeLocalEvent<PointLightComponent, EntMapIdChangedMessage>(LightMapChanged);
+            SubscribeLocalEvent<PointLightComponent, EntParentChangedMessage>(LightParentChanged);
+            SubscribeLocalEvent<PointLightComponent, PointLightRadiusChangedEvent>(PointLightRadiusChanged);
+            SubscribeLocalEvent<PointLightComponent, RenderTreeRemoveLightEvent>(RemoveLight);
+            SubscribeLocalEvent<PointLightComponent, PointLightUpdateEvent>(HandleLightUpdate);
+
+            SubscribeLocalEvent<RenderingTreeComponent, ComponentRemove>(HandleTreeRemove);
+
+            var configManager = IoCManager.Resolve<IConfigurationManager>();
+            configManager.OnValueChanged(CVars.MaxLightRadius, value => MaxLightRadius = value, true);
         }
 
-        // For these next 2 methods (the Remove* ones):
+        private void HandleLightUpdate(EntityUid uid, PointLightComponent component, PointLightUpdateEvent args)
+        {
+            if (component.TreeUpdateQueued) return;
+            QueueLightUpdate(component);
+        }
+
+        private void HandleSpriteUpdate(EntityUid uid, SpriteComponent component, SpriteUpdateEvent args)
+        {
+            if (component.TreeUpdateQueued) return;
+            QueueSpriteUpdate(component);
+        }
+
+        private void AnythingMoved(MoveEvent args)
+        {
+            AnythingMovedSubHandler(args.Sender.Transform);
+        }
+
+        private void AnythingMovedSubHandler(ITransformComponent sender)
+        {
+            // To avoid doing redundant updates (and we don't need to update a grid's children ever)
+            if (!_checkedChildren.Add(sender.Owner.Uid) ||
+                sender.Owner.HasComponent<RenderingTreeComponent>()) return;
+
+            // This recursive search is needed, as MoveEvent is defined to not care about indirect events like children.
+            // WHATEVER YOU DO, DON'T REPLACE THIS WITH SPAMMING EVENTS UNLESS YOU HAVE A GUARANTEE IT WON'T LAG THE GC.
+            // (Struct-based events ok though)
+            // Ironically this was lagging the GC lolz
+            if (sender.Owner.TryGetComponent(out SpriteComponent? sprite))
+                QueueSpriteUpdate(sprite);
+
+            if (sender.Owner.TryGetComponent(out PointLightComponent? light))
+                QueueLightUpdate(light);
+
+            foreach (ITransformComponent child in sender.Children)
+            {
+                AnythingMovedSubHandler(child);
+            }
+        }
+
+        // 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 SpriteParentChanged(EntityUid uid, SpriteComponent component, EntParentChangedMessage args)
         {
-            _mapTrees[ev.Map].SpriteTree.Remove(ev.Sprite);
+            QueueSpriteUpdate(component);
         }
 
-        private void PointLightRadiusChanged(PointLightRadiusChangedMessage ev)
+        private void RemoveSprite(EntityUid uid, SpriteComponent component, ComponentRemove args)
         {
-            QueueUpdateLight(ev.PointLightComponent);
+            ClearSprite(component);
         }
 
-        private void EntParentChanged(EntParentChangedMessage ev)
+        private void ClearSprite(SpriteComponent component)
         {
-            UpdateEntity(ev.Entity);
+            if (component.RenderTree == null) return;
+
+            component.RenderTree.SpriteTree.Remove(component);
+            component.RenderTree = null;
         }
 
-        private void EntMoved(MoveEvent ev)
+        private void QueueSpriteUpdate(SpriteComponent component)
         {
-            UpdateEntity(ev.Sender);
+            if (component.TreeUpdateQueued) return;
+
+            component.TreeUpdateQueued = true;
+            _spriteQueue.Add(component);
+        }
+        #endregion
+
+        #region LightHandlers
+        private void LightMapChanged(EntityUid uid, PointLightComponent component, EntMapIdChangedMessage args)
+        {
+            QueueLightUpdate(component);
         }
 
-        private void UpdateEntity(IEntity entity)
+        private void LightParentChanged(EntityUid uid, PointLightComponent component, EntParentChangedMessage args)
         {
-            if (entity.TryGetComponent(out SpriteComponent? spriteComponent))
+            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 (component.RenderTree == null) return;
+
+            component.RenderTree.LightTree.Remove(component);
+            component.RenderTree = null;
+        }
+
+        private void QueueLightUpdate(PointLightComponent component)
+        {
+            if (component.TreeUpdateQueued) return;
+
+            component.TreeUpdateQueued = true;
+            _lightQueue.Add(component);
+        }
+        #endregion
+
+        public override void Shutdown()
+        {
+            base.Shutdown();
+            _mapManager.MapCreated -= MapManagerOnMapCreated;
+            _mapManager.OnGridCreated -= MapManagerOnGridCreated;
+        }
+
+        private void HandleTreeRemove(EntityUid uid, RenderingTreeComponent component, ComponentRemove args)
+        {
+            foreach (var sprite in component.SpriteTree)
             {
-                if (!spriteComponent.TreeUpdateQueued)
-                {
-                    spriteComponent.TreeUpdateQueued = true;
-
-                    _spriteQueue.Add(spriteComponent);
-                }
+                sprite.RenderTree = null;
             }
 
-            if (entity.TryGetComponent(out PointLightComponent? light))
+            foreach (var light in component.LightTree)
             {
-                QueueUpdateLight(light);
+                light.RenderTree = null;
             }
 
-            foreach (var child in entity.Transform.ChildEntityUids)
-            {
-                UpdateEntity(EntityManager.GetEntity(child));
-            }
-        }
-
-        private void QueueUpdateLight(PointLightComponent light)
-        {
-            if (!light.TreeUpdateQueued)
-            {
-                light.TreeUpdateQueued = true;
-
-                _lightQueue.Add(light);
-            }
-        }
-
-        private void EntMapIdChanged(EntMapIdChangedMessage ev)
-        {
-            // 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 (ev.Entity.TryGetComponent(out SpriteComponent? sprite))
-            {
-                oldMapTrees?.SpriteTree.Remove(sprite);
-
-                newMapTrees?.SpriteTree.AddOrUpdate(sprite);
-            }
-
-            if (ev.Entity.TryGetComponent(out PointLightComponent? light))
-            {
-                oldMapTrees?.LightTree.Remove(light);
-
-                newMapTrees?.LightTree.AddOrUpdate(light);
-            }
-        }
-
-        private void MapManagerOnMapDestroyed(object? sender, MapEventArgs e)
-        {
-            _mapTrees.Remove(e.Map);
+            component.SpriteTree.Clear();
+            component.LightTree.Clear();
         }
 
         private void MapManagerOnMapCreated(object? sender, MapEventArgs e)
@@ -149,86 +251,127 @@ namespace Robust.Client.GameObjects
                 return;
             }
 
-            _mapTrees.Add(e.Map, new MapTrees());
+            _mapManager.GetMapEntity(e.Map).EnsureComponent<RenderingTreeComponent>();
+        }
+
+        private void MapManagerOnGridCreated(MapId mapId, GridId gridId)
+        {
+            EntityManager.GetEntity(_mapManager.GetGrid(gridId).GridEntityId).EnsureComponent<RenderingTreeComponent>();
+        }
+
+        private RenderingTreeComponent? GetRenderTree(IEntity entity)
+        {
+
+            if (entity.Transform.MapID == MapId.Nullspace ||
+                entity.HasComponent<RenderingTreeComponent>()) return null;
+
+            var parent = entity.Transform.Parent?.Owner;
+
+            while (true)
+            {
+                if (parent == null) break;
+
+                if (parent.TryGetComponent(out RenderingTreeComponent? comp)) return comp;
+                parent = parent.Transform.Parent?.Owner;
+            }
+
+            return null;
         }
 
         public override void FrameUpdate(float frameTime)
         {
-            foreach (var queuedUpdateSprite in _spriteQueue)
+            _checkedChildren.Clear();
+
+            foreach (var sprite in _spriteQueue)
             {
-                var transform = queuedUpdateSprite.Owner.Transform;
-                var map = transform.MapID;
-                if (map == MapId.Nullspace)
+                sprite.TreeUpdateQueued = false;
+                if (!sprite.Visible || sprite.ContainerOccluded)
                 {
+                    ClearSprite(sprite);
                     continue;
                 }
-                var updateMapTree = _mapTrees[map].SpriteTree;
 
-                updateMapTree.AddOrUpdate(queuedUpdateSprite);
-                queuedUpdateSprite.TreeUpdateQueued = false;
+                var oldMapTree = sprite.RenderTree;
+                var newMapTree = GetRenderTree(sprite.Owner);
+                // TODO: Temp PVS guard
+                var worldPos = sprite.Owner.Transform.WorldPosition;
+
+                if (float.IsNaN(worldPos.X) || float.IsNaN(worldPos.Y))
+                {
+                    ClearSprite(sprite);
+                    continue;
+                }
+
+                var treePos = newMapTree?.Owner.Transform.WorldPosition ?? Vector2.Zero;
+                var aabb = RenderingTreeComponent.SpriteAabbFunc(sprite, worldPos).Translated(-treePos);
+
+                // If we're on a new map then clear the old one.
+                if (oldMapTree != newMapTree)
+                {
+                    ClearSprite(sprite);
+                    newMapTree?.SpriteTree.Add(sprite, aabb);
+                }
+                else
+                {
+                    newMapTree?.SpriteTree.Update(sprite, aabb);
+                }
+
+                sprite.RenderTree = newMapTree;
             }
 
-            foreach (var queuedUpdateLight in _lightQueue)
+            foreach (var light in _lightQueue)
             {
-                var transform = queuedUpdateLight.Owner.Transform;
-                var map = transform.MapID;
-                if (map == MapId.Nullspace)
+                light.TreeUpdateQueued = false;
+
+                if (!light.Enabled || light.ContainerOccluded)
                 {
+                    ClearLight(light);
                     continue;
                 }
-                var updateMapTree = _mapTrees[map].LightTree;
 
-                updateMapTree.AddOrUpdate(queuedUpdateLight);
-                queuedUpdateLight.TreeUpdateQueued = false;
+                var oldMapTree = light.RenderTree;
+                var newMapTree = GetRenderTree(light.Owner);
+                // TODO: Temp PVS guard
+                var worldPos = light.Owner.Transform.WorldPosition;
+
+                if (float.IsNaN(worldPos.X) || float.IsNaN(worldPos.Y))
+                {
+                    ClearLight(light);
+                    continue;
+                }
+
+                // TODO: Events need a bit of cleanup so we only validate this on initialize and radius changed events
+                // this is fine for now IMO as it's 1 float check for every light that moves
+                if (light.Radius > MaxLightRadius)
+                {
+                    Logger.WarningS(LoggerSawmill, $"Light radius for {light.Owner} set above max radius of {MaxLightRadius}. This may lead to pop-in.");
+                }
+
+                var treePos = newMapTree?.Owner.Transform.WorldPosition ?? Vector2.Zero;
+                var aabb = RenderingTreeComponent.LightAabbFunc(light, worldPos).Translated(-treePos);
+
+                // If we're on a new map then clear the old one.
+                if (oldMapTree != newMapTree)
+                {
+                    ClearLight(light);
+                    newMapTree?.LightTree.Add(light, aabb);
+                }
+                else
+                {
+                    newMapTree?.LightTree.Update(light, aabb);
+                }
+
+                light.RenderTree = newMapTree;
             }
 
             _spriteQueue.Clear();
             _lightQueue.Clear();
         }
-
-        private sealed class MapTrees
-        {
-            public readonly DynamicTree<SpriteComponent> SpriteTree;
-            public readonly DynamicTree<PointLightComponent> LightTree;
-
-            public MapTrees()
-            {
-                SpriteTree = new DynamicTree<SpriteComponent>(SpriteAabbFunc);
-                LightTree = new DynamicTree<PointLightComponent>(LightAabbFunc);
-            }
-
-            private static Box2 SpriteAabbFunc(in SpriteComponent value)
-            {
-                var worldPos = value.Owner.Transform.WorldPosition;
-
-                return new Box2(worldPos, worldPos);
-            }
-
-            private static Box2 LightAabbFunc(in PointLightComponent value)
-            {
-                var worldPos = value.Owner.Transform.WorldPosition;
-
-                var boxSize = value.Radius * 2;
-                return Box2.CenteredAround(worldPos, (boxSize, boxSize));
-            }
-        }
     }
 
-    internal struct RenderTreeRemoveSpriteMessage
+    internal class RenderTreeRemoveLightEvent : EntityEventArgs
     {
-        public RenderTreeRemoveSpriteMessage(SpriteComponent sprite, MapId map)
-        {
-            Sprite = sprite;
-            Map = map;
-        }
-
-        public SpriteComponent Sprite { get; }
-        public MapId Map { get; }
-    }
-
-    internal struct RenderTreeRemoveLightMessage
-    {
-        public RenderTreeRemoveLightMessage(PointLightComponent light, MapId map)
+        public RenderTreeRemoveLightEvent(PointLightComponent light, MapId map)
         {
             Light = light;
             Map = map;

Robust.Client/GameObjects/EntitySystems/SpriteSystem.cs

@@ -1,4 +1,5 @@
-using JetBrains.Annotations;
+using System.Collections.Generic;
+using JetBrains.Annotations;
 using Robust.Client.Graphics;
 using Robust.Shared.GameObjects;
 using Robust.Shared.IoC;
@@ -13,11 +14,31 @@ namespace Robust.Client.GameObjects
     public class SpriteSystem : EntitySystem
     {
         [Dependency] private readonly IEyeManager _eyeManager = default!;
+        [Dependency] private readonly IMapManager _mapManager = default!;
+
+        private RenderingTreeSystem _treeSystem = default!;
+        private readonly Queue<SpriteComponent> _inertUpdateQueue = new();
+
+        public override void Initialize()
+        {
+            base.Initialize();
+
+            _treeSystem = Get<RenderingTreeSystem>();
+            SubscribeLocalEvent<SpriteUpdateInertEvent>(QueueUpdateInert);
+        }
+
+        private void QueueUpdateInert(SpriteUpdateInertEvent ev)
+        {
+            _inertUpdateQueue.Enqueue(ev.Sprite);
+        }
 
         /// <inheritdoc />
         public override void FrameUpdate(float frameTime)
         {
-            var renderTreeSystem = EntitySystemManager.GetEntitySystem<RenderingTreeSystem>();
+            while (_inertUpdateQueue.TryDequeue(out var sprite))
+            {
+                sprite.DoUpdateIsInert();
+            }
 
             // 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.
@@ -29,18 +50,21 @@ namespace Robust.Client.GameObjects
                 return;
             }
 
-            var mapTree = renderTreeSystem.GetSpriteTreeForMap(currentMap);
-
-            mapTree.QueryAabb(ref frameTime, (ref float state, in SpriteComponent value) =>
+            foreach (var comp in _treeSystem.GetRenderTrees(currentMap, pvsBounds))
             {
-                if (value.IsInert)
-                {
-                    return true;
-                }
+                var bounds = pvsBounds.Translated(-comp.Owner.Transform.WorldPosition);
 
-                value.FrameUpdate(state);
-                return true;
-            }, pvsBounds, approx: true);
+                comp.SpriteTree.QueryAabb(ref frameTime, (ref float state, in SpriteComponent value) =>
+                {
+                    if (value.IsInert)
+                    {
+                        return true;
+                    }
+
+                    value.FrameUpdate(state);
+                    return true;
+                }, bounds, 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

@@ -1,12 +1,9 @@
-using System.Collections.Generic;
 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

@@ -1,14 +0,0 @@
-using Robust.Shared.GameObjects;
-
-namespace Robust.Client.GameObjects
-{
-    public class PlayerAttachedMsg : ComponentMessage
-    {
-
-    }
-
-    public class PlayerDetachedMsg : ComponentMessage
-    {
-
-    }
-}

Robust.Client/GameStates/ClientGameStateManager.cs

@@ -1,19 +1,24 @@
+// ReSharper disable once RedundantUsingDirective
+// Used in EXCEPTION_TOLERANCE preprocessor
 using System;
 using System.Collections.Generic;
 using System.Diagnostics;
+using System.Linq;
 using Robust.Client.GameObjects;
 using Robust.Client.Input;
-using Robust.Shared.GameStates;
-using Robust.Shared.IoC;
-using Robust.Shared.Network.Messages;
+using Robust.Client.Map;
 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.GameStates;
 using Robust.Shared.Input;
+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;
 
@@ -27,20 +32,25 @@ namespace Robust.Client.GameStates
         private uint _nextInputCmdSeq = 1;
         private readonly Queue<FullInputCmdMessage> _pendingInputs = new();
 
-        private readonly Queue<(uint sequence, GameTick sourceTick, EntitySystemMessage msg, object sessionMsg)>
+        private readonly Queue<(uint sequence, GameTick sourceTick, EntityEventArgs msg, object sessionMsg)>
             _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;
@@ -71,8 +81,8 @@ namespace Robust.Client.GameStates
         {
             _processor = new GameStateProcessor(_timing);
 
-            _network.RegisterNetMessage<MsgState>(MsgState.NAME, HandleStateMessage);
-            _network.RegisterNetMessage<MsgStateAck>(MsgStateAck.NAME);
+            _network.RegisterNetMessage<MsgState>(HandleStateMessage);
+            _network.RegisterNetMessage<MsgStateAck>();
             _client.RunLevelChanged += RunLevelChanged;
 
             _config.OnValueChanged(CVars.NetInterp, b => _processor.Interpolation = b, true);
@@ -126,7 +136,7 @@ namespace Robust.Client.GameStates
             _nextInputCmdSeq++;
         }
 
-        public uint SystemMessageDispatched<T>(T message) where T : EntitySystemMessage
+        public uint SystemMessageDispatched<T>(T message) where T : EntityEventArgs
         {
             if (!Predicting)
             {
@@ -200,6 +210,11 @@ namespace Robust.Client.GameStates
                     ResetPredictedEntities(_timing.CurTick);
                 }
 
+                if (!curState.Extrapolated)
+                {
+                    _processor.UpdateFullRep(curState);
+                }
+
                 // Store last tick we got from the GameStateProcessor.
                 _lastProcessedTick = _timing.CurTick;
 
@@ -242,69 +257,75 @@ 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);
-                    ((IEntityEventBus) _entities.EventBus).ProcessEventQueue();
-                }
-            }
+            _lookup.Update();
         }
 
         private void ResetPredictedEntities(GameTick curTick)
         {
+            var bus = (EntityEventBus) _entities.EventBus;
+
             foreach (var entity in _entities.GetEntities())
             {
                 // TODO: 99% there's an off-by-one here.
@@ -333,6 +354,7 @@ namespace Robust.Client.GameStates
 
                     Logger.DebugS(CVars.NetPredict.Name, $"  And also its component {comp.Name}");
                     // TODO: Handle interpolation.
+                    bus.RaiseComponentEvent(comp, new ComponentHandleState(compState, null));
                     comp.HandleComponentState(compState, null);
                 }
             }
@@ -380,8 +402,8 @@ namespace Robust.Client.GameStates
         private List<EntityUid> ApplyGameState(GameState curState, GameState? nextState)
         {
             _config.TickProcessMessages();
-            _mapManager.ApplyGameStatePre(curState.MapData);
-            var createdEntities = _entities.ApplyEntityStates(curState.EntityStates, curState.EntityDeletions,
+            _mapManager.ApplyGameStatePre(curState.MapData, curState.EntityStates);
+            var createdEntities = ApplyEntityStates(curState.EntityStates, curState.EntityDeletions,
                 nextState?.EntityStates);
             _players.ApplyPlayerStates(curState.PlayerStates);
             _mapManager.ApplyGameStatePost(curState.MapData);
@@ -389,6 +411,224 @@ namespace Robust.Client.GameStates
             GameStateApplied?.Invoke(new GameStateAppliedArgs(curState));
             return createdEntities;
         }
+
+        private List<EntityUid> ApplyEntityStates(EntityState[]? curEntStates, IEnumerable<EntityUid>? deletions,
+            EntityState[]? nextEntStates)
+        {
+            var toApply = new Dictionary<IEntity, (EntityState?, EntityState?)>();
+            var toInitialize = new List<Entity>();
+            var created = new List<EntityUid>();
+            deletions ??= new EntityUid[0];
+
+            if (curEntStates != null && curEntStates.Length != 0)
+            {
+                foreach (var es in curEntStates)
+                {
+                    //Known entities
+                    if (_entities.TryGetEntity(es.Uid, out var entity))
+                    {
+                        // Logger.Debug($"[{IGameTiming.TickStampStatic}] MOD {es.Uid}");
+                        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($"Server sent new entity state for {es.Uid} without metadata component!");
+                        }
+                        // Logger.Debug($"[{IGameTiming.TickStampStatic}] CREATE {es.Uid} {metaState.PrototypeId}");
+                        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);
+                        }
+                    }
+                }
+            }
+
+            var bus = (EntityEventBus) _entities.EventBus;
+
+            // 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, bus, kvStates.Value.Item1,
+                    kvStates.Value.Item2);
+            }
+
+            foreach (var id in deletions)
+            {
+                // Logger.Debug($"[{IGameTiming.TickStampStatic}] DELETE {id}");
+                _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, EntityEventBus bus, 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
+                    {
+                        bus.RaiseComponentEvent(component, new ComponentHandleState(cur, next));
+                        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/GameStateProcessor.cs

@@ -149,11 +149,6 @@ namespace Robust.Client.GameStates
                 {
                     Logger.DebugS("net.state", $"Applying State:  ext={curState!.Extrapolated}, cTick={_timing.CurTick}, fSeq={curState.FromSequence}, tSeq={curState.ToSequence}, buf={_stateBuffer.Count}");
                 }
-
-                if (!curState!.Extrapolated)
-                {
-                    UpdateFullRep(curState);
-                }
             }
 
             var cState = curState!;
@@ -162,8 +157,10 @@ namespace Robust.Client.GameStates
             return applyNextState;
         }
 
-        private void UpdateFullRep(GameState state)
+        public void UpdateFullRep(GameState state)
         {
+            // Logger.Debug($"UPDATE FULL REP: {string.Join(", ", state.EntityStates?.Select(e => e.Uid) ?? Enumerable.Empty<EntityUid>())}");
+
             if (state.FromSequence == GameTick.Zero)
             {
                 // Full state.

Robust.Client/GameStates/IClientGameStateManager.cs

@@ -70,6 +70,6 @@ namespace Robust.Client.GameStates
         /// <param name="message">Message being dispatched.</param>
         void InputCommandDispatched(FullInputCmdMessage message);
 
-        uint SystemMessageDispatched<T>(T message) where T : EntitySystemMessage;
+        uint SystemMessageDispatched<T>(T message) where T : EntityEventArgs;
     }
 }

Robust.Client/GameStates/NetEntityOverlay.cs

@@ -1,13 +1,16 @@
 using System.Collections.Generic;
 using Robust.Client.Graphics;
+using Robust.Client.Player;
 using Robust.Client.ResourceManagement;
 using Robust.Shared.Configuration;
 using Robust.Shared.Console;
+using Robust.Shared.Enums;
 using Robust.Shared.GameObjects;
 using Robust.Shared.IoC;
 using Robust.Shared.Maths;
 using Robust.Shared.Network;
 using Robust.Shared.Timing;
+using Robust.Shared.Utility;
 
 namespace Robust.Client.GameStates
 {
@@ -27,13 +30,13 @@ 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();
 
-        public NetEntityOverlay() : base(nameof(NetEntityOverlay))
+        public NetEntityOverlay()
         {
             IoCManager.InjectDependencies(this);
             var cache = IoCManager.Resolve<IResourceCache>();
@@ -42,12 +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++)
             {
@@ -74,7 +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;
@@ -94,15 +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.
@@ -123,24 +126,59 @@ 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);
+                screenHandle.DrawString(_font, new Vector2(xPos + (TrafficHistorySize + 4), yPos), name, color);
                 DrawTrafficBox(screenHandle, ref netEnt, xPos, yPos);
             }
         }
@@ -179,22 +217,10 @@ namespace Robust.Client.GameStates
             return Color.Green; // Entity in PVS, but not updated recently.
         }
 
-        protected override void Dispose(bool disposing)
+        protected override void DisposeBehavior()
         {
             _gameStateManager.GameStateApplied -= HandleGameStateApplied;
-
-            base.Dispose(disposing);
-        }
-
-        private static void DrawString(DrawingHandleScreen handle, Font font, Vector2 pos, string str, Color textColor)
-        {
-            var baseLine = new Vector2(pos.X, font.GetAscent(1) + pos.Y);
-
-            foreach (var chr in str)
-            {
-                var advance = font.DrawChar(handle, chr, baseLine, 1, textColor);
-                baseLine += new Vector2(advance, 0);
-            }
+            base.DisposeBehavior();
         }
 
         private struct NetEntity
@@ -225,7 +251,7 @@ 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;
                 }
 
@@ -238,14 +264,14 @@ namespace Robust.Client.GameStates
                 var bValue = iValue > 0;
                 var overlayMan = IoCManager.Resolve<IOverlayManager>();
 
-                if(bValue && !overlayMan.HasOverlay(nameof(NetEntityOverlay)))
+                if(bValue && !overlayMan.HasOverlay(typeof(NetEntityOverlay)))
                 {
                     overlayMan.AddOverlay(new NetEntityOverlay());
                     shell.WriteLine("Enabled network entity report overlay.");
                 }
-                else if(!bValue && overlayMan.HasOverlay(nameof(NetEntityOverlay)))
+                else if(!bValue && overlayMan.HasOverlay(typeof(NetEntityOverlay)))
                 {
-                    overlayMan.RemoveOverlay(nameof(NetEntityOverlay));
+                    overlayMan.RemoveOverlay(typeof(NetEntityOverlay));
                     shell.WriteLine("Disabled network entity report overlay.");
                 }
             }

Robust.Client/GameStates/NetGraphOverlay.cs

@@ -1,7 +1,11 @@
-using System.Collections.Generic;
+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;
@@ -34,7 +38,11 @@ namespace Robust.Client.GameStates
 
         private readonly List<(GameTick Tick, int Payload, int lag, int interp)> _history = new(HistorySize+10);
 
-        public NetGraphOverlay() : base(nameof(NetGraphOverlay))
+        private int _totalHistoryPayload; // sum of all data point sizes in bytes
+
+        public EntityUid WatchEntId { get; set; }
+
+        public NetGraphOverlay()
         {
             IoCManager.InjectDependencies(this);
             var cache = IoCManager.Resolve<IResourceCache>();
@@ -58,7 +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 />
@@ -67,19 +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));
@@ -99,6 +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)
+                {
+                    handle.DrawString(_font, new Vector2(xOff, yoff - _font.GetLineHeight(1)), state.Payload.ToString());
+                }
+
                 // second tick marks
                 if (state.Tick.Value % _gameTiming.TickRate == 0)
                 {
@@ -123,6 +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));
@@ -132,32 +224,21 @@ 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");
+            handle.DrawString(_font, new Vector2(leftMargin + width, warnYoff), "56K");
+            handle.DrawString(_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");
+                handle.DrawString(_font, new Vector2(leftMargin + width, lastLagY), $"{lastLagMs.ToString()}ms");
 
-            DrawString((DrawingHandleScreen)handle, _font, new Vector2(leftMargin, height + LowerGraphOffset), $"{_gameStateManager.CurrentBufferSize.ToString()} states");
+            handle.DrawString(_font, new Vector2(leftMargin, height + LowerGraphOffset), $"{_gameStateManager.CurrentBufferSize.ToString()} states");
         }
 
-        protected override void Dispose(bool disposing)
+        protected override void DisposeBehavior()
         {
             _gameStateManager.GameStateApplied -= HandleGameStateApplied;
 
-            base.Dispose(disposing);
-        }
-
-        private void DrawString(DrawingHandleScreen handle, Font font, Vector2 pos, string str)
-        {
-            var baseLine = new Vector2(pos.X, font.GetAscent(1) + pos.Y);
-
-            foreach (var chr in str)
-            {
-                var advance = font.DrawChar(handle, chr, baseLine, 1, Color.White);
-                baseLine += new Vector2(advance, 0);
-            }
+            base.DisposeBehavior();
         }
 
         private class NetShowGraphCommand : IConsoleCommand
@@ -183,17 +264,48 @@ namespace Robust.Client.GameStates
                 var bValue = iValue > 0;
                 var overlayMan = IoCManager.Resolve<IOverlayManager>();
 
-                if(bValue && !overlayMan.HasOverlay(nameof(NetGraphOverlay)))
+                if(bValue && !overlayMan.HasOverlay(typeof(NetGraphOverlay)))
                 {
                     overlayMan.AddOverlay(new NetGraphOverlay());
                     shell.WriteLine("Enabled network overlay.");
                 }
-                else if(overlayMan.HasOverlay(nameof(NetGraphOverlay)))
+                else if(overlayMan.HasOverlay(typeof(NetGraphOverlay)))
                 {
-                    overlayMan.RemoveOverlay(nameof(NetGraphOverlay));
+                    overlayMan.RemoveOverlay(typeof(NetGraphOverlay));
                     shell.WriteLine("Disabled network overlay.");
                 }
             }
         }
+
+        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

@@ -1,3 +1,4 @@
+using Robust.Shared.Enums;
 using Robust.Client.Graphics;
 using Robust.Shared.Console;
 using Robust.Shared.GameObjects;
@@ -5,6 +6,7 @@ using Robust.Shared.IoC;
 using Robust.Shared.Maths;
 using Robust.Shared.Physics;
 using Robust.Shared.Prototypes;
+using System;
 using Robust.Shared.Timing;
 
 namespace Robust.Client.GameStates
@@ -18,14 +20,15 @@ namespace Robust.Client.GameStates
         public override OverlaySpace Space => OverlaySpace.WorldSpace;
         private readonly ShaderInstance _shader;
 
-        public NetInterpOverlay() : base(nameof(NetInterpOverlay))
+        public NetInterpOverlay()
         {
             IoCManager.InjectDependencies(this);
             _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();
@@ -85,14 +88,14 @@ namespace Robust.Client.GameStates
                 var bValue = iValue > 0;
                 var overlayMan = IoCManager.Resolve<IOverlayManager>();
 
-                if (bValue && !overlayMan.HasOverlay(nameof(NetInterpOverlay)))
+                if (bValue && !overlayMan.HasOverlay<NetInterpOverlay>())
                 {
                     overlayMan.AddOverlay(new NetInterpOverlay());
                     shell.WriteLine("Enabled network interp overlay.");
                 }
-                else if (overlayMan.HasOverlay(nameof(NetInterpOverlay)))
+                else if (overlayMan.HasOverlay<NetInterpOverlay>())
                 {
-                    overlayMan.RemoveOverlay(nameof(NetInterpOverlay));
+                    overlayMan.RemoveOverlay<NetInterpOverlay>();
                     shell.WriteLine("Disabled network interp overlay.");
                 }
             }

Robust.Client/Graphics/AtlasTexture.cs

@@ -1,4 +1,4 @@
-using JetBrains.Annotations;
+using JetBrains.Annotations;
 using Robust.Shared.Maths;
 using Robust.Shared.Utility;
 

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

@@ -44,8 +44,12 @@ namespace Robust.Client.Graphics.Clyde
 
         internal bool IsEfxSupported;
 
+        private ISawmill _openALSawmill = default!;
+
         private void _initializeAudio()
         {
+            _openALSawmill = Logger.GetSawmill("clyde.oal");
+
             _audioOpenDevice();
 
             // Create OpenAL context.
@@ -53,7 +57,7 @@ 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()
@@ -74,14 +78,14 @@ namespace Robust.Client.Graphics.Clyde
                 _alContextExtensions.Add(extension);
             }
 
-            Logger.DebugS("clyde.oal", "OpenAL Vendor: {0}", AL.Get(ALGetString.Vendor));
-            Logger.DebugS("clyde.oal", "OpenAL Renderer: {0}", AL.Get(ALGetString.Renderer));
-            Logger.DebugS("clyde.oal", "OpenAL Version: {0}", AL.Get(ALGetString.Version));
+            _openALSawmill.Debug("OpenAL Vendor: {0}", AL.Get(ALGetString.Vendor));
+            _openALSawmill.Debug("OpenAL Renderer: {0}", AL.Get(ALGetString.Renderer));
+            _openALSawmill.Debug("OpenAL Version: {0}", AL.Get(ALGetString.Version));
         }
 
         private void _audioOpenDevice()
         {
-            var preferredDevice = _configurationManager.GetCVar(CVars.AudioDevice);
+            var preferredDevice = _cfg.GetCVar(CVars.AudioDevice);
 
             // Open device.
             if (!string.IsNullOrEmpty(preferredDevice))
@@ -89,7 +93,7 @@ namespace Robust.Client.Graphics.Clyde
                 _openALDevice = ALC.OpenDevice(preferredDevice);
                 if (_openALDevice == IntPtr.Zero)
                 {
-                    Logger.WarningS("clyde.oal", "Unable to open preferred audio device '{0}': {1}. Falling back default.",
+                    _openALSawmill.Warning("Unable to open preferred audio device '{0}': {1}. Falling back default.",
                         preferredDevice, ALC.GetError(ALDevice.Null));
 
                     _openALDevice = ALC.OpenDevice(null);
@@ -153,7 +157,7 @@ namespace Robust.Client.Graphics.Clyde
             // Clear out finalized audio sources.
             while (_sourceDisposeQueue.TryDequeue(out var handles))
             {
-                Logger.DebugS("clyde.oal", "Cleaning out source {0} which finalized in another thread.", handles.sourceHandle);
+                _openALSawmill.Debug("Cleaning out source {0} which finalized in another thread.", handles.sourceHandle);
                 if (IsEfxSupported) RemoveEfx(handles);
                 AL.DeleteSource(handles.sourceHandle);
                 _checkAlError();
@@ -163,7 +167,7 @@ namespace Robust.Client.Graphics.Clyde
             // Clear out finalized buffered audio sources.
             while (_bufferedSourceDisposeQueue.TryDequeue(out var handles))
             {
-                Logger.DebugS("clyde.oal", "Cleaning out buffered source {0} which finalized in another thread.", handles.sourceHandle);
+                _openALSawmill.Debug("Cleaning out buffered source {0} which finalized in another thread.", handles.sourceHandle);
                 if (IsEfxSupported) RemoveEfx(handles);
                 AL.DeleteSource(handles.sourceHandle);
                 _checkAlError();
@@ -211,24 +215,24 @@ namespace Robust.Client.Graphics.Clyde
             return audioSource;
         }
 
-        private static void _checkAlcError(ALDevice device,
+        private void _checkAlcError(ALDevice device,
             [CallerMemberName] string callerMember = "",
             [CallerLineNumber] int callerLineNumber = -1)
         {
             var error = ALC.GetError(device);
             if (error != AlcError.NoError)
             {
-                Logger.ErrorS("clyde.oal", "[{0}:{1}] ALC error: {2}", callerMember, callerLineNumber, error);
+                _openALSawmill.Error("[{0}:{1}] ALC error: {2}", callerMember, callerLineNumber, error);
             }
         }
 
-        private static void _checkAlError([CallerMemberName] string callerMember = "",
+        private void _checkAlError([CallerMemberName] string callerMember = "",
             [CallerLineNumber] int callerLineNumber = -1)
         {
             var error = AL.GetError();
             if (error != ALError.NoError)
             {
-                Logger.ErrorS("clyde.oal", "[{0}:{1}] AL error: {2}", callerMember, callerLineNumber, error);
+                _openALSawmill.Error("[{0}:{1}] AL error: {2}", callerMember, callerLineNumber, error);
             }
         }
 
@@ -330,6 +334,35 @@ namespace Robust.Client.Graphics.Clyde
             return new AudioStream(handle, length, wav.NumChannels, name);
         }
 
+        public AudioStream LoadAudioRaw(ReadOnlySpan<short> samples, int channels, int sampleRate, string? name = null)
+        {
+            var fmt = channels switch
+            {
+                1 => ALFormat.Mono16,
+                2 => ALFormat.Stereo16,
+                _ => throw new ArgumentOutOfRangeException(
+                    nameof(channels), "Only stereo and mono is currently supported")
+            };
+
+            var buffer = AL.GenBuffer();
+            _checkAlError();
+
+            unsafe
+            {
+                fixed (short* ptr = samples)
+                {
+                    AL.BufferData(buffer, fmt, (IntPtr) ptr, samples.Length * sizeof(short), sampleRate);
+                }
+            }
+
+            _checkAlError();
+
+            var handle = new ClydeHandle(_audioSampleBuffers.Count);
+            var length = TimeSpan.FromSeconds((double) samples.Length / channels / sampleRate);
+            _audioSampleBuffers.Add(new LoadedAudioSample(buffer));
+            return new AudioStream(handle, length, channels, name);
+        }
+
         private sealed class LoadedAudioSample
         {
             public readonly int BufferHandle;
@@ -381,14 +414,14 @@ namespace Robust.Client.Graphics.Clyde
             {
                 _checkDisposed();
                 AL.SourcePlay(SourceHandle);
-                _checkAlError();
+                _master._checkAlError();
             }
 
             public void StopPlaying()
             {
                 _checkDisposed();
                 AL.SourceStop(SourceHandle);
-                _checkAlError();
+                _master._checkAlError();
             }
 
             public bool IsPlaying
@@ -407,14 +440,14 @@ namespace Robust.Client.Graphics.Clyde
                 {
                     _checkDisposed();
                     AL.GetSource(SourceHandle, ALSourceb.Looping, out var ret);
-                    _checkAlError();
+                    _master._checkAlError();
                     return ret;
                 }
                 set
                 {
                     _checkDisposed();
                     AL.Source(SourceHandle, ALSourceb.Looping, value);
-                    _checkAlError();
+                    _master._checkAlError();
                 }
             }
 
@@ -422,7 +455,7 @@ namespace Robust.Client.Graphics.Clyde
             {
                 _checkDisposed();
                 AL.Source(SourceHandle, ALSourceb.SourceRelative, true);
-                _checkAlError();
+                _master._checkAlError();
             }
 
             public void SetVolume(float decibels)
@@ -436,7 +469,21 @@ namespace Robust.Client.Graphics.Clyde
                 }
                 _gain =  MathF.Pow(10, decibels / 10);
                 AL.Source(SourceHandle, ALSourcef.Gain, _gain * priorOcclusion);
-                _checkAlError();
+                _master._checkAlError();
+            }
+
+            public void SetVolumeDirect(float scale)
+            {
+                _checkDisposed();
+                var priorOcclusion = 1f;
+                if (!IsEfxSupported)
+                {
+                    AL.GetSource(SourceHandle, ALSourcef.Gain, out var priorGain);
+                    priorOcclusion = priorGain / _gain;
+                }
+                _gain = scale;
+                AL.Source(SourceHandle, ALSourcef.Gain, _gain * priorOcclusion);
+                _master._checkAlError();
             }
 
             public void SetOcclusion(float blocks)
@@ -453,7 +500,7 @@ namespace Robust.Client.Graphics.Clyde
                     gain *= gain * gain;
                     AL.Source(SourceHandle, ALSourcef.Gain, _gain * gain);
                 }
-                _checkAlError();
+                _master._checkAlError();
             }
 
             private void SetOcclusionEfx(float gain, float cutoff)
@@ -473,7 +520,7 @@ namespace Robust.Client.Graphics.Clyde
             {
                 _checkDisposed();
                 AL.Source(SourceHandle, ALSourcef.SecOffset, seconds);
-                _checkAlError();
+                _master._checkAlError();
             }
 
             public bool SetPosition(Vector2 position)
@@ -482,7 +529,7 @@ namespace Robust.Client.Graphics.Clyde
 
                 var (x, y) = position;
 
-                if (!ValidatePosition(x, y))
+                if (!AreFinite(x, y))
                 {
                     return false;
                 }
@@ -499,11 +546,11 @@ namespace Robust.Client.Graphics.Clyde
 #endif
 
                 AL.Source(SourceHandle, ALSource3f.Position, x, y, 0);
-                _checkAlError();
+                _master._checkAlError();
                 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))
                 {
@@ -513,11 +560,27 @@ 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);
+
+                _master._checkAlError();
+            }
+
             public void SetPitch(float pitch)
             {
                 _checkDisposed();
                 AL.Source(SourceHandle, ALSourcef.Pitch, pitch);
-                _checkAlError();
+                _master._checkAlError();
             }
 
             ~AudioSource()
@@ -543,7 +606,7 @@ namespace Robust.Client.Graphics.Clyde
                     if (FilterHandle != 0) EFX.DeleteFilter(FilterHandle);
                     AL.DeleteSource(SourceHandle);
                     _master._audioSources.Remove(SourceHandle);
-                    _checkAlError();
+                    _master._checkAlError();
                 }
 
                 SourceHandle = -1;
@@ -593,7 +656,7 @@ namespace Robust.Client.Graphics.Clyde
                 _checkDisposed();
                 // ReSharper disable once PossibleInvalidOperationException
                 AL.SourcePlay(stackalloc int[] {SourceHandle!.Value});
-                _checkAlError();
+                _master._checkAlError();
             }
 
             public void StopPlaying()
@@ -601,7 +664,7 @@ namespace Robust.Client.Graphics.Clyde
                 _checkDisposed();
                 // ReSharper disable once PossibleInvalidOperationException
                 AL.SourceStop(SourceHandle!.Value);
-                _checkAlError();
+                _master._checkAlError();
             }
 
             public bool IsPlaying
@@ -627,7 +690,7 @@ namespace Robust.Client.Graphics.Clyde
                 _mono = false;
                 // ReSharper disable once PossibleInvalidOperationException
                 AL.Source(SourceHandle!.Value, ALSourceb.SourceRelative, true);
-                _checkAlError();
+                _master._checkAlError();
             }
 
             public void SetLooping()
@@ -646,7 +709,21 @@ namespace Robust.Client.Graphics.Clyde
                 }
                 _gain =  MathF.Pow(10, decibels / 10);
                 AL.Source(SourceHandle!.Value, ALSourcef.Gain, _gain * priorOcclusion);
-                _checkAlError();
+                _master._checkAlError();
+            }
+
+            public void SetVolumeDirect(float scale)
+            {
+                _checkDisposed();
+                var priorOcclusion = 1f;
+                if (!IsEfxSupported)
+                {
+                    AL.GetSource(SourceHandle!.Value, ALSourcef.Gain, out var priorGain);
+                    priorOcclusion = priorGain / _gain;
+                }
+                _gain = scale;
+                AL.Source(SourceHandle!.Value, ALSourcef.Gain, _gain * priorOcclusion);
+                _master._checkAlError();
             }
 
             public void SetOcclusion(float blocks)
@@ -664,10 +741,9 @@ namespace Robust.Client.Graphics.Clyde
                     AL.Source(SourceHandle!.Value, ALSourcef.Gain, gain * _gain);
                 }
 
-                _checkAlError();
+                _master._checkAlError();
             }
 
-
             private void SetOcclusionEfx(float gain, float cutoff)
             {
                 if (FilterHandle == 0)
@@ -685,7 +761,7 @@ namespace Robust.Client.Graphics.Clyde
                 _checkDisposed();
                 // ReSharper disable once PossibleInvalidOperationException
                 AL.Source(SourceHandle!.Value, ALSourcef.SecOffset, seconds);
-                _checkAlError();
+                _master._checkAlError();
             }
 
             public bool SetPosition(Vector2 position)
@@ -694,7 +770,7 @@ namespace Robust.Client.Graphics.Clyde
 
                 var (x, y) = position;
 
-                if (!ValidatePosition(x, y))
+                if (!AreFinite(x, y))
                 {
                     return false;
                 }
@@ -702,11 +778,11 @@ namespace Robust.Client.Graphics.Clyde
                 _mono = true;
                 // ReSharper disable once PossibleInvalidOperationException
                 AL.Source(SourceHandle!.Value, ALSource3f.Position, x, y, 0);
-                _checkAlError();
+                _master._checkAlError();
                 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))
                 {
@@ -716,12 +792,28 @@ 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);
+
+                _master._checkAlError();
+            }
+
             public void SetPitch(float pitch)
             {
                 _checkDisposed();
                 // ReSharper disable once PossibleInvalidOperationException
                 AL.Source(SourceHandle!.Value, ALSourcef.Pitch, pitch);
-                _checkAlError();
+                _master._checkAlError();
             }
 
             ~BufferedAudioSource()
@@ -739,7 +831,7 @@ 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);
@@ -752,7 +844,7 @@ namespace Robust.Client.Graphics.Clyde
                     AL.DeleteSource(SourceHandle.Value);
                     AL.DeleteBuffers(BufferHandles);
                     _master._bufferedAudioSources.Remove(SourceHandle.Value);
-                    _checkAlError();
+                    _master._checkAlError();
                 }
 
                 SourceHandle = null;

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.DllMap.cs

@@ -11,8 +11,9 @@ namespace Robust.Client.Graphics.Clyde
     {
         static Clyde()
         {
-            if (RuntimeInformation.IsOSPlatform(OSPlatform.Windows) &&
-                RuntimeInformation.ProcessArchitecture == Architecture.X64)
+            if (OperatingSystem.IsWindows() &&
+                RuntimeInformation.ProcessArchitecture == Architecture.X64 &&
+                Environment.GetEnvironmentVariable("ROBUST_INTEGRATED_GPU") != "1")
             {
                 try
                 {
@@ -27,20 +28,20 @@ namespace Robust.Client.Graphics.Clyde
                 }
             }
 
-            if (RuntimeInformation.IsOSPlatform(OSPlatform.Windows))
+            if (OperatingSystem.IsWindows())
             {
                 return;
             }
 
             NativeLibrary.SetDllImportResolver(typeof(GL).Assembly, (name, assembly, path) =>
             {
-                if (RuntimeInformation.IsOSPlatform(OSPlatform.Linux)
+                if (OperatingSystem.IsLinux()
                     && _dllMapLinux.TryGetValue(name, out var mappedName))
                 {
                     return NativeLibrary.Load(mappedName);
                 }
 
-                if (RuntimeInformation.IsOSPlatform(OSPlatform.OSX)
+                if (OperatingSystem.IsMacOS()
                     && _dllMapMacOS.TryGetValue(name, out mappedName))
                 {
                     return NativeLibrary.Load(mappedName);

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

@@ -7,6 +7,9 @@ using Robust.Client.ResourceManagement;
 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
 {
@@ -22,18 +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;
             }
 
@@ -49,7 +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);
@@ -61,71 +74,142 @@ namespace Robust.Client.Graphics.Clyde
             {
                 DrawSplash(_renderHandle);
                 FlushRenderQueue();
-                SwapBuffers();
+                SwapMainBuffers();
                 return;
             }
 
-            RenderOverlays(OverlaySpace.ScreenSpaceBelowWorld);
-
-            _mainViewport.Eye = _eyeManager.CurrentEye;
-            RenderViewport(_mainViewport);
-
+            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)
-                {
-                    if ((overlay.Space & space) != 0)
-                    {
-                        list.Add(overlay);
-                    }
-                }
-
-                list.Sort(OverlayComparer.Instance);
-
+                var list = GetOverlaysForSpace(space);
                 foreach (var overlay in list)
                 {
-                    overlay.ClydeRender(_renderHandle, space);
-                }
+                    if (overlay.RequestScreenTexture)
+                    {
+                        FlushRenderQueue();
+                        UpdateOverlayScreenTexture(space, vp.RenderTarget);
+                    }
 
-                FlushRenderQueue();
+                    if (overlay.OverwriteTargetFrameBuffer())
+                    {
+                        ClearFramebuffer(default);
+                    }
+
+                    overlay.ClydeRender(_renderHandle, space, null, vp, new UIBox2i((0, 0), vp.Size), worldBox);
+                }
             }
         }
 
-        private void DrawEntitiesAndWorldOverlay(Viewport viewport, Box2 worldBounds)
+        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)
+        {
+            //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)
+                {
+                    oTargets.Add(overlay);
+                }
+            }
+
+            if (oTargets.Count > 0 && ScreenBufferTexture != null)
+            {
+                if (lastFrameSize != texture.Size)
+                {
+                    GL.BindTexture(TextureTarget.Texture2D, screenBufferHandle.Handle);
+                    GL.TexImage2D(TextureTarget.Texture2D, 0,
+                        _hasGLSrgb ? PixelInternalFormat.Srgb8Alpha8 : PixelInternalFormat.Rgba8, texture.Size.X,
+                        texture.Size.Y, 0,
+                        PixelFormat.Rgba, PixelType.UnsignedByte, IntPtr.Zero);
+                }
+
+                lastFrameSize = texture.Size;
+                CopyRenderTextureToTexture(texture, ScreenBufferTexture);
+                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))
             {
                 return;
             }
 
+            RenderOverlays(viewport, OverlaySpace.WorldSpaceBelowEntities, worldBounds);
+
             var screenSize = viewport.Size;
 
             // So we could calculate the correct size of the entities based on the contents of their sprite...
@@ -175,7 +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;
                     }
@@ -194,13 +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
@@ -225,8 +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));
@@ -260,6 +350,9 @@ namespace Robust.Client.Graphics.Clyde
 
                     _renderHandle.SetProjView(oldProj, oldView);
                     _renderHandle.UseShader(null);
+
+                    // TODO: cache this properly across frames.
+                    entityPostRenderTarget.DisposeDeferred();
                 }
             }
 
@@ -267,45 +360,33 @@ namespace Robust.Client.Graphics.Clyde
 
             _drawingSpriteList.Clear();
             FlushRenderQueue();
-
-            // Cleanup remainders
-            foreach (var overlay in worldOverlays)
-            {
-                overlay.ClydeRender(_renderHandle, OverlaySpace.WorldSpace);
-            }
-
-            FlushRenderQueue();
         }
 
         [MethodImpl(MethodImplOptions.NoInlining)]
         private void ProcessSpriteEntities(MapId map, Box2 worldBounds,
             RefList<(SpriteComponent sprite, Matrix3 matrix, Angle worldRot, float yWorldPos)> list)
         {
-            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 comp in _entitySystemManager.GetEntitySystem<RenderingTreeSystem>().GetRenderTrees(map, worldBounds))
             {
-                if (value.ContainerOccluded || !value.Visible)
+                var bounds = worldBounds.Translated(-comp.Owner.Transform.WorldPosition);
+
+                comp.SpriteTree.QueryAabb(ref list, ((
+                    ref RefList<(SpriteComponent sprite, Matrix3 matrix, Angle worldRot, float yWorldPos)> state,
+                    in SpriteComponent value) =>
                 {
+                    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;
-                }
 
-                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;
-
-            }), worldBounds, approx: true);
+                }), bounds, true);
+            }
         }
 
         private void DrawSplash(IRenderHandle handle)
@@ -315,13 +396,8 @@ 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;
@@ -330,28 +406,54 @@ 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)
                 {
@@ -360,6 +462,9 @@ namespace Robust.Client.Graphics.Clyde
                         DrawLightsAndFov(viewport, worldBounds, eye);
                     }
 
+                    RenderOverlays(viewport, OverlaySpace.WorldSpaceBelowWorld, worldBounds);
+                    FlushRenderQueue();
+
                     using (DebugGroup("Grids"))
                     {
                         _drawGrids(worldBounds);
@@ -368,9 +473,11 @@ namespace Robust.Client.Graphics.Clyde
                     // We will also render worldspace overlays here so we can do them under / above entities as necessary
                     using (DebugGroup("Entities"))
                     {
-                        DrawEntitiesAndWorldOverlay(viewport, worldBounds);
+                        DrawEntities(viewport, worldBounds);
                     }
 
+                    RenderOverlays(viewport, OverlaySpace.WorldSpaceBelowFOV, worldBounds);
+
                     if (_lightManager.Enabled && _lightManager.DrawHardFov && eye.DrawFov)
                     {
                         ApplyFovToBuffer(viewport, eye);
@@ -389,7 +496,7 @@ 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);
                 }
 
@@ -399,16 +506,25 @@ 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));
                 }
-            }
 
-            PopRenderStateFull(state);
-            _updateUniformConstants(oldVp?.Size ?? _framebufferSize);
+                RenderOverlays(viewport, OverlaySpace.WorldSpace, worldBounds);
+                FlushRenderQueue();
 
-            SetScissorFull(oldScissor);
-            _currentMatrixModel = oldTransform;
-            _currentViewport = oldVp;
+                _currentViewport = oldVp;
+            });
+        }
+
+        private static Box2 CalcWorldBounds(Viewport viewport)
+        {
+            var eye = viewport.Eye;
+            if (eye == null)
+                return default;
+
+            // 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

@@ -5,6 +5,7 @@ using OpenToolkit.Graphics.OpenGL4;
 using Robust.Shared.Log;
 using Robust.Shared.Maths;
 using Robust.Shared.Utility;
+using SixLabors.ImageSharp.PixelFormats;
 using ES20 = OpenToolkit.Graphics.ES20;
 
 namespace Robust.Client.Graphics.Clyde
@@ -31,6 +32,27 @@ namespace Robust.Client.Graphics.Clyde
             CheckGlError();
             GL.BindTexture(TextureTarget.Texture2D, glHandle.Handle);
             CheckGlError();
+            GL.ActiveTexture(TextureUnit.Texture0);
+        }
+
+        private void CopyRenderTextureToTexture(RenderTexture source, ClydeTexture target) {
+            LoadedRenderTarget sourceLoaded = RtToLoaded(source);
+            bool pause = sourceLoaded != _currentBoundRenderTarget;
+            FullStoredRendererState? store = null;
+            if (pause) {
+                store = PushRenderStateFull();
+                BindRenderTargetFull(source);
+                CheckGlError();
+            }
+
+            GL.BindTexture(TextureTarget.Texture2D, _loadedTextures[target.TextureId].OpenGLObject.Handle);
+            CheckGlError();
+            GL.CopyTexSubImage2D(TextureTarget.Texture2D, 0, 0, 0, 0, 0, source.Size.X, source.Size.Y);
+            CheckGlError();
+
+            if (pause && store != null) {
+                PopRenderStateFull((FullStoredRendererState)store);
+            }
         }
 
         private static long EstPixelSize(PixelInternalFormat format)
@@ -138,12 +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}");
             }
         }
 
@@ -254,7 +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
 {
@@ -148,16 +149,16 @@ namespace Robust.Client.Graphics.Clyde
             // FOV FBO.
             _fovRenderTarget = CreateRenderTarget((FovMapSize, 2),
                 new RenderTargetFormatParameters(_hasGLFloatFramebuffers ? RenderTargetColorFormat.RG32F : RenderTargetColorFormat.Rgba8, true),
-                new TextureSampleParameters {WrapMode = TextureWrapMode.Repeat},
+                new TextureSampleParameters { WrapMode = TextureWrapMode.Repeat },
                 nameof(_fovRenderTarget));
 
             if (_hasGLSamplerObjects)
             {
                 _fovFilterSampler = new GLHandle(GL.GenSampler());
-                GL.SamplerParameter(_fovFilterSampler.Handle, SamplerParameterName.TextureMagFilter, (int) All.Linear);
-                GL.SamplerParameter(_fovFilterSampler.Handle, SamplerParameterName.TextureMinFilter, (int) All.Linear);
-                GL.SamplerParameter(_fovFilterSampler.Handle, SamplerParameterName.TextureWrapS, (int) All.Repeat);
-                GL.SamplerParameter(_fovFilterSampler.Handle, SamplerParameterName.TextureWrapT, (int) All.Repeat);
+                GL.SamplerParameter(_fovFilterSampler.Handle, SamplerParameterName.TextureMagFilter, (int)All.Linear);
+                GL.SamplerParameter(_fovFilterSampler.Handle, SamplerParameterName.TextureMinFilter, (int)All.Linear);
+                GL.SamplerParameter(_fovFilterSampler.Handle, SamplerParameterName.TextureWrapS, (int)All.Repeat);
+                GL.SamplerParameter(_fovFilterSampler.Handle, SamplerParameterName.TextureWrapT, (int)All.Repeat);
                 CheckGlError();
             }
 
@@ -179,22 +180,18 @@ namespace Robust.Client.Graphics.Clyde
             _fovCalculationProgram = _compileProgram(depthVert, depthFrag, attribLocations, "Shadow Depth Program");
 
             var debugShader = _resourceCache.GetResource<ShaderSourceResource>("/Shaders/Internal/depth-debug.swsl");
-            _fovDebugShaderInstance = (ClydeShaderInstance) InstanceShader(debugShader.ClydeHandle);
+            _fovDebugShaderInstance = (ClydeShaderInstance)InstanceShader(debugShader.ClydeHandle);
 
             ClydeHandle LoadShaderHandle(string path)
             {
-                try
+                if (_resourceCache.TryGetResource(path, out ShaderSourceResource? resource))
                 {
-                    var shaderSource = _resourceCache.GetResource<ShaderSourceResource>(path);
-                    return shaderSource.ClydeHandle;
+                    return resource.ClydeHandle;
                 }
-                catch (Exception ex)
-                {
-                    Logger.Warning($"Can't load shader {path}\n{ex.GetType().Name}: {ex.Message}");
-                    return default;
-                }
-            }
 
+                Logger.Warning($"Can't load shader {path}\n");
+                return default;
+            }
 
             _lightSoftShaderHandle = LoadShaderHandle("/Shaders/Internal/light-soft.swsl");
             _lightHardShaderHandle = LoadShaderHandle("/Shaders/Internal/light-hard.swsl");
@@ -214,7 +211,7 @@ namespace Robust.Client.Graphics.Clyde
             {
                 // Calculate maximum distance for the projection based on screen size.
                 var screenSizeCut = viewport.Size / EyeManager.PixelsPerMeter;
-                var maxDist = (float) Math.Max(screenSizeCut.X, screenSizeCut.Y);
+                var maxDist = (float)Math.Max(screenSizeCut.X, screenSizeCut.Y);
 
                 // FOV is rendered twice.
                 // Once with back face culling like regular lighting.
@@ -361,16 +358,23 @@ 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 +386,11 @@ 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 +472,11 @@ namespace Robust.Client.Graphics.Clyde
             }
 
             ResetBlendFunc();
+            GL.Disable(EnableCap.StencilTest);
+            _isStencilling = false;
 
             CheckGlError();
 
-            ApplyLightingFovToBuffer(viewport, eye);
-
             BlurOntoWalls(viewport, eye);
 
             MergeWallLayer(viewport);
@@ -485,40 +494,41 @@ namespace Robust.Client.Graphics.Clyde
             GetLightsToRender(MapId map, in Box2 worldBounds)
         {
             var renderingTreeSystem = _entitySystemManager.GetEntitySystem<RenderingTreeSystem>();
-            var lightTree = renderingTreeSystem.GetLightTreeForMap(map);
+            var enlargedBounds = worldBounds.Enlarged(renderingTreeSystem.MaxLightRadius);
 
+            // Use worldbounds for this one as we only care if the light intersects our actual bounds
             var state = (this, worldBounds, count: 0);
 
-            lightTree.QueryAabb(ref state, (ref (Clyde clyde, Box2 worldBounds, int count) state, in PointLightComponent light) =>
+            foreach (var comp in renderingTreeSystem.GetRenderTrees(map, enlargedBounds))
             {
-                var transform = light.Owner.Transform;
+                var bounds = worldBounds.Translated(-comp.Owner.Transform.WorldPosition);
 
-                if (state.count >= LightsToRenderListSize)
+                comp.LightTree.QueryAabb(ref state, (ref (Clyde clyde, Box2 worldBounds, int count) state, in PointLightComponent light) =>
                 {
-                    // There are too many lights to fit in the static memory.
-                    return false;
-                }
+                    var transform = light.Owner.Transform;
+
+                    if (state.count >= LightsToRenderListSize)
+                    {
+                        // There are too many lights to fit in the static memory.
+                        return false;
+                    }
+
+                    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);
 
-                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;
-            }, worldBounds);
+                }, bounds);
+            }
 
             if (state.count > _maxLightsPerScene)
             {
@@ -563,7 +573,7 @@ namespace Robust.Client.Graphics.Clyde
 
             SetupGlobalUniformsImmediate(shader, viewport.LightRenderTarget.Texture);
 
-            shader.SetUniformMaybe("size", (Vector2) viewport.WallBleedIntermediateRenderTarget1.Size);
+            shader.SetUniformMaybe("size", (Vector2)viewport.WallBleedIntermediateRenderTarget1.Size);
             shader.SetUniformTextureMaybe(UniIMainTexture, TextureUnit.Texture0);
 
             var size = viewport.WallBleedIntermediateRenderTarget1.Size;
@@ -577,7 +587,7 @@ 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 +655,12 @@ 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 +674,10 @@ 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 +710,13 @@ 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)
@@ -765,7 +792,7 @@ namespace Robust.Client.Graphics.Clyde
 
                     occluderTree.QueryAabb((in OccluderComponent sOccluder) =>
                     {
-                        var occluder = (ClientOccluderComponent) sOccluder;
+                        var occluder = (ClientOccluderComponent)sOccluder;
                         var transform = occluder.Owner.Transform;
                         if (!occluder.Enabled)
                         {
@@ -849,11 +876,11 @@ namespace Robust.Client.Graphics.Clyde
                                 // DddD
                                 // HHhh
                                 // deflection
-                                arrayVIBuffer[avi++] = (byte) ((((vi + 1) & 2) != 0) ? 0 : 255);
+                                arrayVIBuffer[avi++] = (byte)((((vi + 1) & 2) != 0) ? 0 : 255);
                                 // height
-                                arrayVIBuffer[avi++] = (byte) (((vi & 2) != 0) ? 0 : 255);
+                                arrayVIBuffer[avi++] = (byte)(((vi & 2) != 0) ? 0 : 255);
                             }
-                            QuadBatchIndexWrite(indexBuffer, ref ii, (ushort) aiBase);
+                            QuadBatchIndexWrite(indexBuffer, ref ii, (ushort)aiBase);
                         }
 
                         // North face (TL/TR)
@@ -887,7 +914,7 @@ namespace Robust.Client.Graphics.Clyde
                         arrayMaskBuffer[ami + 3] = new Vector2(blX, blY);
 
                         // Generate mask indices.
-                        QuadBatchIndexWrite(indexMaskBuffer, ref imi, (ushort) ami);
+                        QuadBatchIndexWrite(indexMaskBuffer, ref imi, (ushort)ami);
 
                         ami += 4;
 
@@ -929,7 +956,7 @@ namespace Robust.Client.Graphics.Clyde
             var lightMapSize = GetLightMapSize(viewport.Size);
             var lightMapSizeQuart = GetLightMapSize(viewport.Size, true);
             var lightMapColorFormat = _hasGLFloatFramebuffers ? RenderTargetColorFormat.R11FG11FB10F : RenderTargetColorFormat.Rgba8;
-            var lightMapSampleParameters = new TextureSampleParameters {Filter = true};
+            var lightMapSampleParameters = new TextureSampleParameters { Filter = true };
 
             viewport.LightRenderTarget?.Dispose();
             viewport.WallMaskRenderTarget?.Dispose();
@@ -939,7 +966,8 @@ 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)}");
 
@@ -965,25 +993,25 @@ namespace Robust.Client.Graphics.Clyde
 
         private Vector2i GetLightMapSize(Vector2i screenSize, bool furtherDivide = false)
         {
-            var divider = (float) _lightmapDivider;
+            var divider = (float)_lightmapDivider;
             if (furtherDivide)
             {
                 divider *= 2;
             }
 
-            var w = (int) Math.Ceiling(screenSize.X / divider);
-            var h = (int) Math.Ceiling(screenSize.Y / divider);
+            var w = (int)Math.Ceiling(screenSize.X / divider);
+            var h = (int)Math.Ceiling(screenSize.Y / divider);
 
             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;
 
@@ -998,11 +1026,11 @@ namespace Robust.Client.Graphics.Clyde
             // Shadow FBO.
             _shadowRenderTarget = CreateRenderTarget((ShadowMapSize, _maxLightsPerScene),
                 new RenderTargetFormatParameters(_hasGLFloatFramebuffers ? RenderTargetColorFormat.RG32F : RenderTargetColorFormat.Rgba8, true),
-                new TextureSampleParameters {WrapMode = TextureWrapMode.Repeat, Filter = true},
+                new TextureSampleParameters { WrapMode = TextureWrapMode.Repeat, Filter = true },
                 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

@@ -1,4 +1,4 @@
-using System;
+using System;
 using System.Collections.Concurrent;
 using System.Collections.Generic;
 using System.Runtime.CompilerServices;
@@ -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;
@@ -280,9 +285,19 @@ namespace Robust.Client.Graphics.Clyde
         }
 
         /// <summary>
-        ///     Flush the render handle, processing and re-pooling all the command lists.
+        ///     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)
@@ -371,6 +381,7 @@ namespace Robust.Client.Graphics.Clyde
 
             program.Use();
 
+            int textureUnitVal = 0;
             // Assign shader parameters to uniform since they may be dirty.
             foreach (var (name, value) in instance.Parameters)
             {
@@ -413,6 +424,15 @@ namespace Robust.Client.Graphics.Clyde
                     case Matrix4 matrix4:
                         program.SetUniform(name, matrix4);
                         break;
+                    case ClydeTexture clydeTexture:
+                        //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);
+                        program.SetUniformTexture(name, cTarget);
+                        textureUnitVal++;
+                        break;
                     default:
                         throw new InvalidOperationException($"Unable to handle shader parameter {name}: {value}");
                 }
@@ -490,6 +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);
@@ -515,6 +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).
@@ -556,6 +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);
@@ -591,6 +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);
@@ -605,6 +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();
@@ -763,116 +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);
@@ -903,7 +827,7 @@ namespace Robust.Client.Graphics.Clyde
             _lightingReady = false;
             _currentMatrixModel = Matrix3.Identity;
             SetScissorFull(null);
-            BindRenderTargetFull(_mainWindowRenderTarget);
+            BindRenderTargetFull(_mainMainWindowRenderMainTarget);
             _batchMetaData = null;
             _queuedShader = _defaultShader.Handle;
         }
@@ -917,6 +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
         {