fix: wire complete ImGui window input

CORTEX_ENGINE_ARCHITECTURE.md

@@ -100,7 +100,7 @@ src/
 
 ### 3.1 Initialization
 
-1. **Load `libvulkan.so.1`** via `NativeLibrary.Load()`
+1. **Load the platform Vulkan loader** via `NativeLibrary.Load()` (`vulkan-1.dll` on Windows, `libvulkan.so.1` on Linux)
 2. **`vkGetInstanceProcAddr`** — only directly-loaded function
 3. **Create instance** with SDL3 extensions + `VK_EXT_debug_utils` (if validation available)
 4. **Pick physical device** — prefer `DiscreteGpu`

README.md

@@ -16,7 +16,7 @@ AI-Native 3D game engine with pure P/Invoke Vulkan 1.3 render backend.
 - **ECS** — Flecs.NET with Transform, Mesh, Material, Light, Camera, RigidBody components
 - **SDL3 Window** — cross-platform, Vulkan surface
 
-## Quick Start
+## Quick Start — Linux (main platform)
 
 ```bash
 # Build
@@ -38,6 +38,33 @@ dotnet build CORTEX_ENGINE.sln -c Debug
 dotnet test tests/Engine.Tests/Engine.Tests.csproj -c Debug
 ```
 
+## Quick Start — Windows x64
+
+PowerShell scripts select the Windows native runtime assets explicitly; Bash is
+not required:
+
+```powershell
+# Build and restore Windows native dependencies
+dotnet restore .\CORTEX_ENGINE.sln -r win-x64
+dotnet build .\CORTEX_ENGINE.sln -c Debug -r win-x64 --no-restore
+
+# Run the engine
+.\scripts\run.ps1
+
+# Run a demo scene
+.\scripts\run.ps1 --scene shooter
+
+# Run with AI/MCP server
+.\scripts\start_mcp_engine.ps1 -Port 5000
+
+# Run tests
+dotnet test .\tests\Engine.Tests\Engine.Tests.csproj -c Debug -r win-x64
+```
+
+The project keeps Linux as the default RID on Linux hosts and selects `win-x64`
+automatically on Windows. Use `-r win-x64` when cross-publishing from another
+OS.
+
 ## Controls
 
 - **WASD** — move camera

scripts/run.ps1

@@ -0,0 +1,20 @@
+[CmdletBinding()]
+param(
+    [Parameter(ValueFromRemainingArguments = $true)]
+    [string[]] $EngineArgs
+)
+
+$ErrorActionPreference = 'Stop'
+$engineDir = Split-Path -Parent $PSScriptRoot
+$project = Join-Path $engineDir 'src/CortexEngine.App/CortexEngine.App.csproj'
+
+Push-Location $engineDir
+try {
+    & dotnet run --project $project -c Debug -r win-x64 -- @EngineArgs
+    $exitCode = $LASTEXITCODE
+}
+finally {
+    Pop-Location
+}
+
+exit $exitCode

scripts/start_mcp_engine.ps1

@@ -0,0 +1,19 @@
+[CmdletBinding()]
+param(
+    [int] $Port = 5000
+)
+
+$ErrorActionPreference = 'Stop'
+$engineDir = Split-Path -Parent $PSScriptRoot
+$project = Join-Path $engineDir 'src/CortexEngine.App/CortexEngine.App.csproj'
+
+Push-Location $engineDir
+try {
+    & dotnet run --project $project -c Debug -r win-x64 -- --mcp-port $Port
+    $exitCode = $LASTEXITCODE
+}
+finally {
+    Pop-Location
+}
+
+exit $exitCode

src/CortexEngine.App/CortexEngine.App.csproj

@@ -11,6 +11,15 @@
 
   <PropertyGroup Condition="'$(Configuration)' == 'Debug'">
     <DefineConstants>DEV_MODE</DefineConstants>
+  </PropertyGroup>
+
+  <!-- Keep Linux as the default development platform while selecting the
+       correct native runtime assets automatically on Windows. An explicit
+       -r/-p:RuntimeIdentifier always takes precedence for cross-publishing. -->
+  <PropertyGroup Condition="'$(RuntimeIdentifier)' == '' AND '$(OS)' == 'Windows_NT'">
+    <RuntimeIdentifier>win-x64</RuntimeIdentifier>
+  </PropertyGroup>
+  <PropertyGroup Condition="'$(RuntimeIdentifier)' == '' AND '$(OS)' != 'Windows_NT'">
     <RuntimeIdentifier>linux-x64</RuntimeIdentifier>
   </PropertyGroup>
 

src/CortexEngine.App/Program.cs

@@ -83,6 +83,8 @@ class Program
 
             var lastWidth = window.Width;
             var lastHeight = window.Height;
+            var lastDrawableWidth = window.DrawableWidth;
+            var lastDrawableHeight = window.DrawableHeight;
             var frames = 0;
             var lastFpsTime = 0.0;
             var timing = new Timing();
@@ -132,13 +134,17 @@ class Program
                 }
 #endif
 
-                if (window.Width != lastWidth || window.Height != lastHeight)
+                if (window.Width != lastWidth || window.Height != lastHeight ||
+                    window.DrawableWidth != lastDrawableWidth || window.DrawableHeight != lastDrawableHeight)
                 {
                     lastWidth = window.Width;
                     lastHeight = window.Height;
-                    if (lastWidth > 0 && lastHeight > 0)
+                    lastDrawableWidth = window.DrawableWidth;
+                    lastDrawableHeight = window.DrawableHeight;
+                    if (lastWidth > 0 && lastHeight > 0 &&
+                        lastDrawableWidth > 0 && lastDrawableHeight > 0)
                     {
-                        renderContext.Resize(lastWidth, lastHeight);
+                        renderContext.Resize(lastDrawableWidth, lastDrawableHeight);
                         ref var cam = ref cameraEntity.Ensure<Camera>();
                         cam.AspectRatio = (float)lastWidth / lastHeight;
                         cameraEntity.Set(cam);
@@ -215,14 +221,21 @@ class Program
 
                 if (hasImGui)
                 {
+                    var displayWidth = Math.Max(window.Width, 1);
+                    var displayHeight = Math.Max(window.Height, 1);
+                    var drawableWidth = Math.Max(window.DrawableWidth, 1);
+                    var drawableHeight = Math.Max(window.DrawableHeight, 1);
+                    var framebufferScaleX = (float)drawableWidth / displayWidth;
+                    var framebufferScaleY = (float)drawableHeight / displayHeight;
                     var io = ImGui.GetIO();
-                    io.DisplaySize = new System.Numerics.Vector2(window.Width, window.Height);
-                    io.MousePos = new System.Numerics.Vector2(input.MouseX, input.MouseY);
-                    io.MouseDown[0] = input.MouseLeft;
-                    io.MouseDown[1] = input.MouseRight;
-                    io.MouseDown[2] = input.MouseMiddle;
+                    UpdateImGuiInput(io, input);
 
-                    renderer.BeginImGuiFrame();
+                    renderer.BeginImGuiFrame(
+                        displayWidth,
+                        displayHeight,
+                        framebufferScaleX,
+                        framebufferScaleY,
+                        (float)timing.DeltaTime);
 
                     ImGui.Begin("Cortex Engine Debug");
                     ImGui.Text($"FPS: {frames}");
@@ -388,7 +401,7 @@ class Program
                         }
 
                         var paramsText = sb.ToString();
-                        ImGui.SetClipboardText(paramsText);
+                        window.SetClipboardText(paramsText);
                         Console.WriteLine("[App] Parameters copied to clipboard:");
                         Console.WriteLine(paramsText);
                     }
@@ -406,20 +419,41 @@ class Program
                             recordingPath = $"Videos/cortex_{timestamp}.mp4";
                             Directory.CreateDirectory("Videos");
 
-                            var w = window.Width;
-                            var h = window.Height;
-                            var ffmpegArgs = $"-y -f rawvideo -pixel_format bgra -video_size {w}x{h} -framerate 60 -i - -c:v libx264 -preset fast -crf 23 -pix_fmt yuv420p -vf fps=30 {recordingPath}";
+                            var w = window.DrawableWidth;
+                            var h = window.DrawableHeight;
+                            var outputPath = recordingPath!;
 
+                            // ArgumentList avoids shell-specific quoting rules and works
+                            // for paths on both Windows and Linux.
                             var psi = new ProcessStartInfo
                             {
                                 FileName = "ffmpeg",
-                                Arguments = ffmpegArgs,
                                 UseShellExecute = false,
                                 RedirectStandardInput = true,
-                                RedirectStandardOutput = true,
-                                RedirectStandardError = true,
                                 CreateNoWindow = true,
                             };
+                            psi.ArgumentList.Add("-y");
+                            psi.ArgumentList.Add("-f");
+                            psi.ArgumentList.Add("rawvideo");
+                            psi.ArgumentList.Add("-pixel_format");
+                            psi.ArgumentList.Add("bgra");
+                            psi.ArgumentList.Add("-video_size");
+                            psi.ArgumentList.Add($"{w}x{h}");
+                            psi.ArgumentList.Add("-framerate");
+                            psi.ArgumentList.Add("60");
+                            psi.ArgumentList.Add("-i");
+                            psi.ArgumentList.Add("-");
+                            psi.ArgumentList.Add("-c:v");
+                            psi.ArgumentList.Add("libx264");
+                            psi.ArgumentList.Add("-preset");
+                            psi.ArgumentList.Add("fast");
+                            psi.ArgumentList.Add("-crf");
+                            psi.ArgumentList.Add("23");
+                            psi.ArgumentList.Add("-pix_fmt");
+                            psi.ArgumentList.Add("yuv420p");
+                            psi.ArgumentList.Add("-vf");
+                            psi.ArgumentList.Add("fps=30");
+                            psi.ArgumentList.Add(outputPath);
 
                             try
                             {
@@ -431,7 +465,7 @@ class Program
                             catch (Exception ex)
                             {
                                 Console.WriteLine($"[App] Failed to start FFmpeg: {ex.Message}");
-                                Console.WriteLine("[App] Install FFmpeg: sudo apt install ffmpeg");
+                                Console.WriteLine("[App] Install FFmpeg and ensure the ffmpeg executable is available on PATH.");
                             }
                         }
                     }
@@ -519,6 +553,134 @@ class Program
         await Task.CompletedTask;
     }
 
+    private static void UpdateImGuiInput(ImGuiIOPtr io, IInputState input)
+    {
+        io.AddMousePosEvent(input.MouseX, input.MouseY);
+
+        foreach (var inputEvent in input.Events)
+        {
+            switch (inputEvent.Type)
+            {
+                case InputEventType.KeyDown:
+                case InputEventType.KeyUp:
+                    if (TryMapImGuiKey(inputEvent.Key, out var imguiKey))
+                        io.AddKeyEvent(imguiKey, inputEvent.Type == InputEventType.KeyDown);
+                    break;
+
+                case InputEventType.TextInput:
+                    if (!string.IsNullOrEmpty(inputEvent.Text))
+                        io.AddInputCharactersUTF8(inputEvent.Text);
+                    break;
+
+                case InputEventType.MouseButtonDown:
+                case InputEventType.MouseButtonUp:
+                    io.AddMouseButtonEvent(
+                        inputEvent.MouseButton,
+                        inputEvent.Type == InputEventType.MouseButtonDown);
+                    break;
+
+                case InputEventType.MouseWheel:
+                    io.AddMouseWheelEvent(inputEvent.WheelX, inputEvent.WheelY);
+                    break;
+
+                case InputEventType.FocusGained:
+                    io.AddFocusEvent(true);
+                    break;
+
+                case InputEventType.FocusLost:
+                    io.AddFocusEvent(false);
+                    break;
+            }
+        }
+
+        // ImGui uses separate virtual modifier keys for shortcuts and navigation.
+        io.AddKeyEvent(ImGuiKey.ModCtrl,
+            input.IsKeyDown(Key.LeftControl) || input.IsKeyDown(Key.RightControl));
+        io.AddKeyEvent(ImGuiKey.ModShift,
+            input.IsKeyDown(Key.LeftShift) || input.IsKeyDown(Key.RightShift));
+        io.AddKeyEvent(ImGuiKey.ModAlt,
+            input.IsKeyDown(Key.LeftAlt) || input.IsKeyDown(Key.RightAlt));
+    }
+
+    private static bool TryMapImGuiKey(Key key, out ImGuiKey imguiKey)
+    {
+        imguiKey = key switch
+        {
+            Key.Space => ImGuiKey.Space,
+            Key.Escape => ImGuiKey.Escape,
+            Key.Enter => ImGuiKey.Enter,
+            Key.Tab => ImGuiKey.Tab,
+            Key.Backspace => ImGuiKey.Backspace,
+            Key.Insert => ImGuiKey.Insert,
+            Key.Delete => ImGuiKey.Delete,
+            Key.Home => ImGuiKey.Home,
+            Key.End => ImGuiKey.End,
+            Key.PageUp => ImGuiKey.PageUp,
+            Key.PageDown => ImGuiKey.PageDown,
+            Key.Left => ImGuiKey.LeftArrow,
+            Key.Right => ImGuiKey.RightArrow,
+            Key.Up => ImGuiKey.UpArrow,
+            Key.Down => ImGuiKey.DownArrow,
+            Key.A => ImGuiKey.A,
+            Key.B => ImGuiKey.B,
+            Key.C => ImGuiKey.C,
+            Key.D => ImGuiKey.D,
+            Key.E => ImGuiKey.E,
+            Key.F => ImGuiKey.F,
+            Key.G => ImGuiKey.G,
+            Key.H => ImGuiKey.H,
+            Key.I => ImGuiKey.I,
+            Key.J => ImGuiKey.J,
+            Key.K => ImGuiKey.K,
+            Key.L => ImGuiKey.L,
+            Key.M => ImGuiKey.M,
+            Key.N => ImGuiKey.N,
+            Key.O => ImGuiKey.O,
+            Key.P => ImGuiKey.P,
+            Key.Q => ImGuiKey.Q,
+            Key.R => ImGuiKey.R,
+            Key.S => ImGuiKey.S,
+            Key.T => ImGuiKey.T,
+            Key.U => ImGuiKey.U,
+            Key.V => ImGuiKey.V,
+            Key.W => ImGuiKey.W,
+            Key.X => ImGuiKey.X,
+            Key.Y => ImGuiKey.Y,
+            Key.Z => ImGuiKey.Z,
+            Key.Zero => ImGuiKey._0,
+            Key.One => ImGuiKey._1,
+            Key.Two => ImGuiKey._2,
+            Key.Three => ImGuiKey._3,
+            Key.Four => ImGuiKey._4,
+            Key.Five => ImGuiKey._5,
+            Key.Six => ImGuiKey._6,
+            Key.Seven => ImGuiKey._7,
+            Key.Eight => ImGuiKey._8,
+            Key.Nine => ImGuiKey._9,
+            Key.F1 => ImGuiKey.F1,
+            Key.F2 => ImGuiKey.F2,
+            Key.F3 => ImGuiKey.F3,
+            Key.F4 => ImGuiKey.F4,
+            Key.F5 => ImGuiKey.F5,
+            Key.F6 => ImGuiKey.F6,
+            Key.F7 => ImGuiKey.F7,
+            Key.F8 => ImGuiKey.F8,
+            Key.F9 => ImGuiKey.F9,
+            Key.F10 => ImGuiKey.F10,
+            Key.F11 => ImGuiKey.F11,
+            Key.F12 => ImGuiKey.F12,
+            Key.LeftShift => ImGuiKey.LeftShift,
+            Key.RightShift => ImGuiKey.RightShift,
+            Key.LeftControl => ImGuiKey.LeftCtrl,
+            Key.RightControl => ImGuiKey.RightCtrl,
+            Key.LeftAlt => ImGuiKey.LeftAlt,
+            Key.RightAlt => ImGuiKey.RightAlt,
+            _ => ImGuiKey.None,
+        };
+
+        return imguiKey != ImGuiKey.None;
+    }
+
     static int ParseMcpPort(string[] args)
     {
         for (var i = 0; i < args.Length; i++)

src/Engine.Core/IInputState.cs

@@ -13,6 +13,12 @@ public interface IInputState
     bool MouseMiddle { get; }
     float MouseWheelDelta { get; }
 
+    /// <summary>
+    /// Events received since the last <see cref="BeginFrame"/> call.
+    /// Backends that do not expose an event queue may return an empty list.
+    /// </summary>
+    IReadOnlyList<InputEvent> Events => Array.Empty<InputEvent>();
+
     bool IsKeyDown(Key key);
     bool IsKeyPressed(Key key);
     bool IsKeyReleased(Key key);

src/Engine.Core/IWindow.cs

@@ -9,6 +9,14 @@ public interface IWindow : IDisposable
 {
     int Width { get; }
     int Height { get; }
+
+    /// <summary>
+    /// Size of the drawable Vulkan framebuffer in physical pixels. This can
+    /// differ from <see cref="Width"/>/<see cref="Height"/> on high-DPI displays.
+    /// </summary>
+    int DrawableWidth => Width;
+    int DrawableHeight => Height;
+
     bool ShouldClose { get; }
 
     /// <summary>
@@ -27,6 +35,11 @@ public interface IWindow : IDisposable
     /// </summary>
     void Close();
 
+    /// <summary>
+    /// Places UTF-8 text on the platform clipboard when supported.
+    /// </summary>
+    void SetClipboardText(string text) { }
+
     /// <summary>
     /// Native window handle (e.g. <c>SDL_Window*</c>). Used by backends that need
     /// the raw OS handle for surface creation. Returns 0 if not applicable.

src/Engine.Core/InputEvent.cs

@@ -0,0 +1,25 @@
+namespace Engine.Core;
+
+/// <summary>
+/// Backend-agnostic input event captured during the current frame.
+/// </summary>
+public readonly record struct InputEvent(
+    InputEventType Type,
+    Key Key = Key.Unknown,
+    bool IsRepeat = false,
+    int MouseButton = -1,
+    float WheelX = 0,
+    float WheelY = 0,
+    string? Text = null);
+
+public enum InputEventType
+{
+    KeyDown,
+    KeyUp,
+    TextInput,
+    MouseButtonDown,
+    MouseButtonUp,
+    MouseWheel,
+    FocusGained,
+    FocusLost,
+}

src/Engine.Core/InputMapping.cs

@@ -7,11 +7,12 @@ namespace Engine.Core;
 /// SDL3-backed implementation of <see cref="IInputState"/>.
 /// Populated by polling SDL events via <see cref="ProcessEvent"/> once per frame.
 /// </summary>
-public sealed class InputMapping : IInputState
+public sealed unsafe class InputMapping : IInputState
 {
     private readonly HashSet<Key> _keysPressed = new();
     private readonly HashSet<Key> _keysDown = new();
     private readonly HashSet<Key> _keysReleased = new();
+    private readonly List<InputEvent> _events = new();
 
     public int MouseX { get; private set; }
     public int MouseY { get; private set; }
@@ -19,11 +20,13 @@ public sealed class InputMapping : IInputState
     public bool MouseRight { get; private set; }
     public bool MouseMiddle { get; private set; }
     public float MouseWheelDelta { get; private set; }
+    public IReadOnlyList<InputEvent> Events => _events;
 
     public void BeginFrame()
     {
         _keysPressed.Clear();
         _keysReleased.Clear();
+        _events.Clear();
         MouseWheelDelta = 0;
     }
 
@@ -38,6 +41,10 @@ public sealed class InputMapping : IInputState
                 if (!_keysDown.Contains(key))
                     _keysPressed.Add(key);
                 _keysDown.Add(key);
+                _events.Add(new InputEvent(
+                    InputEventType.KeyDown,
+                    Key: key,
+                    IsRepeat: evt.key.repeat));
                 break;
             }
 
@@ -47,6 +54,7 @@ public sealed class InputMapping : IInputState
                 if (key == Key.Unknown) break;
                 _keysDown.Remove(key);
                 _keysReleased.Add(key);
+                _events.Add(new InputEvent(InputEventType.KeyUp, Key: key));
                 break;
             }
 
@@ -57,14 +65,46 @@ public sealed class InputMapping : IInputState
 
             case SDL_EventType.SDL_EVENT_MOUSE_BUTTON_DOWN:
                 SetMouseButton(evt.button.button, true);
+                if (evt.button.button is >= 1 and <= 3)
+                    _events.Add(new InputEvent(
+                        InputEventType.MouseButtonDown,
+                        MouseButton: evt.button.button - 1));
                 break;
 
             case SDL_EventType.SDL_EVENT_MOUSE_BUTTON_UP:
                 SetMouseButton(evt.button.button, false);
+                if (evt.button.button is >= 1 and <= 3)
+                    _events.Add(new InputEvent(
+                        InputEventType.MouseButtonUp,
+                        MouseButton: evt.button.button - 1));
                 break;
 
             case SDL_EventType.SDL_EVENT_MOUSE_WHEEL:
                 MouseWheelDelta += evt.wheel.y;
+                _events.Add(new InputEvent(
+                    InputEventType.MouseWheel,
+                    WheelX: evt.wheel.x,
+                    WheelY: evt.wheel.y));
+                break;
+
+            case SDL_EventType.SDL_EVENT_TEXT_INPUT:
+            {
+                var text = SDL3.PtrToStringUTF8(evt.text.text);
+                if (!string.IsNullOrEmpty(text))
+                    _events.Add(new InputEvent(InputEventType.TextInput, Text: text));
+                break;
+            }
+
+            case SDL_EventType.SDL_EVENT_WINDOW_FOCUS_GAINED:
+                _events.Add(new InputEvent(InputEventType.FocusGained));
+                break;
+
+            case SDL_EventType.SDL_EVENT_WINDOW_FOCUS_LOST:
+                _keysDown.Clear();
+                MouseLeft = false;
+                MouseRight = false;
+                MouseMiddle = false;
+                _events.Add(new InputEvent(InputEventType.FocusLost));
                 break;
         }
     }

src/Engine.Core/Sdl3Window.cs

@@ -18,16 +18,25 @@ public sealed unsafe class Sdl3Window : IWindow
 
     public int Width { get; private set; }
     public int Height { get; private set; }
+    public int DrawableWidth { get; private set; }
+    public int DrawableHeight { get; private set; }
     public bool ShouldClose { get; private set; }
     public IInputState Input => _input;
     public nint Handle => (nint)_window;
 
     public void Close() => ShouldClose = true;
 
+    public void SetClipboardText(string text)
+    {
+        SDL3.SDL_SetClipboardText(text);
+    }
+
     public Sdl3Window(string title, int width, int height, bool vulkanSurface = true)
     {
         Width = width;
         Height = height;
+        DrawableWidth = width;
+        DrawableHeight = height;
 
         if (!SDL3.SDL_Init(SDL_InitFlags.SDL_INIT_VIDEO))
             throw new InvalidOperationException($"SDL_Init failed: {SDL3.SDL_GetError()}");
@@ -49,6 +58,8 @@ public sealed unsafe class Sdl3Window : IWindow
 
         SDL3.SDL_ShowWindow(_window);
         SDL3.SDL_RaiseWindow(_window);
+        UpdateDrawableSize();
+        SDL3.SDL_StartTextInput(_window);
 
         // On Wayland, the compositor needs an event round-trip before mapping
         // the window. Pump events to flush the show request without blocking.
@@ -80,6 +91,16 @@ public sealed unsafe class Sdl3Window : IWindow
                 case SDL_EventType.SDL_EVENT_WINDOW_RESIZED:
                     Width = evt.window.data1;
                     Height = evt.window.data2;
+                    UpdateDrawableSize();
+                    break;
+
+                case SDL_EventType.SDL_EVENT_WINDOW_PIXEL_SIZE_CHANGED:
+                    DrawableWidth = evt.window.data1;
+                    DrawableHeight = evt.window.data2;
+                    break;
+
+                case SDL_EventType.SDL_EVENT_WINDOW_DISPLAY_SCALE_CHANGED:
+                    UpdateDrawableSize();
                     break;
 
                 case SDL_EventType.SDL_EVENT_KEY_DOWN:
@@ -104,11 +125,25 @@ public sealed unsafe class Sdl3Window : IWindow
         return result;
     }
 
+    private void UpdateDrawableSize()
+    {
+        if (_window == null) return;
+
+        var pixelWidth = Width;
+        var pixelHeight = Height;
+        if (SDL3.SDL_GetWindowSizeInPixels(_window, &pixelWidth, &pixelHeight))
+        {
+            DrawableWidth = pixelWidth;
+            DrawableHeight = pixelHeight;
+        }
+    }
+
     public void Dispose()
     {
         if (_disposed) return;
         _disposed = true;
 
+        SDL3.SDL_StopTextInput(_window);
         SDL3.SDL_DestroyWindow(_window);
         SDL3.SDL_Quit();
     }

src/Engine.Graphics.Vulkan/VulkanImGui.cs

@@ -447,11 +447,13 @@ internal sealed unsafe class VulkanImGui : IDisposable
         _indexMemory = im;
     }
 
-    public void NewFrame()
+    public void NewFrame(float displayWidth, float displayHeight,
+        float framebufferScaleX, float framebufferScaleY, float deltaTime)
     {
         var io = ImGui.GetIO();
-        io.DisplaySize = new System.Numerics.Vector2(1280, 720);
-        io.DeltaTime = 0.016f;
+        io.DisplaySize = new Vector2(displayWidth, displayHeight);
+        io.DisplayFramebufferScale = new Vector2(framebufferScaleX, framebufferScaleY);
+        io.DeltaTime = MathF.Max(deltaTime, 1f / 1000f);
         ImGui.NewFrame();
     }
 
@@ -520,13 +522,21 @@ internal sealed unsafe class VulkanImGui : IDisposable
             {
                 var pcmd = list.CmdBuffer[i];
                 var clip = pcmd.ClipRect;
+                var framebufferScale = io.DisplayFramebufferScale;
+                var clipMinX = MathF.Max(clip.X * framebufferScale.X, 0f);
+                var clipMinY = MathF.Max(clip.Y * framebufferScale.Y, 0f);
+                var clipMaxX = MathF.Min(clip.Z * framebufferScale.X, width);
+                var clipMaxY = MathF.Min(clip.W * framebufferScale.Y, height);
+                if (clipMaxX <= clipMinX || clipMaxY <= clipMinY)
+                    continue;
+
                 var scissor = new VkRect2D
                 {
-                    Offset = new VkOffset2D { X = (int)clip.X, Y = (int)clip.Y },
+                    Offset = new VkOffset2D { X = (int)clipMinX, Y = (int)clipMinY },
                     Extent = new VkExtent2D
                     {
-                        Width = (uint)(clip.Z - clip.X),
-                        Height = (uint)(clip.W - clip.Y),
+                        Width = (uint)(clipMaxX - clipMinX),
+                        Height = (uint)(clipMaxY - clipMinY),
                     },
                 };
                 Vk.vkCmdSetScissor(cmd, 0, 1, &scissor);

src/Engine.Graphics.Vulkan/VulkanRenderContext.cs

@@ -23,7 +23,7 @@ internal sealed class VulkanRenderContext : IRenderContext{
         };
 
         _swapchain = new VulkanSwapchain(_ctx.Device, _ctx.PhysicalDevice, _ctx.Surface,
-            surfaceFormat, window.Width, window.Height, _ctx);
+            surfaceFormat, window.DrawableWidth, window.DrawableHeight, _ctx);
     }
 
     public IRenderer CreateRenderer()

src/Engine.Graphics.Vulkan/VulkanRenderer.cs

@@ -179,9 +179,11 @@ public sealed unsafe class VulkanRenderer : IRenderer, Engine.Graphics.IScreensh
         return result;
     }
 
-    public void BeginImGuiFrame()
+    public void BeginImGuiFrame(float displayWidth, float displayHeight,
+        float framebufferScaleX, float framebufferScaleY, float deltaTime)
     {
-        _imGui?.NewFrame();
+        _imGui?.NewFrame(displayWidth, displayHeight,
+            framebufferScaleX, framebufferScaleY, deltaTime);
     }
 
     public void EndImGuiFrame()
@@ -296,7 +298,7 @@ public sealed unsafe class VulkanRenderer : IRenderer, Engine.Graphics.IScreensh
 
         // A minimized window has no drawable surface. Keep the frame fence signaled and wait
         // for the window event loop to provide a non-zero extent before trying to acquire.
-        if (_window.Width <= 0 || _window.Height <= 0)
+        if (_window.DrawableWidth <= 0 || _window.DrawableHeight <= 0)
             return;
 
         // Read captured frame from previous render (GPU has finished by now)
@@ -324,7 +326,7 @@ public sealed unsafe class VulkanRenderer : IRenderer, Engine.Graphics.IScreensh
         // from this frame would leave the next WaitForFrame blocked forever.
         if (acquireResult == VkResult.ErrorOutOfDateKHR)
         {
-            RecreateSwapchain(_window.Width, _window.Height);
+            RecreateSwapchain(_window.DrawableWidth, _window.DrawableHeight);
             return;
         }
 
@@ -657,7 +659,7 @@ public sealed unsafe class VulkanRenderer : IRenderer, Engine.Graphics.IScreensh
 
         if (presentResult == VkResult.ErrorOutOfDateKHR || presentResult == VkResult.SuboptimalKHR)
         {
-            RecreateSwapchain(_window.Width, _window.Height);
+            RecreateSwapchain(_window.DrawableWidth, _window.DrawableHeight);
         }
 
         _frameIndex = (_frameIndex + 1) % VulkanFrameResources.MaxFramesInFlight;

src/Engine.Graphics/IRenderer.cs

@@ -17,8 +17,11 @@ public interface IRenderer : IDisposable
     /// <summary>
     /// Called before RenderWorld to begin a new ImGui frame.
     /// Null if the backend doesn't support ImGui.
+    /// <paramref name="displayWidth"/> and <paramref name="displayHeight"/> are
+    /// logical window coordinates; framebuffer scale maps them to pixels.
     /// </summary>
-    void BeginImGuiFrame() { }
+    void BeginImGuiFrame(float displayWidth, float displayHeight,
+        float framebufferScaleX, float framebufferScaleY, float deltaTime) { }
 
     /// <summary>
     /// Called after RenderWorld to render ImGui draw data.