Fix anchoring crashes

Co-authored-by: Pieter-Jan Briers <pieterjan.briers+git@gmail.com>

.gitmodules

@@ -16,3 +16,6 @@
 [submodule "Linguini"]
 	path = Linguini
 	url = https://github.com/space-wizards/Linguini
+[submodule "cefglue"]
+	path = cefglue
+	url = https://gitlab.com/xiliumhq/chromiumembedded/cefglue/

OpenToolkit.GraphicsLibraryFramework/Enums/WindowHintBool.cs

@@ -129,5 +129,7 @@ namespace OpenToolkit.GraphicsLibraryFramework
         /// for controlling sRGB rendering and a created OpenGL ES context will always have sRGB rendering enabled.
         /// </summary>
         SrgbCapable = 0x0002100E,
+
+        ScaleToMonitor = 0x0002200C,
     }
 }

OpenToolkit.GraphicsLibraryFramework/GLFW.cs

@@ -5551,5 +5551,15 @@ namespace OpenToolkit.GraphicsLibraryFramework
         {
             return glfwGetX11Window(window);
         }
+
+        public static unsafe IntPtr GetX11Display(Window* window)
+        {
+            return glfwGetX11Display(window);
+        }
+
+        public static unsafe IntPtr GetWin32Window(Window* window)
+        {
+            return glfwGetWin32Window(window);
+        }
     }
 }

OpenToolkit.GraphicsLibraryFramework/GLFWNative.cs

@@ -406,5 +406,11 @@ namespace OpenToolkit.GraphicsLibraryFramework
 
         [DllImport(LibraryName)]
         public static extern uint glfwGetX11Window(Window* window);
+
+        [DllImport(LibraryName)]
+        public static extern IntPtr glfwGetX11Display(Window* window);
+
+        [DllImport(LibraryName)]
+        public static extern IntPtr glfwGetWin32Window(Window* window);
     }
 }

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

@@ -4,4 +4,8 @@ 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
+entity-spawn-window-override-menu-tooltip = Override placement
+
+## Console
+
+console-line-edit-placeholder = Command Here

Robust.Analyzers/FriendAnalyzer.cs

@@ -0,0 +1,107 @@
+using System.Collections.Immutable;
+using System.Diagnostics.CodeAnalysis;
+using System.Linq;
+using Microsoft.CodeAnalysis;
+using Microsoft.CodeAnalysis.CSharp;
+using Microsoft.CodeAnalysis.CSharp.Syntax;
+using Microsoft.CodeAnalysis.Diagnostics;
+
+namespace Robust.Analyzers
+{
+    [DiagnosticAnalyzer(LanguageNames.CSharp)]
+    public class FriendAnalyzer : DiagnosticAnalyzer
+    {
+        const string FriendAttribute = "Robust.Shared.Analyzers.FriendAttribute";
+
+        public const string DiagnosticId = "RA0002";
+
+        private const string Title = "Tried to access friend-only member";
+        private const string MessageFormat = "Tried to access member \"{0}\" in class \"{1}\" which can only be accessed by friend classes";
+        private const string Description = "Make sure to specify the accessing class in the friends attribute.";
+        private const string Category = "Usage";
+
+        [SuppressMessage("ReSharper", "RS2008")]
+        private static readonly DiagnosticDescriptor Rule = new (DiagnosticId, Title, MessageFormat, Category, DiagnosticSeverity.Error, true, Description);
+
+        public override ImmutableArray<DiagnosticDescriptor> SupportedDiagnostics => ImmutableArray.Create(Rule);
+
+        public override void Initialize(AnalysisContext context)
+        {
+            context.ConfigureGeneratedCodeAnalysis(GeneratedCodeAnalysisFlags.Analyze | GeneratedCodeAnalysisFlags.ReportDiagnostics);
+            context.EnableConcurrentExecution();
+            context.RegisterSyntaxNodeAction(CheckFriendship, SyntaxKind.SimpleMemberAccessExpression);
+        }
+
+        private void CheckFriendship(SyntaxNodeAnalysisContext context)
+        {
+            if (context.Node is not MemberAccessExpressionSyntax memberAccess)
+                return;
+
+            // We only do something if our parent is one of a few types.
+            switch (context.Node.Parent)
+            {
+                // If we're being assigned...
+                case AssignmentExpressionSyntax assignParent:
+                {
+                    if (assignParent.Left != memberAccess)
+                        return;
+                    break;
+                }
+
+                // If we're being invoked...
+                case InvocationExpressionSyntax:
+                    break;
+
+                // Otherwise, do nothing.
+                default:
+                    return;
+            }
+
+            // Get the friend attribute
+            var friendAttr = context.Compilation.GetTypeByMetadataName(FriendAttribute);
+
+            // Get the type that is containing this expression, or, the class where this is happening.
+            if (context.ContainingSymbol?.ContainingType is not { } containingType)
+                return;
+
+            // We check all of our children and get only the identifiers.
+            foreach (var identifier in memberAccess.ChildNodes().Select(node => node as IdentifierNameSyntax))
+            {
+                if (identifier == null) continue;
+
+                // Get the type info of the identifier, so we can check the attributes...
+                if (context.SemanticModel.GetTypeInfo(identifier).ConvertedType is not { } type)
+                    continue;
+
+                // Same-type access is always fine.
+                if (SymbolEqualityComparer.Default.Equals(type, containingType))
+                    continue;
+
+                // Finally, get all attributes of the type, to check if we have any friend classes.
+                foreach (var attribute in type.GetAttributes())
+                {
+                    // If the attribute isn't the friend attribute, continue.
+                    if (!SymbolEqualityComparer.Default.Equals(attribute.AttributeClass, friendAttr))
+                        continue;
+
+                    // Check all types allowed in the friend attribute. (We assume there's only one constructor arg.)
+                    foreach (var constant in attribute.ConstructorArguments[0].Values)
+                    {
+                        // Check if the value is a type...
+                        if (constant.Value is not INamedTypeSymbol t)
+                            continue;
+
+                        // If we find that the containing class is specified in the attribute, return! All is good.
+                        if (SymbolEqualityComparer.Default.Equals(containingType, t))
+                            return;
+                    }
+
+                    // Not in a friend class! Report an error.
+                    context.ReportDiagnostic(
+                        Diagnostic.Create(Rule, context.Node.GetLocation(),
+                            $"{context.Node.ToString().Split('.').LastOrDefault()}", $"{type.Name}"));
+                }
+            }
+        }
+    }
+}

Robust.Analyzers/Robust.Analyzers.csproj

@@ -2,6 +2,7 @@
 
   <PropertyGroup>
     <TargetFramework>netstandard2.0</TargetFramework>
+    <LangVersion>9</LangVersion>
   </PropertyGroup>
 
   <ItemGroup>

Robust.Benchmarks/NumericsHelpers/AddBenchmark.cs

@@ -0,0 +1,28 @@
+using BenchmarkDotNet.Attributes;
+
+namespace Robust.Benchmarks.NumericsHelpers
+{
+    public class AddBenchmark
+    {
+        [Params(32, 128)]
+        public int N { get; set; }
+
+        private float[] _inputA = default!;
+        private float[] _inputB = default!;
+        private float[] _output = default!;
+
+        [GlobalSetup]
+        public void Setup()
+        {
+            _inputA = new float[N];
+            _inputB = new float[N];
+            _output = new float[N];
+        }
+
+        [Benchmark]
+        public void Bench()
+        {
+            Shared.Maths.NumericsHelpers.Add(_inputA, _inputB, _output);
+        }
+    }
+}

Robust.Benchmarks/Program.cs

@@ -4,9 +4,11 @@ namespace Robust.Benchmarks
 {
     internal class Program
     {
+        // --allCategories=ctg1,ctg2
+        // --anyCategories=ctg1,ctg2
         public static void Main(string[] args)
         {
-            BenchmarkSwitcher.FromAssembly(typeof(Program).Assembly).Run();
+            BenchmarkSwitcher.FromAssembly(typeof(Program).Assembly).Run(args);
         }
     }
 }

Robust.Benchmarks/Serialization/BenchmarkIntSerializer.cs

@@ -0,0 +1,40 @@
+using System.Globalization;
+using Robust.Shared.IoC;
+using Robust.Shared.Serialization.Manager;
+using Robust.Shared.Serialization.Manager.Result;
+using Robust.Shared.Serialization.Markdown;
+using Robust.Shared.Serialization.Markdown.Validation;
+using Robust.Shared.Serialization.Markdown.Value;
+using Robust.Shared.Serialization.TypeSerializers.Interfaces;
+
+namespace Robust.Benchmarks.Serialization
+{
+    public class BenchmarkIntSerializer : ITypeSerializer<int, ValueDataNode>
+    {
+        public ValidationNode Validate(ISerializationManager serializationManager, ValueDataNode node,
+            IDependencyCollection dependencies, ISerializationContext? context = null)
+        {
+            return int.TryParse(node.Value, out _)
+                ? new ValidatedValueNode(node)
+                : new ErrorNode(node, $"Failed parsing int value: {node.Value}");
+        }
+
+        public DeserializationResult Read(ISerializationManager serializationManager, ValueDataNode node,
+            IDependencyCollection dependencies, bool skipHook, ISerializationContext? context = null)
+        {
+            return new DeserializedValue<int>(int.Parse(node.Value, CultureInfo.InvariantCulture));
+        }
+
+        public DataNode Write(ISerializationManager serializationManager, int value, bool alwaysWrite = false,
+            ISerializationContext? context = null)
+        {
+            return new ValueDataNode(value.ToString(CultureInfo.InvariantCulture));
+        }
+
+        public int Copy(ISerializationManager serializationManager, int source, int target, bool skipHook,
+            ISerializationContext? context = null)
+        {
+            return source;
+        }
+    }
+}

Robust.Benchmarks/Serialization/Copy/SerializationCopyBenchmark.cs

@@ -6,11 +6,13 @@ 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.TypeSerializers.Implementations.Custom;
 using Robust.Shared.Utility;
 using YamlDotNet.RepresentationModel;
 
 namespace Robust.Benchmarks.Serialization.Copy
 {
+    [MemoryDiagnoser]
     public class SerializationCopyBenchmark : SerializationBenchmark
     {
         public SerializationCopyBenchmark()
@@ -35,6 +37,10 @@ namespace Robust.Benchmarks.Serialization.Copy
 
         private SeedDataDefinition Seed { get; }
 
+        private BenchmarkFlagsEnum FlagZero = BenchmarkFlagsEnum.Zero;
+
+        private BenchmarkFlagsEnum FlagThirtyOne = BenchmarkFlagsEnum.ThirtyOne;
+
         [Benchmark]
         public string? CreateCopyString()
         {
@@ -111,5 +117,35 @@ namespace Robust.Benchmarks.Serialization.Copy
 
             return copy;
         }
+
+        [Benchmark]
+        [BenchmarkCategory("flag")]
+        public object? CopyFlagZero()
+        {
+            return SerializationManager.CopyWithTypeSerializer(
+                typeof(FlagSerializer<BenchmarkFlags>),
+                (int) FlagZero,
+                (int) FlagZero);
+        }
+
+        [Benchmark]
+        [BenchmarkCategory("flag")]
+        public object? CopyFlagThirtyOne()
+        {
+            return SerializationManager.CopyWithTypeSerializer(
+                typeof(FlagSerializer<BenchmarkFlags>),
+                (int) FlagThirtyOne,
+                (int) FlagThirtyOne);
+        }
+
+        [Benchmark]
+        [BenchmarkCategory("customTypeSerializer")]
+        public object? CopyIntegerCustomSerializer()
+        {
+            return SerializationManager.CopyWithTypeSerializer(
+                typeof(BenchmarkIntSerializer),
+                Integer,
+                Integer);
+        }
     }
 }

Robust.Benchmarks/Serialization/Definitions/BenchmarkFlags.cs

@@ -0,0 +1,19 @@
+using System;
+using Robust.Shared.Serialization;
+
+namespace Robust.Benchmarks.Serialization.Definitions
+{
+    public class BenchmarkFlags
+    {
+        public const int Zero = 1 << 0;
+        public const int ThirtyOne = 1 << 31;
+    }
+
+    [Flags]
+    [FlagsFor(typeof(BenchmarkFlags))]
+    public enum BenchmarkFlagsEnum
+    {
+        Zero = BenchmarkFlags.Zero,
+        ThirtyOne = BenchmarkFlags.ThirtyOne
+    }
+}

Robust.Benchmarks/Serialization/Definitions/DataDefinitionWithString.cs

@@ -5,7 +5,7 @@ namespace Robust.Benchmarks.Serialization.Definitions
     [DataDefinition]
     public class DataDefinitionWithString
     {
-        [field: DataField("string")]
+        [DataField("string")]
         public string StringField { get; init; } = default!;
     }
 }

Robust.Benchmarks/Serialization/Initialize/SerializationInitializeBenchmark.cs

@@ -3,6 +3,7 @@ using Robust.Shared.Serialization.Manager;
 
 namespace Robust.Benchmarks.Serialization.Initialize
 {
+    [MemoryDiagnoser]
     public class SerializationInitializeBenchmark : SerializationBenchmark
     {
         [IterationCleanup]

Robust.Benchmarks/Serialization/Read/SerializationReadBenchmark.cs

@@ -1,14 +1,17 @@
 using System.IO;
 using BenchmarkDotNet.Attributes;
 using Robust.Benchmarks.Serialization.Definitions;
+using Robust.Shared.Serialization.Manager.Result;
 using Robust.Shared.Serialization.Markdown;
 using Robust.Shared.Serialization.Markdown.Mapping;
 using Robust.Shared.Serialization.Markdown.Sequence;
 using Robust.Shared.Serialization.Markdown.Value;
+using Robust.Shared.Serialization.TypeSerializers.Implementations.Custom;
 using YamlDotNet.RepresentationModel;
 
 namespace Robust.Benchmarks.Serialization.Read
 {
+    [MemoryDiagnoser]
     public class SerializationReadBenchmark : SerializationBenchmark
     {
         public SerializationReadBenchmark()
@@ -32,6 +35,10 @@ namespace Robust.Benchmarks.Serialization.Read
 
         private MappingDataNode SeedNode { get; }
 
+        private ValueDataNode FlagZero { get; } = new("Zero");
+
+        private ValueDataNode FlagThirtyOne { get; } = new("ThirtyOne");
+
         [Benchmark]
         public string? ReadString()
         {
@@ -55,5 +62,35 @@ namespace Robust.Benchmarks.Serialization.Read
         {
             return SerializationManager.ReadValue<SeedDataDefinition>(SeedNode);
         }
+
+        [Benchmark]
+        [BenchmarkCategory("flag")]
+        public DeserializationResult ReadFlagZero()
+        {
+            return SerializationManager.ReadWithTypeSerializer(
+                typeof(int),
+                typeof(FlagSerializer<BenchmarkFlags>),
+                FlagZero);
+        }
+
+        [Benchmark]
+        [BenchmarkCategory("flag")]
+        public DeserializationResult ReadThirtyOne()
+        {
+            return SerializationManager.ReadWithTypeSerializer(
+                typeof(int),
+                typeof(FlagSerializer<BenchmarkFlags>),
+                FlagThirtyOne);
+        }
+
+        [Benchmark]
+        [BenchmarkCategory("customTypeSerializer")]
+        public DeserializationResult ReadIntegerCustomSerializer()
+        {
+            return SerializationManager.ReadWithTypeSerializer(
+                typeof(int),
+                typeof(BenchmarkIntSerializer),
+                IntNode);
+        }
     }
 }

Robust.Benchmarks/Serialization/Write/SerializationWriteBenchmark.cs

@@ -7,10 +7,12 @@ using Robust.Shared.Serialization.Markdown;
 using Robust.Shared.Serialization.Markdown.Mapping;
 using Robust.Shared.Serialization.Markdown.Sequence;
 using Robust.Shared.Serialization.Markdown.Value;
+using Robust.Shared.Serialization.TypeSerializers.Implementations.Custom;
 using YamlDotNet.RepresentationModel;
 
 namespace Robust.Benchmarks.Serialization.Write
 {
+    [MemoryDiagnoser]
     public class SerializationWriteBenchmark : SerializationBenchmark
     {
         public SerializationWriteBenchmark()
@@ -35,6 +37,10 @@ namespace Robust.Benchmarks.Serialization.Write
 
         private SeedDataDefinition Seed { get; }
 
+        private BenchmarkFlagsEnum FlagZero = BenchmarkFlagsEnum.Zero;
+
+        private BenchmarkFlagsEnum FlagThirtyOne = BenchmarkFlagsEnum.ThirtyOne;
+
         [Benchmark]
         public DataNode WriteString()
         {
@@ -94,5 +100,35 @@ namespace Robust.Benchmarks.Serialization.Write
 
             return mapping;
         }
+
+        [Benchmark]
+        [BenchmarkCategory("flag")]
+        public DataNode WriteFlagZero()
+        {
+            return SerializationManager.WriteWithTypeSerializer(
+                typeof(int),
+                typeof(FlagSerializer<BenchmarkFlags>),
+                FlagZero);
+        }
+
+        [Benchmark]
+        [BenchmarkCategory("flag")]
+        public DataNode WriteThirtyOne()
+        {
+            return SerializationManager.WriteWithTypeSerializer(
+                typeof(int),
+                typeof(FlagSerializer<BenchmarkFlags>),
+                FlagThirtyOne);
+        }
+
+        [Benchmark]
+        [BenchmarkCategory("customTypeSerializer")]
+        public DataNode WriteIntegerCustomSerializer()
+        {
+            return SerializationManager.WriteWithTypeSerializer(
+                typeof(int),
+                typeof(BenchmarkIntSerializer),
+                Integer);
+        }
     }
 }

Robust.Client.CEF/BeforeBrowseContext.cs

@@ -0,0 +1,32 @@
+using Xilium.CefGlue;
+
+namespace Robust.Client.CEF
+{
+    public sealed class BeforeBrowseContext
+    {
+        internal readonly CefRequest CefRequest;
+
+        public string Url => CefRequest.Url;
+        public string Method => CefRequest.Method;
+
+        public bool IsRedirect { get; }
+        public bool UserGesture { get; }
+
+        public bool IsCancelled { get; private set; }
+
+        internal BeforeBrowseContext(
+            bool isRedirect,
+            bool userGesture,
+            CefRequest cefRequest)
+        {
+            CefRequest = cefRequest;
+            IsRedirect = isRedirect;
+            UserGesture = userGesture;
+        }
+
+        public void DoCancel()
+        {
+            IsCancelled = true;
+        }
+    }
+}

Robust.Client.CEF/BrowserControl.cs

@@ -0,0 +1,593 @@
+using System;
+using System.Collections.Generic;
+using Robust.Client.Graphics;
+using Robust.Client.Input;
+using Robust.Client.UserInterface;
+using Robust.Shared.IoC;
+using Robust.Shared.Log;
+using Robust.Shared.Maths;
+using Robust.Shared.Utility;
+using Robust.Shared.ViewVariables;
+using SixLabors.ImageSharp.PixelFormats;
+using Xilium.CefGlue;
+using static Robust.Client.CEF.CefKeyCodes;
+using static Robust.Client.CEF.CefKeyCodes.ChromiumKeyboardCode;
+using static Robust.Client.Input.Keyboard;
+
+namespace Robust.Client.CEF
+{
+    // Funny browser control to integrate in UI.
+    public class BrowserControl : Control, IBrowserControl, IRawInputControl
+    {
+        private const int ScrollSpeed = 50;
+
+        [Dependency] private readonly IClyde _clyde = default!;
+        [Dependency] private readonly IInputManager _inputMgr = default!;
+        [Dependency] private readonly CefManager _cef = default!;
+
+        private RobustRequestHandler _requestHandler = new RobustRequestHandler(Logger.GetSawmill("root"));
+        private LiveData? _data;
+        private string _startUrl = "about:blank";
+
+        [ViewVariables(VVAccess.ReadWrite)]
+        public string Url
+        {
+            get => _data == null ? _startUrl : _data.Browser.GetMainFrame().Url;
+            set
+            {
+                if (_data == null)
+                    _startUrl = value;
+                else
+                    _data.Browser.GetMainFrame().LoadUrl(value);
+            }
+        }
+
+        [ViewVariables] public bool IsLoading => _data?.Browser.IsLoading ?? false;
+
+        private readonly Dictionary<Key, ChromiumKeyboardCode> _keyMap = new()
+        {
+            [Key.A] = VKEY_A,
+            [Key.B] = VKEY_B,
+            [Key.C] = VKEY_C,
+            [Key.D] = VKEY_D,
+            [Key.E] = VKEY_E,
+            [Key.F] = VKEY_F,
+            [Key.G] = VKEY_G,
+            [Key.H] = VKEY_H,
+            [Key.I] = VKEY_I,
+            [Key.J] = VKEY_J,
+            [Key.K] = VKEY_K,
+            [Key.L] = VKEY_L,
+            [Key.M] = VKEY_M,
+            [Key.N] = VKEY_N,
+            [Key.O] = VKEY_O,
+            [Key.P] = VKEY_P,
+            [Key.Q] = VKEY_Q,
+            [Key.R] = VKEY_R,
+            [Key.S] = VKEY_S,
+            [Key.T] = VKEY_T,
+            [Key.U] = VKEY_U,
+            [Key.V] = VKEY_V,
+            [Key.W] = VKEY_W,
+            [Key.X] = VKEY_X,
+            [Key.Y] = VKEY_Y,
+            [Key.Z] = VKEY_Z,
+            [Key.Num0] = VKEY_0,
+            [Key.Num1] = VKEY_1,
+            [Key.Num2] = VKEY_2,
+            [Key.Num3] = VKEY_3,
+            [Key.Num4] = VKEY_4,
+            [Key.Num5] = VKEY_5,
+            [Key.Num6] = VKEY_6,
+            [Key.Num7] = VKEY_7,
+            [Key.Num8] = VKEY_8,
+            [Key.Num9] = VKEY_9,
+            [Key.NumpadNum0] = VKEY_NUMPAD0,
+            [Key.NumpadNum1] = VKEY_NUMPAD1,
+            [Key.NumpadNum2] = VKEY_NUMPAD2,
+            [Key.NumpadNum3] = VKEY_NUMPAD3,
+            [Key.NumpadNum4] = VKEY_NUMPAD4,
+            [Key.NumpadNum5] = VKEY_NUMPAD5,
+            [Key.NumpadNum6] = VKEY_NUMPAD6,
+            [Key.NumpadNum7] = VKEY_NUMPAD7,
+            [Key.NumpadNum8] = VKEY_NUMPAD8,
+            [Key.NumpadNum9] = VKEY_NUMPAD9,
+            [Key.Escape] = VKEY_ESCAPE,
+            [Key.Control] = VKEY_CONTROL,
+            [Key.Shift] = VKEY_SHIFT,
+            [Key.Alt] = VKEY_MENU,
+            [Key.LSystem] = VKEY_LWIN,
+            [Key.RSystem] = VKEY_RWIN,
+            [Key.LBracket] = VKEY_OEM_4,
+            [Key.RBracket] = VKEY_OEM_6,
+            [Key.SemiColon] = VKEY_OEM_1,
+            [Key.Comma] = VKEY_OEM_COMMA,
+            [Key.Period] = VKEY_OEM_PERIOD,
+            [Key.Apostrophe] = VKEY_OEM_7,
+            [Key.Slash] = VKEY_OEM_2,
+            [Key.BackSlash] = VKEY_OEM_5,
+            [Key.Tilde] = VKEY_OEM_3,
+            [Key.Equal] = VKEY_OEM_PLUS,
+            [Key.Space] = VKEY_SPACE,
+            [Key.Return] = VKEY_RETURN,
+            [Key.BackSpace] = VKEY_BACK,
+            [Key.Tab] = VKEY_TAB,
+            [Key.PageUp] = VKEY_PRIOR,
+            [Key.PageDown] = VKEY_NEXT,
+            [Key.End] = VKEY_END,
+            [Key.Home] = VKEY_HOME,
+            [Key.Insert] = VKEY_INSERT,
+            [Key.Delete] = VKEY_DELETE,
+            [Key.Minus] = VKEY_OEM_MINUS,
+            [Key.NumpadAdd] = VKEY_ADD,
+            [Key.NumpadSubtract] = VKEY_SUBTRACT,
+            [Key.NumpadDivide] = VKEY_DIVIDE,
+            [Key.NumpadMultiply] = VKEY_MULTIPLY,
+            [Key.NumpadDecimal] = VKEY_DECIMAL,
+            [Key.Left] = VKEY_LEFT,
+            [Key.Right] = VKEY_RIGHT,
+            [Key.Up] = VKEY_UP,
+            [Key.Down] = VKEY_DOWN,
+            [Key.F1] = VKEY_F1,
+            [Key.F2] = VKEY_F2,
+            [Key.F3] = VKEY_F3,
+            [Key.F4] = VKEY_F4,
+            [Key.F5] = VKEY_F5,
+            [Key.F6] = VKEY_F6,
+            [Key.F7] = VKEY_F7,
+            [Key.F8] = VKEY_F8,
+            [Key.F9] = VKEY_F9,
+            [Key.F10] = VKEY_F10,
+            [Key.F11] = VKEY_F11,
+            [Key.F12] = VKEY_F12,
+            [Key.F13] = VKEY_F13,
+            [Key.F14] = VKEY_F14,
+            [Key.F15] = VKEY_F15,
+            [Key.Pause] = VKEY_PAUSE,
+        };
+
+        public BrowserControl()
+        {
+            CanKeyboardFocus = true;
+            KeyboardFocusOnClick = true;
+            MouseFilter = MouseFilterMode.Stop;
+
+            IoCManager.InjectDependencies(this);
+        }
+
+        protected override void EnteredTree()
+        {
+            base.EnteredTree();
+
+            _cef.CheckInitialized();
+
+            DebugTools.AssertNull(_data);
+
+            // A funny render handler that will allow us to render to the control.
+            var renderer = new ControlRenderHandler(this);
+
+            // A funny web cef client. This can actually be shared by multiple browsers, but I'm not sure how the
+            // rendering would work in that case? TODO CEF: Investigate a way to share the web client?
+            var client = new RobustCefClient(renderer, _requestHandler, new RobustLoadHandler());
+
+            var info = CefWindowInfo.Create();
+
+            // FUNFACT: If you DO NOT set these below and set info.Width/info.Height instead, you get an external window
+            // Good to know, huh? Setup is the same, except you can pass a dummy render handler to the CEF client.
+            info.SetAsWindowless(IntPtr.Zero, false); // TODO CEF: Pass parent handle?
+            info.WindowlessRenderingEnabled = true;
+
+            var settings = new CefBrowserSettings()
+            {
+                WindowlessFrameRate = 60
+            };
+
+            // Create the web browser! And by default, we go to about:blank.
+            var browser = CefBrowserHost.CreateBrowserSync(info, client, settings, _startUrl);
+
+            var texture = _clyde.CreateBlankTexture<Bgra32>(Vector2i.One);
+
+            _data = new LiveData(texture, client, browser, renderer);
+        }
+
+        protected override void ExitedTree()
+        {
+            base.ExitedTree();
+
+            DebugTools.AssertNotNull(_data);
+
+            _data!.Texture.Dispose();
+            _data.Browser.GetHost().CloseBrowser(true);
+            _data = null;
+        }
+
+        protected internal override void MouseMove(GUIMouseMoveEventArgs args)
+        {
+            base.MouseMove(args);
+
+            if (_data == null)
+                return;
+
+            // Logger.Debug();
+            var modifiers = CalcMouseModifiers();
+            var mouseEvent = new CefMouseEvent(
+                (int) args.RelativePosition.X, (int) args.RelativePosition.Y,
+                modifiers);
+
+            _data.Browser.GetHost().SendMouseMoveEvent(mouseEvent, false);
+        }
+
+        protected internal override void MouseExited()
+        {
+            base.MouseExited();
+
+            if (_data == null)
+                return;
+
+            var modifiers = CalcMouseModifiers();
+
+            _data.Browser.GetHost().SendMouseMoveEvent(new CefMouseEvent(0, 0, modifiers), true);
+        }
+
+        protected internal override void MouseWheel(GUIMouseWheelEventArgs args)
+        {
+            base.MouseWheel(args);
+
+            if (_data == null)
+                return;
+
+            var modifiers = CalcMouseModifiers();
+            var mouseEvent = new CefMouseEvent(
+                (int) args.RelativePosition.X, (int) args.RelativePosition.Y,
+                modifiers);
+
+            _data.Browser.GetHost().SendMouseWheelEvent(
+                mouseEvent,
+                (int) args.Delta.X * ScrollSpeed,
+                (int) args.Delta.Y * ScrollSpeed);
+        }
+
+        bool IRawInputControl.RawKeyEvent(in GuiRawKeyEvent guiRawEvent)
+        {
+            if (_data == null)
+                return false;
+
+            var host = _data.Browser.GetHost();
+
+            if (guiRawEvent.Key is Key.MouseLeft or Key.MouseMiddle or Key.MouseRight)
+            {
+                var key = guiRawEvent.Key switch
+                {
+                    Key.MouseLeft => CefMouseButtonType.Left,
+                    Key.MouseMiddle => CefMouseButtonType.Middle,
+                    Key.MouseRight => CefMouseButtonType.Right,
+                    _ => default // not possible
+                };
+
+                var mouseEvent = new CefMouseEvent(
+                    guiRawEvent.MouseRelative.X, guiRawEvent.MouseRelative.Y,
+                    CefEventFlags.None);
+
+                // Logger.Debug($"MOUSE: {guiRawEvent.Action} {guiRawEvent.Key} {guiRawEvent.ScanCode} {key}");
+
+                // TODO: double click support?
+                host.SendMouseClickEvent(mouseEvent, key, guiRawEvent.Action == RawKeyAction.Up, 1);
+            }
+            else
+            {
+                // TODO: Handle left/right modifier keys??
+                if (!_keyMap.TryGetValue(guiRawEvent.Key, out var vkKey))
+                    vkKey = default;
+
+                // Logger.Debug($"{guiRawEvent.Action} {guiRawEvent.Key} {guiRawEvent.ScanCode} {vkKey}");
+
+                var lParam = 0;
+                lParam |= (guiRawEvent.ScanCode & 0xFF) << 16;
+                if (guiRawEvent.Action != RawKeyAction.Down)
+                    lParam |= 1 << 30;
+
+                if (guiRawEvent.Action == RawKeyAction.Up)
+                    lParam |= 1 << 31;
+
+                var modifiers = CalcModifiers(guiRawEvent.Key);
+
+                host.SendKeyEvent(new CefKeyEvent
+                {
+                    // Repeats are sent as key downs, I guess?
+                    EventType = guiRawEvent.Action == RawKeyAction.Up
+                        ? CefKeyEventType.KeyUp
+                        : CefKeyEventType.RawKeyDown,
+                    NativeKeyCode = lParam,
+                    // NativeKeyCode = guiRawEvent.ScanCode,
+                    WindowsKeyCode = (int) vkKey,
+                    IsSystemKey = false, // TODO
+                    Modifiers = modifiers
+                });
+
+                if (guiRawEvent.Action != RawKeyAction.Up && guiRawEvent.Key == Key.Return)
+                {
+                    host.SendKeyEvent(new CefKeyEvent
+                    {
+                        EventType = CefKeyEventType.Char,
+                        WindowsKeyCode = '\r',
+                        NativeKeyCode = lParam,
+                        Modifiers = modifiers
+                    });
+                }
+            }
+
+            return true;
+        }
+
+        private CefEventFlags CalcModifiers(Key key)
+        {
+            CefEventFlags modifiers = default;
+
+            if (_inputMgr.IsKeyDown(Key.Control))
+                modifiers |= CefEventFlags.ControlDown;
+
+            if (_inputMgr.IsKeyDown(Key.Alt))
+                modifiers |= CefEventFlags.AltDown;
+
+            if (_inputMgr.IsKeyDown(Key.Shift))
+                modifiers |= CefEventFlags.ShiftDown;
+
+            if (_inputMgr.IsKeyDown(Key.Shift))
+                modifiers |= CefEventFlags.ShiftDown;
+
+            return modifiers;
+        }
+
+        private CefEventFlags CalcMouseModifiers()
+        {
+            CefEventFlags modifiers = default;
+
+            if (_inputMgr.IsKeyDown(Key.Control))
+                modifiers |= CefEventFlags.ControlDown;
+
+            if (_inputMgr.IsKeyDown(Key.Alt))
+                modifiers |= CefEventFlags.AltDown;
+
+            if (_inputMgr.IsKeyDown(Key.Shift))
+                modifiers |= CefEventFlags.ShiftDown;
+
+            if (_inputMgr.IsKeyDown(Key.Shift))
+                modifiers |= CefEventFlags.ShiftDown;
+
+            if (_inputMgr.IsKeyDown(Key.MouseLeft))
+                modifiers |= CefEventFlags.LeftMouseButton;
+
+            if (_inputMgr.IsKeyDown(Key.MouseMiddle))
+                modifiers |= CefEventFlags.MiddleMouseButton;
+
+            if (_inputMgr.IsKeyDown(Key.MouseRight))
+                modifiers |= CefEventFlags.RightMouseButton;
+
+            return modifiers;
+        }
+
+        protected internal override void TextEntered(GUITextEventArgs args)
+        {
+            base.TextEntered(args);
+
+            if (_data == null)
+                return;
+
+            var host = _data.Browser.GetHost();
+
+            Span<char> buf = stackalloc char[2];
+            var written = args.AsRune.EncodeToUtf16(buf);
+
+            for (var i = 0; i < written; i++)
+            {
+                host.SendKeyEvent(new CefKeyEvent
+                {
+                    EventType = CefKeyEventType.Char,
+                    WindowsKeyCode = buf[i],
+                    Character = buf[i],
+                    UnmodifiedCharacter = buf[i]
+                });
+            }
+        }
+
+        protected override void Resized()
+        {
+            base.Resized();
+
+            if (_data == null)
+                return;
+
+            _data.Browser.GetHost().NotifyMoveOrResizeStarted();
+            _data.Browser.GetHost().WasResized();
+            _data.Texture.Dispose();
+            _data.Texture = _clyde.CreateBlankTexture<Bgra32>((PixelWidth, PixelHeight));
+        }
+
+        protected internal override void Draw(DrawingHandleScreen handle)
+        {
+            base.Draw(handle);
+
+            if (_data == null)
+                return;
+
+            var bufImg = _data.Renderer.Buffer.Buffer;
+
+            _data.Texture.SetSubImage(
+                Vector2i.Zero,
+                bufImg,
+                new UIBox2i(
+                    0, 0,
+                    Math.Min(PixelWidth, bufImg.Width),
+                    Math.Min(PixelHeight, bufImg.Height)));
+
+            handle.DrawTexture(_data.Texture, Vector2.Zero);
+        }
+
+        public void StopLoad()
+        {
+            if (_data == null)
+                throw new InvalidOperationException();
+
+            _data.Browser.StopLoad();
+        }
+
+        public void Reload()
+        {
+            if (_data == null)
+                throw new InvalidOperationException();
+
+            _data.Browser.Reload();
+        }
+
+        public bool GoBack()
+        {
+            if (_data == null)
+                throw new InvalidOperationException();
+
+            if (!_data.Browser.CanGoBack)
+                return false;
+
+            _data.Browser.GoBack();
+            return true;
+        }
+
+        public bool GoForward()
+        {
+            if (_data == null)
+                throw new InvalidOperationException();
+
+            if (!_data.Browser.CanGoForward)
+                return false;
+
+            _data.Browser.GoForward();
+            return true;
+        }
+
+        public void ExecuteJavaScript(string code)
+        {
+            if (_data == null)
+                throw new InvalidOperationException();
+
+            // TODO: this should not run until the browser is done loading seriously does this even work?
+            _data.Browser.GetMainFrame().ExecuteJavaScript(code, string.Empty, 1);
+        }
+
+        public void AddResourceRequestHandler(Action<RequestHandlerContext> handler)
+        {
+            _requestHandler.AddResourceRequestHandler(handler);
+        }
+
+        public void RemoveResourceRequestHandler(Action<RequestHandlerContext> handler)
+        {
+            _requestHandler.RemoveResourceRequestHandler(handler);
+        }
+
+        public void AddBeforeBrowseHandler(Action<BeforeBrowseContext> handler)
+        {
+            _requestHandler.AddBeforeBrowseHandler(handler);
+        }
+
+        public void RemoveBeforeBrowseHandler(Action<BeforeBrowseContext> handler)
+        {
+            _requestHandler.RemoveBeforeBrowseHandler(handler);
+        }
+
+        private sealed class LiveData
+        {
+            public OwnedTexture Texture;
+            public readonly RobustCefClient Client;
+            public readonly CefBrowser Browser;
+            public readonly ControlRenderHandler Renderer;
+
+            public LiveData(
+                OwnedTexture texture,
+                RobustCefClient client,
+                CefBrowser browser,
+                ControlRenderHandler renderer)
+            {
+                Texture = texture;
+                Client = client;
+                Browser = browser;
+                Renderer = renderer;
+            }
+        }
+    }
+
+    internal class ControlRenderHandler : CefRenderHandler
+    {
+        public ImageBuffer Buffer { get; }
+        private Control _control;
+
+        internal ControlRenderHandler(Control control)
+        {
+            Buffer = new ImageBuffer(control);
+            _control = control;
+        }
+
+        protected override CefAccessibilityHandler? GetAccessibilityHandler() => null;
+
+        protected override void GetViewRect(CefBrowser browser, out CefRectangle rect)
+        {
+            if (_control.Disposed)
+            {
+                rect = new CefRectangle();
+                return;
+            }
+
+            // TODO CEF: Do we need to pass real screen coords? Cause what we do already works...
+            //var screenCoords = _control.ScreenCoordinates;
+            //rect = new CefRectangle((int) screenCoords.X, (int) screenCoords.Y, (int)Math.Max(_control.Size.X, 1), (int)Math.Max(_control.Size.Y, 1));
+
+            // We do the max between size and 1 because it will LITERALLY CRASH WITHOUT AN ERROR otherwise.
+            rect = new CefRectangle(0, 0, (int) Math.Max(_control.Size.X, 1), (int) Math.Max(_control.Size.Y, 1));
+        }
+
+        protected override bool GetScreenInfo(CefBrowser browser, CefScreenInfo screenInfo)
+        {
+            if (_control.Disposed)
+                return false;
+
+            // TODO CEF: Get actual scale factor?
+            screenInfo.DeviceScaleFactor = 1.0f;
+
+            return true;
+        }
+
+        protected override void OnPopupSize(CefBrowser browser, CefRectangle rect)
+        {
+            if (_control.Disposed)
+                return;
+        }
+
+        protected override void OnPaint(CefBrowser browser, CefPaintElementType type, CefRectangle[] dirtyRects,
+            IntPtr buffer, int width, int height)
+        {
+            if (_control.Disposed)
+                return;
+
+            foreach (var dirtyRect in dirtyRects)
+            {
+                Buffer.UpdateBuffer(width, height, buffer, dirtyRect);
+            }
+        }
+
+        protected override void OnAcceleratedPaint(CefBrowser browser, CefPaintElementType type,
+            CefRectangle[] dirtyRects, IntPtr sharedHandle)
+        {
+            // Unused, but we're forced to implement it so.. NOOP.
+        }
+
+        protected override void OnScrollOffsetChanged(CefBrowser browser, double x, double y)
+        {
+            if (_control.Disposed)
+                return;
+        }
+
+        protected override void OnImeCompositionRangeChanged(CefBrowser browser, CefRange selectedRange,
+            CefRectangle[] characterBounds)
+        {
+            if (_control.Disposed)
+                return;
+        }
+    }
+}

Robust.Client.CEF/BrowserWindowCreateParameters.cs

@@ -0,0 +1,16 @@
+namespace Robust.Client.CEF
+{
+    public sealed class BrowserWindowCreateParameters
+    {
+        public int Width { get; set; }
+        public int Height { get; set; }
+
+        public string Url { get; set; } = "about:blank";
+
+        public BrowserWindowCreateParameters(int width, int height)
+        {
+            Width = width;
+            Height = height;
+        }
+    }
+}

Robust.Client.CEF/CefKeyCodes.cs

@@ -0,0 +1,225 @@
+
+using System.Diagnostics.CodeAnalysis;
+
+namespace Robust.Client.CEF
+{
+    [SuppressMessage("ReSharper", "InconsistentNaming")]
+    [SuppressMessage("ReSharper", "UnusedMember.Global")]
+    [SuppressMessage("ReSharper", "IdentifierTypo")]
+    [SuppressMessage("ReSharper", "CA1069")]
+    [SuppressMessage("ReSharper", "CommentTypo")]
+    internal static class CefKeyCodes
+    {
+        // Taken from https://chromium.googlesource.com/chromium/src/+/refs/heads/main/ui/events/keycodes/keyboard_codes_posix.h
+        // See also https://docs.microsoft.com/en-us/windows/win32/inputdev/virtual-key-codes
+        public enum ChromiumKeyboardCode
+        {
+            VKEY_CANCEL = 0x03,
+            VKEY_BACK = 0x08,
+            VKEY_TAB = 0x09,
+            VKEY_BACKTAB = 0x0A,
+            VKEY_CLEAR = 0x0C,
+            VKEY_RETURN = 0x0D,
+            VKEY_SHIFT = 0x10,
+            VKEY_CONTROL = 0x11,
+            VKEY_MENU = 0x12,
+            VKEY_PAUSE = 0x13,
+            VKEY_CAPITAL = 0x14,
+            VKEY_KANA = 0x15,
+            VKEY_HANGUL = 0x15,
+            VKEY_PASTE = 0x16,
+            VKEY_JUNJA = 0x17,
+            VKEY_FINAL = 0x18,
+            VKEY_HANJA = 0x19,
+            VKEY_KANJI = 0x19,
+            VKEY_ESCAPE = 0x1B,
+            VKEY_CONVERT = 0x1C,
+            VKEY_NONCONVERT = 0x1D,
+            VKEY_ACCEPT = 0x1E,
+            VKEY_MODECHANGE = 0x1F,
+            VKEY_SPACE = 0x20,
+            VKEY_PRIOR = 0x21,
+            VKEY_NEXT = 0x22,
+            VKEY_END = 0x23,
+            VKEY_HOME = 0x24,
+            VKEY_LEFT = 0x25,
+            VKEY_UP = 0x26,
+            VKEY_RIGHT = 0x27,
+            VKEY_DOWN = 0x28,
+            VKEY_SELECT = 0x29,
+            VKEY_PRINT = 0x2A,
+            VKEY_EXECUTE = 0x2B,
+            VKEY_SNAPSHOT = 0x2C, // Print Screen / SysRq
+            VKEY_INSERT = 0x2D,
+            VKEY_DELETE = 0x2E,
+            VKEY_HELP = 0x2F,
+            VKEY_0 = 0x30,
+            VKEY_1 = 0x31,
+            VKEY_2 = 0x32,
+            VKEY_3 = 0x33,
+            VKEY_4 = 0x34,
+            VKEY_5 = 0x35,
+            VKEY_6 = 0x36,
+            VKEY_7 = 0x37,
+            VKEY_8 = 0x38,
+            VKEY_9 = 0x39,
+            VKEY_A = 0x41,
+            VKEY_B = 0x42,
+            VKEY_C = 0x43,
+            VKEY_D = 0x44,
+            VKEY_E = 0x45,
+            VKEY_F = 0x46,
+            VKEY_G = 0x47,
+            VKEY_H = 0x48,
+            VKEY_I = 0x49,
+            VKEY_J = 0x4A,
+            VKEY_K = 0x4B,
+            VKEY_L = 0x4C,
+            VKEY_M = 0x4D,
+            VKEY_N = 0x4E,
+            VKEY_O = 0x4F,
+            VKEY_P = 0x50,
+            VKEY_Q = 0x51,
+            VKEY_R = 0x52,
+            VKEY_S = 0x53,
+            VKEY_T = 0x54,
+            VKEY_U = 0x55,
+            VKEY_V = 0x56,
+            VKEY_W = 0x57,
+            VKEY_X = 0x58,
+            VKEY_Y = 0x59,
+            VKEY_Z = 0x5A,
+            VKEY_LWIN = 0x5B,
+            VKEY_COMMAND = VKEY_LWIN, // Provide the Mac name for convenience.
+            VKEY_RWIN = 0x5C,
+            VKEY_APPS = 0x5D,
+            VKEY_SLEEP = 0x5F,
+            VKEY_NUMPAD0 = 0x60,
+            VKEY_NUMPAD1 = 0x61,
+            VKEY_NUMPAD2 = 0x62,
+            VKEY_NUMPAD3 = 0x63,
+            VKEY_NUMPAD4 = 0x64,
+            VKEY_NUMPAD5 = 0x65,
+            VKEY_NUMPAD6 = 0x66,
+            VKEY_NUMPAD7 = 0x67,
+            VKEY_NUMPAD8 = 0x68,
+            VKEY_NUMPAD9 = 0x69,
+            VKEY_MULTIPLY = 0x6A,
+            VKEY_ADD = 0x6B,
+            VKEY_SEPARATOR = 0x6C,
+            VKEY_SUBTRACT = 0x6D,
+            VKEY_DECIMAL = 0x6E,
+            VKEY_DIVIDE = 0x6F,
+            VKEY_F1 = 0x70,
+            VKEY_F2 = 0x71,
+            VKEY_F3 = 0x72,
+            VKEY_F4 = 0x73,
+            VKEY_F5 = 0x74,
+            VKEY_F6 = 0x75,
+            VKEY_F7 = 0x76,
+            VKEY_F8 = 0x77,
+            VKEY_F9 = 0x78,
+            VKEY_F10 = 0x79,
+            VKEY_F11 = 0x7A,
+            VKEY_F12 = 0x7B,
+            VKEY_F13 = 0x7C,
+            VKEY_F14 = 0x7D,
+            VKEY_F15 = 0x7E,
+            VKEY_F16 = 0x7F,
+            VKEY_F17 = 0x80,
+            VKEY_F18 = 0x81,
+            VKEY_F19 = 0x82,
+            VKEY_F20 = 0x83,
+            VKEY_F21 = 0x84,
+            VKEY_F22 = 0x85,
+            VKEY_F23 = 0x86,
+            VKEY_F24 = 0x87,
+            VKEY_NUMLOCK = 0x90,
+            VKEY_SCROLL = 0x91,
+            VKEY_LSHIFT = 0xA0,
+            VKEY_RSHIFT = 0xA1,
+            VKEY_LCONTROL = 0xA2,
+            VKEY_RCONTROL = 0xA3,
+            VKEY_LMENU = 0xA4,
+            VKEY_RMENU = 0xA5,
+            VKEY_BROWSER_BACK = 0xA6,
+            VKEY_BROWSER_FORWARD = 0xA7,
+            VKEY_BROWSER_REFRESH = 0xA8,
+            VKEY_BROWSER_STOP = 0xA9,
+            VKEY_BROWSER_SEARCH = 0xAA,
+            VKEY_BROWSER_FAVORITES = 0xAB,
+            VKEY_BROWSER_HOME = 0xAC,
+            VKEY_VOLUME_MUTE = 0xAD,
+            VKEY_VOLUME_DOWN = 0xAE,
+            VKEY_VOLUME_UP = 0xAF,
+            VKEY_MEDIA_NEXT_TRACK = 0xB0,
+            VKEY_MEDIA_PREV_TRACK = 0xB1,
+            VKEY_MEDIA_STOP = 0xB2,
+            VKEY_MEDIA_PLAY_PAUSE = 0xB3,
+            VKEY_MEDIA_LAUNCH_MAIL = 0xB4,
+            VKEY_MEDIA_LAUNCH_MEDIA_SELECT = 0xB5,
+            VKEY_MEDIA_LAUNCH_APP1 = 0xB6,
+            VKEY_MEDIA_LAUNCH_APP2 = 0xB7,
+            VKEY_OEM_1 = 0xBA,
+            VKEY_OEM_PLUS = 0xBB,
+            VKEY_OEM_COMMA = 0xBC,
+            VKEY_OEM_MINUS = 0xBD,
+            VKEY_OEM_PERIOD = 0xBE,
+            VKEY_OEM_2 = 0xBF,
+            VKEY_OEM_3 = 0xC0,
+            VKEY_OEM_4 = 0xDB,
+            VKEY_OEM_5 = 0xDC,
+            VKEY_OEM_6 = 0xDD,
+            VKEY_OEM_7 = 0xDE,
+            VKEY_OEM_8 = 0xDF,
+            VKEY_OEM_102 = 0xE2,
+            VKEY_OEM_103 = 0xE3, // GTV KEYCODE_MEDIA_REWIND
+            VKEY_OEM_104 = 0xE4, // GTV KEYCODE_MEDIA_FAST_FORWARD
+            VKEY_PROCESSKEY = 0xE5,
+            VKEY_PACKET = 0xE7,
+            VKEY_OEM_ATTN = 0xF0, // JIS DomKey::ALPHANUMERIC
+            VKEY_OEM_FINISH = 0xF1, // JIS DomKey::KATAKANA
+            VKEY_OEM_COPY = 0xF2, // JIS DomKey::HIRAGANA
+            VKEY_DBE_SBCSCHAR = 0xF3, // JIS DomKey::HANKAKU
+            VKEY_DBE_DBCSCHAR = 0xF4, // JIS DomKey::ZENKAKU
+            VKEY_OEM_BACKTAB = 0xF5, // JIS DomKey::ROMAJI
+            VKEY_ATTN = 0xF6, // DomKey::ATTN or JIS DomKey::KANA_MODE
+            VKEY_CRSEL = 0xF7,
+            VKEY_EXSEL = 0xF8,
+            VKEY_EREOF = 0xF9,
+            VKEY_PLAY = 0xFA,
+            VKEY_ZOOM = 0xFB,
+            VKEY_NONAME = 0xFC,
+            VKEY_PA1 = 0xFD,
+            VKEY_OEM_CLEAR = 0xFE,
+            VKEY_UNKNOWN = 0,
+
+            // POSIX specific VKEYs. Note that as of Windows SDK 7.1, 0x97-9F, 0xD8-DA,
+            // and 0xE8 are unassigned.
+            VKEY_WLAN = 0x97,
+            VKEY_POWER = 0x98,
+            VKEY_ASSISTANT = 0x99,
+            VKEY_SETTINGS = 0x9A,
+            VKEY_PRIVACY_SCREEN_TOGGLE = 0x9B,
+            VKEY_BRIGHTNESS_DOWN = 0xD8,
+            VKEY_BRIGHTNESS_UP = 0xD9,
+            VKEY_KBD_BRIGHTNESS_DOWN = 0xDA,
+            VKEY_KBD_BRIGHTNESS_UP = 0xE8,
+
+            // Windows does not have a specific key code for AltGr. We use the unused 0xE1
+            // (VK_OEM_AX) code to represent AltGr, matching the behaviour of Firefox on
+            // Linux.
+            VKEY_ALTGR = 0xE1,
+
+            // Windows does not have a specific key code for Compose. We use the unused
+            // 0xE6 (VK_ICO_CLEAR) code to represent Compose.
+            VKEY_COMPOSE = 0xE6,
+
+            // Windows does not have specific key codes for Media Play and Media Pause. We
+            // use the unused 0xE9 (VK_OEM_RESET) and 0xEA (VK_OEM_JUMP) codes to
+            // represent them.
+            VKEY_MEDIA_PLAY = 0xE9,
+            VKEY_MEDIA_PAUSE = 0xEA,
+        };
+    }
+}

Robust.Client.CEF/CefManager.BrowserWindow.cs

@@ -0,0 +1,186 @@
+using System;
+using System.Collections.Generic;
+using Robust.Client.Graphics;
+using Robust.Shared.IoC;
+using Robust.Shared.Log;
+using Robust.Shared.ViewVariables;
+using Xilium.CefGlue;
+
+namespace Robust.Client.CEF
+{
+    public partial class CefManager
+    {
+        [Dependency] private readonly IClydeInternal _clyde = default!;
+
+        private readonly List<BrowserWindowImpl> _browserWindows = new();
+
+        public IEnumerable<IBrowserWindow> AllBrowserWindows => _browserWindows;
+
+        public IBrowserWindow CreateBrowserWindow(BrowserWindowCreateParameters createParams)
+        {
+            var mainHWnd = (_clyde.MainWindow as IClydeWindowInternal)?.WindowsHWnd ?? 0;
+
+            var info = CefWindowInfo.Create();
+            info.Width = createParams.Width;
+            info.Height = createParams.Height;
+            info.SetAsPopup(mainHWnd, "ss14cef");
+
+            var impl = new BrowserWindowImpl(this);
+
+            var lifeSpanHandler = new WindowLifeSpanHandler(impl);
+            var reqHandler = new RobustRequestHandler(Logger.GetSawmill("root"));
+            var client = new WindowCefClient(lifeSpanHandler, reqHandler);
+            var settings = new CefBrowserSettings();
+
+            impl.Browser = CefBrowserHost.CreateBrowserSync(info, client, settings, createParams.Url);
+            impl.RequestHandler = reqHandler;
+
+            _browserWindows.Add(impl);
+
+            return impl;
+        }
+
+        private sealed class BrowserWindowImpl : IBrowserWindow
+        {
+            private readonly CefManager _manager;
+            internal CefBrowser Browser = default!;
+            internal RobustRequestHandler RequestHandler = default!;
+
+            public Action<RequestHandlerContext>? OnResourceRequest { get; set; }
+
+            [ViewVariables(VVAccess.ReadWrite)]
+            public string Url
+            {
+                get
+                {
+                    CheckClosed();
+                    return Browser.GetMainFrame().Url;
+                }
+                set
+                {
+                    CheckClosed();
+                    Browser.GetMainFrame().LoadUrl(value);
+                }
+            }
+
+            [ViewVariables]
+            public bool IsLoading
+            {
+                get
+                {
+                    CheckClosed();
+                    return Browser.IsLoading;
+                }
+            }
+
+            public BrowserWindowImpl(CefManager manager)
+            {
+                _manager = manager;
+            }
+
+            public void StopLoad()
+            {
+                CheckClosed();
+                Browser.StopLoad();
+            }
+
+            public void Reload()
+            {
+                CheckClosed();
+                Browser.Reload();
+            }
+
+            public bool GoBack()
+            {
+                CheckClosed();
+                if (!Browser.CanGoBack)
+                    return false;
+
+                Browser.GoBack();
+                return true;
+            }
+
+            public bool GoForward()
+            {
+                CheckClosed();
+                if (!Browser.CanGoForward)
+                    return false;
+
+                Browser.GoForward();
+                return true;
+            }
+
+            public void ExecuteJavaScript(string code)
+            {
+                CheckClosed();
+                Browser.GetMainFrame().ExecuteJavaScript(code, string.Empty, 1);
+            }
+
+            public void AddResourceRequestHandler(Action<RequestHandlerContext> handler)
+            {
+                RequestHandler.AddResourceRequestHandler(handler);
+            }
+
+            public void RemoveResourceRequestHandler(Action<RequestHandlerContext> handler)
+            {
+                RequestHandler.RemoveResourceRequestHandler(handler);
+            }
+
+            public void Dispose()
+            {
+                if (Closed)
+                    return;
+
+                Browser.GetHost().CloseBrowser(true);
+                Closed = true;
+            }
+
+            public bool Closed { get; private set; }
+
+            public void OnClose()
+            {
+                Closed = true;
+                _manager._browserWindows.Remove(this);
+                Logger.Debug("Removing window");
+            }
+
+            private void CheckClosed()
+            {
+                if (Closed)
+                    throw new ObjectDisposedException("BrowserWindow");
+            }
+        }
+
+        private sealed class WindowCefClient : CefClient
+        {
+            private readonly CefLifeSpanHandler _lifeSpanHandler;
+            private readonly CefRequestHandler _requestHandler;
+
+            public WindowCefClient(CefLifeSpanHandler lifeSpanHandler, CefRequestHandler requestHandler)
+            {
+                _lifeSpanHandler = lifeSpanHandler;
+                _requestHandler = requestHandler;
+            }
+
+            protected override CefLifeSpanHandler GetLifeSpanHandler() => _lifeSpanHandler;
+            protected override CefRequestHandler GetRequestHandler() => _requestHandler;
+        }
+
+        private sealed class WindowLifeSpanHandler : CefLifeSpanHandler
+        {
+            private readonly BrowserWindowImpl _windowImpl;
+
+            public WindowLifeSpanHandler(BrowserWindowImpl windowImpl)
+            {
+                _windowImpl = windowImpl;
+            }
+
+            protected override void OnBeforeClose(CefBrowser browser)
+            {
+                base.OnBeforeClose(browser);
+
+                _windowImpl.OnClose();
+            }
+        }
+    }
+}

Robust.Client.CEF/CefManager.cs

@@ -0,0 +1,104 @@
+using System;
+using System.IO;
+using JetBrains.Annotations;
+using Robust.Shared.ContentPack;
+using Robust.Shared.Log;
+using Robust.Shared.Utility;
+
+// The library we're using right now. TODO CEF: Do we want to use something else? We will need to ship it ourselves if so.
+using Xilium.CefGlue;
+
+namespace Robust.Client.CEF
+{
+    // Register this with IoC.
+    // TODO CEF: think if making this inherit CefApp is a good idea...
+    // TODO CEF: A way to handle external window browsers...
+    [UsedImplicitly]
+    public partial class CefManager
+    {
+        private CefApp _app = default!;
+        private bool _initialized = false;
+
+        /// <summary>
+        ///     Call this to initialize CEF.
+        /// </summary>
+        public void Initialize()
+        {
+            DebugTools.Assert(!_initialized);
+
+            string subProcessName;
+            if (OperatingSystem.IsWindows())
+                subProcessName = "Robust.Client.CEF.exe";
+            else if (OperatingSystem.IsLinux())
+                subProcessName = "Robust.Client.CEF";
+            else
+                throw new NotSupportedException("Unsupported platform for CEF!");
+
+            var subProcessPath = PathHelpers.ExecutableRelativeFile(subProcessName);
+
+            var settings = new CefSettings()
+            {
+                WindowlessRenderingEnabled = true, // So we can render to our UI controls.
+                ExternalMessagePump = false, // Unsure, honestly. TODO CEF: Research this?
+                NoSandbox = true, // Not disabling the sandbox crashes CEF.
+                BrowserSubprocessPath = subProcessPath,
+                LocalesDirPath = Path.Combine(PathHelpers.GetExecutableDirectory(), "locales"),
+                ResourcesDirPath = PathHelpers.GetExecutableDirectory(),
+                RemoteDebuggingPort = 9222
+            };
+
+            Logger.Info($"CEF Version: {CefRuntime.ChromeVersion}");
+
+            // --------------------------- README --------------------------------------------------
+            // By the way! You're gonna need the CEF binaries in your client's bin folder.
+            // More specifically, version cef_binary_91.1.21+g9dd45fe+chromium-91.0.4472.114
+            // https://cef-builds.spotifycdn.com/cef_binary_91.1.21%2Bg9dd45fe%2Bchromium-91.0.4472.114_windows64_minimal.tar.bz2
+            // https://cef-builds.spotifycdn.com/cef_binary_91.1.21%2Bg9dd45fe%2Bchromium-91.0.4472.114_linux64_minimal.tar.bz2
+            // Here's how to get it to work:
+            // 1. Copy all the contents of "Release" to the bin folder.
+            // 2. Copy all the contents of "Resources" to the bin folder.
+            // Supposedly, you should just need libcef.so in Release and icudtl.dat in Resources...
+            // The rest might be optional.
+            // Maybe. Good luck! If you get odd crashes with no info and a weird exit code, use GDB!
+            // -------------------------------------------------------------------------------------
+
+            _app = new RobustCefApp();
+
+            // We pass no main arguments...
+            CefRuntime.Initialize(new CefMainArgs(null), settings, _app, IntPtr.Zero);
+
+            // TODO CEF: After this point, debugging breaks. No, literally. My client crashes but ONLY with the debugger.
+            // I have tried using the DEBUG and RELEASE versions of libcef.so, stripped or non-stripped...
+            // And nothing seemed to work. Odd.
+
+            _initialized = true;
+        }
+
+        public void CheckInitialized()
+        {
+            if (!_initialized)
+                throw new InvalidOperationException("CefManager has not been initialized!");
+        }
+
+        /// <summary>
+        ///     Needs to be called regularly for CEF to keep working.
+        /// </summary>
+        public void Update()
+        {
+            DebugTools.Assert(_initialized);
+
+            // Calling this makes CEF do its work, without using its own update loop.
+            CefRuntime.DoMessageLoopWork();
+        }
+
+        /// <summary>
+        ///     Call before program shutdown.
+        /// </summary>
+        public void Shutdown()
+        {
+            DebugTools.Assert(_initialized);
+
+            CefRuntime.Shutdown();
+        }
+    }
+}

Robust.Client.CEF/IBrowserControl.cs

@@ -0,0 +1,48 @@
+using System;
+
+namespace Robust.Client.CEF
+{
+    public interface IBrowserControl
+    {
+        /// <summary>
+        ///     Current URL of the browser. Set to load a new page.
+        /// </summary>
+        string Url { get; set; }
+
+        /// <summary>
+        ///     Whether the browser is currently loading a page.
+        /// </summary>
+        bool IsLoading { get; }
+
+        /// <summary>
+        ///     Stops loading the current page.
+        /// </summary>
+        void StopLoad();
+
+        /// <summary>
+        ///     Reload the current page.
+        /// </summary>
+        void Reload();
+
+        /// <summary>
+        ///     Navigate back.
+        /// </summary>
+        /// <returns>Whether the browser could navigate back.</returns>
+        bool GoBack();
+
+        /// <summary>
+        ///     Navigate forward.
+        /// </summary>
+        /// <returns>Whether the browser could navigate forward.</returns>
+        bool GoForward();
+
+        /// <summary>
+        ///     Execute arbitrary JavaScript on the current page.
+        /// </summary>
+        /// <param name="code">JavaScript code.</param>
+        void ExecuteJavaScript(string code);
+
+        void AddResourceRequestHandler(Action<RequestHandlerContext> handler);
+        void RemoveResourceRequestHandler(Action<RequestHandlerContext> handler);
+    }
+}

Robust.Client.CEF/IBrowserWindow.cs

@@ -0,0 +1,9 @@
+using System;
+
+namespace Robust.Client.CEF
+{
+    public interface IBrowserWindow : IBrowserControl, IDisposable
+    {
+        bool Closed { get; }
+    }
+}

Robust.Client.CEF/ImageBuffer.cs

@@ -0,0 +1,42 @@
+using System;
+using Robust.Client.UserInterface;
+using Robust.Client.Utility;
+using Robust.Shared.Maths;
+using SixLabors.ImageSharp;
+using SixLabors.ImageSharp.PixelFormats;
+using Xilium.CefGlue;
+
+namespace Robust.Client.CEF
+{
+    internal sealed class ImageBuffer
+    {
+        private readonly Control _control;
+
+        public ImageBuffer(Control control)
+        {
+            _control = control;
+        }
+
+        public Image<Bgra32> Buffer { get; private set; } = new(1, 1);
+
+        public unsafe void UpdateBuffer(int width, int height, IntPtr buffer, CefRectangle dirtyRect)
+        {
+            if (width != Buffer.Width || height != Buffer.Height)
+                UpdateSize(width, height);
+
+            var span = new ReadOnlySpan<Bgra32>((void*) buffer, width * height);
+
+            ImageSharpExt.Blit(
+                span,
+                width,
+                UIBox2i.FromDimensions(dirtyRect.X, dirtyRect.Y, dirtyRect.Width, dirtyRect.Height),
+                Buffer,
+                (dirtyRect.X, dirtyRect.Y));
+        }
+
+        private void UpdateSize(int width, int height)
+        {
+            Buffer = new Image<Bgra32>(width, height);
+        }
+    }
+}

Robust.Client.CEF/Program.cs

@@ -0,0 +1,33 @@
+using System;
+using Xilium.CefGlue;
+
+namespace Robust.Client.CEF
+{
+    public static class Program
+    {
+        // This was supposed to be the main entry for the subprocess program... It doesn't work.
+        public static int Main(string[] args)
+        {
+            // This is a workaround for this to work on UNIX.
+            var argv = args;
+            if (CefRuntime.Platform != CefRuntimePlatform.Windows)
+            {
+                argv = new string[args.Length + 1];
+                Array.Copy(args, 0, argv, 1, args.Length);
+                argv[0] = "-";
+            }
+
+            var mainArgs = new CefMainArgs(argv);
+
+            // This will block executing until the subprocess is shut down.
+            var code = CefRuntime.ExecuteProcess(mainArgs, null, IntPtr.Zero);
+
+            if (code != 0)
+            {
+                System.Console.WriteLine($"CEF Subprocess exited unsuccessfully with exit code {code}! Arguments: {string.Join(' ', argv)}");
+            }
+
+            return code;
+        }
+    }
+}

Robust.Client.CEF/RequestHandlerContext.cs

@@ -0,0 +1,56 @@
+using System;
+using System.IO;
+using System.Net;
+using Xilium.CefGlue;
+
+namespace Robust.Client.CEF
+{
+    public sealed class RequestHandlerContext
+    {
+        internal readonly CefRequest CefRequest;
+
+        public bool IsNavigation { get; }
+        public bool IsDownload { get; }
+        public string RequestInitiator { get; }
+
+        public string Url => CefRequest.Url;
+        public string Method => CefRequest.Method;
+
+        public bool IsHandled { get; private set; }
+
+        public bool IsCancelled { get; private set; }
+
+        internal IRequestResult? Result { get; private set; }
+
+        internal RequestHandlerContext(
+            bool isNavigation,
+            bool isDownload,
+            string requestInitiator,
+            CefRequest cefRequest)
+        {
+            CefRequest = cefRequest;
+            IsNavigation = isNavigation;
+            IsDownload = isDownload;
+            RequestInitiator = requestInitiator;
+        }
+
+        public void DoCancel()
+        {
+            CheckNotHandled();
+
+            IsHandled = true;
+            IsCancelled = true;
+        }
+
+        public void DoRespondStream(Stream stream, string contentType, HttpStatusCode code = HttpStatusCode.OK)
+        {
+            Result = new RequestResultStream(stream, contentType, code);
+        }
+
+        private void CheckNotHandled()
+        {
+            if (IsHandled)
+                throw new InvalidOperationException("Request has already been handled");
+        }
+    }
+}

Robust.Client.CEF/RequestResults.cs

@@ -0,0 +1,93 @@
+using System;
+using System.IO;
+using System.Net;
+using Xilium.CefGlue;
+
+namespace Robust.Client.CEF
+{
+    internal interface IRequestResult
+    {
+        CefResourceHandler MakeHandler();
+    }
+
+    internal sealed class RequestResultStream : IRequestResult
+    {
+        private readonly Stream _stream;
+        private readonly HttpStatusCode _code;
+        private readonly string _contentType;
+
+        public RequestResultStream(Stream stream, string contentType, HttpStatusCode code)
+        {
+            _stream = stream;
+            _code = code;
+            _contentType = contentType;
+        }
+
+        public CefResourceHandler MakeHandler()
+        {
+            return new Handler(_stream, _contentType, _code);
+        }
+
+        private sealed class Handler : CefResourceHandler
+        {
+            // TODO: async
+            // TODO: exception handling
+
+            private readonly Stream _stream;
+            private readonly HttpStatusCode _code;
+            private readonly string _contentType;
+
+            public Handler(Stream stream, string contentType, HttpStatusCode code)
+            {
+                _stream = stream;
+                _code = code;
+                _contentType = contentType;
+            }
+
+            protected override bool Open(CefRequest request, out bool handleRequest, CefCallback callback)
+            {
+                handleRequest = true;
+                return true;
+            }
+
+            protected override void GetResponseHeaders(CefResponse response, out long responseLength, out string? redirectUrl)
+            {
+                response.Status = (int) _code;
+                response.StatusText = _code.ToString();
+                response.MimeType = _contentType;
+
+                if (_stream.CanSeek)
+                    responseLength = _stream.Length;
+                else
+                    responseLength = -1;
+
+                redirectUrl = default;
+            }
+
+            protected override bool Skip(long bytesToSkip, out long bytesSkipped, CefResourceSkipCallback callback)
+            {
+                if (!_stream.CanSeek)
+                {
+                    bytesSkipped = -2;
+                    return false;
+                }
+
+                bytesSkipped = _stream.Seek(bytesToSkip, SeekOrigin.Begin);
+                return true;
+            }
+
+            protected override unsafe bool Read(IntPtr dataOut, int bytesToRead, out int bytesRead, CefResourceReadCallback callback)
+            {
+                var byteSpan = new Span<byte>((void*) dataOut, bytesToRead);
+
+                bytesRead = _stream.Read(byteSpan);
+
+                return bytesRead != 0;
+            }
+
+            protected override void Cancel()
+            {
+            }
+        }
+    }
+}

Robust.Client.CEF/Robust.Client.CEF.csproj

@@ -0,0 +1,25 @@
+<Project Sdk="Microsoft.NET.Sdk">
+    <Import Project="..\MSBuild\Robust.Properties.targets" />
+    <Import Project="..\MSBuild\Robust.Engine.props" />
+    <PropertyGroup>
+        <TargetFramework>net5.0</TargetFramework>
+        <PlatformTarget>x64</PlatformTarget>
+        <AllowUnsafeBlocks>true</AllowUnsafeBlocks>
+        <OutputType>WinExe</OutputType>
+    </PropertyGroup>
+
+    <Import Project="..\MSBuild\Robust.DefineConstants.targets" />
+    <Target Name="RobustAfterBuild" AfterTargets="Build" />
+    <Import Project="..\MSBuild\Robust.Engine.targets" />
+
+    <ItemGroup>
+      <PackageReference Include="JetBrains.Annotations" Version="2020.3.0" />
+      <PackageReference Include="System.Drawing.Common" Version="5.0.2" />
+    </ItemGroup>
+
+    <ItemGroup>
+      <ProjectReference Include="..\cefglue\CefGlue\CefGlue.csproj" />
+      <ProjectReference Include="..\Robust.Client\Robust.Client.csproj" />
+    </ItemGroup>
+
+</Project>

Robust.Client.CEF/RobustCefApp.cs

@@ -0,0 +1,48 @@
+using System;
+using Robust.Shared.IoC;
+using Robust.Shared.Log;
+using Xilium.CefGlue;
+
+namespace Robust.Client.CEF
+{
+    internal class RobustCefApp : CefApp
+    {
+        private readonly BrowserProcessHandler _browserProcessHandler = new();
+        private readonly RenderProcessHandler _renderProcessHandler = new();
+
+        protected override CefBrowserProcessHandler GetBrowserProcessHandler()
+        {
+            return _browserProcessHandler;
+        }
+
+        protected override CefRenderProcessHandler GetRenderProcessHandler()
+        {
+            return _renderProcessHandler;
+        }
+
+        protected override void OnBeforeCommandLineProcessing(string processType, CefCommandLine commandLine)
+        {
+            // Disable zygote on Linux.
+            commandLine.AppendSwitch("--no-zygote");
+
+            //commandLine.AppendSwitch("--disable-gpu");
+            //commandLine.AppendSwitch("--disable-gpu-compositing");
+            //commandLine.AppendSwitch("--in-process-gpu");
+
+            commandLine.AppendSwitch("disable-threaded-scrolling", "1");
+            commandLine.AppendSwitch("disable-features", "TouchpadAndWheelScrollLatching,AsyncWheelEvents");
+
+            if(IoCManager.Instance != null)
+                Logger.Debug($"{commandLine}");
+        }
+
+        private class BrowserProcessHandler : CefBrowserProcessHandler
+        {
+        }
+
+        // TODO CEF: Research - Is this even needed?
+        private class RenderProcessHandler : CefRenderProcessHandler
+        {
+        }
+    }
+}

Robust.Client.CEF/RobustCefClient.cs

@@ -0,0 +1,23 @@
+using Xilium.CefGlue;
+
+namespace Robust.Client.CEF
+{
+    // Simple CEF client.
+    internal class RobustCefClient : CefClient
+    {
+        private readonly CefRenderHandler _renderHandler;
+        private readonly CefRequestHandler _requestHandler;
+        private readonly CefLoadHandler _loadHandler;
+
+        internal RobustCefClient(CefRenderHandler handler, CefRequestHandler requestHandler, CefLoadHandler loadHandler)
+        {
+            _renderHandler = handler;
+            _requestHandler = requestHandler;
+            _loadHandler = loadHandler;
+        }
+
+        protected override CefRenderHandler GetRenderHandler() => _renderHandler;
+        protected override CefRequestHandler GetRequestHandler() => _requestHandler;
+        protected override CefLoadHandler GetLoadHandler() => _loadHandler;
+    }
+}

Robust.Client.CEF/RobustLoadHandler.cs

@@ -0,0 +1,17 @@
+using Xilium.CefGlue;
+
+namespace Robust.Client.CEF
+{
+    public sealed class RobustLoadHandler : CefLoadHandler
+    {
+        protected override void OnLoadStart(CefBrowser browser, CefFrame frame, CefTransitionType transitionType)
+        {
+            base.OnLoadStart(browser, frame, transitionType);
+        }
+
+        protected override void OnLoadEnd(CefBrowser browser, CefFrame frame, int httpStatusCode)
+        {
+            base.OnLoadEnd(browser, frame, httpStatusCode);
+        }
+    }
+}

Robust.Client.CEF/RobustRequestHandler.cs

@@ -0,0 +1,128 @@
+using System;
+using System.Collections.Generic;
+using Robust.Shared.Log;
+using Xilium.CefGlue;
+
+namespace Robust.Client.CEF
+{
+    internal sealed class RobustRequestHandler : CefRequestHandler
+    {
+        private readonly ISawmill _sawmill;
+        private readonly List<Action<RequestHandlerContext>> _resourceRequestHandlers = new();
+        private readonly List<Action<BeforeBrowseContext>> _beforeBrowseHandlers = new();
+
+        public RobustRequestHandler(ISawmill sawmill)
+        {
+            _sawmill = sawmill;
+        }
+
+        public void AddResourceRequestHandler(Action<RequestHandlerContext> handler)
+        {
+            lock (_resourceRequestHandlers)
+            {
+                _resourceRequestHandlers.Add(handler);
+            }
+        }
+
+        public void RemoveResourceRequestHandler(Action<RequestHandlerContext> handler)
+        {
+            lock (_resourceRequestHandlers)
+            {
+                _resourceRequestHandlers.Remove(handler);
+            }
+        }
+
+        public void AddBeforeBrowseHandler(Action<BeforeBrowseContext> handler)
+        {
+            lock (_beforeBrowseHandlers)
+            {
+                _beforeBrowseHandlers.Add(handler);
+            }
+        }
+
+        public void RemoveBeforeBrowseHandler(Action<BeforeBrowseContext> handler)
+        {
+            lock (_beforeBrowseHandlers)
+            {
+                _beforeBrowseHandlers.Remove(handler);
+            }
+        }
+
+        protected override CefResourceRequestHandler? GetResourceRequestHandler(
+            CefBrowser browser,
+            CefFrame frame,
+            CefRequest request,
+            bool isNavigation,
+            bool isDownload,
+            string requestInitiator,
+            ref bool disableDefaultHandling)
+        {
+            lock (_resourceRequestHandlers)
+            {
+                _sawmill.Debug($"HANDLING REQUEST: {request.Url}");
+
+                var context = new RequestHandlerContext(isNavigation, isDownload, requestInitiator, request);
+
+                foreach (var handler in _resourceRequestHandlers)
+                {
+                    handler(context);
+
+                    if (context.IsHandled)
+                        disableDefaultHandling = true;
+
+                    if (context.IsCancelled)
+                        return null;
+
+                    if (context.Result != null)
+                        return new WrapReaderResourceHandler(context.Result.MakeHandler());
+                }
+            }
+
+            return null;
+        }
+
+        protected override bool OnBeforeBrowse(CefBrowser browser, CefFrame frame, CefRequest request, bool userGesture, bool isRedirect)
+        {
+            lock (_beforeBrowseHandlers)
+            {
+                var context = new BeforeBrowseContext(isRedirect, userGesture, request);
+
+                foreach (var handler in _beforeBrowseHandlers)
+                {
+                    handler(context);
+
+                    if (context.IsCancelled)
+                        return true;
+                }
+            }
+
+            return false;
+        }
+
+        private sealed class WrapReaderResourceHandler : CefResourceRequestHandler
+        {
+            private readonly CefResourceHandler _handler;
+
+            public WrapReaderResourceHandler(CefResourceHandler handler)
+            {
+                _handler = handler;
+            }
+
+            protected override CefCookieAccessFilter? GetCookieAccessFilter(
+                CefBrowser browser,
+                CefFrame frame,
+                CefRequest request)
+            {
+                return null;
+            }
+
+            protected override CefResourceHandler GetResourceHandler(
+                CefBrowser browser,
+                CefFrame frame,
+                CefRequest request)
+            {
+                return _handler;
+            }
+        }
+    }
+}

Robust.Client.Injectors/Program.cs

@@ -29,26 +29,27 @@ namespace Robust.Build.Tasks
         }
     }
 
+    //formatted according to https://github.com/dotnet/msbuild/blob/main/src/Shared/CanonicalError.cs#L57
     class ConsoleBuildEngine : IBuildEngine
     {
         public void LogErrorEvent(BuildErrorEventArgs e)
         {
-            Console.WriteLine($"ERROR: {e.Code} {e.Message} in {e.File} {e.LineNumber}:{e.ColumnNumber}-{e.EndLineNumber}:{e.EndColumnNumber}");
+            Console.WriteLine($"{e.File} ({e.LineNumber},{e.ColumnNumber},{e.EndLineNumber},{e.EndColumnNumber}): XAMLIL ERROR {e.Code}: {e.Message}");
         }
 
         public void LogWarningEvent(BuildWarningEventArgs e)
         {
-            Console.WriteLine($"WARNING: {e.Code} {e.Message} in {e.File} {e.LineNumber}:{e.ColumnNumber}-{e.EndLineNumber}:{e.EndColumnNumber}");
+            Console.WriteLine($"{e.File} ({e.LineNumber},{e.ColumnNumber},{e.EndLineNumber},{e.EndColumnNumber}): XAMLIL WARNING {e.Code}: {e.Message}");
         }
 
         public void LogMessageEvent(BuildMessageEventArgs e)
         {
-            Console.WriteLine($"MESSAGE: {e.Code} {e.Message} in {e.File} {e.LineNumber}:{e.ColumnNumber}-{e.EndLineNumber}:{e.EndColumnNumber}");
+            Console.WriteLine($"{e.File} ({e.LineNumber},{e.ColumnNumber},{e.EndLineNumber},{e.EndColumnNumber}): XAMLIL MESSAGE {e.Code}: {e.Message}");
         }
 
         public void LogCustomEvent(CustomBuildEventArgs e)
         {
-            Console.WriteLine($"CUSTOM: {e.Message}");
+            Console.WriteLine(e.Message);
         }
 
         public bool BuildProjectFile(string projectFileName, string[] targetNames, IDictionary globalProperties,

Robust.Client.Injectors/RobustXamlILCompiler.cs

@@ -1,4 +1,6 @@
-using System.Linq;
+using System.Diagnostics;
+using System.Linq;
+using XamlX;
 using XamlX.Ast;
 using XamlX.Emit;
 using XamlX.IL;
@@ -11,11 +13,14 @@ namespace Robust.Build.Tasks
     /// Emitters & Transformers based on:
     /// - https://github.com/AvaloniaUI/Avalonia/blob/c85fa2b9977d251a31886c2534613b4730fbaeaf/src/Markup/Avalonia.Markup.Xaml.Loader/CompilerExtensions/Transformers/AvaloniaXamlIlRootObjectScopeTransformer.cs
     /// - https://github.com/AvaloniaUI/Avalonia/blob/c85fa2b9977d251a31886c2534613b4730fbaeaf/src/Markup/Avalonia.Markup.Xaml.Loader/CompilerExtensions/Transformers/AddNameScopeRegistration.cs
+    /// - https://github.com/AvaloniaUI/Avalonia/blob/afb8ae6f3c517dae912729511483995b16cb31af/src/Markup/Avalonia.Markup.Xaml.Loader/CompilerExtensions/Transformers/IgnoredDirectivesTransformer.cs
     /// </summary>
     public class RobustXamlILCompiler : XamlILCompiler
     {
         public RobustXamlILCompiler(TransformerConfiguration configuration, XamlLanguageEmitMappings<IXamlILEmitter, XamlILNodeEmitResult> emitMappings, bool fillWithDefaults) : base(configuration, emitMappings, fillWithDefaults)
         {
+            Transformers.Insert(0, new IgnoredDirectivesTransformer());
+
             Transformers.Add(new AddNameScopeRegistration());
             Transformers.Add(new RobustMarkRootObjectScopeNode());
 
@@ -197,5 +202,24 @@ namespace Robust.Build.Tasks
                 }
             }
         }
+
+        class IgnoredDirectivesTransformer : IXamlAstTransformer
+        {
+            public IXamlAstNode Transform(AstTransformationContext context, IXamlAstNode node)
+            {
+                if (node is XamlAstObjectNode astNode)
+                {
+                    astNode.Children.RemoveAll(n =>
+                        n is XamlAstXmlDirective dir &&
+                        dir.Namespace == XamlNamespaces.Xaml2006 &&
+                        (dir.Name == "Class" ||
+                         dir.Name == "Precompile" ||
+                         dir.Name == "FieldModifier" ||
+                         dir.Name == "ClassModifier"));
+                }
+
+                return node;
+            }
+        }
     }
 }

Robust.Client.Injectors/XamlCompiler.cs

@@ -280,8 +280,8 @@ namespace Robust.Build.Tasks
                     }
                     catch (Exception e)
                     {
-                        engine.LogWarningEvent(new BuildWarningEventArgs("XAMLIL", "", res.Uri, 0, 0, 0, 0,
-                            e.ToString(), "", "CompileRobustXaml"));
+                        engine.LogErrorEvent(new BuildErrorEventArgs("XAMLIL", "", res.FilePath, 0, 0, 0, 0,
+                            $"{res.FilePath}: {e.Message}", "", "CompileRobustXaml"));
                     }
                 }
                 return true;

Robust.Client/Audio/Midi/MidiManager.cs

@@ -65,7 +65,7 @@ namespace Robust.Client.Audio.Midi
         [Dependency] private readonly IEntityManager _entityManager = default!;
         [Dependency] private readonly IConfigurationManager _cfgMan = default!;
 
-        private SharedBroadPhaseSystem _broadPhaseSystem = default!;
+        private SharedBroadphaseSystem _broadPhaseSystem = default!;
 
         [ViewVariables]
         public bool IsAvailable
@@ -175,7 +175,7 @@ namespace Robust.Client.Audio.Midi
             _midiThread = new Thread(ThreadUpdate);
             _midiThread.Start();
 
-            _broadPhaseSystem = EntitySystem.Get<SharedBroadPhaseSystem>();
+            _broadPhaseSystem = EntitySystem.Get<SharedBroadphaseSystem>();
             FluidsynthInitialized = true;
         }
 

Robust.Client/Audio/Midi/MidiRenderer.cs

@@ -1,5 +1,4 @@
 using System;
-using System.Runtime.Intrinsics.X86;
 using NFluidsynth;
 using Robust.Client.Graphics;
 using Robust.Shared.Asynchronous;
@@ -8,7 +7,6 @@ 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;
 
@@ -220,7 +218,7 @@ namespace Robust.Client.Audio.Midi
             set
             {
                 lock (_playerStateLock)
-                    for (var i = 0; i < 16; i++)
+                    for (var i = 0; i < _synth.MidiChannelCount; i++)
                         _synth.ProgramChange(i, value);
 
                 _midiProgram = value;
@@ -234,7 +232,7 @@ namespace Robust.Client.Audio.Midi
             set
             {
                 lock (_playerStateLock)
-                    for (var i = 0; i < 16; i++)
+                    for (var i = 0; i < _synth.MidiChannelCount; i++)
                         _synth.BankSelect(i, value);
 
                 _midiBank = value;
@@ -248,7 +246,7 @@ namespace Robust.Client.Audio.Midi
             set
             {
                 lock (_playerStateLock)
-                    for (var i = 0; i < 16; i++)
+                    for (var i = 0; i < _synth.MidiChannelCount; i++)
                         _synth.SoundFontSelect(i, value);
 
                 _midiSoundfont = value;
@@ -575,16 +573,20 @@ namespace Robust.Client.Audio.Midi
                         // Sometimes MIDI files spam these for no good reason and I can't find any info on what they are.
                         case 1:
                         case 5:
+                        // MetaEvent -- SetTempo - 0x51
                         case 81:
+                            // Already handled by the player.
+                            return;
                         // System Messages - 0xF0
                         case 240:
-                            switch (midiEvent.Control)
+                            switch ((byte)midiEvent.Control)
                             {
                                 case 11:
                                     _synth.AllNotesOff(midiEvent.Channel);
                                     break;
                             }
-                            return;
+
+                            break;
 
                         default:
                             _midiSawmill.Warning("Unhandled midi event of type {0}", midiEvent.Type, midiEvent);
@@ -634,7 +636,7 @@ namespace Robust.Client.Audio.Midi
             _sequencer?.UnregisterClient(_debugRegister);
             _sequencer?.UnregisterClient(_synthRegister);
             _sequencer?.Dispose();
-            
+
             _synth?.Dispose();
             _player?.Dispose();
         }

Robust.Client/BaseClient.cs

@@ -1,4 +1,4 @@
-using System;
+using System;
 using System.Net;
 using Robust.Client.Debugging;
 using Robust.Client.GameObjects;

Robust.Client/ClientIoC.cs

@@ -25,6 +25,7 @@ using Robust.Shared.GameObjects;
 using Robust.Shared.IoC;
 using Robust.Shared.Map;
 using Robust.Shared.Network;
+using Robust.Shared.Physics;
 using Robust.Shared.Players;
 using Robust.Shared.Prototypes;
 using Robust.Shared.Reflection;
@@ -46,13 +47,15 @@ namespace Robust.Client
             IoCManager.Register<IClientMapManager, ClientMapManager>();
             IoCManager.Register<IEntityManager, ClientEntityManager>();
             IoCManager.Register<IEntityLookup, EntityLookup>();
+            IoCManager.Register<IReflectionManager, ClientReflectionManager>();
+            IoCManager.Register<IConsoleHost, ClientConsoleHost>();
+            IoCManager.Register<IClientConsoleHost, ClientConsoleHost>();
             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>();
             IoCManager.Register<IResourceManager, ResourceCache>();
             IoCManager.Register<IResourceManagerInternal, ResourceCache>();
             IoCManager.Register<IResourceCache, ResourceCache>();
@@ -72,10 +75,9 @@ namespace Robust.Client
             IoCManager.Register<IDebugDrawingManager, DebugDrawingManager>();
             IoCManager.Register<ILightManager, LightManager>();
             IoCManager.Register<IDiscordRichPresence, DiscordRichPresence>();
-            IoCManager.Register<IClientConsoleHost, ClientConsoleHost>();
-            IoCManager.Register<IConsoleHost, ClientConsoleHost>();
             IoCManager.Register<IMidiManager, MidiManager>();
             IoCManager.Register<IAuthManager, AuthManager>();
+            IoCManager.Register<IPhysicsManager, PhysicsManager>();
             switch (mode)
             {
                 case GameController.DisplayMode.Headless:

Robust.Client/Console/ClientConsoleHost.cs

@@ -49,7 +49,11 @@ namespace Robust.Client.Console
             NetManager.RegisterNetMessage<MsgConCmdAck>(HandleConCmdAck);
             NetManager.RegisterNetMessage<MsgConCmd>(ProcessCommand);
 
-            Reset();
+            _requestedCommands = false;
+            NetManager.Connected += OnNetworkConnected;
+
+            LoadConsoleCommands();
+            SendServerCommandRequest();
             LogManager.RootSawmill.AddHandler(new DebugConsoleLogHandler(this));
         }
 
@@ -61,17 +65,6 @@ namespace Robust.Client.Console
             ExecuteCommand(null, text);
         }
 
-        /// <inheritdoc />
-        public void Reset()
-        {
-            AvailableCommands.Clear();
-            _requestedCommands = false;
-            NetManager.Connected += OnNetworkConnected;
-
-            LoadConsoleCommands();
-            SendServerCommandRequest();
-        }
-
         /// <inheritdoc />
         public event EventHandler<AddStringArgs>? AddString;
 
@@ -90,6 +83,8 @@ namespace Robust.Client.Console
             OutputText(text, true, true);
         }
 
+        public override event ConAnyCommandCallback? AnyCommandExecuted;
+
         /// <inheritdoc />
         public override void ExecuteCommand(ICommonSession? session, string command)
         {
@@ -97,7 +92,7 @@ namespace Robust.Client.Console
                 return;
 
             // echo the command locally
-            WriteError(null, "> " + command);
+            WriteLine(null, "> " + command);
 
             //Commands are processed locally and then sent to the server to be processed there again.
             var args = new List<string>();
@@ -110,7 +105,11 @@ namespace Robust.Client.Console
             {
                 var command1 = AvailableCommands[commandName];
                 args.RemoveAt(0);
-                command1.Execute(new ConsoleShell(this, null), command, args.ToArray());
+                var shell = new ConsoleShell(this, null);
+                var cmdArgs = args.ToArray();
+
+                AnyCommandExecuted?.Invoke(shell, commandName, command, cmdArgs);
+                command1.Execute(shell, command, cmdArgs);
             }
             else
                 WriteError(null, "Unknown command: " + commandName);
@@ -142,6 +141,9 @@ namespace Robust.Client.Console
         private void OutputText(string text, bool local, bool error)
         {
             AddString?.Invoke(this, new AddStringArgs(text, local, error));
+
+            var level = error ? LogLevel.Warning : LogLevel.Info;
+            Logger.LogS(level, "CON", text);
         }
 
         private void OnNetworkConnected(object? sender, NetChannelArgs netChannelArgs)

Robust.Client/Console/Commands/Debug.cs

@@ -27,6 +27,7 @@ using Robust.Shared.Reflection;
 using Robust.Shared.Serialization;
 using Robust.Shared.Utility;
 using Robust.Shared.ViewVariables;
+using static Robust.Client.UserInterface.Controls.BoxContainer;
 
 namespace Robust.Client.Console.Commands
 {
@@ -77,7 +78,7 @@ namespace Robust.Client.Console.Commands
                     message.Append($"net ID: {registration.NetID}");
                 }
 
-                message.Append($", NSE: {registration.NetworkSynchronizeExistence}, references:");
+                message.Append($", References:");
 
                 shell.WriteLine(message.ToString());
 
@@ -459,13 +460,18 @@ namespace Robust.Client.Console.Commands
 
         public void Execute(IConsoleShell shell, string argStr, string[] args)
         {
-            var root = IoCManager.Resolve<IUserInterfaceManager>().RootControl;
+            var uiMgr = IoCManager.Resolve<IUserInterfaceManager>();
             var res = IoCManager.Resolve<IResourceManager>();
 
             using (var stream = res.UserData.Create(new ResourcePath("/guidump.txt")))
             using (var writer = new StreamWriter(stream, EncodingHelpers.UTF8))
             {
-                _writeNode(root, 0, writer);
+                foreach (var root in uiMgr.AllRoots)
+                {
+                    writer.WriteLine($"ROOT: {root}");
+                    _writeNode(root, 0, writer);
+                    writer.WriteLine("---------------");
+                }
             }
 
             shell.WriteLine("Saved guidump");
@@ -475,7 +481,7 @@ namespace Robust.Client.Console.Commands
         {
             var indentation = new string(' ', indents * 2);
             writer.WriteLine("{0}{1}", indentation, control);
-            foreach (var (key, value) in _propertyValuesFor(control))
+            foreach (var (key, value) in PropertyValuesFor(control))
             {
                 writer.WriteLine("{2} * {0}: {1}", key, value, indentation);
             }
@@ -486,14 +492,14 @@ namespace Robust.Client.Console.Commands
             }
         }
 
-        private static List<(string, string)> _propertyValuesFor(Control control)
+        internal static List<(string, string)> PropertyValuesFor(Control control)
         {
             var members = new List<(string, string)>();
             var type = control.GetType();
 
             foreach (var fieldInfo in type.GetAllFields())
             {
-                if (fieldInfo.GetCustomAttribute<ViewVariablesAttribute>() == null)
+                if (!ViewVariablesUtility.TryGetViewVariablesAccess(fieldInfo, out _))
                 {
                     continue;
                 }
@@ -503,7 +509,7 @@ namespace Robust.Client.Console.Commands
 
             foreach (var propertyInfo in type.GetAllProperties())
             {
-                if (propertyInfo.GetCustomAttribute<ViewVariablesAttribute>() == null)
+                if (!ViewVariablesUtility.TryGetViewVariablesAccess(propertyInfo, out _))
                 {
                     continue;
                 }
@@ -536,7 +542,10 @@ namespace Robust.Client.Console.Commands
             var scroll = new ScrollContainer();
             tabContainer.AddChild(scroll);
             //scroll.SetAnchorAndMarginPreset(Control.LayoutPreset.Wide);
-            var vBox = new VBoxContainer();
+            var vBox = new BoxContainer
+            {
+                Orientation = LayoutOrientation.Vertical
+            };
             scroll.AddChild(vBox);
 
             var progressBar = new ProgressBar { MaxValue = 10, Value = 5 };
@@ -594,7 +603,10 @@ namespace Robust.Client.Console.Commands
             }
 
             var group = new ButtonGroup();
-            var vBoxRadioButtons = new VBoxContainer();
+            var vBoxRadioButtons = new BoxContainer
+            {
+                Orientation = LayoutOrientation.Vertical
+            };
             for (var i = 0; i < 10; i++)
             {
                 vBoxRadioButtons.AddChild(new Button
@@ -610,8 +622,9 @@ namespace Robust.Client.Console.Commands
 
             TabContainer.SetTabTitle(vBoxRadioButtons, "Radio buttons!!");
 
-            tabContainer.AddChild(new VBoxContainer
+            tabContainer.AddChild(new BoxContainer
             {
+                Orientation = LayoutOrientation.Vertical,
                 Name = "Slider",
                 Children =
                 {
@@ -863,7 +876,7 @@ namespace Robust.Client.Console.Commands
             var chunkIndex = grid.LocalToChunkIndices(grid.MapToGrid(mousePos));
             var chunk = internalGrid.GetChunk(chunkIndex);
 
-            shell.WriteLine($"worldBounds: {chunk.CalcWorldBounds()} localBounds: {chunk.CalcLocalBounds()}");
+            shell.WriteLine($"worldBounds: {chunk.CalcWorldAABB()} localBounds: {chunk.CalcLocalBounds()}");
         }
     }
 

Robust.Client/Console/Commands/GridChunkBBCommand.cs

@@ -0,0 +1,17 @@
+using Robust.Client.GameObjects;
+using Robust.Shared.Console;
+using Robust.Shared.GameObjects;
+
+namespace Robust.Client.Console.Commands
+{
+    public class GridChunkBBCommand : IConsoleCommand
+    {
+        public string Command => "showchunkbb";
+        public string Description => "Displays chunk bounds for the purposes of rendering";
+        public string Help => $"{Command}";
+        public void Execute(IConsoleShell shell, string argStr, string[] args)
+        {
+            EntitySystem.Get<GridChunkBoundsDebugSystem>().Enabled ^= true;
+        }
+    }
+}

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/IClientConsoleHost.cs

@@ -11,11 +11,6 @@ namespace Robust.Client.Console
         /// </summary>
         void Initialize();
 
-        /// <summary>
-        /// Resets the console to a post-initialized state.
-        /// </summary>
-        void Reset();
-
         event EventHandler<AddStringArgs> AddString;
         event EventHandler<AddFormattedMessageArgs> AddFormatted;
 

Robust.Client/Console/ScriptConsoleClient.cs

@@ -13,10 +13,11 @@ using Microsoft.CodeAnalysis.Text;
 using Robust.Client.UserInterface.CustomControls;
 using Robust.Client.ViewVariables;
 using Robust.Shared.IoC;
-using Robust.Shared.Maths;
 using Robust.Shared.Reflection;
 using Robust.Shared.Scripting;
 using Robust.Shared.Utility;
+using SixLabors.ImageSharp;
+using Color = Robust.Shared.Maths.Color;
 
 #nullable enable
 
@@ -116,7 +117,7 @@ namespace Robust.Client.Console
             }
             else
             {
-                var options = ScriptInstanceShared.GetScriptOptions(_reflectionManager);
+                var options = ScriptInstanceShared.GetScriptOptions(_reflectionManager).AddReferences(typeof(Image).Assembly);
                 newScript = CSharpScript.Create(code, options, typeof(ScriptGlobals));
             }
 

Robust.Client/Console/WatchWindow.cs

@@ -11,6 +11,7 @@ using Robust.Shared.IoC;
 using Robust.Shared.Reflection;
 using Robust.Shared.Scripting;
 using Robust.Shared.Timing;
+using static Robust.Client.UserInterface.Controls.BoxContainer;
 
 namespace Robust.Client.Console
 {
@@ -18,7 +19,7 @@ namespace Robust.Client.Console
     {
         private readonly IReflectionManager _reflectionManager;
 
-        private readonly VBoxContainer _watchesVBox;
+        private readonly BoxContainer _watchesVBox;
         private readonly LineEdit _addWatchEdit;
         private readonly Button _addWatchButton;
 
@@ -31,17 +32,20 @@ namespace Robust.Client.Console
 
             Title = "Watch Window";
 
-            var mainVBox = new VBoxContainer
+            var mainVBox = new BoxContainer
             {
+                Orientation = LayoutOrientation.Vertical,
                 MinSize = (500, 300),
                 Children =
                 {
-                    (_watchesVBox = new VBoxContainer
+                    (_watchesVBox = new BoxContainer
                     {
+                        Orientation = LayoutOrientation.Vertical,
                         VerticalExpand = true
                     }),
-                    new HBoxContainer
+                    new BoxContainer
                     {
+                        Orientation = LayoutOrientation.Horizontal,
                         Children =
                         {
                             (_addWatchEdit = new HistoryLineEdit
@@ -105,8 +109,9 @@ namespace Robust.Client.Console
                 Button delButton;
                 _runner = runner;
 
-                AddChild(new HBoxContainer
+                AddChild(new BoxContainer
                 {
+                    Orientation = LayoutOrientation.Horizontal,
                     Children =
                     {
                         (_outputLabel = new Label
@@ -166,8 +171,9 @@ namespace Robust.Client.Console
             public CompilationErrorControl(string message)
             {
                 Button delButton;
-                AddChild(new HBoxContainer
+                AddChild(new BoxContainer
                 {
+                    Orientation = LayoutOrientation.Horizontal,
                     Children =
                     {
                         new Label

Robust.Client/ContentStart.cs

@@ -7,13 +7,13 @@ namespace Robust.Client
 #if 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, true, null, options);
+            GameController.Start(args, options, true, null);
         }
     }
 }

Robust.Client/Debugging/DebugDrawing.cs

@@ -162,12 +162,13 @@ namespace Robust.Client.Debugging
                 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))
+                foreach (var physBody in EntitySystem.Get<SharedBroadphaseSystem>().GetCollidingEntities(mapId, viewport))
                 {
+                    if (physBody.Owner.HasComponent<MapGridComponent>()) continue;
+
                     // all entities have a TransformComponent
                     var transform = physBody.Owner.Transform;
 
@@ -177,8 +178,9 @@ namespace Robust.Client.Debugging
                     foreach (var fixture in physBody.Fixtures)
                     {
                         var shape = fixture.Shape;
-                        var sleepPercent = physBody.Awake ? physBody.SleepTime / sleepThreshold : 1.0f;
+                        var sleepPercent = physBody.Awake ? 0.0f : 1.0f;
                         shape.DebugDraw(drawing, transform.WorldMatrix, in viewport, sleepPercent);
+                        drawing.SetTransform(in Matrix3.Identity);
                     }
 
                     foreach (var joint in physBody.Joints)
@@ -187,6 +189,7 @@ namespace Robust.Client.Debugging
                         drawnJoints.Add(joint);
 
                         joint.DebugDraw(drawing, in viewport);
+                        drawing.SetTransform(in Matrix3.Identity);
                     }
 
                     if (worldBox.Contains(mouseWorldPos))

Robust.Client/Debugging/DebugPhysicsSystem.cs

@@ -28,6 +28,7 @@ using Robust.Shared.Enums;
 using Robust.Shared.GameObjects;
 using Robust.Shared.IoC;
 using Robust.Shared.Maths;
+using Robust.Shared.Physics;
 using Robust.Shared.Physics.Collision;
 using Robust.Shared.Physics.Dynamics;
 using Robust.Shared.Physics.Dynamics.Contacts;
@@ -40,6 +41,8 @@ namespace Robust.Client.Debugging
          * Used for debugging shapes, controllers, joints, contacts
          */
 
+        [Dependency] private readonly IPhysicsManager _physicsManager = default!;
+
         private const int MaxContactPoints = 2048;
         internal int PointCount;
 
@@ -79,8 +82,7 @@ namespace Robust.Client.Debugging
                 CollisionManager.GetPointStates(out state1, out state2, oldManifold, manifold);
 
                 Span<Vector2> points = stackalloc Vector2[2];
-                Vector2 normal;
-                contact.GetWorldManifold(out normal, points);
+                contact.GetWorldManifold(_physicsManager, out var normal, points);
 
                 for (int i = 0; i < manifold.PointCount && PointCount < MaxContactPoints; ++i)
                 {

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

@@ -22,10 +22,10 @@ namespace Robust.Client
 
         public static void Main(string[] args)
         {
-            Start(args);
+            Start(args, new GameControllerOptions());
         }
 
-        public static void Start(string[] args, bool contentStart = false, IMainArgs? loaderArgs=null, GameControllerOptions? options = null)
+        public static void Start(string[] args, GameControllerOptions options, bool contentStart = false, IMainArgs? loaderArgs=null)
         {
             if (_hasStarted)
             {
@@ -40,7 +40,7 @@ namespace Robust.Client
             }
         }
 
-        private static void ParsedMain(CommandLineArgs args, bool contentStart, IMainArgs? loaderArgs, GameControllerOptions? options)
+        private static void ParsedMain(CommandLineArgs args, bool contentStart, IMainArgs? loaderArgs, GameControllerOptions options)
         {
             IoCManager.InitThread();
 
@@ -51,15 +51,13 @@ namespace Robust.Client
             var gc = IoCManager.Resolve<GameController>();
             gc.SetCommandLineArgs(args);
             gc._loaderArgs = loaderArgs;
-            if(options != null)
-                gc.Options = options;
 
             // When the game is ran with the startup executable being content,
             // we have to disable the separate load context.
             // Otherwise the content assemblies will be loaded twice which causes *many* fun bugs.
             gc.ContentStart = contentStart;
 
-            gc.Run(mode);
+            gc.Run(mode, options);
         }
 
         public void OverrideMainLoop(IGameLoop gameLoop)
@@ -67,9 +65,9 @@ namespace Robust.Client
             _mainLoop = gameLoop;
         }
 
-        public void Run(DisplayMode mode, Func<ILogHandler>? logHandlerFactory = null)
+        public void Run(DisplayMode mode, GameControllerOptions options, Func<ILogHandler>? logHandlerFactory = null)
         {
-            if (!StartupSystemSplash(logHandlerFactory))
+            if (!StartupSystemSplash(options, logHandlerFactory))
             {
                 Logger.Fatal("Failed to start game controller!");
                 return;

Robust.Client/GameController/GameController.cs

@@ -2,6 +2,7 @@ using System;
 using System.Collections.Generic;
 using System.IO;
 using System.Net;
+using System.Runtime;
 using System.Threading.Tasks;
 using Robust.Client.Audio.Midi;
 using Robust.Client.Console;
@@ -75,8 +76,6 @@ namespace Robust.Client
         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;
@@ -95,7 +94,7 @@ namespace Robust.Client
             _modLoader.SetUseLoadContext(!ContentStart);
             _modLoader.SetEnableSandboxing(Options.Sandboxing);
 
-            if (!_modLoader.TryLoadModulesFrom(new ResourcePath("/Assemblies/"), Options.ContentModulePrefix))
+            if (!_modLoader.TryLoadModulesFrom(Options.AssemblyDirectory, Options.ContentModulePrefix))
             {
                 Logger.Fatal("Errors while loading content assemblies.");
                 return false;
@@ -141,6 +140,7 @@ namespace Robust.Client
 
             _authManager.LoadFromEnv();
 
+            GCSettings.LargeObjectHeapCompactionMode = GCLargeObjectHeapCompactionMode.CompactOnce;
             GC.Collect();
 
             // Setup main loop
@@ -196,8 +196,9 @@ namespace Robust.Client
             return true;
         }
 
-        internal bool StartupSystemSplash(Func<ILogHandler>? logHandlerFactory)
+        internal bool StartupSystemSplash(GameControllerOptions options, Func<ILogHandler>? logHandlerFactory)
         {
+            Options = options;
             ReadInitialLaunchState();
 
             SetupLogging(_logManager, logHandlerFactory ?? (() => new ConsoleLogHandler()));
@@ -234,7 +235,7 @@ namespace Robust.Client
             _configurationManager.LoadCVarsFromAssembly(typeof(GameController).Assembly); // Client
             _configurationManager.LoadCVarsFromAssembly(typeof(IConfigurationManager).Assembly); // Shared
 
-            if (LoadConfigAndUserData)
+            if (Options.LoadConfigAndUserData)
             {
                 var configFile = Path.Combine(userDataDir, Options.ConfigFileName);
                 if (File.Exists(configFile))
@@ -256,15 +257,24 @@ namespace Robust.Client
                 _configurationManager.OverrideConVars(_commandLineArgs.CVars);
             }
 
+            {
+                // Handle GameControllerOptions implicit CVar overrides.
+                _configurationManager.OverrideConVars(new []
+                {
+                    (CVars.DisplayWindowIconSet.Name, options.WindowIconSet.ToString()),
+                    (CVars.DisplaySplashLogo.Name, options.SplashLogo.ToString())
+                });
+            }
+
             ProfileOptSetup.Setup(_configurationManager);
 
-            _resourceCache.Initialize(LoadConfigAndUserData ? userDataDir : null);
+            _resourceCache.Initialize(Options.LoadConfigAndUserData ? userDataDir : null);
 
             var mountOptions = _commandLineArgs != null
                 ? MountOptions.Merge(_commandLineArgs.MountOptions, Options.MountOptions) : Options.MountOptions;
 
-            ProgramShared.DoMounts(_resourceCache, mountOptions, Options.ContentBuildDirectory,
-                _loaderArgs != null && !Options.ResourceMountDisabled, ContentStart);
+            ProgramShared.DoMounts(_resourceCache, mountOptions, Options.ContentBuildDirectory, Options.AssemblyDirectory,
+                Options.LoadContentResources, _loaderArgs != null && !Options.ResourceMountDisabled, ContentStart);
 
             if (_loaderArgs != null)
             {
@@ -473,6 +483,8 @@ namespace Robust.Client
 
         internal void Cleanup()
         {
+            _modLoader.Shutdown();
+
             _networkManager.Shutdown("Client shutting down");
             _midiManager.Shutdown();
             IoCManager.Resolve<IEntityLookup>().Shutdown();

Robust.Client/GameControllerOptions.cs

@@ -42,16 +42,41 @@ namespace Robust.Client
         /// </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>
+        /// Directory resource path containing window icons to load.
+        /// </summary>
+        public ResourcePath WindowIconSet { get; init; } = new("/Textures/Logo/icon");
+
+        /// <summary>
+        /// Resource path for splash image to show when the game starts up.
+        /// </summary>
+        public ResourcePath SplashLogo { get; init; } = new("/Textures/Logo/logo.png");
+
         /// <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>

Robust.Client/GameObjects/ClientComponentFactory.cs

@@ -1,12 +1,15 @@
+using Robust.Shared.Console;
 using Robust.Shared.Containers;
 using Robust.Shared.GameObjects;
-using Robust.Shared.Physics;
+using Robust.Shared.IoC;
+using Robust.Shared.Reflection;
 
 namespace Robust.Client.GameObjects
 {
-    public class ClientComponentFactory : ComponentFactory
+    internal class ClientComponentFactory : ComponentFactory
     {
-        public ClientComponentFactory()
+        public ClientComponentFactory(IDynamicTypeFactoryInternal typeFactory, IReflectionManager reflectionManager, IConsoleHost conHost)
+            : base(typeFactory, reflectionManager, conHost)
         {
             // Required for the engine to work
             RegisterIgnore("KeyBindingInput");
@@ -22,6 +25,7 @@ namespace Robust.Client.GameObjects
             RegisterClass<InputComponent>();
             RegisterClass<SpriteComponent>();
             RegisterClass<ClientOccluderComponent>();
+            RegisterClass<OccluderTreeComponent>();
             RegisterClass<EyeComponent>();
             RegisterClass<AppearanceComponent>();
             RegisterClass<AppearanceTestComponent>();

Robust.Client/GameObjects/ClientEntityManager.cs

@@ -109,13 +109,15 @@ namespace Robust.Client.GameObjects
         [Obsolete("Component Messages are deprecated, use Entity Events instead.")]
         public void SendComponentNetworkMessage(INetChannel? channel, IEntity entity, IComponent component, ComponentMessage message)
         {
-            if (!component.NetID.HasValue)
+            var netId = ComponentFactory.GetRegistration(component.GetType()).NetID;
+
+            if (!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.NetId = netId.Value;
             msg.ComponentMessage = message;
             msg.SourceTick = _gameTiming.CurTick;
 

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

@@ -84,6 +84,23 @@ namespace Robust.Client.GameObjects
             if (curState is not AppearanceComponentState actualState)
                 return;
 
+            var stateDiff = data.Count != actualState.Data.Count;
+
+            if (!stateDiff)
+            {
+                foreach (var (key, value) in data)
+                {
+                    if (!actualState.Data.TryGetValue(key, out var stateValue) ||
+                        !value.Equals(stateValue))
+                    {
+                        stateDiff = true;
+                        break;
+                    }
+                }
+            }
+
+            if (!stateDiff) return;
+
             data = actualState.Data;
             MarkDirty();
         }

Robust.Client/GameObjects/Components/Input/InputComponent.cs

@@ -1,7 +1,5 @@
 using Robust.Shared.GameObjects;
 using Robust.Shared.Input;
-using Robust.Shared.Prototypes;
-using Robust.Shared.Serialization;
 using Robust.Shared.Serialization.Manager.Attributes;
 using Robust.Shared.ViewVariables;
 
@@ -10,7 +8,7 @@ namespace Robust.Client.GameObjects
     /// <summary>
     ///     Defines data fields used in the <see cref="InputSystem"/>.
     /// </summary>
-    class InputComponent : Component
+    public class InputComponent : Component
     {
         /// <inheritdoc />
         public override string Name => "Input";

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

@@ -1,11 +1,6 @@
-using System;
-using System.Collections.Generic;
 using Robust.Client.Graphics;
-using Robust.Client.ResourceManagement;
 using Robust.Shared.Animations;
 using Robust.Shared.GameObjects;
-using Robust.Shared.IoC;
-using Robust.Shared.Map;
 using Robust.Shared.Maths;
 using Robust.Shared.Serialization;
 using Robust.Shared.Serialization.Manager.Attributes;
@@ -14,41 +9,28 @@ using Robust.Shared.ViewVariables;
 namespace Robust.Client.GameObjects
 {
     [RegisterComponent]
-    [ComponentReference(typeof(IPointLightComponent))]
-    public class PointLightComponent : Component, IPointLightComponent, ISerializationHooks
+    [ComponentReference(typeof(SharedPointLightComponent))]
+    public class PointLightComponent : SharedPointLightComponent, ISerializationHooks
     {
-        [Dependency] private readonly IResourceCache _resourceCache = default!;
-
-        public override string Name => "PointLight";
-        public override uint? NetID => NetIDs.POINT_LIGHT;
-
         internal bool TreeUpdateQueued { get; set; }
 
         [ViewVariables(VVAccess.ReadWrite)]
         [Animatable]
-        public Color Color
+        public override Color Color
         {
             get => _color;
-            set => _color = value;
-        }
-
-        [ViewVariables(VVAccess.ReadWrite)]
-        public Vector2 Offset
-        {
-            get => _offset;
-            set => _offset = value;
+            set => base.Color = value;
         }
 
         [ViewVariables(VVAccess.ReadWrite)]
         [Animatable]
-        public bool Enabled
+        public override bool Enabled
         {
             get => _enabled;
             set
             {
                 if (_enabled == value) return;
-
-                _enabled = value;
+                base.Enabled = value;
                 Owner.EntityManager.EventBus.RaiseLocalEvent(Owner.Uid, new PointLightUpdateEvent());
             }
         }
@@ -89,7 +71,6 @@ namespace Robust.Client.GameObjects
             set => _rotation = value;
         }
 
-        /// <inheritdoc />
         /// <summary>
         /// The resource path to the mask texture the light will use.
         /// </summary>
@@ -99,8 +80,9 @@ namespace Robust.Client.GameObjects
             get => _maskPath;
             set
             {
+                if (_maskPath?.Equals(value) != false) return;
                 _maskPath = value;
-                UpdateMask();
+                EntitySystem.Get<PointLightSystem>().UpdateMask(this);
             }
         }
 
@@ -138,16 +120,8 @@ namespace Robust.Client.GameObjects
             set => _visibleNested = value;
         }
 
-        [DataField("radius")]
-        private float _radius = 5f;
         [DataField("nestedvisible")]
         private bool _visibleNested = true;
-        [DataField("color")]
-        private Color _color = Color.White;
-        [DataField("offset")]
-        private Vector2 _offset = Vector2.Zero;
-        [DataField("enabled")]
-        private bool _enabled = true;
         [DataField("autoRot")]
         private bool _maskAutoRotate;
         private Angle _rotation;
@@ -156,81 +130,27 @@ namespace Robust.Client.GameObjects
         [DataField("softness")]
         private float _softness = 1f;
         [DataField("mask")]
-        private string? _maskPath;
+        internal string? _maskPath;
 
         /// <summary>
         ///     Radius, in meters.
         /// </summary>
         [ViewVariables(VVAccess.ReadWrite)]
         [Animatable]
-        public float Radius
+        public override float Radius
         {
             get => _radius;
             set
             {
-                _radius = MathF.Max(value, 0.01f); // setting radius to 0 causes exceptions, so just use a value close enough to zero that it's unnoticeable.
+                if (MathHelper.CloseTo(value, _radius)) return;
+
+                base.Radius = value;
                 Owner.EntityManager.EventBus.RaiseEvent(EventSource.Local, new PointLightRadiusChangedEvent(this));
             }
         }
 
-        private void UpdateMask()
-        {
-            if (_maskPath is not null)
-                Mask = _resourceCache.GetResource<TextureResource>(_maskPath);
-            else
-                Mask = null;
-        }
-
-        /// <summary>
-        /// What MapId we are intersecting for RenderingTreeSystem.
-        /// </summary>
         [ViewVariables]
-        internal MapId IntersectingMapId { get; set; } = MapId.Nullspace;
-
-        /// <summary>
-        /// What grids we're on for RenderingTreeSystem.
-        /// </summary>
-        [ViewVariables]
-        internal List<GridId> IntersectingGrids = new();
-
-        void ISerializationHooks.AfterDeserialization()
-        {
-            if (_maskPath != null)
-            {
-                Mask = IoCManager.Resolve<IResourceCache>().GetResource<TextureResource>(_maskPath);
-            }
-        }
-
-        protected override void Initialize()
-        {
-            base.Initialize();
-            UpdateMask();
-        }
-
-        protected override void OnRemove()
-        {
-            base.OnRemove();
-
-            var map = Owner.Transform.MapID;
-            if (map != MapId.Nullspace)
-            {
-                Owner.EntityManager.EventBus.RaiseEvent(EventSource.Local,
-                    new RenderTreeRemoveLightEvent(this, map));
-            }
-        }
-
-        /// <inheritdoc />
-        public override void HandleComponentState(ComponentState? curState, ComponentState? nextState)
-        {
-            if (curState == null)
-                return;
-
-            var newState = (PointLightComponentState) curState;
-            Enabled = newState.Enabled;
-            Radius = newState.Radius;
-            Offset = newState.Offset;
-            Color = newState.Color;
-        }
+        internal RenderingTreeComponent? RenderTree { get; set; }
     }
 
     public class PointLightRadiusChangedEvent : EntityEventArgs

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

@@ -228,6 +228,6 @@ namespace Robust.Client.GameObjects
         /// <summary>
         ///     Calculate sprite bounding box in world-space coordinates.
         /// </summary>
-        Box2 CalculateBoundingBox();
+        Box2 CalculateBoundingBox(Vector2 worldPos);
     }
 }

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

@@ -0,0 +1,90 @@
+using System.Collections.Generic;
+using Robust.Client.Graphics;
+using Robust.Client.Graphics.Clyde;
+using Robust.Shared.Console;
+using Robust.Shared.Enums;
+using Robust.Shared.GameObjects;
+using Robust.Shared.IoC;
+using Robust.Shared.Maths;
+using Robust.Shared.Utility;
+
+namespace Robust.Client.GameObjects
+{
+    public sealed class ShowSpriteBBCommand : IConsoleCommand
+    {
+        public string Command => "showspritebb";
+        public string Description => "Toggle whether sprite bounds are shown";
+        public string Help => $"{Command}";
+        public void Execute(IConsoleShell shell, string argStr, string[] args)
+        {
+            EntitySystem.Get<SpriteBoundsSystem>().Enabled ^= true;
+        }
+    }
+
+    public sealed class SpriteBoundsSystem : EntitySystem
+    {
+        private SpriteBoundsOverlay? _overlay;
+
+        public bool Enabled
+        {
+            get => _enabled;
+            set
+            {
+                if (_enabled == value) return;
+
+                _enabled = value;
+
+                if (_enabled)
+                {
+                    DebugTools.AssertNull(_overlay);
+                    var overlayManager = IoCManager.Resolve<IOverlayManager>();
+                    _overlay = new SpriteBoundsOverlay(EntitySystem.Get<RenderingTreeSystem>(), IoCManager.Resolve<IEyeManager>());
+                    overlayManager.AddOverlay(_overlay);
+                }
+                else
+                {
+                    if (_overlay == null) return;
+                    var overlayManager = IoCManager.Resolve<IOverlayManager>();
+                    overlayManager.RemoveOverlay(_overlay);
+                    _overlay = null;
+                }
+            }
+        }
+
+        private bool _enabled;
+    }
+
+    public class SpriteBoundsOverlay : Overlay
+    {
+        public override OverlaySpace Space => OverlaySpace.WorldSpace;
+
+        private readonly IEyeManager _eyeManager = default!;
+        private RenderingTreeSystem _renderTree;
+
+        public SpriteBoundsOverlay(RenderingTreeSystem renderTree, IEyeManager eyeManager)
+        {
+            _renderTree = renderTree;
+            _eyeManager = eyeManager;
+        }
+
+        protected internal override void Draw(in OverlayDrawArgs args)
+        {
+            var handle = args.WorldHandle;
+            var currentMap = _eyeManager.CurrentMap;
+            var viewport = _eyeManager.GetWorldViewport();
+
+            foreach (var comp in _renderTree.GetRenderTrees(currentMap, viewport))
+            {
+                var localAABB = viewport.Translated(-comp.Owner.Transform.WorldPosition);
+
+                foreach (var sprite in comp.SpriteTree.QueryAabb(localAABB))
+                {
+                    var worldPos = sprite.Owner.Transform.WorldPosition;
+                    var bounds = sprite.CalculateBoundingBox(worldPos);
+                    handle.DrawRect(bounds, Color.Red.WithAlpha(0.2f));
+                    handle.DrawRect(bounds.Scale(0.2f).Translated(-new Vector2(0f, bounds.Extents.Y)), Color.Blue.WithAlpha(0.5f));
+                }
+            }
+        }
+    }
+}

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

@@ -131,17 +131,8 @@ namespace Robust.Client.GameObjects
         [DataField("directional")]
         private bool _directional = true;
 
-        /// <summary>
-        /// What MapId we are intersecting for RenderingTreeSystem.
-        /// </summary>
         [ViewVariables]
-        internal MapId IntersectingMapId { get; set; } = MapId.Nullspace;
-
-        /// <summary>
-        /// What grids we're on for RenderingTreeSystem.
-        /// </summary>
-        [ViewVariables]
-        internal List<GridId> IntersectingGrids { get; } = new();
+        internal RenderingTreeComponent? RenderTree { get; set; } = null;
 
         [DataField("layerDatums")]
         private List<PrototypeLayerData> LayerDatums
@@ -374,7 +365,7 @@ namespace Robust.Client.GameObjects
                     }
                     else
                     {
-                        Logger.ErrorS(LogCategory, "Unable to load RSI '{0}'. Trace:\n{1}", rsiPath);
+                        Logger.ErrorS(LogCategory, "Unable to load RSI '{0}'.", rsiPath);
                     }
                 }
             }
@@ -1221,9 +1212,9 @@ namespace Robust.Client.GameObjects
         public IEnumerable<ISpriteLayer> AllLayers => Layers;
 
         // Lobby SpriteView rendering path
-        internal void Render(DrawingHandleWorld drawingHandle, Angle worldRotation, Direction? overrideDirection = null)
+        internal void Render(DrawingHandleWorld drawingHandle, Angle eyeRotation, Angle worldRotation, Direction? overrideDirection = null)
         {
-            RenderInternal(drawingHandle, worldRotation, Vector2.Zero, overrideDirection);
+            RenderInternal(drawingHandle, eyeRotation, worldRotation, Vector2.Zero, overrideDirection);
         }
 
         [DataField("noRot")]
@@ -1248,7 +1239,7 @@ namespace Robust.Client.GameObjects
         public bool EnableDirectionOverride { get => _enableOverrideDirection; set => _enableOverrideDirection = value; }
 
         // Sprite rendering path
-        internal void Render(DrawingHandleWorld drawingHandle, in Angle worldRotation, in Vector2 worldPosition)
+        internal void Render(DrawingHandleWorld drawingHandle, Angle eyeRotation, in Angle worldRotation, in Vector2 worldPosition)
         {
             Direction? overrideDir = null;
             if (_enableOverrideDirection)
@@ -1256,16 +1247,18 @@ namespace Robust.Client.GameObjects
                 overrideDir = _overrideDirection;
             }
 
-            RenderInternal(drawingHandle, worldRotation, worldPosition, overrideDir);
+            RenderInternal(drawingHandle, eyeRotation, worldRotation, worldPosition, overrideDir);
         }
 
-        private void CalcModelMatrix(int numDirs, Angle worldRotation, Vector2 worldPosition, out Matrix3 modelMatrix)
+        private void CalcModelMatrix(int numDirs, Angle eyeRotation, Angle worldRotation, Vector2 worldPosition, out Matrix3 modelMatrix)
         {
             Angle angle;
 
             if (_screenLock)
             {
-                angle = Angle.Zero;
+                // Negate the eye rotation in the model matrix, so that later when the view matrix is applied the
+                // sprite will be locked upright to the screen
+                angle = new Angle(-eyeRotation.Theta);
             }
             else
             {
@@ -1276,7 +1269,7 @@ namespace Robust.Client.GameObjects
             modelMatrix = Matrix3.CreateTransform(in worldPosition, in sWorldRotation);
         }
 
-        private void RenderInternal(DrawingHandleWorld drawingHandle, Angle worldRotation, Vector2 worldPosition, Direction? overrideDirection)
+        private void RenderInternal(DrawingHandleWorld drawingHandle, Angle eyeRotation, Angle worldRotation, Vector2 worldPosition, Direction? overrideDirection)
         {
             var localMatrix = GetLocalMatrix();
 
@@ -1289,7 +1282,7 @@ namespace Robust.Client.GameObjects
 
                 var numDirs = GetLayerDirectionCount(layer);
 
-                CalcModelMatrix(numDirs, worldRotation, worldPosition, out var modelMatrix);
+                CalcModelMatrix(numDirs, eyeRotation, worldRotation, worldPosition, out var modelMatrix);
                 Matrix3.Multiply(ref localMatrix, ref modelMatrix, out var transformMatrix);
                 drawingHandle.SetTransform(in transformMatrix);
 
@@ -1519,6 +1512,11 @@ namespace Robust.Client.GameObjects
 
         private void QueueUpdateIsInert()
         {
+            // Look this was an easy way to get bounds checks for layer updates.
+            // If you really want it optimal you'll need to comb through all 2k lines of spritecomponent.
+            if (Owner?.EntityManager?.EventBus != null)
+                UpdateBounds();
+
             if (_inertUpdateQueued)
                 return;
 
@@ -1633,11 +1631,11 @@ namespace Robust.Client.GameObjects
         }
 
         /// <inheritdoc/>
-        public Box2 CalculateBoundingBox()
+        public Box2 CalculateBoundingBox(Vector2 worldPos)
         {
             // fast check for empty sprites
             if (Layers.Count == 0)
-                return new Box2();
+                return new Box2(worldPos, worldPos);
 
             // we need to calculate bounding box taking into account all nested layers
             // because layers can have offsets, scale or rotation we need to calculate a new BB
@@ -1660,11 +1658,15 @@ namespace Robust.Client.GameObjects
                 new Box2Rotated(spriteBox, Rotation).CalcBoundingBox() : spriteBox;
 
             // move it all to world transform system (with sprite offset)
-            var worldPosition = Owner.Transform.WorldPosition;
-            var worldBB = spriteBB.Translated(Offset + worldPosition);
+            var worldBB = spriteBB.Translated(Offset + worldPos);
             return worldBB;
         }
 
+        internal void UpdateBounds()
+        {
+            Owner.EntityManager.EventBus.RaiseLocalEvent(Owner.Uid, new SpriteUpdateEvent());
+        }
+
         /// <summary>
         ///     Enum to "offset" a cardinal direction.
         /// </summary>
@@ -1720,7 +1722,19 @@ namespace Robust.Client.GameObjects
             public bool AutoAnimated = true;
 
             [ViewVariables(VVAccess.ReadWrite)]
-            public Vector2 Offset { get; set; }
+            public Vector2 Offset
+            {
+                get => _offset;
+                set
+                {
+                    if (_offset.EqualsApprox(value)) return;
+
+                    _offset = value;
+                    _parent.UpdateBounds();
+                }
+            }
+
+            private Vector2 _offset;
 
             [ViewVariables]
             public DirectionOffset DirOffset { get; set; }
@@ -1992,7 +2006,6 @@ namespace Robust.Client.GameObjects
                 // TODO: scale & rotation for layers is currently unimplemented.
                 return Box2.CenteredAround(Offset, PixelSize / EyeManager.PixelsPerMeter);
             }
-
         }
 
         void IAnimationProperties.SetAnimatableProperty(string name, object value)

Robust.Client/GameObjects/Components/RenderingTreeComponent.cs

@@ -0,0 +1,59 @@
+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;
+            var bounds = value.CalculateBoundingBox(worldPos);
+            var tree = RenderingTreeSystem.GetRenderTree(value.Owner);
+
+            var offset = -tree?.Owner.Transform.WorldPosition ?? Vector2.Zero;
+
+            return bounds.Translated(offset);
+        }
+
+        private static Box2 LightAabbFunc(in PointLightComponent value)
+        {
+            var worldPos = value.Owner.Transform.WorldPosition;
+            var tree = RenderingTreeSystem.GetRenderTree(value.Owner);
+            var boxSize = value.Radius * 2;
+
+            var pos = worldPos - tree?.Owner.Transform.WorldPosition ?? Vector2.Zero;
+
+            return Box2.CenteredAround(pos, (boxSize, boxSize));
+        }
+
+        internal static Box2 SpriteAabbFunc(SpriteComponent value, Vector2? worldPos = null)
+        {
+            worldPos ??= value.Owner.Transform.WorldPosition;
+            var bounds = value.CalculateBoundingBox(worldPos.Value);
+            var tree = RenderingTreeSystem.GetRenderTree(value.Owner);
+
+            var offset = -tree?.Owner.Transform.WorldPosition ?? Vector2.Zero;
+
+            return bounds.Translated(offset);
+        }
+
+        internal static Box2 LightAabbFunc(PointLightComponent value, Vector2? worldPos = null)
+        {
+            worldPos ??= value.Owner.Transform.WorldPosition;
+            var tree = RenderingTreeSystem.GetRenderTree(value.Owner);
+            var boxSize = value.Radius * 2;
+
+            var pos = worldPos - tree?.Owner.Transform.WorldPosition ?? Vector2.Zero;
+
+            return Box2.CenteredAround(pos, (boxSize, boxSize));
+        }
+    }
+}

Robust.Client/GameObjects/EntitySystems/AudioSystem.cs

@@ -1,4 +1,6 @@
+using System;
 using System.Collections.Generic;
+using System.IO;
 using JetBrains.Annotations;
 using Robust.Client.Audio;
 using Robust.Client.Graphics;
@@ -8,6 +10,7 @@ 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;
@@ -23,8 +26,7 @@ namespace Robust.Client.GameObjects
         [Dependency] private readonly IClydeAudio _clyde = default!;
         [Dependency] private readonly IEyeManager _eyeManager = default!;
         [Dependency] private readonly IEntityManager _entityManager = default!;
-
-        private SharedBroadPhaseSystem _broadPhaseSystem = default!;
+        [Dependency] private readonly SharedBroadphaseSystem _broadPhaseSystem = default!;
 
         private readonly List<PlayingStream> _playingClydeStreams = new();
 
@@ -38,7 +40,6 @@ namespace Robust.Client.GameObjects
             SubscribeNetworkEvent<StopAudioMessageClient>(StopAudioMessageHandler);
 
             SubscribeLocalEvent<SoundSystem.QueryAudioSystem>((ev => ev.Audio = this));
-            _broadPhaseSystem = Get<SharedBroadPhaseSystem>();
         }
 
         private void StopAudioMessageHandler(StopAudioMessageClient ev)
@@ -98,6 +99,8 @@ namespace Robust.Client.GameObjects
             // Update positions of streams every frame.
             try
             {
+                var ourPos = _eyeManager.CurrentEye.Position.Position;
+
                 foreach (var stream in _playingClydeStreams)
                 {
                     if (!stream.Source.IsPlaying)
@@ -141,7 +144,7 @@ namespace Robust.Client.GameObjects
                         }
                         else
                         {
-                            var sourceRelative = _eyeManager.CurrentEye.Position.Position - pos.Position;
+                            var sourceRelative = ourPos - pos.Position;
                             var occlusion = 0f;
                             if (sourceRelative.Length > 0)
                             {
@@ -155,14 +158,54 @@ namespace Robust.Client.GameObjects
                                     stream.TrackingEntity);
                             }
 
-                            stream.Source.SetVolume(stream.Volume);
+                            var distance = MathF.Max(stream.ReferenceDistance, MathF.Min(sourceRelative.Length, stream.MaxDistance));
+                            float gain;
+
+                            // Technically these are formulas for gain not decibels but EHHHHHHHH.
+                            switch (stream.Attenuation)
+                            {
+                                case Attenuation.Default:
+                                    gain = 1f;
+                                    break;
+                                // You thought I'd implement clamping per source? Hell no that's just for the overall OpenAL setting
+                                // I didn't even wanna implement this much for linear but figured it'd be cleaner.
+                                case Attenuation.InverseDistanceClamped:
+                                case Attenuation.InverseDistance:
+                                    gain = stream.ReferenceDistance /
+                                           (stream.ReferenceDistance + stream.RolloffFactor * (distance - stream.ReferenceDistance));
+
+                                    break;
+                                case Attenuation.LinearDistanceClamped:
+                                case Attenuation.LinearDistance:
+                                    gain = 1f - stream.RolloffFactor * (distance - stream.ReferenceDistance) /
+                                        (stream.MaxDistance - stream.ReferenceDistance);
+
+                                    break;
+                                case Attenuation.ExponentDistanceClamped:
+                                case Attenuation.ExponentDistance:
+                                    gain = MathF.Pow((distance / stream.ReferenceDistance),
+                                        (-stream.RolloffFactor));
+                                    break;
+                                default:
+                                    throw new ArgumentOutOfRangeException($"No implemented attenuation for {stream.Attenuation.ToString()}");
+                            }
+
+                            var volume = MathF.Pow(10, stream.Volume / 10);
+                            var actualGain = MathF.Max(0f, volume * gain);
+
+                            stream.Source.SetVolumeDirect(actualGain);
                             stream.Source.SetOcclusion(occlusion);
                         }
 
-                        if (!stream.Source.SetPosition(pos.Position))
+                        SetAudioPos(stream, stream.Attenuation != Attenuation.NoAttenuation ? pos.Position : ourPos);
+
+                        void SetAudioPos(PlayingStream stream, Vector2 pos)
                         {
-                            Logger.Warning("Interrupting positional audio, can't set position.");
-                            stream.Source.StopPlaying();
+                            if (!stream.Source.SetPosition(pos))
+                            {
+                                Logger.Warning("Interrupting positional audio, can't set position.");
+                                stream.Source.StopPlaying();
+                            }
                         }
 
                         if (stream.TrackingEntity != null)
@@ -219,6 +262,10 @@ namespace Robust.Client.GameObjects
             var playing = new PlayingStream
             {
                 Source = source,
+                Attenuation = audioParams?.Attenuation ?? Attenuation.Default,
+                MaxDistance = audioParams?.MaxDistance ?? float.MaxValue,
+                ReferenceDistance = audioParams?.ReferenceDistance ?? 1f,
+                RolloffFactor = audioParams?.RolloffFactor ?? 1f,
                 Volume = audioParams?.Volume ?? 0
             };
             _playingClydeStreams.Add(playing);
@@ -265,6 +312,10 @@ namespace Robust.Client.GameObjects
             {
                 Source = source,
                 TrackingEntity = entity,
+                Attenuation = audioParams?.Attenuation ?? Attenuation.Default,
+                MaxDistance = audioParams?.MaxDistance ?? float.MaxValue,
+                ReferenceDistance = audioParams?.ReferenceDistance ?? 1f,
+                RolloffFactor = audioParams?.RolloffFactor ?? 1f,
                 Volume = audioParams?.Volume ?? 0
             };
             _playingClydeStreams.Add(playing);
@@ -301,7 +352,7 @@ namespace Robust.Client.GameObjects
             if (!source.SetPosition(coordinates.ToMapPos(EntityManager)))
             {
                 source.Dispose();
-                Logger.Warning("Can't play positional audio \"{stream.Name}\", can't set position.");
+                Logger.Warning($"Can't play positional audio \"{stream.Name}\", can't set position.");
                 return null;
             }
 
@@ -312,6 +363,10 @@ namespace Robust.Client.GameObjects
             {
                 Source = source,
                 TrackingCoordinates = coordinates,
+                Attenuation = audioParams?.Attenuation ?? Attenuation.Default,
+                MaxDistance = audioParams?.MaxDistance ?? float.MaxValue,
+                ReferenceDistance = audioParams?.ReferenceDistance ?? 1f,
+                RolloffFactor = audioParams?.RolloffFactor ?? 1f,
                 Volume = audioParams?.Volume ?? 0
             };
             _playingClydeStreams.Add(playing);
@@ -327,6 +382,9 @@ namespace Robust.Client.GameObjects
 
             source.SetPitch(audioParams.Value.PitchScale);
             source.SetVolume(audioParams.Value.Volume);
+            source.SetRolloffFactor(audioParams.Value.RolloffFactor);
+            source.SetMaxDistance(audioParams.Value.MaxDistance);
+            source.SetReferenceDistance(audioParams.Value.ReferenceDistance);
             source.SetPlaybackPosition(audioParams.Value.PlayOffsetSeconds);
             source.IsLooping = audioParams.Value.Loop;
         }
@@ -340,6 +398,27 @@ namespace Robust.Client.GameObjects
             public bool Done;
             public float Volume;
 
+            public float MaxDistance;
+            public float ReferenceDistance;
+            public float RolloffFactor;
+
+            public Attenuation Attenuation
+            {
+                get => _attenuation;
+                set
+                {
+                    if (value == _attenuation) return;
+                    _attenuation = value;
+                    if (_attenuation != Attenuation.Default)
+                    {
+                        // Need to disable default attenuation when using a custom one
+                        // Damn Sloth wanting linear ambience sounds so they smoothly cut-off and are short-range
+                        Source.SetRolloffFactor(0f);
+                    }
+                }
+            }
+            private Attenuation _attenuation = Attenuation.Default;
+
             public void Stop()
             {
                 Source.StopPlaying();

Robust.Client/GameObjects/EntitySystems/ClientContainerSystem.cs

@@ -1,94 +0,0 @@
-using System.Collections.Generic;
-using Robust.Shared.Containers;
-using Robust.Shared.GameObjects;
-
-namespace Robust.Client.GameObjects
-{
-    public class ClientContainerSystem : ContainerSystem
-    {
-        private readonly HashSet<IEntity> _updateQueue = new();
-
-        public override void Initialize()
-        {
-            base.Initialize();
-
-            SubscribeLocalEvent<UpdateContainerOcclusionMessage>(UpdateContainerOcclusion);
-
-            UpdatesBefore.Add(typeof(SpriteSystem));
-        }
-
-        private void UpdateContainerOcclusion(UpdateContainerOcclusionMessage ev)
-        {
-            _updateQueue.Add(ev.Entity);
-        }
-
-        public override void FrameUpdate(float frameTime)
-        {
-            base.FrameUpdate(frameTime);
-
-            foreach (var toUpdate in _updateQueue)
-            {
-                if (toUpdate.Deleted)
-                {
-                    continue;
-                }
-
-                UpdateEntityRecursively(toUpdate);
-            }
-
-            _updateQueue.Clear();
-        }
-
-        private static void UpdateEntityRecursively(IEntity entity)
-        {
-            // TODO: Since we are recursing down,
-            // we could cache ShowContents data here to speed it up for children.
-            // Am lazy though.
-            UpdateEntity(entity);
-
-            foreach (var child in entity.Transform.Children)
-            {
-                UpdateEntityRecursively(child.Owner);
-            }
-        }
-
-        private static void UpdateEntity(IEntity entity)
-        {
-            if (entity.TryGetComponent(out SpriteComponent? sprite))
-            {
-                sprite.ContainerOccluded = false;
-
-                // We have to recursively scan for containers upwards in case of nested containers.
-                var tempParent = entity;
-                while (tempParent.TryGetContainer(out var container))
-                {
-                    if (!container.ShowContents)
-                    {
-                        sprite.ContainerOccluded = true;
-                        break;
-                    }
-
-                    tempParent = container.Owner;
-                }
-            }
-
-            if (entity.TryGetComponent(out PointLightComponent? light))
-            {
-                light.ContainerOccluded = false;
-
-                // We have to recursively scan for containers upwards in case of nested containers.
-                var tempParent = entity;
-                while (tempParent.TryGetContainer(out var container))
-                {
-                    if (container.OccludesLight)
-                    {
-                        light.ContainerOccluded = true;
-                        break;
-                    }
-
-                    tempParent = container.Owner;
-                }
-            }
-        }
-    }
-}

Robust.Client/GameObjects/EntitySystems/ClientOccluderSystem.cs

@@ -62,7 +62,7 @@ namespace Robust.Client.GameObjects
             }
         }
 
-        private static void HandleAnchorChanged(EntityUid uid, ClientOccluderComponent component, AnchorStateChangedEvent args)
+        private static void HandleAnchorChanged(EntityUid uid, ClientOccluderComponent component, ref AnchorStateChangedEvent args)
         {
             component.AnchorStateChanged();
         }

Robust.Client/GameObjects/EntitySystems/ContainerSystem.cs

@@ -0,0 +1,237 @@
+using System;
+using System.Collections.Generic;
+using System.Linq;
+using Robust.Shared.Containers;
+using Robust.Shared.GameObjects;
+using Robust.Shared.GameStates;
+using Robust.Shared.IoC;
+using Robust.Shared.Serialization;
+using static Robust.Shared.Containers.ContainerManagerComponent;
+
+namespace Robust.Client.GameObjects
+{
+    public class ContainerSystem : SharedContainerSystem
+    {
+        [Dependency] private readonly IRobustSerializer _serializer = default!;
+        [Dependency] private readonly IDynamicTypeFactoryInternal _dynFactory = default!;
+
+        private readonly HashSet<IEntity> _updateQueue = new();
+
+        public readonly Dictionary<EntityUid, IContainer> ExpectedEntities = new();
+
+        public override void Initialize()
+        {
+            base.Initialize();
+
+            SubscribeLocalEvent<UpdateContainerOcclusionMessage>(UpdateContainerOcclusion);
+            SubscribeLocalEvent<EntityInitializedMessage>(HandleEntityInitialized);
+            SubscribeLocalEvent<ContainerManagerComponent, ComponentHandleState>(HandleComponentState);
+
+            UpdatesBefore.Add(typeof(SpriteSystem));
+        }
+
+        private void UpdateContainerOcclusion(UpdateContainerOcclusionMessage ev)
+        {
+            _updateQueue.Add(ev.Entity);
+        }
+
+        private void HandleEntityInitialized(EntityInitializedMessage ev)
+        {
+            if (!ExpectedEntities.TryGetValue(ev.Entity.Uid, out var container))
+                return;
+
+            RemoveExpectedEntity(ev.Entity.Uid);
+
+            if (container.Deleted)
+                return;
+
+            container.Insert(ev.Entity);
+        }
+
+        private void HandleComponentState(EntityUid uid, ContainerManagerComponent component, ref ComponentHandleState args)
+        {
+            if (args.Current is not ContainerManagerComponentState cast)
+                return;
+
+            // Delete now-gone containers.
+            List<string>? toDelete = null;
+            foreach (var (id, container) in component.Containers)
+            {
+                if (!cast.ContainerSet.Any(data => data.Id == id))
+                {
+                    container.Shutdown();
+                    toDelete ??= new List<string>();
+                    toDelete.Add(id);
+                }
+            }
+
+            if (toDelete != null)
+            {
+                foreach (var dead in toDelete)
+                {
+                    component.Containers.Remove(dead);
+                }
+            }
+
+            // Add new containers and update existing contents.
+
+            foreach (var (containerType, id, showEnts, occludesLight, entityUids) in cast.ContainerSet)
+            {
+                if (!component.Containers.TryGetValue(id, out var container))
+                {
+                    container = ContainerFactory(component, containerType, id);
+                    component.Containers.Add(id, container);
+                }
+
+                // sync show flag
+                container.ShowContents = showEnts;
+                container.OccludesLight = occludesLight;
+
+                // Remove gone entities.
+                List<IEntity>? toRemove = null;
+                foreach (var entity in container.ContainedEntities)
+                {
+                    if (!entityUids.Contains(entity.Uid))
+                    {
+                        toRemove ??= new List<IEntity>();
+                        toRemove.Add(entity);
+                    }
+                }
+
+                if (toRemove != null)
+                {
+                    foreach (var goner in toRemove)
+                        container.Remove(goner);
+                }
+
+                // Remove entities that were expected, but have been removed from the container.
+                List<EntityUid>? removedExpected = null;
+                foreach (var entityUid in container.ExpectedEntities)
+                {
+                    if (!entityUids.Contains(entityUid))
+                    {
+                        removedExpected ??= new List<EntityUid>();
+                        removedExpected.Add(entityUid);
+                    }
+                }
+
+                if (removedExpected != null)
+                {
+                    foreach (var entityUid in removedExpected)
+                        RemoveExpectedEntity(entityUid);
+                }
+
+                // Add new entities.
+                foreach (var entityUid in entityUids)
+                {
+                    if (!EntityManager.TryGetEntity(entityUid, out var entity))
+                    {
+                        AddExpectedEntity(entityUid, container);
+                        continue;
+                    }
+
+                    if (!container.ContainedEntities.Contains(entity))
+                        container.Insert(entity);
+                }
+            }
+        }
+
+        private IContainer ContainerFactory(ContainerManagerComponent component, string containerType, string id)
+        {
+            var type = _serializer.FindSerializedType(typeof(IContainer), containerType);
+            if (type is null) throw new ArgumentException($"Container of type {containerType} for id {id} cannot be found.");
+
+            var newContainer = _dynFactory.CreateInstanceUnchecked<BaseContainer>(type);
+            newContainer.ID = id;
+            newContainer.Manager = component;
+            return newContainer;
+        }
+
+        public void AddExpectedEntity(EntityUid uid, IContainer container)
+        {
+            if (ExpectedEntities.ContainsKey(uid))
+                return;
+
+            ExpectedEntities.Add(uid, container);
+            container.ExpectedEntities.Add(uid);
+        }
+
+        public void RemoveExpectedEntity(EntityUid uid)
+        {
+            if (!ExpectedEntities.TryGetValue(uid, out var container))
+                return;
+
+            ExpectedEntities.Remove(uid);
+            container.ExpectedEntities.Remove(uid);
+        }
+
+        public override void FrameUpdate(float frameTime)
+        {
+            base.FrameUpdate(frameTime);
+
+            foreach (var toUpdate in _updateQueue)
+            {
+                if (toUpdate.Deleted)
+                {
+                    continue;
+                }
+
+                UpdateEntityRecursively(toUpdate);
+            }
+
+            _updateQueue.Clear();
+        }
+
+        private static void UpdateEntityRecursively(IEntity entity)
+        {
+            // TODO: Since we are recursing down,
+            // we could cache ShowContents data here to speed it up for children.
+            // Am lazy though.
+            UpdateEntity(entity);
+
+            foreach (var child in entity.Transform.Children)
+            {
+                UpdateEntityRecursively(child.Owner);
+            }
+        }
+
+        private static void UpdateEntity(IEntity entity)
+        {
+            if (entity.TryGetComponent(out SpriteComponent? sprite))
+            {
+                sprite.ContainerOccluded = false;
+
+                // We have to recursively scan for containers upwards in case of nested containers.
+                var tempParent = entity;
+                while (tempParent.TryGetContainer(out var container))
+                {
+                    if (!container.ShowContents)
+                    {
+                        sprite.ContainerOccluded = true;
+                        break;
+                    }
+
+                    tempParent = container.Owner;
+                }
+            }
+
+            if (entity.TryGetComponent(out PointLightComponent? light))
+            {
+                light.ContainerOccluded = false;
+
+                // We have to recursively scan for containers upwards in case of nested containers.
+                var tempParent = entity;
+                while (tempParent.TryGetContainer(out var container))
+                {
+                    if (container.OccludesLight)
+                    {
+                        light.ContainerOccluded = true;
+                        break;
+                    }
+
+                    tempParent = container.Owner;
+                }
+            }
+        }
+    }
+}

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/GridChunkBoundsDebugSystem.cs

@@ -0,0 +1,90 @@
+using Robust.Client.Graphics;
+using Robust.Shared.Enums;
+using Robust.Shared.GameObjects;
+using Robust.Shared.IoC;
+using Robust.Shared.Map;
+using Robust.Shared.Maths;
+using Robust.Shared.Utility;
+
+namespace Robust.Client.GameObjects
+{
+    public class GridChunkBoundsDebugSystem : EntitySystem
+    {
+        private GridChunkBoundsOverlay? _overlay;
+
+        public bool Enabled
+        {
+            get => _enabled;
+            set
+            {
+                if (_enabled == value) return;
+
+                _enabled = value;
+
+                if (_enabled)
+                {
+                    DebugTools.Assert(_overlay == null);
+                    _overlay = new GridChunkBoundsOverlay(
+                        IoCManager.Resolve<IEntityManager>(),
+                        IoCManager.Resolve<IEyeManager>(),
+                        IoCManager.Resolve<IMapManager>());
+
+                    IoCManager.Resolve<IOverlayManager>().AddOverlay(_overlay);
+                }
+                else
+                {
+                    IoCManager.Resolve<IOverlayManager>().RemoveOverlay(_overlay!);
+                    _overlay = null;
+                }
+            }
+        }
+
+        private bool _enabled;
+    }
+
+    internal sealed class GridChunkBoundsOverlay : Overlay
+    {
+        private readonly IEntityManager _entityManager;
+        private readonly IEyeManager _eyeManager;
+        private readonly IMapManager _mapManager;
+
+        public override OverlaySpace Space => OverlaySpace.WorldSpace;
+
+        public GridChunkBoundsOverlay(IEntityManager entManager, IEyeManager eyeManager, IMapManager mapManager)
+        {
+            _entityManager = entManager;
+            _eyeManager = eyeManager;
+            _mapManager = mapManager;
+        }
+
+        protected internal override void Draw(in OverlayDrawArgs args)
+        {
+            var currentMap = _eyeManager.CurrentMap;
+            var viewport = _eyeManager.GetWorldViewport();
+
+            foreach (var grid in _mapManager.FindGridsIntersecting(currentMap, viewport))
+            {
+                var mapGrid = (IMapGridInternal) grid;
+                var gridEnt = _entityManager.GetEntity(grid.GridEntityId);
+
+                var worldPos = gridEnt.Transform.WorldPosition;
+                var worldRot = gridEnt.Transform.WorldRotation;
+
+                foreach (var (_, chunk) in mapGrid.GetMapChunks())
+                {
+                    var chunkBounds = chunk.CalcWorldBounds(worldPos, worldRot);
+                    var aabb = chunkBounds.CalcBoundingBox();
+
+                    // Calc world bounds for chunk.
+                    if (!aabb.Intersects(in viewport))
+                    {
+                        continue;
+                    }
+
+                    args.WorldHandle.DrawRect(chunkBounds, Color.Green.WithAlpha(0.2f), true);
+                    args.WorldHandle.DrawRect(aabb, Color.Red, false);
+                }
+            }
+        }
+    }
+}

Robust.Client/GameObjects/EntitySystems/GridFixtureSystem.cs

@@ -0,0 +1,9 @@
+using Robust.Shared.GameObjects;
+
+namespace Robust.Client.GameObjects
+{
+    internal sealed class GridFixtureSystem : SharedGridFixtureSystem
+    {
+
+    }
+}

Robust.Client/GameObjects/EntitySystems/MapSystem.cs

@@ -0,0 +1,9 @@
+using Robust.Shared.GameObjects;
+
+namespace Robust.Client.GameObjects
+{
+    internal sealed class MapSystem : SharedMapSystem
+    {
+
+    }
+}

Robust.Client/GameObjects/EntitySystems/PointLightSystem.cs

@@ -0,0 +1,44 @@
+using Robust.Client.ResourceManagement;
+using Robust.Shared.GameObjects;
+using Robust.Shared.IoC;
+using Robust.Shared.Map;
+
+namespace Robust.Client.GameObjects
+{
+    public sealed class PointLightSystem : SharedPointLightSystem
+    {
+        [Dependency] private readonly IResourceCache _resourceCache = default!;
+
+        public override void Initialize()
+        {
+            base.Initialize();
+            SubscribeLocalEvent<PointLightComponent, ComponentInit>(HandleInit);
+            SubscribeLocalEvent<PointLightComponent, ComponentRemove>(HandleRemove);
+        }
+
+        private void HandleInit(EntityUid uid, PointLightComponent component, ComponentInit args)
+        {
+            UpdateMask(component);
+        }
+
+        private void HandleRemove(EntityUid uid, PointLightComponent component, ComponentRemove args)
+        {
+            var ent = EntityManager.GetEntity(uid);
+            var map = ent.Transform.MapID;
+            // TODO: Just make this update the tree directly and not allocate
+            if (map != MapId.Nullspace)
+            {
+                EntityManager.EventBus.RaiseEvent(EventSource.Local,
+                    new RenderTreeRemoveLightEvent(component, map));
+            }
+        }
+
+        internal void UpdateMask(PointLightComponent component)
+        {
+            if (component._maskPath is not null)
+                component.Mask = _resourceCache.GetResource<TextureResource>(component._maskPath);
+            else
+                component.Mask = null;
+        }
+    }
+}

Robust.Client/GameObjects/EntitySystems/RenderingTreeSystem.cs

@@ -3,8 +3,11 @@ 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;
@@ -18,25 +21,48 @@ 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, Dictionary<GridId, MapTrees>> _gridTrees = new();
+        [Dependency] private readonly IMapManager _mapManager = default!;
 
         private readonly List<SpriteComponent> _spriteQueue = new();
         private readonly List<PointLightComponent> _lightQueue = new();
 
         private HashSet<EntityUid> _checkedChildren = new();
 
-        internal DynamicTree<SpriteComponent> GetSpriteTreeForMap(MapId map, GridId grid)
+        /// <summary>
+        /// <see cref="CVars.MaxLightRadius"/>
+        /// </summary>
+        public float MaxLightRadius { get; private set; }
+
+        internal IEnumerable<RenderingTreeComponent> GetRenderTrees(MapId mapId, Box2 worldAABB)
         {
-            return _gridTrees[map][grid].SpriteTree;
+            if (mapId == MapId.Nullspace) yield break;
+
+            foreach (var grid in _mapManager.FindGridsIntersecting(mapId, worldAABB))
+            {
+                yield return EntityManager.GetEntity(grid.GridEntityId).GetComponent<RenderingTreeComponent>();
+            }
+
+            yield return _mapManager.GetMapEntity(mapId).GetComponent<RenderingTreeComponent>();
         }
 
-        internal DynamicTree<PointLightComponent> GetLightTreeForMap(MapId map, GridId grid)
+        internal IEnumerable<DynamicTree<SpriteComponent>> GetSpriteTrees(MapId mapId, Box2 worldAABB)
         {
-            return _gridTrees[map][grid].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()
@@ -48,9 +74,7 @@ namespace Robust.Client.GameObjects
             UpdatesAfter.Add(typeof(PhysicsSystem));
 
             _mapManager.MapCreated += MapManagerOnMapCreated;
-            _mapManager.MapDestroyed += MapManagerOnMapDestroyed;
             _mapManager.OnGridCreated += MapManagerOnGridCreated;
-            _mapManager.OnGridRemoved += MapManagerOnGridRemoved;
 
             // Due to how recursion works, this must be done.
             SubscribeLocalEvent<MoveEvent>(AnythingMoved);
@@ -65,6 +89,11 @@ namespace Robust.Client.GameObjects
             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);
         }
 
         private void HandleLightUpdate(EntityUid uid, PointLightComponent component, PointLightUpdateEvent args)
@@ -79,7 +108,7 @@ namespace Robust.Client.GameObjects
             QueueSpriteUpdate(component);
         }
 
-        private void AnythingMoved(MoveEvent args)
+        private void AnythingMoved(ref MoveEvent args)
         {
             AnythingMovedSubHandler(args.Sender.Transform);
         }
@@ -88,12 +117,12 @@ namespace Robust.Client.GameObjects
         {
             // 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<MapGridComponent>() ||
-                sender.Owner.HasComponent<MapComponent>()) return;
+                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);
 
@@ -117,7 +146,7 @@ namespace Robust.Client.GameObjects
             QueueSpriteUpdate(component);
         }
 
-        private void SpriteParentChanged(EntityUid uid, SpriteComponent component, EntParentChangedMessage args)
+        private void SpriteParentChanged(EntityUid uid, SpriteComponent component, ref EntParentChangedMessage args)
         {
             QueueSpriteUpdate(component);
         }
@@ -129,16 +158,10 @@ namespace Robust.Client.GameObjects
 
         private void ClearSprite(SpriteComponent component)
         {
-            if (_gridTrees.TryGetValue(component.IntersectingMapId, out var gridTrees))
-            {
-                foreach (var gridId in component.IntersectingGrids)
-                {
-                    if (!gridTrees.TryGetValue(gridId, out var tree)) continue;
-                    tree.SpriteTree.Remove(component);
-                }
-            }
+            if (component.RenderTree == null) return;
 
-            component.IntersectingGrids.Clear();
+            component.RenderTree.SpriteTree.Remove(component);
+            component.RenderTree = null;
         }
 
         private void QueueSpriteUpdate(SpriteComponent component)
@@ -156,7 +179,7 @@ namespace Robust.Client.GameObjects
             QueueLightUpdate(component);
         }
 
-        private void LightParentChanged(EntityUid uid, PointLightComponent component, EntParentChangedMessage args)
+        private void LightParentChanged(EntityUid uid, PointLightComponent component, ref EntParentChangedMessage args)
         {
             QueueLightUpdate(component);
         }
@@ -173,16 +196,10 @@ namespace Robust.Client.GameObjects
 
         private void ClearLight(PointLightComponent component)
         {
-            if (_gridTrees.TryGetValue(component.IntersectingMapId, out var gridTrees))
-            {
-                foreach (var gridId in component.IntersectingGrids)
-                {
-                    if (!gridTrees.TryGetValue(gridId, out var tree)) continue;
-                    tree.LightTree.Remove(component);
-                }
-            }
+            if (component.RenderTree == null) return;
 
-            component.IntersectingGrids.Clear();
+            component.RenderTree.LightTree.Remove(component);
+            component.RenderTree = null;
         }
 
         private void QueueLightUpdate(PointLightComponent component)
@@ -198,31 +215,23 @@ namespace Robust.Client.GameObjects
         {
             base.Shutdown();
             _mapManager.MapCreated -= MapManagerOnMapCreated;
-            _mapManager.MapDestroyed -= MapManagerOnMapDestroyed;
             _mapManager.OnGridCreated -= MapManagerOnGridCreated;
-            _mapManager.OnGridRemoved -= MapManagerOnGridRemoved;
         }
 
-        private void MapManagerOnMapDestroyed(object? sender, MapEventArgs e)
+        private void HandleTreeRemove(EntityUid uid, RenderingTreeComponent component, ComponentRemove args)
         {
-            foreach (var (_, gridTree) in _gridTrees[e.Map])
+            foreach (var sprite in component.SpriteTree)
             {
-                foreach (var comp in gridTree.LightTree)
-                {
-                    comp.IntersectingGrids.Clear();
-                }
-
-                foreach (var comp in gridTree.SpriteTree)
-                {
-                    comp.IntersectingGrids.Clear();
-                }
-
-                // Just in case?
-                gridTree.LightTree.Clear();
-                gridTree.SpriteTree.Clear();
+                sprite.RenderTree = null;
             }
 
-            _gridTrees.Remove(e.Map);
+            foreach (var light in component.LightTree)
+            {
+                light.RenderTree = null;
+            }
+
+            component.SpriteTree.Clear();
+            component.LightTree.Clear();
         }
 
         private void MapManagerOnMapCreated(object? sender, MapEventArgs e)
@@ -232,35 +241,35 @@ namespace Robust.Client.GameObjects
                 return;
             }
 
-            _gridTrees.Add(e.Map, new Dictionary<GridId, MapTrees>
-            {
-                {GridId.Invalid, new MapTrees()}
-            });
+            _mapManager.GetMapEntity(e.Map).EnsureComponent<RenderingTreeComponent>();
         }
 
         private void MapManagerOnGridCreated(MapId mapId, GridId gridId)
         {
-            _gridTrees[mapId].Add(gridId, new MapTrees());
+            EntityManager.GetEntity(_mapManager.GetGrid(gridId).GridEntityId).EnsureComponent<RenderingTreeComponent>();
         }
 
-        private void MapManagerOnGridRemoved(MapId mapId, GridId gridId)
+        internal static RenderingTreeComponent? GetRenderTree(IEntity entity)
         {
-            var gridTree = _gridTrees[mapId][gridId];
+            if (entity.Transform.MapID == MapId.Nullspace ||
+                entity.HasComponent<RenderingTreeComponent>()) return null;
 
-            foreach (var sprite in gridTree.SpriteTree)
+            var parent = entity.Transform.Parent?.Owner;
+
+            while (true)
             {
-                sprite.IntersectingGrids.Remove(gridId);
+                if (parent == null) break;
+
+                if (parent.TryGetComponent(out RenderingTreeComponent? comp)) return comp;
+                parent = parent.Transform.Parent?.Owner;
             }
 
-            foreach (var light in gridTree.LightTree)
-            {
-                light.IntersectingGrids.Remove(gridId);
-            }
+            return null;
+        }
 
-            // Clear in case
-            gridTree.LightTree.Clear();
-            gridTree.SpriteTree.Clear();
-            _gridTrees[mapId].Remove(gridId);
+        private bool IsVisible(SpriteComponent component)
+        {
+            return component.Visible && !component.ContainerOccluded;
         }
 
         public override void FrameUpdate(float frameTime)
@@ -270,55 +279,42 @@ namespace Robust.Client.GameObjects
             foreach (var sprite in _spriteQueue)
             {
                 sprite.TreeUpdateQueued = false;
-                var mapId = sprite.Owner.Transform.MapID;
-
-                if (!sprite.Visible || sprite.ContainerOccluded)
+                if (!IsVisible(sprite))
                 {
                     ClearSprite(sprite);
                     continue;
                 }
 
-                // If we're on a new map then clear the old one.
-                if (sprite.IntersectingMapId != mapId)
+                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;
                 }
 
-                sprite.IntersectingMapId = mapId;
+                var aabb = RenderingTreeComponent.SpriteAabbFunc(sprite, worldPos);
 
-                if (mapId == MapId.Nullspace) continue;
-
-                var mapTree = _gridTrees[mapId];
-                var aabb = MapTrees.SpriteAabbFunc(sprite);
-                var intersectingGrids = _mapManager.FindGridIdsIntersecting(mapId, aabb, true).ToList();
-
-                // Remove from old
-                foreach (var gridId in sprite.IntersectingGrids)
+                // If we're on a new map then clear the old one.
+                if (oldMapTree != newMapTree)
                 {
-                    if (intersectingGrids.Contains(gridId)) continue;
-                    mapTree[gridId].SpriteTree.Remove(sprite);
+                    ClearSprite(sprite);
+                    newMapTree?.SpriteTree.Add(sprite, aabb);
                 }
-
-                // Rebuild in the update below
-                sprite.IntersectingGrids.Clear();
-
-                // Update / add to new
-                foreach (var gridId in intersectingGrids)
+                else
                 {
-                    var translated = aabb.Translated(gridId == GridId.Invalid
-                        ? Vector2.Zero
-                        : -_mapManager.GetGrid(gridId).WorldPosition);
-
-                    mapTree[gridId].SpriteTree.AddOrUpdate(sprite, translated);
-
-                    sprite.IntersectingGrids.Add(gridId);
+                    newMapTree?.SpriteTree.Update(sprite, aabb);
                 }
+
+                sprite.RenderTree = newMapTree;
             }
 
             foreach (var light in _lightQueue)
             {
                 light.TreeUpdateQueued = false;
-                var mapId = light.Owner.Transform.MapID;
 
                 if (!light.Enabled || light.ContainerOccluded)
                 {
@@ -326,72 +322,44 @@ namespace Robust.Client.GameObjects
                     continue;
                 }
 
-                // If we're on a new map then clear the old one.
-                if (light.IntersectingMapId != mapId)
+                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;
                 }
 
-                light.IntersectingMapId = mapId;
-
-                if (mapId == MapId.Nullspace) continue;
-
-                var mapTree = _gridTrees[mapId];
-                var aabb = MapTrees.LightAabbFunc(light);
-                var intersectingGrids = _mapManager.FindGridIdsIntersecting(mapId, aabb, true).ToList();
-
-                // Remove from old
-                foreach (var gridId in light.IntersectingGrids)
+                // 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)
                 {
-                    if (intersectingGrids.Contains(gridId)) continue;
-                    mapTree[gridId].LightTree.Remove(light);
+                    Logger.WarningS(LoggerSawmill, $"Light radius for {light.Owner} set above max radius of {MaxLightRadius}. This may lead to pop-in.");
                 }
 
-                // Rebuild in the update below
-                light.IntersectingGrids.Clear();
+                var treePos = newMapTree?.Owner.Transform.WorldPosition ?? Vector2.Zero;
+                var aabb = RenderingTreeComponent.LightAabbFunc(light, worldPos);
 
-                // Update / add to new
-                foreach (var gridId in intersectingGrids)
+                // If we're on a new map then clear the old one.
+                if (oldMapTree != newMapTree)
                 {
-                    var translated = aabb.Translated(gridId == GridId.Invalid
-                        ? Vector2.Zero
-                        : -_mapManager.GetGrid(gridId).WorldPosition);
-
-                    mapTree[gridId].LightTree.AddOrUpdate(light, translated);
-                    light.IntersectingGrids.Add(gridId);
+                    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);
-            }
-
-            internal static Box2 SpriteAabbFunc(in SpriteComponent value)
-            {
-                var worldPos = value.Owner.Transform.WorldPosition;
-
-                return new Box2(worldPos, worldPos);
-            }
-
-            internal static Box2 LightAabbFunc(in PointLightComponent value)
-            {
-                var worldPos = value.Owner.Transform.WorldPosition;
-
-                var boxSize = value.Radius * 2;
-                return Box2.CenteredAround(worldPos, (boxSize, boxSize));
-            }
-        }
     }
 
     internal class RenderTreeRemoveLightEvent : EntityEventArgs

Robust.Client/GameObjects/EntitySystems/SpriteSystem.cs

@@ -15,15 +15,14 @@ namespace Robust.Client.GameObjects
     {
         [Dependency] private readonly IEyeManager _eyeManager = default!;
         [Dependency] private readonly IMapManager _mapManager = default!;
+        [Dependency] private readonly RenderingTreeSystem _treeSystem = default!;
 
-        private RenderingTreeSystem _treeSystem = default!;
         private readonly Queue<SpriteComponent> _inertUpdateQueue = new();
 
         public override void Initialize()
         {
             base.Initialize();
 
-            _treeSystem = Get<RenderingTreeSystem>();
             SubscribeLocalEvent<SpriteUpdateInertEvent>(QueueUpdateInert);
         }
 
@@ -50,13 +49,11 @@ namespace Robust.Client.GameObjects
                 return;
             }
 
-            foreach (var gridId in _mapManager.FindGridIdsIntersecting(currentMap, pvsBounds, true))
+            foreach (var comp in _treeSystem.GetRenderTrees(currentMap, pvsBounds))
             {
-                var gridBounds = gridId == GridId.Invalid ? pvsBounds : pvsBounds.Translated(-_mapManager.GetGrid(gridId).WorldPosition);
+                var bounds = pvsBounds.Translated(-comp.Owner.Transform.WorldPosition);
 
-                var mapTree = _treeSystem.GetSpriteTreeForMap(currentMap, gridId);
-
-                mapTree.QueryAabb(ref frameTime, (ref float state, in SpriteComponent value) =>
+                comp.SpriteTree.QueryAabb(ref frameTime, (ref float state, in SpriteComponent value) =>
                 {
                     if (value.IsInert)
                     {
@@ -65,7 +62,7 @@ namespace Robust.Client.GameObjects
 
                     value.FrameUpdate(state);
                     return true;
-                }, gridBounds, approx: true);
+                }, bounds, true);
             }
         }
     }

Robust.Client/GameStates/ClientGameStateManager.cs

@@ -4,6 +4,7 @@ using System;
 using System.Collections.Generic;
 using System.Diagnostics;
 using System.Linq;
+using JetBrains.Annotations;
 using Robust.Client.GameObjects;
 using Robust.Client.Input;
 using Robust.Client.Map;
@@ -19,12 +20,14 @@ using Robust.Shared.IoC;
 using Robust.Shared.Log;
 using Robust.Shared.Network;
 using Robust.Shared.Network.Messages;
+using Robust.Shared.Players;
 using Robust.Shared.Timing;
 using Robust.Shared.Utility;
 
 namespace Robust.Client.GameStates
 {
     /// <inheritdoc />
+    [UsedImplicitly]
     public class ClientGameStateManager : IClientGameStateManager
     {
         private GameStateProcessor _processor = default!;
@@ -36,6 +39,8 @@ namespace Robust.Client.GameStates
             _pendingSystemMessages
                 = new();
 
+        private uint _metaCompNetId;
+
         [Dependency] private readonly IComponentFactory _compFactory = default!;
         [Dependency] private readonly IClientEntityManagerInternal _entities = default!;
         [Dependency] private readonly IEntityLookup _lookup = default!;
@@ -46,6 +51,7 @@ namespace Robust.Client.GameStates
         [Dependency] private readonly IClientGameTiming _timing = default!;
         [Dependency] private readonly INetConfigurationManager _config = default!;
         [Dependency] private readonly IEntitySystemManager _entitySystemManager = default!;
+        [Dependency] private readonly IClientEntityManager _entityManager = default!;
         [Dependency] private readonly IComponentManager _componentManager = default!;
         [Dependency] private readonly IInputManager _inputManager = default!;
 #if EXCEPTION_TOLERANCE
@@ -99,6 +105,12 @@ namespace Robust.Client.GameStates
             Predicting = _config.GetCVar(CVars.NetPredict);
             PredictTickBias = _config.GetCVar(CVars.NetPredictTickBias);
             PredictLagBias = _config.GetCVar(CVars.NetPredictLagBias);
+
+            var metaId = _compFactory.GetRegistration(typeof(MetaDataComponent)).NetID;
+            if (!metaId.HasValue)
+                throw new InvalidOperationException("MetaDataComponent does not have a NetId.");
+
+            _metaCompNetId = metaId.Value;
         }
 
         /// <inheritdoc />
@@ -210,6 +222,11 @@ namespace Robust.Client.GameStates
                     ResetPredictedEntities(_timing.CurTick);
                 }
 
+                if (!curState.Extrapolated)
+                {
+                    _processor.UpdateFullRep(curState);
+                }
+
                 // Store last tick we got from the GameStateProcessor.
                 _lastProcessedTick = _timing.CurTick;
 
@@ -319,8 +336,6 @@ namespace Robust.Client.GameStates
 
         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.
@@ -338,18 +353,19 @@ namespace Robust.Client.GameStates
                 }
 
                 // TODO: handle component deletions/creations.
-                foreach (var comp in _componentManager.GetNetComponents(entity.Uid))
+                foreach (var (netId, comp) in _componentManager.GetNetComponents(entity.Uid))
                 {
-                    DebugTools.AssertNotNull(comp.NetID);
+                    DebugTools.AssertNotNull(netId);
 
-                    if (comp.LastModifiedTick < curTick || !last.TryGetValue(comp.NetID!.Value, out var compState))
+                    if (comp.LastModifiedTick < curTick || !last.TryGetValue(netId, out var compState))
                     {
                         continue;
                     }
 
                     Logger.DebugS(CVars.NetPredict.Name, $"  And also its component {comp.Name}");
                     // TODO: Handle interpolation.
-                    bus.RaiseComponentEvent(comp, new ComponentHandleState(compState, null));
+                    var handleState = new ComponentHandleState(compState, null);
+                    _entities.EventBus.RaiseComponentEvent(comp, ref handleState);
                     comp.HandleComponentState(compState, null);
                 }
             }
@@ -363,24 +379,24 @@ namespace Robust.Client.GameStates
             // so that we can later roll back to it (if necessary).
             var outputData = new Dictionary<EntityUid, Dictionary<uint, ComponentState>>();
 
+            Debug.Assert(_players.LocalPlayer != null, "_players.LocalPlayer != null");
+            var player = _players.LocalPlayer.Session;
+
+            var bus = _entityManager.EventBus;
+
             foreach (var createdEntity in createdEntities)
             {
                 var compData = new Dictionary<uint, ComponentState>();
                 outputData.Add(createdEntity, compData);
 
-                foreach (var component in _componentManager.GetNetComponents(createdEntity))
+                foreach (var (netId, component) in _componentManager.GetNetComponents(createdEntity))
                 {
-                    Debug.Assert(_players.LocalPlayer != null, "_players.LocalPlayer != null");
+                    var state = _componentManager.GetComponentState(bus, component, player);
 
-                    var player = _players.LocalPlayer.Session;
-                    var state = component.GetComponentState(player);
-
-                    if (state.GetType() == typeof(ComponentState))
-                    {
+                    if(state.GetType() == typeof(ComponentState))
                         continue;
-                    }
 
-                    compData.Add(state.NetID, state);
+                    compData.Add(netId, state);
                 }
             }
 
@@ -422,16 +438,17 @@ namespace Robust.Client.GameStates
                     //Known entities
                     if (_entities.TryGetEntity(es.Uid, out var entity))
                     {
+                        // Logger.Debug($"[{IGameTiming.TickStampStatic}] MOD {es.Uid}");
                         toApply.Add(entity, (es, null));
                     }
                     else //Unknown entities
                     {
-                        var metaState = (MetaDataComponentState?) es.ComponentStates
-                            ?.FirstOrDefault(c => c.NetID == NetIDs.META_DATA);
+                        var metaState = (MetaDataComponentState?) es.ComponentChanges?.FirstOrDefault(c => c.NetID == _metaCompNetId).State;
                         if (metaState == null)
                         {
                             throw new InvalidOperationException($"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);
@@ -458,19 +475,18 @@ namespace Robust.Client.GameStates
                 }
             }
 
-            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,
+                HandleEntityState(entity.EntityManager.ComponentManager, entity, _entities.EventBus, kvStates.Value.Item1,
                     kvStates.Value.Item2);
             }
 
             foreach (var id in deletions)
             {
+                // Logger.Debug($"[{IGameTiming.TickStampStatic}] DELETE {id}");
                 _entities.DeleteEntity(id);
             }
 
@@ -532,10 +548,10 @@ namespace Robust.Client.GameStates
             return created;
         }
 
-        private void HandleEntityState(IComponentManager compMan, IEntity entity, EntityEventBus bus, EntityState? curState,
+        private void HandleEntityState(IComponentManager compMan, IEntity entity, IEventBus bus, EntityState? curState,
             EntityState? nextState)
         {
-            var compStateWork = new Dictionary<uint, (ComponentState? curState, ComponentState? nextState)>();
+            var compStateWork = new Dictionary<ushort, (ComponentState? curState, ComponentState? nextState)>();
             var entityUid = entity.Uid;
 
             if (curState?.ComponentChanges != null)
@@ -551,46 +567,51 @@ namespace Robust.Client.GameStates
                     }
                     else
                     {
+                        //Right now we just assume every state from an unseen entity is added
+
                         if (compMan.HasComponent(entityUid, compChange.NetID))
                             continue;
 
-                        var newComp = (Component) _compFactory.GetComponent(compChange.ComponentName!);
+                        var newComp = (Component) _compFactory.GetComponent(compChange.NetID);
                         newComp.Owner = entity;
                         compMan.AddComponent(entity, newComp, true);
+
+                        compStateWork[compChange.NetID] = (compChange.State, null);
                     }
                 }
             }
 
-            if (curState?.ComponentStates != null)
+            if (curState?.ComponentChanges != null)
             {
-                foreach (var compState in curState.ComponentStates)
+                foreach (var compChange in curState.ComponentChanges)
                 {
-                    compStateWork[compState.NetID] = (compState, null);
+                    compStateWork[compChange.NetID] = (compChange.State, null);
                 }
             }
 
-            if (nextState?.ComponentStates != null)
+            if (nextState?.ComponentChanges != null)
             {
-                foreach (var compState in nextState.ComponentStates)
+                foreach (var compState in nextState.ComponentChanges)
                 {
                     if (compStateWork.TryGetValue(compState.NetID, out var state))
                     {
-                        compStateWork[compState.NetID] = (state.curState, compState);
+                        compStateWork[compState.NetID] = (state.curState, compState.State);
                     }
                     else
                     {
-                        compStateWork[compState.NetID] = (null, compState);
+                        compStateWork[compState.NetID] = (null, compState.State);
                     }
                 }
             }
 
             foreach (var (netId, (cur, next)) in compStateWork)
             {
-                if (compMan.TryGetComponent(entityUid, netId, out var component))
+                if (compMan.TryGetComponent(entityUid, (ushort) netId, out var component))
                 {
                     try
                     {
-                        bus.RaiseComponentEvent(component, new ComponentHandleState(cur, next));
+                        var handleState = new ComponentHandleState(cur, next);
+                        bus.RaiseComponentEvent(component, ref handleState);
                         component.HandleComponentState(cur, next);
                     }
                     catch (Exception e)

Robust.Client/GameStates/GameStateProcessor.cs

@@ -1,4 +1,4 @@
-using System.Collections.Generic;
+using System.Collections.Generic;
 using System.Diagnostics.CodeAnalysis;
 using System.Linq;
 using Robust.Shared.GameObjects;
@@ -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.
@@ -198,14 +195,10 @@ namespace Robust.Client.GameStates
                             {
                                 compData.Remove(change.NetID);
                             }
-                        }
-                    }
-
-                    if (entityState.ComponentStates != null)
-                    {
-                        foreach (var compState in entityState.ComponentStates)
-                        {
-                            compData[compState.NetID] = compState;
+                            else if (change.State is not null)
+                            {
+                                compData[change.NetID] = change.State;
+                            }
                         }
                     }
                 }

Robust.Client/GameStates/NetGraphOverlay.cs

@@ -21,6 +21,7 @@ namespace Robust.Client.GameStates
         [Dependency] private readonly IGameTiming _gameTiming = default!;
         [Dependency] private readonly IClientNetManager _netManager = default!;
         [Dependency] private readonly IClientGameStateManager _gameStateManager = default!;
+        [Dependency] private readonly IComponentFactory _componentFactory = default!;
 
         private const int HistorySize = 60 * 3; // number of ticks to keep in history.
         private const int TargetPayloadBps = 56000 / 8; // Target Payload size in Bytes per second. A mind-numbing fifty-six thousand bits per second, who would ever need more?
@@ -90,17 +91,14 @@ namespace Robust.Client.GameStates
                             sb.Append($"\n  Changes:");
                             foreach (var compChange in entState.ComponentChanges)
                             {
-                                var del = compChange.Deleted ? 'D' : 'C';
-                                sb.Append($"\n    [{del}]{compChange.NetID}:{compChange.ComponentName}");
-                            }
-                        }
+                                var registration = _componentFactory.GetRegistration(compChange.NetID);
+                                var create = compChange.Created ? 'C' : '\0';
+                                var mod = !(compChange.Created || compChange.Created) ? 'M' : '\0';
+                                var del = compChange.Deleted ? 'D' : '\0';
+                                sb.Append($"\n    [{create}{mod}{del}]{compChange.NetID}:{registration.Name}");
 
-                        if (entState.ComponentStates is not null)
-                        {
-                            sb.Append($"\n  States:");
-                            foreach (var compState in entState.ComponentStates)
-                            {
-                                sb.Append($"\n    {compState.NetID}:{compState.GetType().Name}");
+                                if(compChange.State is not null)
+                                    sb.Append($"\n      STATE:{compChange.State.GetType().Name}");
                             }
                         }
                     }

Robust.Client/Graphics/ClientEye/EyeManager.cs

@@ -111,10 +111,11 @@ namespace Robust.Client.Graphics
         public MapCoordinates ScreenToMap(ScreenCoordinates point)
         {
             var (pos, window) = point;
-            if (window != MainViewport.Window?.Id)
+
+            if (_uiManager.MouseGetControl(point) is not IViewportControl viewport)
                 return default;
 
-            return MainViewport.ScreenToMap(pos);
+            return viewport.ScreenToMap(pos);
         }
 
         /// <inheritdoc />

Robust.Client/Graphics/ClientEye/IEyeManager.cs

@@ -53,7 +53,7 @@ namespace Robust.Client.Graphics
         ScreenCoordinates CoordinatesToScreen(EntityCoordinates point);
 
         /// <summary>
-        /// Unprojects a point from UI screen space to world space using the current camera.
+        /// Unprojects a point from UI screen space to world space using the viewport under the screen coordinates.
         /// </summary>
         /// <remarks>
         /// The game exists on the 2D X/Y plane, so this function returns a point o the plane
@@ -64,7 +64,7 @@ namespace Robust.Client.Graphics
         MapCoordinates ScreenToMap(ScreenCoordinates point);
 
         /// <summary>
-        /// Unprojects a point from UI screen space to world space using the current camera.
+        /// Unprojects a point from UI screen space to world space using the main viewport.
         /// </summary>
         /// <remarks>
         /// The game exists on the 2D X/Y plane, so this function returns a point o the plane

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

@@ -9,6 +9,7 @@ using OpenToolkit.Audio.OpenAL;
 using OpenToolkit.Audio.OpenAL.Extensions.Creative.EFX;
 using Robust.Client.Audio;
 using Robust.Shared;
+using Robust.Shared.Audio;
 using Robust.Shared.Log;
 using Vector2 = Robust.Shared.Maths.Vector2;
 
@@ -58,6 +59,7 @@ namespace Robust.Client.Graphics.Clyde
             IsEfxSupported = HasAlDeviceExtension("ALC_EXT_EFX");
 
             _cfg.OnValueChanged(CVars.AudioMasterVolume, SetMasterVolume, true);
+            _cfg.OnValueChanged(CVars.AudioAttenuation, SetAudioAttenuation, true);
         }
 
         private void _audioCreateContext()
@@ -192,6 +194,43 @@ namespace Robust.Client.Graphics.Clyde
             AL.Listener(ALListenerf.Gain, _baseGain * newVolume);
         }
 
+        public void SetAudioAttenuation(int value)
+        {
+            var attenuation = (Attenuation) value;
+
+            switch (attenuation)
+            {
+                case Attenuation.NoAttenuation:
+                    AL.DistanceModel(ALDistanceModel.None);
+                    break;
+                case Attenuation.InverseDistance:
+                    AL.DistanceModel(ALDistanceModel.InverseDistance);
+                    break;
+                case Attenuation.Default:
+                case Attenuation.InverseDistanceClamped:
+                    AL.DistanceModel(ALDistanceModel.InverseDistanceClamped);
+                    break;
+                case Attenuation.LinearDistance:
+                    AL.DistanceModel(ALDistanceModel.LinearDistance);
+                    break;
+                case Attenuation.LinearDistanceClamped:
+                    AL.DistanceModel(ALDistanceModel.LinearDistanceClamped);
+                    break;
+                case Attenuation.ExponentDistance:
+                    AL.DistanceModel(ALDistanceModel.ExponentDistance);
+                    break;
+                case Attenuation.ExponentDistanceClamped:
+                    AL.DistanceModel(ALDistanceModel.ExponentDistanceClamped);
+                    break;
+                default:
+                    throw new ArgumentOutOfRangeException($"No implementation to set {attenuation.ToString()} for DistanceModel!");
+            }
+
+            var attToString = attenuation == Attenuation.Default ? Attenuation.InverseDistanceClamped : attenuation;
+
+            _openALSawmill.Info($"Set audio attenuation to {attToString.ToString()}");
+        }
+
         public IClydeAudioSource CreateAudioSource(AudioStream stream)
         {
             var source = AL.GenSource();
@@ -486,6 +525,27 @@ namespace Robust.Client.Graphics.Clyde
                 _master._checkAlError();
             }
 
+            public void SetMaxDistance(float distance)
+            {
+                _checkDisposed();
+                AL.Source(SourceHandle, ALSourcef.MaxDistance, distance);
+                _master._checkAlError();
+            }
+
+            public void SetRolloffFactor(float rolloffFactor)
+            {
+                _checkDisposed();
+                AL.Source(SourceHandle, ALSourcef.RolloffFactor, rolloffFactor);
+                _master._checkAlError();
+            }
+
+            public void SetReferenceDistance(float refDistance)
+            {
+                _checkDisposed();
+                AL.Source(SourceHandle, ALSourcef.ReferenceDistance, refDistance);
+                _master._checkAlError();
+            }
+
             public void SetOcclusion(float blocks)
             {
                 _checkDisposed();
@@ -726,6 +786,27 @@ namespace Robust.Client.Graphics.Clyde
                 _master._checkAlError();
             }
 
+            public void SetMaxDistance(float distance)
+            {
+                _checkDisposed();
+                AL.Source(SourceHandle!.Value, ALSourcef.MaxDistance, distance);
+                _master._checkAlError();
+            }
+
+            public void SetRolloffFactor(float rolloffFactor)
+            {
+                _checkDisposed();
+                AL.Source(SourceHandle!.Value, ALSourcef.RolloffFactor, rolloffFactor);
+                _master._checkAlError();
+            }
+
+            public void SetReferenceDistance(float refDistance)
+            {
+                _checkDisposed();
+                AL.Source(SourceHandle!.Value, ALSourcef.ReferenceDistance, refDistance);
+                _master._checkAlError();
+            }
+
             public void SetOcclusion(float blocks)
             {
                 _checkDisposed();

Robust.Client/Graphics/Clyde/Clyde.Constants.cs

@@ -2,7 +2,8 @@ namespace Robust.Client.Graphics.Clyde
 {
     internal sealed partial class Clyde
     {
-        private static readonly (string, uint)[] BaseShaderAttribLocations = {
+        private static readonly (string, uint)[] BaseShaderAttribLocations =
+        {
             ("aPos", 0),
             ("tCoord", 1)
         };
@@ -30,14 +31,21 @@ namespace Robust.Client.Graphics.Clyde
         // To be clear: You shouldn't change this. This just helps with understanding where Primitive Restart is being used.
         private const ushort PrimitiveRestartIndex = ushort.MaxValue;
 
-        private enum Renderer : short
+        private enum Renderer : sbyte
         {
-            // Default: Try all supported renderers (not necessarily the renderers shown here)
-            Default = default,
-            OpenGL33 = 1,
-            OpenGL31 = 2,
-            OpenGLES2 = 3,
+            // Auto: Try all supported renderers (not necessarily the renderers shown here)
+            Auto = default,
+            OpenGL = 1,
             Explode = -1,
         }
+
+        private enum RendererOpenGLVersion : byte
+        {
+            Auto = default,
+            GL33 = 1,
+            GL31 = 2,
+            GLES3 = 3,
+            GLES2 = 4,
+        }
     }
 }

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

@@ -62,7 +62,7 @@ namespace Robust.Client.Graphics.Clyde
                     TextEntered?.Invoke(args);
                     break;
                 case DEventWindowClosed(var reg, var args):
-                    reg.Closed?.Invoke(args);
+                    reg.RequestClosed?.Invoke(args);
                     CloseWindow?.Invoke(args);
 
                     if (reg.DisposeOnClose && !reg.IsMainWindow)
@@ -95,24 +95,17 @@ namespace Robust.Client.Graphics.Clyde
             _eventDispatchQueue.Enqueue(new DEventScroll(ev));
         }
 
-        private void SendCloseWindow(WindowReg windowReg, WindowClosedEventArgs ev)
+        private void SendCloseWindow(WindowReg windowReg, WindowRequestClosedEventArgs 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 loaded = RtToLoaded(reg.RenderTarget);
+            loaded.Size = reg.FramebufferSize;
+
+            _glContext!.WindowResized(reg, oldSize);
 
             var eventArgs = new WindowResizedEventArgs(
                 oldSize,
@@ -156,7 +149,7 @@ namespace Robust.Client.Graphics.Clyde
 
         private sealed record DEventScroll(MouseWheelEventArgs Args) : DEventBase;
 
-        private sealed record DEventWindowClosed(WindowReg Reg, WindowClosedEventArgs Args) : DEventBase;
+        private sealed record DEventWindowClosed(WindowReg Reg, WindowRequestClosedEventArgs Args) : DEventBase;
 
         private sealed record DEventWindowResized(WindowResizedEventArgs Args) : DEventBase;
 

Robust.Client/Graphics/Clyde/Clyde.GLContext.cs

@@ -0,0 +1,85 @@
+using System;
+using Robust.Shared;
+using Robust.Shared.Log;
+
+namespace Robust.Client.Graphics.Clyde
+{
+    internal sealed partial class Clyde
+    {
+        private GLContextBase? _glContext;
+
+        // Current OpenGL version we managed to initialize with.
+        private RendererOpenGLVersion _openGLVersion;
+
+        private void InitGLContextManager()
+        {
+            // Advanced GL contexts currently disabled due to lack of testing etc.
+            if (OperatingSystem.IsWindows() && _cfg.GetCVar(CVars.DisplayAngle))
+            {
+                /*
+                if (_cfg.GetCVar(CVars.DisplayAngleCustomSwapChain))
+                {
+                    _sawmillOgl.Debug("Trying custom swap chain ANGLE.");
+                    var ctxAngle = new GLContextAngle(this);
+
+                    if (ctxAngle.TryInitialize())
+                    {
+                        _sawmillOgl.Debug("Successfully initialized custom ANGLE");
+                        _glContext = ctxAngle;
+
+                        ctxAngle.EarlyInit();
+                        return;
+                    }
+                }
+                */
+
+                /*
+                if (_cfg.GetCVar(CVars.DisplayEgl))
+                {
+                    _sawmillOgl.Debug("Trying EGL");
+                    var ctxEgl = new GLContextEgl(this);
+                    ctxEgl.InitializePublic();
+                    _glContext = ctxEgl;
+                    return;
+                }
+                */
+            }
+
+            /*
+            if (OperatingSystem.IsLinux() && _cfg.GetCVar(CVars.DisplayEgl))
+            {
+                _sawmillOgl.Debug("Trying EGL");
+                var ctxEgl = new GLContextEgl(this);
+                ctxEgl.InitializePublic();
+                _glContext = ctxEgl;
+                return;
+            }
+            */
+
+            _glContext = new GLContextWindow(this);
+        }
+
+        private struct GLContextSpec
+        {
+            public int Major;
+            public int Minor;
+            public GLContextProfile Profile;
+            public GLContextCreationApi CreationApi;
+            // Used by GLContextWindow to figure out which GL version managed to initialize.
+            public RendererOpenGLVersion OpenGLVersion;
+        }
+
+        private enum GLContextProfile
+        {
+            Compatibility,
+            Core,
+            Es
+        }
+
+        private enum GLContextCreationApi
+        {
+            Native,
+            Egl,
+        }
+    }
+}

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

@@ -1,7 +1,6 @@
 using System.Collections.Generic;
 using System.Diagnostics.CodeAnalysis;
 using OpenToolkit.Graphics.OpenGL4;
-using Robust.Shared.Log;
 
 namespace Robust.Client.Graphics.Clyde
 {
@@ -24,6 +23,7 @@ namespace Robust.Client.Graphics.Clyde
         private bool _hasGLVertexArrayObject;
         private bool _hasGLVertexArrayObjectOes;
         private bool _hasGLFloatFramebuffers;
+        private bool _hasGLES3Shaders;
         private bool HasGLAnyMapBuffer => _hasGLMapBuffer || _hasGLMapBufferRange || _hasGLMapBufferOes;
         private bool _hasGLMapBuffer;
         private bool _hasGLMapBufferOes;
@@ -72,6 +72,12 @@ namespace Robust.Client.Graphics.Clyde
                 CheckGLCap(ref _hasGLMapBufferRange, "map_buffer_range", (3, 0));
                 CheckGLCap(ref _hasGLPixelBufferObjects, "pixel_buffer_object", (2, 1));
                 CheckGLCap(ref _hasGLStandardDerivatives, "standard_derivatives", (2, 1));
+
+                _hasGLSrgb = true;
+                _hasGLReadFramebuffer = true;
+                _hasGLPrimitiveRestart = true;
+                _hasGLUniformBuffers = true;
+                _hasGLFloatFramebuffers = true;
             }
             else
             {
@@ -94,15 +100,31 @@ namespace Robust.Client.Graphics.Clyde
                 CheckGLCap(ref _hasGLMapBufferRange, "map_buffer_range", (3, 0));
                 CheckGLCap(ref _hasGLPixelBufferObjects, "pixel_buffer_object", (3, 0));
                 CheckGLCap(ref _hasGLStandardDerivatives, "standard_derivatives", (3, 0), "GL_OES_standard_derivatives");
-            }
+                CheckGLCap(ref _hasGLReadFramebuffer, "read_framebuffer", (3, 0));
+                CheckGLCap(ref _hasGLPrimitiveRestart, "primitive_restart", (3, 1));
+                CheckGLCap(ref _hasGLUniformBuffers, "uniform_buffers", (3, 0));
+                CheckGLCap(ref _hasGLFloatFramebuffers, "float_framebuffers", (3, 2), "GL_EXT_color_buffer_float");
+                CheckGLCap(ref _hasGLES3Shaders, "gles3_shaders", (3, 0));
 
-            // TODO: Enable these on ES 3.0
-            _hasGLSrgb = !_isGLES;
-            _hasGLReadFramebuffer = !_isGLES;
-            _hasGLPrimitiveRestart = !_isGLES;
-            _hasGLUniformBuffers = !_isGLES;
-            // This is 3.2 or extensions
-            _hasGLFloatFramebuffers = !_isGLES;
+                if (major >= 3)
+                {
+                    if (_glContext!.HasBrokenWindowSrgb)
+                    {
+                        _hasGLSrgb = false;
+                        _sawmillOgl.Debug("  sRGB: false (window broken sRGB)");
+                    }
+                    else
+                    {
+                        _hasGLSrgb = true;
+                        _sawmillOgl.Debug("  sRGB: true");
+                    }
+                }
+                else
+                {
+                    _hasGLSrgb = false;
+                    _sawmillOgl.Debug("  sRGB: false");
+                }
+            }
 
             _sawmillOgl.Debug($"  GLES: {_isGLES}");
 
@@ -141,7 +163,12 @@ namespace Robust.Client.Graphics.Clyde
                 "map_buffer_range",
                 "pixel_buffer_object",
                 "map_buffer_oes",
-                "standard_derivatives"
+                "standard_derivatives",
+                "read_framebuffer",
+                "primitive_restart",
+                "uniform_buffers",
+                "float_framebuffers",
+                "gles3_shaders",
             };
 
             foreach (var cvar in cvars)

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

@@ -4,6 +4,7 @@ using System.Collections.Generic;
 using OpenToolkit.Graphics.OpenGL4;
 using Robust.Shared.GameObjects;
 using Robust.Shared.IoC;
+using Robust.Shared.Log;
 using Robust.Shared.Map;
 using Robust.Shared.Maths;
 
@@ -19,18 +20,17 @@ namespace Robust.Client.Graphics.Clyde
         private int _verticesPerChunk(IMapChunk chunk) => chunk.ChunkSize * chunk.ChunkSize * 4;
         private int _indicesPerChunk(IMapChunk chunk) => chunk.ChunkSize * chunk.ChunkSize * GetQuadBatchIndexCount();
 
-        private void _drawGrids(Box2 worldBounds)
+        private void _drawGrids(Viewport viewport, Box2 worldBounds, IEye eye)
         {
-            var mapId = _eyeManager.CurrentMap;
+            var mapId = eye.Position.MapId;
             if (!_mapManager.MapExists(mapId))
             {
-                // fall back to the default eye's map
-                _eyeManager.ClearCurrentEye();
-                mapId = _eyeManager.CurrentMap;
+                // fall back to nullspace map
+                mapId = MapId.Nullspace;
             }
 
             SetTexture(TextureUnit.Texture0, _tileDefinitionManager.TileTextureAtlas);
-            SetTexture(TextureUnit.Texture1, _lightingReady ? _currentViewport!.LightRenderTarget.Texture : _stockTextureWhite);
+            SetTexture(TextureUnit.Texture1, _lightingReady ? viewport.LightRenderTarget.Texture : _stockTextureWhite);
 
             var (gridProgram, _) = ActivateShaderInstance(_defaultShader.Handle);
             SetupGlobalUniformsImmediate(gridProgram, (ClydeTexture) _tileDefinitionManager.TileTextureAtlas);
@@ -53,14 +53,8 @@ namespace Robust.Client.Graphics.Clyde
                 var transform = compMan.GetComponent<ITransformComponent>(grid.GridEntityId);
                 gridProgram.SetUniform(UniIModelMatrix, transform.WorldMatrix);
 
-                foreach (var (_, chunk) in grid.GetMapChunks())
+                foreach (var chunk in grid.GetMapChunks(worldBounds))
                 {
-                    // Calc world bounds for chunk.
-                    if (!chunk.CalcWorldBounds().Intersects(in worldBounds))
-                    {
-                        continue;
-                    }
-
                     if (_isChunkDirty(grid, chunk))
                     {
                         _updateChunkMesh(grid, chunk);
@@ -210,11 +204,14 @@ namespace Robust.Client.Graphics.Clyde
 
         private void _updateOnGridCreated(MapId mapId, GridId gridId)
         {
+            Logger.DebugS("grid", $"Adding {gridId} to grid renderer");
             _mapChunkData.Add(gridId, new Dictionary<Vector2i, MapChunkData>());
         }
 
         private void _updateOnGridRemoved(MapId mapId, GridId gridId)
         {
+            Logger.DebugS("grid", $"Removing {gridId} from grid renderer");
+
             var data = _mapChunkData[gridId];
             foreach (var chunkDatum in data.Values)
             {

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

@@ -2,6 +2,7 @@ using System;
 using System.Buffers;
 using System.Collections.Generic;
 using System.Runtime.CompilerServices;
+using System.Threading;
 using Robust.Client.GameObjects;
 using Robust.Client.ResourceManagement;
 using Robust.Shared.Map;
@@ -9,6 +10,7 @@ using Robust.Shared.Maths;
 using Robust.Shared.Utility;
 using OpenToolkit.Graphics.OpenGL4;
 using Robust.Client.UserInterface.CustomControls;
+using Robust.Shared;
 using Robust.Shared.Enums;
 
 namespace Robust.Client.Graphics.Clyde
@@ -25,12 +27,12 @@ namespace Robust.Client.Graphics.Clyde
                 =
                 new();
 
-        public unsafe void Render()
+        public void Render()
         {
             CheckTransferringScreenshots();
 
             var allMinimized = true;
-            foreach (var windowReg in _windowing!.AllWindows)
+            foreach (var windowReg in _windows)
             {
                 if (!windowReg.IsMinimized)
                 {
@@ -44,9 +46,8 @@ namespace Robust.Client.Graphics.Clyde
             {
                 ClearFramebuffer(Color.Black);
 
-                // We have to keep running swapbuffers here
-                // or else the user's PC will turn into a heater!!
-                SwapMainBuffers();
+                // Sleep to avoid turning the computer into a heater.
+                Thread.Sleep(16);
                 return;
             }
 
@@ -58,11 +59,9 @@ namespace Robust.Client.Graphics.Clyde
             _debugStats.Reset();
 
             // Basic pre-render busywork.
-            // Clear screen to black.
-            ClearFramebuffer(Color.Black);
 
             // Update shared UBOs.
-            _updateUniformConstants(_windowing.MainWindow!.FramebufferSize);
+            _updateUniformConstants(_mainWindow!.FramebufferSize);
 
             {
                 CalcScreenMatrices(ScreenSize, out var proj, out var view);
@@ -74,7 +73,7 @@ namespace Robust.Client.Graphics.Clyde
             {
                 DrawSplash(_renderHandle);
                 FlushRenderQueue();
-                SwapMainBuffers();
+                SwapAllBuffers();
                 return;
             }
 
@@ -84,6 +83,9 @@ namespace Robust.Client.Graphics.Clyde
                     RenderViewport(viewport);
             }
 
+            // Clear screen to correct color.
+            ClearFramebuffer(_userInterfaceManager.GetMainClearColor());
+
             using (DebugGroup("UI"))
             {
                 _userInterfaceManager.Render(_renderHandle);
@@ -92,10 +94,8 @@ namespace Robust.Client.Graphics.Clyde
 
             TakeScreenshot(ScreenshotType.Final);
 
-            BlitSecondaryWindows();
-
             // And finally, swap those buffers!
-            SwapMainBuffers();
+            SwapAllBuffers();
         }
 
         private void RenderOverlays(Viewport vp, OverlaySpace space, in Box2 worldBox)
@@ -201,9 +201,10 @@ namespace Robust.Client.Graphics.Clyde
         }
 
 
-        private void DrawEntities(Viewport viewport, Box2 worldBounds)
+        private void DrawEntities(Viewport viewport, Box2 worldBounds, IEye eye)
         {
-            if (_eyeManager.CurrentMap == MapId.Nullspace || !_mapManager.HasMapEntity(_eyeManager.CurrentMap))
+            var mapId = eye.Position.MapId;
+            if (mapId == MapId.Nullspace || !_mapManager.HasMapEntity(mapId))
             {
                 return;
             }
@@ -212,12 +213,7 @@ namespace Robust.Client.Graphics.Clyde
 
             var screenSize = viewport.Size;
 
-            // 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.
-            // TODO: Make this check more accurate.
-            var widerBounds = worldBounds.Enlarged(5);
-
-            ProcessSpriteEntities(_eyeManager.CurrentMap, widerBounds, _drawingSpriteList);
+            ProcessSpriteEntities(mapId, worldBounds, _drawingSpriteList);
 
             var worldOverlays = new List<Overlay>();
 
@@ -273,13 +269,15 @@ namespace Robust.Client.Graphics.Clyde
                     break;
                 }
 
+                var matrix = entry.worldMatrix;
+                var worldPosition = new Vector2(matrix.R0C2, matrix.R1C2);
 
                 RenderTexture? entityPostRenderTarget = null;
                 Vector2i roundedPos = default;
                 if (entry.sprite.PostShader != null)
                 {
                     // calculate world bounding box
-                    var spriteBB = entry.sprite.CalculateBoundingBox();
+                    var spriteBB = entry.sprite.CalculateBoundingBox(worldPosition);
                     var spriteLB = spriteBB.BottomLeft;
                     var spriteRT = spriteBB.TopRight;
 
@@ -291,6 +289,9 @@ namespace Robust.Client.Graphics.Clyde
                     // scale can be passed with PostShader as variable in future
                     var postShadeScale = 1.25f;
                     var screenSpriteSize = (Vector2i) ((screenRT - screenLB) * postShadeScale).Rounded();
+
+                    // Rotate the vector by the eye angle, otherwise the bounding box will be incorrect
+                    screenSpriteSize = (Vector2i) eye.Rotation.RotateVec(screenSpriteSize).Rounded();
                     screenSpriteSize.Y = -screenSpriteSize.Y;
 
                     // I'm not 100% sure why it works, but without it post-shader
@@ -323,9 +324,7 @@ namespace Robust.Client.Graphics.Clyde
                     }
                 }
 
-                var matrix = entry.worldMatrix;
-                var worldPosition = new Vector2(matrix.R0C2, matrix.R1C2);
-                entry.sprite.Render(_renderHandle.DrawingHandleWorld, in entry.worldRotation, in worldPosition);
+                entry.sprite.Render(_renderHandle.DrawingHandleWorld, eye.Rotation, in entry.worldRotation, in worldPosition);
 
                 if (entry.sprite.PostShader != null && entityPostRenderTarget != null)
                 {
@@ -366,24 +365,11 @@ namespace Robust.Client.Graphics.Clyde
         private void ProcessSpriteEntities(MapId map, Box2 worldBounds,
             RefList<(SpriteComponent sprite, Matrix3 matrix, Angle worldRot, float yWorldPos)> list)
         {
-            var spriteSystem = _entitySystemManager.GetEntitySystem<RenderingTreeSystem>();
-
-            foreach (var gridId in _mapManager.FindGridIdsIntersecting(map, worldBounds, true))
+            foreach (var comp in _entitySystemManager.GetEntitySystem<RenderingTreeSystem>().GetRenderTrees(map, worldBounds))
             {
-                Box2 gridBounds;
+                var bounds = worldBounds.Translated(-comp.Owner.Transform.WorldPosition);
 
-                if (gridId == GridId.Invalid)
-                {
-                    gridBounds = worldBounds;
-                }
-                else
-                {
-                    gridBounds = worldBounds.Translated(-_mapManager.GetGrid(gridId).WorldPosition);
-                }
-
-                var tree = spriteSystem.GetSpriteTreeForMap(map, gridId);
-
-                tree.QueryAabb(ref list, ((
+                comp.SpriteTree.QueryAabb(ref list, (
                     ref RefList<(SpriteComponent sprite, Matrix3 matrix, Angle worldRot, float yWorldPos)> state,
                     in SpriteComponent value) =>
                 {
@@ -394,22 +380,28 @@ namespace Robust.Client.Graphics.Clyde
                     entry.sprite = value;
                     entry.worldRot = transform.WorldRotation;
                     entry.matrix = transform.WorldMatrix;
-                    var worldPos = entry.matrix.Transform(transform.LocalPosition);
-                    entry.yWorldPos = worldPos.Y;
+                    var worldPos = new Vector2(entry.matrix.R0C2, entry.matrix.R1C2);
+                    // Didn't use the bounds from the query as that has to be re-calculated (and is probably more expensive than this).
+                    var bounds = value.CalculateBoundingBox(worldPos);
+                    entry.yWorldPos = worldPos.Y - bounds.Extents.Y;
                     return true;
 
-                }), gridBounds, approx: true);
+                }, bounds);
             }
         }
 
         private void DrawSplash(IRenderHandle handle)
         {
-            var texture = _resourceCache.GetResource<TextureResource>("/Textures/Logo/logo.png").Texture;
+            // Clear screen to black for splash.
+            ClearFramebuffer(Color.Black);
+
+            var splashTex = _cfg.GetCVar(CVars.DisplaySplashLogo);
+            var texture = _resourceCache.GetResource<TextureResource>(splashTex).Texture;
 
             handle.DrawingHandleScreen.DrawTexture(texture, (ScreenSize - texture.Size) / 2);
         }
 
-        private void RenderInRenderTarget(RenderTargetBase rt, Action a)
+        private void RenderInRenderTarget(RenderTargetBase rt, Action a, Color clearColor=default)
         {
             // TODO: for the love of god all this state pushing/popping needs to be cleaned up.
 
@@ -423,7 +415,7 @@ namespace Robust.Client.Graphics.Clyde
 
             {
                 BindRenderTargetFull(RtToLoaded(rt));
-                ClearFramebuffer(default);
+                ClearFramebuffer(clearColor);
                 SetViewportImmediate(Box2i.FromDimensions(Vector2i.Zero, rt.Size));
                 _updateUniformConstants(rt.Size);
                 CalcScreenMatrices(rt.Size, out var proj, out var view);
@@ -480,13 +472,13 @@ namespace Robust.Client.Graphics.Clyde
 
                     using (DebugGroup("Grids"))
                     {
-                        _drawGrids(worldBounds);
+                        _drawGrids(viewport, worldBounds, eye);
                     }
 
                     // We will also render worldspace overlays here so we can do them under / above entities as necessary
                     using (DebugGroup("Entities"))
                     {
-                        DrawEntities(viewport, worldBounds);
+                        DrawEntities(viewport, worldBounds, eye);
                     }
 
                     RenderOverlays(viewport, OverlaySpace.WorldSpaceBelowFOV, worldBounds);

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

@@ -2,10 +2,8 @@ using System;
 using System.Runtime.CompilerServices;
 using System.Runtime.InteropServices;
 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
@@ -276,7 +274,7 @@ namespace Robust.Client.Graphics.Clyde
 
         private void LoadGLProc<T>(string name, out T field) where T : Delegate
         {
-            var proc = _windowing!.GraphicsBindingContext.GetProcAddress(name);
+            var proc = _glBindingsContext.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

@@ -5,6 +5,7 @@ using OpenToolkit.Graphics.OpenGL4;
 using Robust.Client.GameObjects;
 using Robust.Client.ResourceManagement;
 using Robust.Shared.GameObjects;
+using Robust.Shared.IoC;
 using Robust.Shared.Log;
 using Robust.Shared.Map;
 using Robust.Shared.Maths;
@@ -323,11 +324,17 @@ namespace Robust.Client.Graphics.Clyde
                 return;
             }
 
-            var map = eye.Position.MapId;
+            var mapId = eye.Position.MapId;
 
-            var (lights, count, expandedBounds) = GetLightsToRender(map, worldBounds);
+            // If this map has lighting disabled, return
+            if (!_mapManager.GetMapEntity(mapId).GetComponent<IMapComponent>().LightingEnabled)
+            {
+                return;
+            }
 
-            UpdateOcclusionGeometry(map, expandedBounds, eye.Position.Position);
+            var (lights, count, expandedBounds) = GetLightsToRender(mapId, worldBounds);
+
+            UpdateOcclusionGeometry(mapId, expandedBounds, eye.Position.Position);
 
             DrawFov(viewport, eye);
 
@@ -494,24 +501,16 @@ namespace Robust.Client.Graphics.Clyde
             GetLightsToRender(MapId map, in Box2 worldBounds)
         {
             var renderingTreeSystem = _entitySystemManager.GetEntitySystem<RenderingTreeSystem>();
+            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);
 
-            foreach (var gridId in _mapManager.FindGridIdsIntersecting(map, worldBounds, true))
+            foreach (var comp in renderingTreeSystem.GetRenderTrees(map, enlargedBounds))
             {
-                Box2 gridBounds;
+                var bounds = worldBounds.Translated(-comp.Owner.Transform.WorldPosition);
 
-                if (gridId == GridId.Invalid)
-                {
-                    gridBounds = worldBounds;
-                }
-                else
-                {
-                    gridBounds = worldBounds.Translated(-_mapManager.GetGrid(gridId).WorldPosition);
-                }
-
-                var lightTree = renderingTreeSystem.GetLightTreeForMap(map, gridId);
-
-                lightTree.QueryAabb(ref state, (ref (Clyde clyde, Box2 worldBounds, int count) state, in PointLightComponent light) =>
+                comp.LightTree.QueryAabb(ref state, (ref (Clyde clyde, Box2 worldBounds, int count) state, in PointLightComponent light) =>
                 {
                     var transform = light.Owner.Transform;
 
@@ -535,7 +534,7 @@ namespace Robust.Client.Graphics.Clyde
                     state.clyde._lightsToRenderList[state.count++] = (light, lightPos, distanceSquared);
 
                     return true;
-                }, gridBounds);
+                }, bounds);
             }
 
             if (state.count > _maxLightsPerScene)
@@ -781,24 +780,13 @@ namespace Robust.Client.Graphics.Clyde
                 var ii = 0;
                 var imi = 0;
 
-                foreach (var gridId in _mapManager.FindGridIdsIntersecting(map, expandedBounds, true))
+                foreach (var comp in occluderSystem.GetOccluderTrees(map, expandedBounds))
                 {
-                    if (!occluderSystem.TryGetOccluderTreeForGrid(map, gridId, out var occluderTree)) continue;
+                    // TODO: I know this doesn't work with rotated grids but when I come back to these I'm adding tests
+                    // because rotation bugs are common.
+                    var treeBounds = expandedBounds.Translated(-comp.Owner.Transform.WorldPosition);
 
-                    Box2 gridBounds;
-
-                    if (gridId == GridId.Invalid)
-                    {
-                        gridBounds = expandedBounds;
-                    }
-                    else
-                    {
-                        // TODO: Ideally this would clamp to the outer border of what we can see
-                        var grid = _mapManager.GetGrid(gridId);
-                        gridBounds = expandedBounds.Translated(-grid.WorldPosition);
-                    }
-
-                    occluderTree.QueryAabb((in OccluderComponent sOccluder) =>
+                    comp.Tree.QueryAabb((in OccluderComponent sOccluder) =>
                     {
                         var occluder = (ClientOccluderComponent)sOccluder;
                         var transform = occluder.Owner.Transform;
@@ -927,7 +915,7 @@ namespace Robust.Client.Graphics.Clyde
                         ami += 4;
 
                         return true;
-                    }, gridBounds);
+                    }, treeBounds);
                 }
 
                 _occlusionDataLength = ii;

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

@@ -112,9 +112,9 @@ namespace Robust.Client.Graphics.Clyde
                 return clydeTexture;
             }
 
-            public void RenderInRenderTarget(IRenderTarget target, Action a)
+            public void RenderInRenderTarget(IRenderTarget target, Action a, Color clearColor=default)
             {
-                _clyde.RenderInRenderTarget((RenderTargetBase) target, a);
+                _clyde.RenderInRenderTarget((RenderTargetBase) target, a, clearColor);
             }
 
             public void SetScissor(UIBox2i? scissorBox)
@@ -136,7 +136,7 @@ namespace Robust.Client.Graphics.Clyde
 
                 // Switch rendering to pseudo-world space.
                 {
-                    CalcWorldProjMatrix(_clyde._currentRenderTarget.Size, out var proj);
+                    _clyde.CalcWorldProjMatrix(_clyde._currentRenderTarget.Size, out var proj);
 
                     var ofsX = position.X - _clyde.ScreenSize.X / 2f;
                     var ofsY = position.Y - _clyde.ScreenSize.Y / 2f;
@@ -153,6 +153,7 @@ namespace Robust.Client.Graphics.Clyde
                 // Draw the entity.
                 sprite.Render(
                     DrawingHandleWorld,
+                    Angle.Zero,
                     overrideDirection == null
                         ? entity.Transform.WorldRotation
                         : Angle.Zero,
@@ -354,18 +355,17 @@ namespace Robust.Client.Graphics.Clyde
 
                 public override void DrawCircle(Vector2 position, float radius, Color color, bool filled = true)
                 {
-                    //TODO: Scale number of sides based on radius
-                    const int Divisions = 8;
-                    const float ArcLength = MathF.PI * 2 / Divisions;
+                    int divisions = Math.Max(16,(int)(radius * 16));
+                    float arcLength = MathF.PI * 2 / divisions;
 
                     var filledTriangle = new Vector2[3];
 
                     // Draws a "circle", but its just a polygon with a bunch of sides
                     // this is the GL_LINES version, not GL_LINE_STRIP
-                    for (int i = 0; i < Divisions; i++)
+                    for (int i = 0; i < divisions; i++)
                     {
-                        var startPos = new Vector2(MathF.Cos(ArcLength * i) * radius, MathF.Sin(ArcLength * i) * radius);
-                        var endPos = new Vector2(MathF.Cos(ArcLength * (i+1)) * radius, MathF.Sin(ArcLength * (i + 1)) * radius);
+                        var startPos = new Vector2(MathF.Cos(arcLength * i) * radius, MathF.Sin(arcLength * i) * radius);
+                        var endPos = new Vector2(MathF.Cos(arcLength * (i+1)) * radius, MathF.Sin(arcLength * (i + 1)) * radius);
 
                         if(!filled)
                             _renderHandle.DrawLine(startPos, endPos, color);

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

@@ -3,9 +3,9 @@ using System.Collections.Concurrent;
 using System.Collections.Generic;
 using System.Runtime.CompilerServices;
 using OpenToolkit.Graphics.OpenGL4;
+using Robust.Shared.Map;
 using Robust.Shared.Maths;
 using Robust.Shared.Utility;
-using Robust.Shared.Log;
 using SixLabors.ImageSharp.PixelFormats;
 
 // ReSharper disable once IdentifierTypo
@@ -24,9 +24,6 @@ namespace Robust.Client.Graphics.Clyde
         private readonly ConcurrentQueue<ClydeHandle> _renderTargetDisposeQueue
             = new();
 
-        // Initialized in Clyde's constructor
-        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.
         // It, like _mainWindowRenderTarget, is initialized in Clyde's constructor
@@ -248,8 +245,7 @@ namespace Robust.Client.Graphics.Clyde
             // NOTE: It's critically important that this be the "focal point" of all framebuffer bindings.
             if (rt.IsWindow)
             {
-                GL.BindFramebuffer(FramebufferTarget.Framebuffer, 0);
-                CheckGlError();
+                _glContext!.BindWindowRenderTarget(rt.WindowId);
             }
             else
             {
@@ -267,18 +263,16 @@ namespace Robust.Client.Graphics.Clyde
             }
         }
 
-        private void UpdateMainWindowLoadedRtSize()
-        {
-            var loadedRt = RtToLoaded(_mainMainWindowRenderMainTarget);
-            loadedRt.Size = _windowing!.MainWindow!.FramebufferSize;
-        }
-
         private sealed class LoadedRenderTarget
         {
             public bool IsWindow;
+            public WindowId WindowId;
+
             public Vector2i Size;
             public bool IsSrgb;
 
+            public bool FlipY;
+
             public RTCF ColorFormat;
 
             // Remaining properties only apply if the render target is NOT a window.
@@ -386,11 +380,11 @@ namespace Robust.Client.Graphics.Clyde
             }
         }
 
-        private sealed class RenderMainWindow : RenderTargetBase
+        private sealed class RenderWindow : RenderTargetBase
         {
-            public override Vector2i Size => Clyde._windowing!.MainWindow!.FramebufferSize;
+            public override Vector2i Size => Clyde._renderTargets[Handle].Size;
 
-            public RenderMainWindow(Clyde clyde, ClydeHandle handle) : base(clyde, handle)
+            public RenderWindow(Clyde clyde, ClydeHandle handle) : base(clyde, handle)
             {
             }
         }

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

@@ -6,7 +6,6 @@ using System.Runtime.InteropServices;
 using OpenToolkit.Graphics.OpenGL4;
 using Robust.Client.GameObjects;
 using Robust.Client.Utility;
-using Robust.Shared;
 using Robust.Shared.Maths;
 using Robust.Shared.Utility;
 using Color = Robust.Shared.Maths.Color;
@@ -106,7 +105,7 @@ namespace Robust.Client.Graphics.Clyde
             UniformConstantsUBO.Reallocate(constants);
         }
 
-        private static void CalcScreenMatrices(in Vector2i screenSize, out Matrix3 proj, out Matrix3 view)
+        private void CalcScreenMatrices(in Vector2i screenSize, out Matrix3 proj, out Matrix3 view)
         {
             proj = Matrix3.Identity;
             proj.R0C0 = 2f / screenSize.X;
@@ -114,10 +113,16 @@ namespace Robust.Client.Graphics.Clyde
             proj.R0C2 = -1;
             proj.R1C2 = 1;
 
+            if (_currentRenderTarget.FlipY)
+            {
+                proj.R1C1 *= -1;
+                proj.R1C2 *= -1;
+            }
+
             view = Matrix3.Identity;
         }
 
-        private static void CalcWorldMatrices(in Vector2i screenSize, in Vector2 renderScale, IEye eye,
+        private void CalcWorldMatrices(in Vector2i screenSize, in Vector2 renderScale, IEye eye,
             out Matrix3 proj, out Matrix3 view)
         {
             eye.GetViewMatrix(out view, renderScale);
@@ -126,11 +131,17 @@ namespace Robust.Client.Graphics.Clyde
         }
 
         [MethodImpl(MethodImplOptions.AggressiveInlining)]
-        private static void CalcWorldProjMatrix(in Vector2i screenSize, out Matrix3 proj)
+        private void CalcWorldProjMatrix(in Vector2i screenSize, out Matrix3 proj)
         {
             proj = Matrix3.Identity;
             proj.R0C0 = EyeManager.PixelsPerMeter * 2f / screenSize.X;
             proj.R1C1 = EyeManager.PixelsPerMeter * 2f / screenSize.Y;
+
+            if (_currentRenderTarget.FlipY)
+            {
+                proj.R1C1 *= -1;
+                proj.R1C2 *= -1;
+            }
         }
 
         private void SetProjViewBuffer(in Matrix3 proj, in Matrix3 view)
@@ -353,7 +364,15 @@ namespace Robust.Client.Graphics.Clyde
 
                 // Don't forget to flip it, these coordinates have bottom left as origin.
                 // TODO: Broken when rendering to non-screen render targets.
-                GL.Scissor(box.Left, _currentRenderTarget.Size.Y - box.Bottom, box.Width, box.Height);
+
+                if (_currentRenderTarget.FlipY)
+                {
+                    GL.Scissor(box.Left, box.Top, box.Width, box.Height);
+                }
+                else
+                {
+                    GL.Scissor(box.Left, _currentRenderTarget.Size.Y - box.Bottom, box.Width, box.Height);
+                }
                 CheckGlError();
             }
             else if (oldIsScissoring)
@@ -827,9 +846,11 @@ namespace Robust.Client.Graphics.Clyde
             _lightingReady = false;
             _currentMatrixModel = Matrix3.Identity;
             SetScissorFull(null);
-            BindRenderTargetFull(_mainMainWindowRenderMainTarget);
+            BindRenderTargetFull(_mainWindow!.RenderTarget);
             _batchMetaData = null;
             _queuedShader = _defaultShader.Handle;
+
+            GL.Viewport(0, 0, _mainWindow!.FramebufferSize.X, _mainWindow!.FramebufferSize.Y);
         }
 
         private void ResetBlendFunc()
@@ -841,98 +862,6 @@ 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)
@@ -1078,7 +1007,7 @@ namespace Robust.Client.Graphics.Clyde
                 var a = _drawList[x].Item1;
                 var b = _drawList[y].Item1;
 
-                var cmp = (a.DrawDepth).CompareTo(b.DrawDepth);
+                var cmp = a.DrawDepth.CompareTo(b.DrawDepth);
                 if (cmp != 0)
                 {
                     return cmp;
@@ -1091,7 +1020,7 @@ namespace Robust.Client.Graphics.Clyde
                     return cmp;
                 }
 
-                cmp = _drawList[x].Item4.CompareTo(_drawList[y].Item4);
+                cmp = _drawList[y].Item4.CompareTo(_drawList[x].Item4);
 
                 if (cmp != 0)
                 {

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

@@ -150,12 +150,20 @@ namespace Robust.Client.Graphics.Clyde
 
             if (_isGLES)
             {
-                // GLES2 uses a different GLSL versioning scheme to desktop GL.
-                versionHeader = "#version 100\n#define HAS_VARYING_ATTRIBUTE\n";
-                if (_hasGLStandardDerivatives)
+                if (_hasGLES3Shaders)
                 {
-                    versionHeader += "#extension GL_OES_standard_derivatives : enable\n";
+                    versionHeader = "#version 300 es\n";
                 }
+                else
+                {
+                    // GLES2 uses a different GLSL versioning scheme to desktop GL.
+                    versionHeader = "#version 100\n#define HAS_VARYING_ATTRIBUTE\n";
+                    if (_hasGLStandardDerivatives)
+                    {
+                        versionHeader += "#extension GL_OES_standard_derivatives : enable\n";
+                    }
+                }
+
             }
 
             if (_hasGLStandardDerivatives)

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

@@ -1,7 +1,9 @@
 using System;
+using System.Buffers;
 using System.Collections.Concurrent;
 using System.Collections.Generic;
 using System.IO;
+using System.Runtime.InteropServices;
 using System.Threading;
 using OpenToolkit.Graphics.OpenGL4;
 using Robust.Client.Utility;
@@ -153,6 +155,10 @@ namespace Robust.Client.Graphics.Clyde
             {
                 isActuallySrgb = loadParams.Srgb;
             }
+            else if (pixelType == typeof(Bgra32))
+            {
+                isActuallySrgb = loadParams.Srgb;
+            }
             else if (pixelType == typeof(A8))
             {
                 DebugTools.Assert(_hasGLTextureSwizzle);
@@ -258,6 +264,7 @@ namespace Robust.Client.Graphics.Clyde
                 // Note that if _hasGLSrgb is off, we import an sRGB texture as non-sRGB.
                 // Shaders are expected to compensate for this
                 Rgba32 => (srgb && _hasGLSrgb ? PIF.Srgb8Alpha8 : PIF.Rgba8, PF.Rgba, PT.UnsignedByte),
+                Bgra32 => (srgb && _hasGLSrgb ? PIF.Srgb8Alpha8 : PIF.Rgba8, PF.Bgra, PT.UnsignedByte),
                 A8 or L8 => (PIF.R8, PF.Red, PT.UnsignedByte),
                 _ => throw new NotSupportedException("Unsupported pixel type."),
             };
@@ -315,27 +322,80 @@ namespace Robust.Client.Graphics.Clyde
         private unsafe void SetSubImage<T>(
             ClydeTexture texture,
             Vector2i dstTl,
-            Image<T> srcImage,
+            Image<T> img,
             in UIBox2i srcBox)
             where T : unmanaged, IPixel<T>
         {
-            if (!_hasGLTextureSwizzle)
+            if (srcBox.Left < 0 ||
+                srcBox.Top < 0 ||
+                srcBox.Right > srcBox.Width ||
+                srcBox.Bottom > srcBox.Height)
             {
-                if (typeof(T) == typeof(A8))
-                {
-                    SetSubImage(texture, dstTl, ApplyA8Swizzle((Image<A8>) (object) srcImage), srcBox);
-                    return;
-                }
+                throw new ArgumentOutOfRangeException(nameof(srcBox), "Source rectangle out of bounds.");
+            }
 
-                if (typeof(T) == typeof(L8))
-                {
-                    SetSubImage(texture, dstTl, ApplyL8Swizzle((Image<L8>) (object) srcImage), srcBox);
-                    return;
-                }
+            var size = srcBox.Width * srcBox.Height;
+
+            T[]? pooled = null;
+            // C# won't let me use an if due to the stackalloc.
+            var copyBuffer = size < 16 * 16
+                ? stackalloc T[size]
+                : (pooled = ArrayPool<T>.Shared.Rent(size)).AsSpan(0, size);
+
+            var srcSpan = img.GetPixelSpan();
+            var w = img.Width;
+            FlipCopySubRegion(srcBox, w, srcSpan, copyBuffer);
+
+            SetSubImageImpl<T>(texture, dstTl, (srcBox.Width, srcBox.Height), copyBuffer);
+
+            if (pooled != null)
+                ArrayPool<T>.Shared.Return(pooled);
+        }
+
+        private unsafe void SetSubImage<T>(
+            ClydeTexture texture,
+            Vector2i dstTl,
+            Vector2i size,
+            ReadOnlySpan<T> buf)
+            where T : unmanaged, IPixel<T>
+        {
+            T[]? pooled = null;
+            // C# won't let me use an if due to the stackalloc.
+            var copyBuffer = buf.Length < 16 * 16
+                ? stackalloc T[buf.Length]
+                : (pooled = ArrayPool<T>.Shared.Rent(buf.Length)).AsSpan(0, buf.Length);
+
+            FlipCopy(buf, copyBuffer, size.X, size.Y);
+
+            SetSubImageImpl<T>(texture, dstTl, size, copyBuffer);
+
+            if (pooled != null)
+                ArrayPool<T>.Shared.Return(pooled);
+        }
+
+        private unsafe void SetSubImageImpl<T>(
+            ClydeTexture texture,
+            Vector2i dstTl,
+            Vector2i size,
+            ReadOnlySpan<T> buf)
+            where T : unmanaged, IPixel<T>
+        {
+            if (!_hasGLTextureSwizzle && (typeof(T) == typeof(A8) || typeof(T) == typeof(L8)))
+            {
+                var swizzleBuf = ArrayPool<Rgba32>.Shared.Rent(buf.Length);
+
+                var destSpan = swizzleBuf.AsSpan(0, buf.Length);
+                if (typeof(T) == typeof(A8))
+                    ApplyA8Swizzle(MemoryMarshal.Cast<T, A8>(buf), destSpan);
+                else if (typeof(T) == typeof(L8))
+                    ApplyL8Swizzle(MemoryMarshal.Cast<T, L8>(buf), destSpan);
+
+                SetSubImageImpl<Rgba32>(texture, dstTl, size, destSpan);
+                ArrayPool<Rgba32>.Shared.Return(swizzleBuf);
+                return;
             }
 
             var loaded = _loadedTextures[texture.TextureId];
-
             var pixType = GetTexturePixelType<T>();
 
             if (pixType != loaded.TexturePixelType)
@@ -346,11 +406,8 @@ namespace Robust.Client.Graphics.Clyde
                 throw new InvalidOperationException("Mismatching pixel type for texture.");
             }
 
-            if (loaded.Width < dstTl.X + srcBox.Width || loaded.Height < dstTl.Y + srcBox.Height)
-                throw new ArgumentOutOfRangeException(nameof(srcBox), "Destination rectangle out of bounds.");
-
-            if (srcBox.Left < 0 || srcBox.Top < 0 || srcBox.Right > srcImage.Width || srcBox.Bottom > srcImage.Height)
-                throw new ArgumentOutOfRangeException(nameof(srcBox), "Source rectangle out of bounds.");
+            if (loaded.Width < dstTl.X + size.X || loaded.Height < dstTl.Y + size.Y)
+                throw new ArgumentOutOfRangeException(nameof(size), "Destination rectangle out of bounds.");
 
             if (sizeof(T) != 4)
             {
@@ -364,24 +421,14 @@ namespace Robust.Client.Graphics.Clyde
             GL.BindTexture(TextureTarget.Texture2D, loaded.OpenGLObject.Handle);
             CheckGlError();
 
-            var size = srcBox.Width * srcBox.Height;
-
-            var copyBuffer = size < 16 * 16 ? stackalloc T[size] : new T[size];
-
-            for (var y = 0; y < srcBox.Height; y++)
-            for (var x = 0; x < srcBox.Width; x++)
+            fixed (T* aPtr = buf)
             {
-                copyBuffer[(srcBox.Height - y - 1) * srcBox.Width + x] = srcImage[x + srcBox.Left, srcBox.Top + y];
-            }
-
-            fixed (T* aPtr = copyBuffer)
-            {
-                var dstY = loaded.Height - dstTl.Y - srcBox.Height;
+                var dstY = loaded.Height - dstTl.Y - size.Y;
                 GL.TexSubImage2D(
                     TextureTarget.Texture2D,
                     0,
                     dstTl.X, dstY,
-                    srcBox.Width, srcBox.Height,
+                    size.X, size.Y,
                     pf, pt,
                     (IntPtr) aPtr);
                 CheckGlError();
@@ -398,7 +445,7 @@ namespace Robust.Client.Graphics.Clyde
         {
             return default(T) switch
             {
-                Rgba32 => TexturePixelType.Rgba32,
+                Rgba32 or Bgra32 => TexturePixelType.Rgba32,
                 L8 => TexturePixelType.L8,
                 A8 => TexturePixelType.A8,
                 _ => throw new NotSupportedException("Unsupported pixel type."),
@@ -452,17 +499,35 @@ namespace Robust.Client.Graphics.Clyde
             }
         }
 
+        private static void FlipCopySubRegion<T>(
+            UIBox2i srcBox,
+            int w,
+            ReadOnlySpan<T> srcSpan,
+            Span<T> copyBuffer)
+            where T : unmanaged, IPixel<T>
+        {
+            var subH = srcBox.Height;
+            var subW = srcBox.Width;
+
+            var dr = subH - 1;
+            for (var r = 0; r < subH; r++, dr--)
+            {
+                var si = r * w + srcBox.Left;
+                var di = dr * subW;
+                var srcRow = srcSpan[si..(si + subW)];
+                var dstRow = copyBuffer[di..(di + subW)];
+
+                srcRow.CopyTo(dstRow);
+            }
+        }
+
         private static Image<Rgba32> ApplyA8Swizzle(Image<A8> source)
         {
             var newImage = new Image<Rgba32>(source.Width, source.Height);
             var sourceSpan = source.GetPixelSpan();
             var destSpan = newImage.GetPixelSpan();
 
-            for (var i = 0; i < sourceSpan.Length; i++)
-            {
-                var px = sourceSpan[i].PackedValue;
-                destSpan[i] = new Rgba32(255, 255, 255, px);
-            }
+            ApplyA8Swizzle(sourceSpan, destSpan);
 
             return newImage;
         }
@@ -473,15 +538,28 @@ namespace Robust.Client.Graphics.Clyde
             var sourceSpan = source.GetPixelSpan();
             var destSpan = newImage.GetPixelSpan();
 
-            for (var i = 0; i < sourceSpan.Length; i++)
-            {
-                var px = sourceSpan[i].PackedValue;
-                destSpan[i] = new Rgba32(px, px, px, 255);
-            }
+            ApplyL8Swizzle(sourceSpan, destSpan);
 
             return newImage;
         }
 
+        private static void ApplyL8Swizzle(ReadOnlySpan<L8> src, Span<Rgba32> dst)
+        {
+            for (var i = 0; i < src.Length; i++)
+            {
+                var px = src[i].PackedValue;
+                dst[i] = new Rgba32(px, px, px, 255);
+            }
+        }
+
+        private static void ApplyA8Swizzle(ReadOnlySpan<A8> src, Span<Rgba32> dst)
+        {
+            for (var i = 0; i < src.Length; i++)
+            {
+                var px = src[i].PackedValue;
+                dst[i] = new Rgba32(255, 255, 255, px);
+            }
+        }
 
         private sealed class LoadedTexture
         {
@@ -525,6 +603,11 @@ namespace Robust.Client.Graphics.Clyde
                 _clyde.SetSubImage(this, topLeft, sourceImage, sourceRegion);
             }
 
+            public override void SetSubImage<T>(Vector2i topLeft, Vector2i size, ReadOnlySpan<T> buffer)
+            {
+                _clyde.SetSubImage(this, topLeft, size, buffer);
+            }
+
             protected override void Dispose(bool disposing)
             {
                 if (disposing)

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

@@ -1,9 +1,9 @@
 using System;
 using System.Collections.Generic;
-using System.Runtime.InteropServices;
+using System.Diagnostics.CodeAnalysis;
 using System.Threading;
-using System.Threading.Channels;
 using System.Threading.Tasks;
+using OpenToolkit.Graphics.OpenGL4;
 using Robust.Client.Input;
 using Robust.Client.UserInterface;
 using Robust.Shared;
@@ -13,19 +13,24 @@ using Robust.Shared.Maths;
 using Robust.Shared.Utility;
 using SixLabors.ImageSharp;
 using SixLabors.ImageSharp.PixelFormats;
-using static Robust.Client.Utility.LiterallyJustMessageBox;
+using static Robust.Client.Utility.Win32;
 using FrameEventArgs = Robust.Shared.Timing.FrameEventArgs;
 
 namespace Robust.Client.Graphics.Clyde
 {
-    internal partial class Clyde
+    internal partial class  Clyde
     {
+        private readonly List<WindowReg> _windows = new();
         private readonly List<WindowHandle> _windowHandles = new();
-        private readonly List<MonitorHandle> _monitorHandles = new();
+        private readonly Dictionary<int, MonitorHandle> _monitorHandles = new();
+
+        private int _primaryMonitorId;
+        private WindowReg? _mainWindow;
 
         private IWindowingImpl? _windowing;
         private Renderer _chosenRenderer;
 
+        private ResourcePath? _windowIconPath;
         private Thread? _windowingThread;
         private bool _vSync;
         private WindowMode _windowMode;
@@ -39,7 +44,7 @@ namespace Robust.Client.Graphics.Clyde
         public event Action<KeyEventArgs>? KeyUp;
         public event Action<KeyEventArgs>? KeyDown;
         public event Action<MouseWheelEventArgs>? MouseWheel;
-        public event Action<WindowClosedEventArgs>? CloseWindow;
+        public event Action<WindowRequestClosedEventArgs>? CloseWindow;
         public event Action<WindowDestroyedEventArgs>? DestroyWindow;
         public event Action<WindowContentScaleEventArgs>? OnWindowScaleChanged;
         public event Action<WindowResizedEventArgs>? OnWindowResized;
@@ -47,18 +52,18 @@ namespace Robust.Client.Graphics.Clyde
 
         // NOTE: in engine we pretend the framebuffer size is the screen size..
         // For practical reasons like UI rendering.
-        public IClydeWindow MainWindow => _windowing?.MainWindow?.Handle ??
+        public IClydeWindow MainWindow => _mainWindow?.Handle ??
                                           throw new InvalidOperationException("Windowing is not initialized");
 
-        public Vector2i ScreenSize => _windowing?.MainWindow?.FramebufferSize ??
+        public Vector2i ScreenSize => _mainWindow?.FramebufferSize ??
                                       throw new InvalidOperationException("Windowing is not initialized");
 
-        public bool IsFocused => _windowing?.MainWindow?.IsFocused ??
+        public bool IsFocused => _mainWindow?.IsFocused ??
                                  throw new InvalidOperationException("Windowing is not initialized");
 
         public IEnumerable<IClydeWindow> AllWindows => _windowHandles;
 
-        public Vector2 DefaultWindowScale => _windowing?.MainWindow?.WindowScale ??
+        public Vector2 DefaultWindowScale => _mainWindow?.WindowScale ??
                                              throw new InvalidOperationException("Windowing is not initialized");
 
         public ScreenCoordinates MouseScreenPosition
@@ -82,11 +87,15 @@ namespace Robust.Client.Graphics.Clyde
 
         public uint? GetX11WindowId()
         {
-            return _windowing?.WindowGetX11Id(_windowing.MainWindow!) ?? null;
+            return _windowing?.WindowGetX11Id(_mainWindow!) ?? null;
         }
 
         private bool InitWindowing()
         {
+            var iconPath = _cfg.GetCVar(CVars.DisplayWindowIconSet);
+            if (!string.IsNullOrWhiteSpace(iconPath))
+                _windowIconPath = new ResourcePath(iconPath);
+
             _windowingThread = Thread.CurrentThread;
 
             _windowing = new GlfwWindowingImpl(this);
@@ -94,40 +103,93 @@ namespace Robust.Client.Graphics.Clyde
             return _windowing.Init();
         }
 
+        private bool TryInitMainWindow(GLContextSpec? glSpec, [NotNullWhen(false)] out string? error)
+        {
+            DebugTools.AssertNotNull(_glContext);
+
+            var width = _cfg.GetCVar(CVars.DisplayWidth);
+            var height = _cfg.GetCVar(CVars.DisplayHeight);
+            var prevWidth = width;
+            var prevHeight = height;
+
+            IClydeMonitor? monitor = null;
+            var fullscreen = false;
+
+            if (_windowMode == WindowMode.Fullscreen)
+            {
+                monitor = _monitorHandles[_primaryMonitorId];
+                width = monitor.Size.X;
+                height = monitor.Size.Y;
+                fullscreen = true;
+            }
+
+            var parameters = new WindowCreateParameters
+            {
+                Width = width,
+                Height = height,
+                Monitor = monitor,
+                Fullscreen = fullscreen
+            };
+
+            var (reg, err) = SharedWindowCreate(glSpec, parameters, null, isMain: true);
+
+            if (reg == null)
+            {
+                error = err!;
+                return false;
+            }
+
+            DebugTools.Assert(reg.Id == WindowId.Main);
+
+            if (fullscreen)
+            {
+                reg.PrevWindowSize = (prevWidth, prevHeight);
+                reg.PrevWindowPos = (50, 50);
+            }
+
+            error = null;
+            return true;
+        }
+
         private unsafe bool InitMainWindowAndRenderer()
         {
             DebugTools.AssertNotNull(_windowing);
+            DebugTools.AssertNotNull(_glContext);
 
-            _chosenRenderer = (Renderer) _cfg.GetCVar(CVars.DisplayRenderer);
-
-            var renderers = _chosenRenderer == Renderer.Default
-                ? stackalloc Renderer[]
-                {
-                    Renderer.OpenGL33,
-                    Renderer.OpenGL31,
-                    Renderer.OpenGLES2
-                }
-                : stackalloc Renderer[] {_chosenRenderer};
+            _chosenRenderer = Renderer.OpenGL;
 
             var succeeded = false;
             string? lastError = null;
-            foreach (var renderer in renderers)
+
+            if (_glContext!.RequireWindowGL)
             {
-                if (!_windowing!.TryInitMainWindow(renderer, out lastError))
+                var specs = _glContext!.SpecsToTry;
+
+                foreach (var glSpec in specs)
                 {
-                    Logger.DebugS("clyde.win", $"{renderer} unsupported: {lastError}");
-                    continue;
+                    if (!TryInitMainWindow(glSpec, out lastError))
+                    {
+                        Logger.DebugS("clyde.win", $"OpenGL {glSpec.OpenGLVersion} unsupported: {lastError}");
+                        continue;
+                    }
+
+                    succeeded = true;
+                    break;
                 }
-
-                // We should have a main window now.
-                DebugTools.AssertNotNull(_windowing.MainWindow);
-
-                succeeded = true;
-                _chosenRenderer = renderer;
-                _isGLES = _chosenRenderer == Renderer.OpenGLES2;
-                _isCore = _chosenRenderer == Renderer.OpenGL33;
-                break;
             }
+            else
+            {
+                if (!TryInitMainWindow(null, out lastError))
+                    Logger.DebugS("clyde.win", $"Failed to create window: {lastError}");
+                else
+                    succeeded = true;
+            }
+
+            // We should have a main window now.
+            DebugTools.AssertNotNull(_mainWindow);
+
+            // _openGLVersion must be set by _glContext.
+            DebugTools.Assert(_openGLVersion != RendererOpenGLVersion.Auto);
 
             if (!succeeded)
             {
@@ -153,24 +215,28 @@ namespace Robust.Client.Graphics.Clyde
                 return false;
             }
 
-            _windowing!.GLInitMainContext(_isGLES);
-
-            UpdateMainWindowLoadedRtSize();
-
-            _windowing.GLMakeContextCurrent(_windowing.MainWindow!);
             InitOpenGL();
+
+            _sawmillOgl.Debug("Setting viewport and rendering splash...");
+
+            GL.Viewport(0, 0, ScreenSize.X, ScreenSize.Y);
+            CheckGlError();
+
+            // Quickly do a render with _drawingSplash = true so the screen isn't blank.
+            Render();
+
             return true;
         }
 
         private IEnumerable<Image<Rgba32>> LoadWindowIcons()
         {
-            if (OperatingSystem.IsMacOS())
+            if (OperatingSystem.IsMacOS() || _windowIconPath == null)
             {
                 // Does nothing on macOS so don't bother.
                 yield break;
             }
 
-            foreach (var file in _resourceCache.ContentFindFiles("/Textures/Logo/icon"))
+            foreach (var file in _resourceCache.ContentFindFiles(_windowIconPath))
             {
                 if (file.Extension != "png")
                 {
@@ -190,31 +256,89 @@ namespace Robust.Client.Graphics.Clyde
         public void SetWindowTitle(string title)
         {
             DebugTools.AssertNotNull(_windowing);
+            DebugTools.AssertNotNull(_mainWindow);
 
-            _windowing!.WindowSetTitle(_windowing.MainWindow!, title);
+            _windowing!.WindowSetTitle(_mainWindow!, title);
         }
 
         public void SetWindowMonitor(IClydeMonitor monitor)
         {
             DebugTools.AssertNotNull(_windowing);
+            DebugTools.AssertNotNull(_mainWindow);
 
-            var window = _windowing!.MainWindow!;
-
-            _windowing.WindowSetMonitor(window, monitor);
+            _windowing!.WindowSetMonitor(_mainWindow!, monitor);
         }
 
         public void RequestWindowAttention()
         {
             DebugTools.AssertNotNull(_windowing);
+            DebugTools.AssertNotNull(_mainWindow);
 
-            _windowing!.WindowRequestAttention(_windowing.MainWindow!);
+            _windowing!.WindowRequestAttention(_mainWindow!);
         }
 
-        public async Task<IClydeWindow> CreateWindow(WindowCreateParameters parameters)
+        public IClydeWindow CreateWindow(WindowCreateParameters parameters)
         {
             DebugTools.AssertNotNull(_windowing);
+            DebugTools.AssertNotNull(_glContext);
+            DebugTools.AssertNotNull(_mainWindow);
 
-            return await _windowing!.WindowCreate(parameters);
+            var glSpec = _glContext!.GetNewWindowSpec();
+
+            _glContext.BeforeSharedWindowCreateUnbind();
+
+            var (reg, error) = SharedWindowCreate(
+                glSpec,
+                parameters,
+                glSpec == null ? null : _mainWindow,
+                isMain: false);
+
+            // Rebinding is handed by WindowCreated in the GL context.
+
+            if (error != null)
+                throw new Exception(error);
+
+            return reg!.Handle;
+        }
+
+        private (WindowReg?, string? error) SharedWindowCreate(
+            GLContextSpec? glSpec,
+            WindowCreateParameters parameters,
+            WindowReg? share,
+            bool isMain)
+        {
+            WindowReg? owner = null;
+            if (parameters.Owner != null)
+                owner = ((WindowHandle)parameters.Owner).Reg;
+
+            var (reg, error) = _windowing!.WindowCreate(glSpec, parameters, share, owner);
+
+            if (reg != null)
+            {
+                // Window init succeeded, do setup.
+                reg.IsMainWindow = isMain;
+                if (isMain)
+                    _mainWindow = reg;
+
+                _windows.Add(reg);
+                _windowHandles.Add(reg.Handle);
+
+                var rtId = AllocRid();
+                _renderTargets.Add(rtId, new LoadedRenderTarget
+                {
+                    Size = reg.FramebufferSize,
+                    IsWindow = true,
+                    WindowId = reg.Id,
+                    IsSrgb = true
+                });
+
+                reg.RenderTarget = new RenderWindow(this, rtId);
+
+                _glContext!.WindowCreated(glSpec, reg);
+            }
+
+            // Pass through result whether successful or not, caller handles it.
+            return (reg, error);
         }
 
         private void DoDestroyWindow(WindowReg reg)
@@ -222,8 +346,20 @@ namespace Robust.Client.Graphics.Clyde
             if (reg.IsMainWindow)
                 throw new InvalidOperationException("Cannot destroy main window.");
 
+            if (reg.IsDisposed)
+                return;
+
+            reg.IsDisposed = true;
+
+            _glContext!.WindowDestroyed(reg);
             _windowing!.WindowDestroy(reg);
-            reg.BlitDoneEvent?.Set();
+
+            _windows.Remove(reg);
+            _windowHandles.Remove(reg.Handle);
+
+            var destroyed = new WindowDestroyedEventArgs(reg.Handle);
+            DestroyWindow?.Invoke(destroyed);
+            reg.Closed?.Invoke(destroyed);
         }
 
         public void ProcessInput(FrameEventArgs frameEventArgs)
@@ -232,28 +368,15 @@ namespace Robust.Client.Graphics.Clyde
             DispatchEvents();
         }
 
-        private void SwapMainBuffers()
+        private void SwapAllBuffers()
         {
-            _windowing?.WindowSwapBuffers(_windowing.MainWindow!);
+            _glContext?.SwapAllBuffers();
         }
 
         private void VSyncChanged(bool newValue)
         {
             _vSync = newValue;
-            _windowing?.UpdateVSync();
-        }
-
-        private void CreateWindowRenderTexture(WindowReg reg)
-        {
-            reg.RenderTexture?.Dispose();
-
-            reg.RenderTexture = CreateRenderTarget(reg.FramebufferSize, new RenderTargetFormatParameters
-            {
-                ColorFormat = RenderTargetColorFormat.Rgba8Srgb,
-                HasDepthStencil = true
-            });
-            // Necessary to correctly sync multi-context blitting.
-            reg.RenderTexture.MakeGLFence = true;
+            _glContext?.UpdateVSync();
         }
 
         private void WindowModeChanged(int mode)
@@ -264,17 +387,17 @@ namespace Robust.Client.Graphics.Clyde
 
         Task<string> IClipboardManager.GetText()
         {
-            return _windowing?.ClipboardGetText() ?? Task.FromResult("");
+            return _windowing?.ClipboardGetText(_mainWindow!) ?? Task.FromResult("");
         }
 
         void IClipboardManager.SetText(string text)
         {
-            _windowing?.ClipboardSetText(text);
+            _windowing?.ClipboardSetText(_mainWindow!, text);
         }
 
         public IEnumerable<IClydeMonitor> EnumerateMonitors()
         {
-            return _monitorHandles;
+            return _monitorHandles.Values;
         }
 
         public ICursor GetStandardCursor(StandardCursorShape shape)
@@ -295,7 +418,7 @@ namespace Robust.Client.Graphics.Clyde
         {
             DebugTools.AssertNotNull(_windowing);
 
-            _windowing!.CursorSet(_windowing.MainWindow!, cursor);
+            _windowing!.CursorSet(_mainWindow!, cursor);
         }
 
 
@@ -306,68 +429,6 @@ namespace Robust.Client.Graphics.Clyde
             _windowing!.WindowSetVisible(reg, visible);
         }
 
-        private void InitWindowBlitThread(WindowReg reg)
-        {
-            if (EffectiveThreadWindowBlit)
-            {
-                reg.BlitStartEvent = new ManualResetEventSlim();
-                reg.BlitDoneEvent = new ManualResetEventSlim();
-                reg.BlitThread = new Thread(() => BlitThread(reg))
-                {
-                    Name = $"WinBlitThread ID:{reg.Id}",
-                    IsBackground = true
-                };
-
-                // System.Console.WriteLine("A");
-                reg.BlitThread.Start();
-                // Wait for thread to finish init.
-                reg.BlitDoneEvent.Wait();
-            }
-            else
-            {
-                // Binds GL context.
-                BlitThreadInit(reg);
-
-                _windowing!.GLMakeContextCurrent(_windowing.MainWindow!);
-            }
-        }
-
-        private void BlitThread(WindowReg reg)
-        {
-            BlitThreadInit(reg);
-
-            reg.BlitDoneEvent!.Set();
-
-            try
-            {
-                while (true)
-                {
-                    reg.BlitStartEvent!.Wait();
-                    if (reg.IsDisposed)
-                    {
-                        BlitThreadCleanup(reg);
-                        return;
-                    }
-
-                    reg.BlitStartEvent!.Reset();
-
-                    // Do channel blit.
-                    BlitThreadDoSecondaryWindowBlit(reg);
-                }
-            }
-            catch (AggregateException e)
-            {
-                // ok channel closed, we exit.
-                e.Handle(ec => ec is ChannelClosedException);
-            }
-        }
-
-        private static void BlitThreadCleanup(WindowReg reg)
-        {
-            reg.BlitDoneEvent!.Dispose();
-            reg.BlitStartEvent!.Dispose();
-        }
-
         private abstract class WindowReg
         {
             public bool IsDisposed;
@@ -385,21 +446,18 @@ namespace Robust.Client.Graphics.Clyde
             public bool IsMinimized;
             public string Title = "";
             public bool IsVisible;
+            public IClydeWindow? Owner;
 
             public bool DisposeOnClose;
 
-            // Used EXCLUSIVELY to run the two rendering commands to blit to the window.
-            public Thread? BlitThread;
-            public ManualResetEventSlim? BlitStartEvent;
-            public ManualResetEventSlim? BlitDoneEvent;
-
             public bool IsMainWindow;
             public WindowHandle Handle = default!;
-            public RenderTexture? RenderTexture;
-            public Action<WindowClosedEventArgs>? Closed;
+            public RenderWindow RenderTarget = default!;
+            public Action<WindowRequestClosedEventArgs>? RequestClosed;
+            public Action<WindowDestroyedEventArgs>? Closed;
         }
 
-        private sealed class WindowHandle : IClydeWindow
+        private sealed class WindowHandle : IClydeWindowInternal
         {
             // So funny story
             // When this class was a record, the C# compiler on .NET 5 stack overflowed
@@ -407,65 +465,62 @@ namespace Robust.Client.Graphics.Clyde
             // VERY funny.
 
             private readonly Clyde _clyde;
-            private readonly WindowReg _reg;
+            public readonly WindowReg Reg;
 
-            public bool IsDisposed => _reg.IsDisposed;
-            public WindowId Id => _reg.Id;
+            public bool IsDisposed => Reg.IsDisposed;
+            public WindowId Id => Reg.Id;
 
             public WindowHandle(Clyde clyde, WindowReg reg)
             {
                 _clyde = clyde;
-                _reg = reg;
+                Reg = reg;
             }
 
             public void Dispose()
             {
-                _clyde.DoDestroyWindow(_reg);
+                _clyde.DoDestroyWindow(Reg);
             }
 
-            public Vector2i Size => _reg.FramebufferSize;
+            public Vector2i Size => Reg.FramebufferSize;
 
-            public IRenderTarget RenderTarget
-            {
-                get
-                {
-                    if (_reg.IsMainWindow)
-                    {
-                        return _clyde._mainMainWindowRenderMainTarget;
-                    }
-
-                    return _reg.RenderTexture!;
-                }
-            }
+            public IRenderTarget RenderTarget => Reg.RenderTarget;
 
             public string Title
             {
-                get => _reg.Title;
-                set => _clyde._windowing!.WindowSetTitle(_reg, value);
+                get => Reg.Title;
+                set => _clyde._windowing!.WindowSetTitle(Reg, value);
             }
 
-            public bool IsFocused => _reg.IsFocused;
-            public bool IsMinimized => _reg.IsMinimized;
+            public bool IsFocused => Reg.IsFocused;
+            public bool IsMinimized => Reg.IsMinimized;
 
             public bool IsVisible
             {
-                get => _reg.IsVisible;
-                set => _clyde.SetWindowVisible(_reg, value);
+                get => Reg.IsVisible;
+                set => _clyde.SetWindowVisible(Reg, value);
             }
 
-            public Vector2 ContentScale => _reg.WindowScale;
+            public Vector2 ContentScale => Reg.WindowScale;
 
             public bool DisposeOnClose
             {
-                get => _reg.DisposeOnClose;
-                set => _reg.DisposeOnClose = value;
+                get => Reg.DisposeOnClose;
+                set => Reg.DisposeOnClose = value;
             }
 
-            public event Action<WindowClosedEventArgs> Closed
+            public event Action<WindowRequestClosedEventArgs> RequestClosed
             {
-                add => _reg.Closed += value;
-                remove => _reg.Closed -= value;
+                add => Reg.RequestClosed += value;
+                remove => Reg.RequestClosed -= value;
             }
+
+            public event Action<WindowDestroyedEventArgs>? Destroyed
+            {
+                add => Reg.Closed += value;
+                remove => Reg.Closed -= value;
+            }
+
+            public nint? WindowsHWnd => _clyde._windowing!.WindowGetWin32Window(Reg);
         }
 
         private sealed class MonitorHandle : IClydeMonitor

Robust.Client/Graphics/Clyde/Clyde.cs

@@ -3,6 +3,7 @@ using System.Diagnostics;
 using System.Globalization;
 using System.Runtime.InteropServices;
 using System.Threading;
+using OpenToolkit;
 using OpenToolkit.Graphics.OpenGL4;
 using Robust.Client.Map;
 using Robust.Client.ResourceManagement;
@@ -24,6 +25,7 @@ namespace Robust.Client.Graphics.Clyde
     internal sealed partial class Clyde : IClydeInternal, IClydeAudio, IPostInjectInit
     {
         [Dependency] private readonly IClydeTileDefinitionManager _tileDefinitionManager = default!;
+        [Dependency] private readonly IEntityLookup _lookup = default!;
         [Dependency] private readonly IEyeManager _eyeManager = default!;
         [Dependency] private readonly ILightManager _lightManager = default!;
         [Dependency] private readonly ILogManager _logManager = default!;
@@ -64,21 +66,12 @@ namespace Robust.Client.Graphics.Clyde
 
         private ISawmill _sawmillOgl = default!;
 
+        private IBindingsContext _glBindingsContext = default!;
+
         public Clyde()
         {
-            // Init main window render target.
-            var windowRid = AllocRid();
-            var window = new RenderMainWindow(this, windowRid);
-            var loadedData = new LoadedRenderTarget
-            {
-                IsWindow = true,
-                IsSrgb = true
-            };
-            _renderTargets.Add(windowRid, loadedData);
-
-            _mainMainWindowRenderMainTarget = window;
-            _currentRenderTarget = RtToLoaded(window);
-            _currentBoundRenderTarget = _currentRenderTarget;
+            _currentBoundRenderTarget = default!;
+            _currentRenderTarget = default!;
         }
 
         public bool InitializePreWindowing()
@@ -100,6 +93,8 @@ namespace Robust.Client.Graphics.Clyde
         public bool InitializePostWindowing()
         {
             _gameThread = Thread.CurrentThread;
+
+            InitGLContextManager();
             if (!InitMainWindowAndRenderer())
                 return false;
 
@@ -152,13 +147,31 @@ namespace Robust.Client.Graphics.Clyde
             RegisterBlockCVars();
         }
 
+        private void GLInitBindings(bool gles)
+        {
+            _glBindingsContext = _glContext!.BindingsContext;
+            GL.LoadBindings(_glBindingsContext);
+
+            if (gles)
+            {
+                // On GLES we use some OES and KHR functions so make sure to initialize them.
+                OpenToolkit.Graphics.ES20.GL.LoadBindings(_glBindingsContext);
+            }
+        }
+
         private void InitOpenGL()
         {
+            _isGLES = _openGLVersion is RendererOpenGLVersion.GLES2 or RendererOpenGLVersion.GLES3;
+            _isCore = _openGLVersion is RendererOpenGLVersion.GL33;
+
+            GLInitBindings(_isGLES);
+
             var vendor = GL.GetString(StringName.Vendor);
             var renderer = GL.GetString(StringName.Renderer);
             var version = GL.GetString(StringName.Version);
-            var major = GL.GetInteger(GetPName.MajorVersion);
-            var minor = GL.GetInteger(GetPName.MinorVersion);
+            // GLES2 doesn't allow you to query major/minor version. Seriously.
+            var major = _openGLVersion == RendererOpenGLVersion.GLES2 ? 2 : GL.GetInteger(GetPName.MajorVersion);
+            var minor = _openGLVersion == RendererOpenGLVersion.GLES2 ? 0 :GL.GetInteger(GetPName.MinorVersion);
 
             _sawmillOgl.Debug("OpenGL Vendor: {0}", vendor);
             _sawmillOgl.Debug("OpenGL Renderer: {0}", renderer);
@@ -182,7 +195,7 @@ namespace Robust.Client.Graphics.Clyde
             DebugInfo = new ClydeDebugInfo(glVersion, renderer, vendor, version, overrideVersion != null);
 
             GL.Enable(EnableCap.Blend);
-            if (_hasGLSrgb)
+            if (_hasGLSrgb && !_isGLES)
             {
                 GL.Enable(EnableCap.FramebufferSrgb);
                 CheckGlError();
@@ -221,14 +234,6 @@ namespace Robust.Client.Graphics.Clyde
             _sawmillOgl.Debug("Setting up RenderHandle...");
 
             _renderHandle = new RenderHandle(this);
-
-            _sawmillOgl.Debug("Setting viewport and rendering splash...");
-
-            GL.Viewport(0, 0, ScreenSize.X, ScreenSize.Y);
-            CheckGlError();
-
-            // Quickly do a render with _drawingSplash = true so the screen isn't blank.
-            Render();
         }
 
         private (int major, int minor)? ParseGLOverrideVersion()
@@ -324,7 +329,8 @@ namespace Robust.Client.Graphics.Clyde
             screenBufferHandle = new GLHandle(GL.GenTexture());
             GL.BindTexture(TextureTarget.Texture2D, screenBufferHandle.Handle);
             ApplySampleParameters(TextureSampleParameters.Default);
-            ScreenBufferTexture = GenTexture(screenBufferHandle, _windowing!.MainWindow!.FramebufferSize, true, null, TexturePixelType.Rgba32);
+            // TODO: This is atrocious and broken and awful why did I merge this
+            ScreenBufferTexture = GenTexture(screenBufferHandle, (1920, 1080), true, null, TexturePixelType.Rgba32);
         }
 
         private GLHandle MakeQuadVao()
@@ -467,7 +473,7 @@ namespace Robust.Client.Graphics.Clyde
         [Conditional("DEBUG")]
         private void PushDebugGroupMaybe(string group)
         {
-            if (!_hasGLKhrDebug)
+            if (!_hasGLKhrDebug || true)
             {
                 return;
             }
@@ -485,7 +491,7 @@ namespace Robust.Client.Graphics.Clyde
         [Conditional("DEBUG")]
         private void PopDebugGroupMaybe()
         {
-            if (!_hasGLKhrDebug)
+            if (!_hasGLKhrDebug || true)
             {
                 return;
             }
@@ -502,6 +508,7 @@ namespace Robust.Client.Graphics.Clyde
 
         public void Shutdown()
         {
+            _glContext?.Shutdown();
             ShutdownWindowing();
             _shutdownAudio();
         }

Robust.Client/Graphics/Clyde/ClydeHeadless.cs

@@ -54,7 +54,7 @@ namespace Robust.Client.Graphics.Clyde
         public event Action<KeyEventArgs>? KeyUp { add { } remove { } }
         public event Action<KeyEventArgs>? KeyDown { add { } remove { } }
         public event Action<MouseWheelEventArgs>? MouseWheel { add { } remove { } }
-        public event Action<WindowClosedEventArgs>? CloseWindow { add { } remove { } }
+        public event Action<WindowRequestClosedEventArgs>? CloseWindow { add { } remove { } }
         public event Action<WindowDestroyedEventArgs>? DestroyWindow { add { } remove { } }
 
         public Texture GetStockTexture(ClydeStockTexture stockTexture)
@@ -210,7 +210,7 @@ namespace Robust.Client.Graphics.Clyde
             yield break;
         }
 
-        public Task<IClydeWindow> CreateWindow(WindowCreateParameters parameters)
+        public IClydeWindow CreateWindow(WindowCreateParameters parameters)
         {
             var window = new DummyWindow(CreateRenderTarget((123, 123), default))
             {
@@ -218,7 +218,7 @@ namespace Robust.Client.Graphics.Clyde
             };
             _windows.Add(window);
 
-            return Task.FromResult<IClydeWindow>(window);
+            return window;
         }
 
         public ClydeHandle LoadShader(ParsedShader shader, string? name = null)
@@ -334,6 +334,21 @@ namespace Robust.Client.Graphics.Clyde
                 // Nada.
             }
 
+            public void SetMaxDistance(float maxDistance)
+            {
+                // Nada.
+            }
+
+            public void SetRolloffFactor(float rolloffFactor)
+            {
+                // Nada.
+            }
+
+            public void SetReferenceDistance(float refDistance)
+            {
+                // Nada.
+            }
+
             public void SetOcclusion(float blocks)
             {
                 // Nada.
@@ -396,6 +411,11 @@ namespace Robust.Client.Graphics.Clyde
             {
                 // Just do nothing on mutate.
             }
+
+            public override void SetSubImage<T>(Vector2i topLeft, Vector2i size, ReadOnlySpan<T> buffer)
+            {
+                // Just do nothing on mutate.
+            }
         }
 
         private sealed class DummyShaderInstance : ShaderInstance
@@ -605,7 +625,8 @@ namespace Robust.Client.Graphics.Clyde
             public bool IsVisible { get; set; } = true;
             public Vector2 ContentScale => Vector2.One;
             public bool DisposeOnClose { get; set; }
-            public event Action<WindowClosedEventArgs>? Closed { add { } remove { } }
+            public event Action<WindowRequestClosedEventArgs>? RequestClosed { add { } remove { } }
+            public event Action<WindowDestroyedEventArgs>? Destroyed;
 
             public void MaximizeOnMonitor(IClydeMonitor monitor)
             {
@@ -614,6 +635,8 @@ namespace Robust.Client.Graphics.Clyde
             public void Dispose()
             {
                 IsDisposed = true;
+
+                Destroyed?.Invoke(new WindowDestroyedEventArgs(this));
             }
         }
     }

Robust.Client/Graphics/Clyde/Egl.cs

@@ -0,0 +1,140 @@
+using System.Diagnostics.CodeAnalysis;
+using System.Runtime.InteropServices;
+
+namespace Robust.Client.Graphics.Clyde
+{
+    /// <summary>
+    ///     Minimal ANGLE EGL API P/Invokes.
+    /// </summary>
+    [SuppressMessage("ReSharper", "InconsistentNaming")]
+    [SuppressMessage("ReSharper", "IdentifierTypo")]
+    internal static unsafe class Egl
+    {
+        // ANGLE exports all the functions we need directly on the dll. No need to do eglGetProcAddress for EGL itself.
+        // Still need it for OpenGL functions, however.
+
+        private const string LibraryName = "libEGL.dll";
+
+        public const int EGL_FALSE = 0;
+        public const int EGL_TRUE = 1;
+
+        public const int EGL_NONE = 0x3038;
+        public const int EGL_VENDOR = 0x3053;
+        public const int EGL_VERSION = 0x3054;
+        public const int EGL_EXTENSIONS = 0x3055;
+        public const int EGL_CONFIG_ID = 0x3028;
+        public const int EGL_COLOR_BUFFER_TYPE = 0x303F;
+        public const int EGL_SAMPLES = 0x3031;
+        public const int EGL_SAMPLE_BUFFERS = 0x3032;
+        public const int EGL_CONFIG_CAVEAT = 0x3027;
+        public const int EGL_CONFORMANT = 0x3042;
+        public const int EGL_NATIVE_VISUAL_ID = 0x302E;
+        public const int EGL_SURFACE_TYPE = 0x3033;
+        public const int EGL_ALPHA_SIZE = 0x3021;
+        public const int EGL_BLUE_SIZE = 0x3022;
+        public const int EGL_GREEN_SIZE = 0x3023;
+        public const int EGL_RED_SIZE = 0x3024;
+        public const int EGL_DEPTH_SIZE = 0x3025;
+        public const int EGL_STENCIL_SIZE = 0x3026;
+        public const int EGL_WINDOW_BIT = 0x0004;
+        public const int EGL_OPENGL_ES_API = 0x30A0;
+        public const int EGL_RENDERABLE_TYPE = 0x3040;
+        public const int EGL_OPENGL_ES2_BIT = 0x00000004;
+        public const int EGL_OPENGL_ES3_BIT = 0x00000040;
+        public const int EGL_CONTEXT_CLIENT_VERSION = 0x3098;
+        public const int EGL_TEXTURE_FORMAT = 0x3080;
+        public const int EGL_TEXTURE_RGBA = 0x305E;
+        public const int EGL_TEXTURE_TARGET = 0x3081;
+        public const int EGL_TEXTURE_2D = 0x305F;
+        public const int EGL_GL_COLORSPACE = 0x309D;
+        public const int EGL_GL_COLORSPACE_SRGB = 0x3089;
+        public const int EGL_PLATFORM_ANGLE_ANGLE = 0x3202;
+
+        public const nint EGL_NO_CONTEXT = 0;
+        public const nint EGL_NO_DEVICE_EXT = 0;
+        public const nint EGL_NO_SURFACE = 0;
+
+        public const int EGL_D3D_TEXTURE_ANGLE = 0x33A3;
+        public const int EGL_D3D11_DEVICE_ANGLE = 0x33A1;
+        public const int EGL_PLATFORM_DEVICE_EXT = 0x313F;
+        public const int EGL_OPTIMAL_SURFACE_ORIENTATION_ANGLE = 0x33A7;
+
+        [DllImport(LibraryName)]
+        public static extern int eglInitialize(void* display, int* major, int* minor);
+
+        [DllImport(LibraryName)]
+        public static extern int eglTerminate(void* display);
+
+        [DllImport(LibraryName)]
+        public static extern void* eglGetDisplay(void* display);
+
+        [DllImport(LibraryName)]
+        public static extern void* eglGetPlatformDisplayEXT(int platform, void* native_display, nint* attrib_list);
+
+        [DllImport(LibraryName)]
+        public static extern int eglBindAPI(int api);
+
+        [DllImport(LibraryName)]
+        public static extern void* eglCreateDeviceANGLE(int device_type, void* native_device, nint* attrib_list);
+
+        [DllImport(LibraryName)]
+        public static extern int eglReleaseDeviceANGLE(void* device);
+
+        [DllImport(LibraryName)]
+        public static extern void* eglGetProcAddress(byte* procname);
+
+        [DllImport(LibraryName)]
+        public static extern int eglChooseConfig(
+            void* display,
+            int* attrib_list,
+            void** configs,
+            int config_size,
+            int* num_config);
+
+        [DllImport(LibraryName)]
+        public static extern int eglGetConfigAttrib(void* display, void* config, int attribute, int* value);
+
+        [DllImport(LibraryName)]
+        public static extern void* eglCreateContext(void* display, void* config, void* share_context, int* attrib_list);
+
+        [DllImport(LibraryName)]
+        public static extern int eglGetError();
+
+        [DllImport(LibraryName)]
+        public static extern byte* eglQueryString(void* display, int name);
+
+        [DllImport(LibraryName)]
+        public static extern void* eglCreatePbufferFromClientBuffer(
+            void* display,
+            int buftype,
+            void* buffer,
+            void* config,
+            int* attrib_list);
+
+        [DllImport(LibraryName)]
+        public static extern void* eglCreateWindowSurface(
+            void* display,
+            void* config,
+            void* native_window,
+            int* attrib_list);
+
+        [DllImport(LibraryName)]
+        public static extern int eglMakeCurrent(
+            void* display,
+            void* draw,
+            void* read,
+            void* context);
+
+        [DllImport(LibraryName)]
+        public static extern void* eglGetCurrentContext();
+
+        [DllImport(LibraryName)]
+        public static extern int eglSwapBuffers(void* display, void* surface);
+
+        [DllImport(LibraryName)]
+        public static extern int eglSwapInterval(void* display, int interval);
+
+        [DllImport(LibraryName)]
+        public static extern int eglDestroySurface(void* display, void* surface);
+    }
+}