some cleanup

Program.cs

@@ -18,7 +18,7 @@ public class Program
     public static void Main()
     {
         SDL3Window window = new SDL3Window("SDL3 Testing Suite", 100, 100, 1280, 720);
-        window.RenderCallback = () =>
+        window.RenderCallback += () =>
         {
             ImGuiViewportPtr viewport = ImGui.GetMainViewport();
             ImGui.SetNextWindowPos(viewport.WorkPos);
@@ -65,7 +65,7 @@ public class Program
                     fontName = string.IsNullOrEmpty(fontName) ? _font.FontId.ToString() : fontName;
                     if (!_initialized || change)
                     {
-                        if (!GlyphsByName.TryGetValue(fontName, out List<uint> glyphs))
+                        if (!GlyphsByName.TryGetValue(fontName, out List<uint>? glyphs))
                         {
                             glyphs = new List<uint>();
 

SDL3/DelegateHelpers.cs

@@ -0,0 +1,8 @@
+using System.Runtime.InteropServices;
+
+namespace SDL3_TestingSuite.SDL3;
+
+public unsafe static class DelegateHelpers
+{
+    public static void* GetPtrForDelegate<TDelegate>(this TDelegate _delegate) where TDelegate : notnull => (void*)Marshal.GetFunctionPointerForDelegate(_delegate);
+}

SDL3/FontFind.cs

@@ -51,7 +51,7 @@ public static class FontFind
             bool flag = false;
             ImVector<ImFontPtr> fonts = io.Fonts.Fonts;
             List<ImFontPtr> toRemove = new List<ImFontPtr>();
-            
+
             for (int i = 0; i < fonts.Size; i++)
             {
                 ImFontPtr font = fonts[i];
@@ -61,13 +61,13 @@ public static class FontFind
                     flag = true;
                 }
             }
-            
+
             foreach (ImFontPtr font in toRemove)
             {
                 io.Fonts.RemoveFont(font);
                 Program.Logger.Log("Removed font: " + fontName);
             }
-            
+
             return flag;
         }
     }
@@ -110,11 +110,9 @@ public static class FontFind
             metrics.WinDescent = ReadS16Be(os2Offset + 76);
         }
 
-        metrics.TypoLineHeight =
+        metrics.TypoLineHeight = metrics.TypoAscender - metrics.TypoDescender + metrics.TypoLineGap;
-            metrics.TypoAscender - metrics.TypoDescender + metrics.TypoLineGap;
 
-        metrics.WinLineHeight =
+        metrics.WinLineHeight = metrics.WinAscent + metrics.WinDescent;
-            metrics.WinAscent + metrics.WinDescent;
 
         return metrics;
 
@@ -142,7 +140,7 @@ public static class FontFind
             return new string(new char[] { c1, c2, c3, c4 });
         }
     }
-    
+
     public static int GetRecommendedPixelSize(FontMetrics metrics)
     {
         if (metrics.UnitsPerEm == 0 || metrics.TypoLineHeight == 0)

SDL3/ImGuiSDL3Renderer.cs

@@ -1,4 +1,6 @@
+using System.Diagnostics;
 using System.Numerics;
+using System.Runtime.CompilerServices;
 using System.Runtime.InteropServices;
 using Hexa.NET.ImGui;
 using SDL3;
@@ -11,8 +13,6 @@ namespace SDL3_TestingSuite.SDL3;
 /// </summary>
 public unsafe static class ImGuiSDL3Renderer
 {
-    public static SDL3Window Parent;
-
     public class RendererData
     {
         public nint Renderer; // Main viewport's renderer
@@ -25,34 +25,15 @@ public unsafe static class ImGuiSDL3Renderer
     private struct BackupSDLRendererState
     {
         public SDL.Rect Viewport;
-        public bool ViewportEnabled;
         public bool ClipEnabled;
         public SDL.Rect ClipRect;
     }
 
-    [UnmanagedFunctionPointer(CallingConvention.Cdecl)]
+    public static RendererData GetRendererData() => ImGui.GetCurrentContext().Handle != null ? ImGuiUserData<RendererData>.Get(ImGui.GetIO().BackendRendererUserData)! : null!;
-    private delegate void RendererCreateWindowFn(ImGuiViewportPtr viewport);
 
-    private static readonly RendererCreateWindowFn RendererCreateWindowDelegate = RendererCreateWindow;
+    public static SDL3Window? Parent;
 
-    [UnmanagedFunctionPointer(CallingConvention.Cdecl)]
+    public static bool Init(nint renderer, SDL3Window? parentWindow = null)
-    private delegate void RendererDestroyWindowFn(ImGuiViewportPtr viewport);
-
-    private static readonly RendererDestroyWindowFn RendererDestroyWindowDelegate = RendererDestroyWindow;
-
-    [UnmanagedFunctionPointer(CallingConvention.Cdecl)]
-    private delegate void RendererRenderWindowFn(ImGuiViewportPtr viewport);
-
-    private static readonly RendererRenderWindowFn RendererRenderWindowDelegate = RendererRenderWindow;
-
-    [UnmanagedFunctionPointer(CallingConvention.Cdecl)]
-    private delegate void RendererSwapBuffersFn(ImGuiViewportPtr viewport);
-
-    private static readonly RendererSwapBuffersFn RendererSwapBuffersDelegate = RendererSwapBuffers;
-
-    public static RendererData Data => ImGui.GetCurrentContext().Handle != null ? ImGuiUserData<RendererData>.Get(ImGui.GetIO().BackendRendererUserData)! : null!;
-
-    public static bool Init(nint renderer, SDL3Window parentWindow = null)
     {
         Parent = parentWindow;
         ImGuiIOPtr io = ImGui.GetIO();
@@ -67,88 +48,45 @@ public unsafe static class ImGuiSDL3Renderer
         bd.Renderer = renderer;
 
         ImGuiPlatformIOPtr platformIO = ImGui.GetPlatformIO();
-        platformIO.RendererCreateWindow = (void*)Marshal.GetFunctionPointerForDelegate(RendererCreateWindowDelegate);
+        platformIO.RendererCreateWindow = DelegateStorage.RendererCreateWindowDelegate.GetPtrForDelegate();
-        platformIO.RendererDestroyWindow = (void*)Marshal.GetFunctionPointerForDelegate(RendererDestroyWindowDelegate);
+        platformIO.RendererDestroyWindow = DelegateStorage.RendererDestroyWindowDelegate.GetPtrForDelegate();
-        platformIO.RendererRenderWindow = (void*)Marshal.GetFunctionPointerForDelegate(RendererRenderWindowDelegate);
+        platformIO.RendererRenderWindow = DelegateStorage.RendererRenderWindowDelegate.GetPtrForDelegate();
-        platformIO.RendererSwapBuffers = (void*)Marshal.GetFunctionPointerForDelegate(RendererSwapBuffersDelegate);
+        platformIO.RendererSwapBuffers = DelegateStorage.RendererSwapBuffersDelegate.GetPtrForDelegate();
 
         return true;
     }
 
     public static void Dispose()
     {
-        var io = ImGui.GetIO();
+        ImGuiIOPtr io = ImGui.GetIO();
-        var platformIO = ImGui.GetPlatformIO();
+        ImGuiPlatformIOPtr platformIO = ImGui.GetPlatformIO();
 
-        DestroyDeviceObjects();
+        if (io.BackendRendererName != null)
+        {
+            Marshal.FreeHGlobal((nint)io.BackendRendererName);
+        }
 
+        ImGuiUserData<RendererData>.Free(io.BackendRendererUserData);
         io.BackendRendererName = null;
         io.BackendRendererUserData = null;
-        io.BackendFlags &= ~(ImGuiBackendFlags.RendererHasVtxOffset | ImGuiBackendFlags.RendererHasTextures);
+        io.BackendFlags &= ~(ImGuiBackendFlags.RendererHasVtxOffset | ImGuiBackendFlags.RendererHasTextures | ImGuiBackendFlags.RendererHasViewports);
         platformIO.RendererTextureMaxWidth = 0;
         platformIO.RendererTextureMaxHeight = 0;
         platformIO.RendererRenderState = null;
-        platformIO.RendererCreateWindow = null;
-        platformIO.RendererDestroyWindow = null;
-        platformIO.RendererSetWindowSize = null;
-        platformIO.RendererRenderWindow = null;
-        platformIO.RendererSwapBuffers = null;
     }
 
-    public static void NewFrame() { }
+    public static void SetupRenderState(nint renderer)
-
-    private static void RendererCreateWindow(ImGuiViewportPtr viewport)
     {
-        ImGuiSDL3Platform.ViewPortData? vd = ImGuiUserData<ImGuiSDL3Platform.ViewPortData>.Get(viewport.PlatformUserData);
+        // Clear out any viewports and cliprect set by the user
-        if (vd == null || vd.Window == nint.Zero)
+        // FIXME: Technically speaking there are lots of other things we could backup/setup/restore during our render process.
-            return;
+        SDL.SetRenderViewport(renderer, nint.Zero);
-
+        SDL.SetRenderClipRect(renderer, nint.Zero);
-        if (vd.Renderer == nint.Zero)
-        {
-            vd.Renderer = SDL.CreateRenderer(vd.Window, null);
-            vd.RendererOwned = true;
-        }
     }
 
-    private static void RendererDestroyWindow(ImGuiViewportPtr viewport)
+    public static void NewFrame()
     {
-        ImGuiSDL3Platform.ViewPortData? vd = ImGuiUserData<ImGuiSDL3Platform.ViewPortData>.Get(viewport.PlatformUserData);
+        RendererData bd = GetRendererData();
-        if (vd == null)
+        Debug.Assert(bd != null, "Context or backend not initialized! Did you call ImGuiSDL3Renderer.Init()?");
-            return;
-
-        if (vd.RendererOwned && vd.Renderer != nint.Zero)
-        {
-            SDL.DestroyRenderer(vd.Renderer);
-        }
-
-        vd.Renderer = nint.Zero;
-        vd.RendererOwned = false;
-    }
-
-    private static void RendererRenderWindow(ImGuiViewportPtr viewport)
-    {
-        ImGuiSDL3Platform.ViewPortData? vd = ImGuiUserData<ImGuiSDL3Platform.ViewPortData>.Get(viewport.PlatformUserData);
-        if (vd == null || vd.Renderer == nint.Zero)
-        {
-            return;
-        }
-
-        if (Parent != null)
-        {
-            SDL.SetRenderDrawColorFloat(vd.Renderer, Parent.ClearColor.X, Parent.ClearColor.Y, Parent.ClearColor.Z, 0f);
-            SDL.RenderClear(vd.Renderer);
-        }
-
-        RenderDrawData(viewport.DrawData, vd.Renderer);
-    }
-
-    private static void RendererSwapBuffers(ImGuiViewportPtr viewport)
-    {
-        ImGuiSDL3Platform.ViewPortData? vd = ImGuiUserData<ImGuiSDL3Platform.ViewPortData>.Get(viewport.PlatformUserData);
-        if (vd == null || vd.Renderer == nint.Zero)
-            return;
-
-        SDL.RenderPresent(vd.Renderer);
     }
 
     public static void RenderDrawData(ImDrawDataPtr drawData, nint renderer)
@@ -167,22 +105,23 @@ public unsafe static class ImGuiSDL3Renderer
 
         for (int i = 0; i < drawData.Textures.Size; i++)
         {
-            var texture = drawData.Textures[i];
+            ImTextureDataPtr texture = drawData.Textures[i];
-            UpdateTexture(texture, renderer);
+            if (texture.Handle != null)
+            {
+                UpdateTexture(texture, renderer);
+            }
         }
 
         // Backup SDL renderer state
         BackupSDLRendererState old = new BackupSDLRendererState
         {
-            ViewportEnabled = SDL.RenderViewportSet(renderer),
             ClipEnabled = SDL.RenderClipEnabled(renderer)
         };
         SDL.GetRenderViewport(renderer, out old.Viewport);
         SDL.GetRenderClipRect(renderer, out old.ClipRect);
 
         // Set up render state
-        SDL.SetRenderViewport(renderer, nint.Zero);
+        SetupRenderState(renderer);
-        SDL.SetRenderClipRect(renderer, nint.Zero);
 
         // Set render state in platform IO
         ImGuiPlatformIOPtr platformIo = ImGui.GetPlatformIO();
@@ -193,45 +132,103 @@ public unsafe static class ImGuiSDL3Renderer
         // Render command lists
         for (int n = 0; n < drawData.CmdListsCount; n++)
         {
-            ImDrawListPtr cmdList = drawData.CmdLists[n];
+            ImDrawListPtr drawList = drawData.CmdLists[n];
 
-            for (int cmdIndex = 0; cmdIndex < cmdList.CmdBuffer.Size; cmdIndex++)
+            for (int cmdIndex = 0; cmdIndex < drawList.CmdBuffer.Size; cmdIndex++)
             {
-                ImDrawCmd cmd = cmdList.CmdBuffer[cmdIndex];
+                ImDrawCmd cmd = drawList.CmdBuffer[cmdIndex];
 
                 if (cmd.UserCallback != null)
                 {
-                    continue; // User callback not implemented
+                    if (cmd.UserCallback == DelegateStorage.DrawCallbackResetRenderStateDelegate.GetPtrForDelegate())
+                    {
+                        SetupRenderState(renderer);
+                    }
+                    else
+                    {
+                        // this is cursed af and idk if it even works :)
+                        ImDrawCmdPtr cmdPtr = new ImDrawCmdPtr
+                        {
+                            Handle = (ImDrawCmd*)Unsafe.AsPointer(ref cmd)
+                        };
+                        ((delegate* unmanaged[Cdecl]<ImDrawListPtr, ImDrawCmdPtr, void>)cmd.UserCallback)(drawList, cmdPtr);
+                    }
                 }
-
+                else
-                // Apply clipping rectangle
-                Vector4 clipRect = cmd.ClipRect;
-                Vector2 clipMin = new Vector2((clipRect.X - clipOffset.X) * renderScale.X, (clipRect.Y - clipOffset.Y) * renderScale.Y);
-                Vector2 clipMax = new Vector2((clipRect.Z - clipOffset.X) * renderScale.X, (clipRect.W - clipOffset.Y) * renderScale.Y);
-
-                clipMin.X = Math.Max(0, clipMin.X);
-                clipMin.Y = Math.Max(0, clipMin.Y);
-                clipMax.X = Math.Min(fbWidth, clipMax.X);
-                clipMax.Y = Math.Min(fbHeight, clipMax.Y);
-                if (clipMax.X <= clipMin.X || clipMax.Y <= clipMin.Y)
-                    continue;
-
-                SDL.Rect r = new SDL.Rect
                 {
-                    X = (int)clipMin.X,
+                    // Apply clipping rectangle
-                    Y = (int)clipMin.Y,
+                    Vector4 clipRect = cmd.ClipRect;
-                    W = (int)(clipMax.X - clipMin.X),
+                    Vector2 clipMin = new Vector2((clipRect.X - clipOffset.X) * renderScale.X, (clipRect.Y - clipOffset.Y) * renderScale.Y);
-                    H = (int)(clipMax.Y - clipMin.Y)
+                    Vector2 clipMax = new Vector2((clipRect.Z - clipOffset.X) * renderScale.X, (clipRect.W - clipOffset.Y) * renderScale.Y);
-                };
-                SDL.SetRenderClipRect(renderer, r);
 
-                // Get texture
+                    clipMin.X = Math.Max(0, clipMin.X);
-                nint texId = cmd.GetTexID();
+                    clipMin.Y = Math.Max(0, clipMin.Y);
+                    clipMax.X = Math.Min(fbWidth, clipMax.X);
+                    clipMax.Y = Math.Min(fbHeight, clipMax.Y);
+                    if (clipMax.X <= clipMin.X || clipMax.Y <= clipMin.Y)
+                        continue;
 
-                // Convert ImGui vertices to SDL vertices
+                    SDL.Rect r = new SDL.Rect
-                if (!RenderDrawCommand(cmdList, cmd, renderer, texId, renderScale, clipOffset))
+                    {
-                {
+                        X = (int)clipMin.X,
-                    Console.WriteLine($"Failed to render ImGui draw command: {SDL.GetError()}");
+                        Y = (int)clipMin.Y,
+                        W = (int)(clipMax.X - clipMin.X),
+                        H = (int)(clipMax.Y - clipMin.Y)
+                    };
+                    SDL.SetRenderClipRect(renderer, r);
+
+                    // Convert ImGui vertices to SDL vertices
+                    uint indexOffset = cmd.IdxOffset;
+                    uint vertexOffset = cmd.VtxOffset;
+                    uint elemCount = cmd.ElemCount;
+
+                    SDL.Vertex[] vertices = new SDL.Vertex[elemCount];
+                    int[] indices = new int[elemCount];
+
+                    for (int i = 0; i < elemCount; i++)
+                    {
+                        ushort idx = drawList.IdxBuffer[(int)indexOffset + i];
+                        int vertIdx = (int)(vertexOffset + idx);
+
+                        ImDrawVert srcVert = drawList.VtxBuffer[vertIdx];
+
+                        uint col = srcVert.Col;
+
+                        byte colR = (byte)((col >> 0) & 0xFF);
+                        byte colG = (byte)((col >> 8) & 0xFF);
+                        byte colB = (byte)((col >> 16) & 0xFF);
+                        byte colA = (byte)((col >> 24) & 0xFF);
+
+                        vertices[i] = new SDL.Vertex
+                        {
+                            Position = new SDL.FPoint
+                            {
+                                X = (srcVert.Pos.X - clipOffset.X) * renderScale.X,
+                                Y = (srcVert.Pos.Y - clipOffset.Y) * renderScale.Y
+                            },
+                            Color = new SDL.FColor
+                            {
+                                R = colR / 255f,
+                                G = colG / 255f,
+                                B = colB / 255f,
+                                A = colA / 255f
+                            },
+                            TexCoord = new SDL.FPoint
+                            {
+                                X = srcVert.Uv.X,
+                                Y = srcVert.Uv.Y
+                            }
+                        };
+
+                        indices[i] = i;
+                    }
+
+                    // Get texture
+                    ImTextureID texId = cmd.GetTexID();
+                    if (!SDL.RenderGeometry(renderer, texId, vertices, vertices.Length, indices, indices.Length))
+                    {
+                        Program.Logger.Log($"Failed to render ImGui draw command: {SDL.GetError()}");
+                    }
                 }
             }
         }
@@ -240,7 +237,7 @@ public unsafe static class ImGuiSDL3Renderer
         platformIo.RendererRenderState = null;
 
         // Restore renderer state
-        SDL.SetRenderViewport(renderer, old.ViewportEnabled ? old.Viewport : new SDL.Rect());
+        SDL.SetRenderViewport(renderer, old.Viewport);
         SDL.SetRenderClipRect(renderer, old.ClipEnabled ? old.ClipRect : new SDL.Rect());
     }
 
@@ -281,7 +278,7 @@ public unsafe static class ImGuiSDL3Renderer
             nint sdlTexture = tex.TexID;
             for (int i = 0; i < tex.Updates.Size; i++)
             {
-                var r = tex.Updates[i];
+                ImTextureRect r = tex.Updates[i];
                 SDL.Rect sdlR = new SDL.Rect { X = r.X, Y = r.Y, W = r.W, H = r.H };
                 SDL.UpdateTexture(sdlTexture, sdlR, (nint)tex.GetPixelsAt(r.X, r.Y), tex.GetPitch());
             }
@@ -289,67 +286,92 @@ public unsafe static class ImGuiSDL3Renderer
         }
     }
 
-
-    private static bool RenderDrawCommand(ImDrawListPtr drawList, ImDrawCmd cmd, nint renderer, nint texId, Vector2 scale, Vector2 displayPos)
-    {
-        uint indexOffset = cmd.IdxOffset;
-        uint vertexOffset = cmd.VtxOffset;
-        uint elemCount = cmd.ElemCount;
-
-        SDL.Vertex[] vertices = new SDL.Vertex[elemCount];
-        int[] indices = new int[elemCount];
-
-        for (int i = 0; i < elemCount; i++)
-        {
-            ushort idx = drawList.IdxBuffer[(int)indexOffset + i];
-            int vertIdx = (int)(vertexOffset + idx);
-
-            ImDrawVert srcVert = drawList.VtxBuffer[vertIdx];
-
-            uint col = srcVert.Col;
-
-            byte r = (byte)((col >> 0) & 0xFF);
-            byte g = (byte)((col >> 8) & 0xFF);
-            byte b = (byte)((col >> 16) & 0xFF);
-            byte a = (byte)((col >> 24) & 0xFF);
-
-            vertices[i] = new SDL.Vertex
-            {
-                Position = new SDL.FPoint
-                {
-                    X = (srcVert.Pos.X - displayPos.X) * scale.X,
-                    Y = (srcVert.Pos.Y - displayPos.Y) * scale.Y
-                },
-                Color = new SDL.FColor
-                {
-                    R = r / 255f,
-                    G = g / 255f,
-                    B = b / 255f,
-                    A = a / 255f
-                },
-                TexCoord = new SDL.FPoint
-                {
-                    X = srcVert.Uv.X,
-                    Y = srcVert.Uv.Y
-                }
-            };
-
-            indices[i] = i;
-        }
-
-        return SDL.RenderGeometry(renderer, texId, vertices, vertices.Length, indices, indices.Length);
-    }
-
     public static void CreateDeviceObjects() { }
 
     public static void DestroyDeviceObjects()
     {
-        var texures = ImGui.GetPlatformIO().Textures;
+        ImVector<ImTextureDataPtr> texures = ImGui.GetPlatformIO().Textures;
         for (int i = 0; i < texures.Size; i++)
         {
-            var texture = texures[i];
+            ImTextureDataPtr texture = texures[i];
             texture.Status = ImTextureStatus.WantDestroy;
-            UpdateTexture(texture, Data.Renderer);
+            UpdateTexture(texture, GetRendererData().Renderer);
         }
     }
+
+    // @formatter:off — disable formatter after this line
+    public static class DelegateStorage
+    {
+        [UnmanagedFunctionPointer(CallingConvention.Cdecl)]
+        internal delegate void DrawCallbackResetRenderStateFn(ImDrawListPtr drawList, ImDrawCmdPtr cmd);
+        internal static readonly DrawCallbackResetRenderStateFn DrawCallbackResetRenderStateDelegate = DrawCallbackResetRenderState;
+        private static void DrawCallbackResetRenderState(ImDrawListPtr drawList, ImDrawCmdPtr cmd) { } // Intentionally empty. Used as an identifier for rendering loop to call its code. Simpler to implement this way.
+
+        [UnmanagedFunctionPointer(CallingConvention.Cdecl)]
+        internal delegate void RendererCreateWindowFn(ImGuiViewportPtr viewport);
+        internal static readonly RendererCreateWindowFn RendererCreateWindowDelegate = RendererCreateWindow;
+        private static void RendererCreateWindow(ImGuiViewportPtr viewport)
+        {
+            ImGuiSDL3Platform.ViewPortData? vd = ImGuiUserData<ImGuiSDL3Platform.ViewPortData>.Get(viewport.PlatformUserData);
+            if (vd == null || vd.Window == nint.Zero)
+                return;
+
+            if (vd.Renderer == nint.Zero)
+            {
+                vd.Renderer = SDL.CreateRenderer(vd.Window, null);
+                vd.RendererOwned = true;
+            }
+        }
+
+        [UnmanagedFunctionPointer(CallingConvention.Cdecl)]
+        internal delegate void RendererDestroyWindowFn(ImGuiViewportPtr viewport);
+        internal static readonly RendererDestroyWindowFn RendererDestroyWindowDelegate = RendererDestroyWindow;
+        private static void RendererDestroyWindow(ImGuiViewportPtr viewport)
+        {
+            ImGuiSDL3Platform.ViewPortData? vd = ImGuiUserData<ImGuiSDL3Platform.ViewPortData>.Get(viewport.PlatformUserData);
+            if (vd == null)
+                return;
+
+            if (vd.RendererOwned && vd.Renderer != nint.Zero)
+            {
+                SDL.DestroyRenderer(vd.Renderer);
+            }
+
+            vd.Renderer = nint.Zero;
+            vd.RendererOwned = false;
+        }
+
+        [UnmanagedFunctionPointer(CallingConvention.Cdecl)]
+        internal delegate void RendererRenderWindowFn(ImGuiViewportPtr viewport);
+        internal static readonly RendererRenderWindowFn RendererRenderWindowDelegate = RendererRenderWindow;
+        private static void RendererRenderWindow(ImGuiViewportPtr viewport)
+        {
+            ImGuiSDL3Platform.ViewPortData? vd = ImGuiUserData<ImGuiSDL3Platform.ViewPortData>.Get(viewport.PlatformUserData);
+            if (vd == null || vd.Renderer == nint.Zero)
+            {
+                return;
+            }
+
+            if (Parent != null)
+            {
+                SDL.SetRenderDrawColorFloat(vd.Renderer, Parent.ClearColor.X, Parent.ClearColor.Y, Parent.ClearColor.Z, 0f);
+                SDL.RenderClear(vd.Renderer);
+            }
+
+            RenderDrawData(viewport.DrawData, vd.Renderer);
+        }
+
+        [UnmanagedFunctionPointer(CallingConvention.Cdecl)]
+        internal delegate void RendererSwapBuffersFn(ImGuiViewportPtr viewport);
+        internal static readonly RendererSwapBuffersFn RendererSwapBuffersDelegate = RendererSwapBuffers;
+        private static void RendererSwapBuffers(ImGuiViewportPtr viewport)
+        {
+            ImGuiSDL3Platform.ViewPortData? vd = ImGuiUserData<ImGuiSDL3Platform.ViewPortData>.Get(viewport.PlatformUserData);
+            if (vd == null || vd.Renderer == nint.Zero)
+                return;
+
+            SDL.RenderPresent(vd.Renderer);
+        }
+    }
+    // @formatter:on — enable formatter after this line
 }

SDL3/ImGuiUserData.cs

@@ -0,0 +1,35 @@
+using System.Runtime.InteropServices;
+
+namespace SDL3_TestingSuite.SDL3;
+
+public unsafe static class ImGuiUserData<T> where T : class
+{
+    public static void* Store(T value)
+    {
+        if (value == null)
+            return null;
+
+        GCHandle handle = GCHandle.Alloc(value, GCHandleType.Normal);
+        return (void*)GCHandle.ToIntPtr(handle);
+    }
+
+    public static T? Get(void* ptr)
+    {
+        if (ptr == null)
+            return null;
+
+        GCHandle handle = GCHandle.FromIntPtr((nint)ptr);
+        return (T?)handle.Target;
+    }
+
+    public static void Free(void* ptr)
+    {
+        if (ptr == null)
+            return;
+
+        GCHandle handle = GCHandle.FromIntPtr((nint)ptr);
+
+        if (handle.IsAllocated)
+            handle.Free();
+    }
+}

SDL3/SDL3Window.cs

@@ -1,8 +1,8 @@
-using System.Diagnostics;
+using System.Numerics;
-using System.Numerics;
 using Hexa.NET.ImGui;
 using Hexa.NET.ImGuizmo;
 using Hexa.NET.ImPlot;
+using Hexa.NET.ImPlot3D;
 using SDL3;
 
 namespace SDL3_TestingSuite.SDL3;
@@ -12,15 +12,13 @@ public sealed unsafe class SDL3Window : IDisposable
     public readonly nint Window;
     public readonly nint Renderer;
 
-    internal Action? RenderCallback { get; set; }
+    public event Action RenderCallback;
 
     public Vector4 ClearColor = new Vector4(0.06f, 0.05882353f, 0.05882353f, 1f);
 
-    private readonly Stopwatch _timer = Stopwatch.StartNew();
-    private TimeSpan _time = TimeSpan.Zero;
-
-    private SDL.Rect _screenClipRect;
     private ImGuiContextPtr _imGuiContext;
+    private ImPlotContextPtr _imPlotContext;
+    private ImPlot3DContextPtr _imPlot3DContext;
 
     public bool Disposed => _disposed;
     private bool _disposed;
@@ -41,18 +39,18 @@ public sealed unsafe class SDL3Window : IDisposable
         SDL.ShowWindow(Window);
 
         // Create ImGui context
-        var context = ImGui.CreateContext();
+        _imGuiContext = ImGui.CreateContext();
-        ImPlot.CreateContext();
+        _imPlotContext = ImPlot.CreateContext();
-        ImPlot.SetImGuiContext(context);
+        // _imPlot3DContext = ImPlot3D.CreateContext();
-        ImGuizmo.SetImGuiContext(context);
+        ImPlot.SetImGuiContext(_imGuiContext);
-        // ImPlot3D.SetImGuiContext(context);
+        ImGuizmo.SetImGuiContext(_imGuiContext);
-        // ImPlot3D.CreateContext();
+        // ImPlot3D.SetImGuiContext(_imGuiContext);
 
         ImGuiIOPtr io = ImGui.GetIO();
         io.ConfigFlags |= ImGuiConfigFlags.NavEnableKeyboard | ImGuiConfigFlags.NavEnableGamepad | ImGuiConfigFlags.DockingEnable;
         io.ConfigFlags |= ImGuiConfigFlags.ViewportsEnable;
-        io.Fonts.Flags |= ImFontAtlasFlags.NoBakedLines;
 
+        io.Fonts.Flags |= ImFontAtlasFlags.NoBakedLines;
         io.Fonts.AddFontDefault();
 
         try
@@ -96,20 +94,54 @@ public sealed unsafe class SDL3Window : IDisposable
         ImGuiSDL3Renderer.Init(Renderer, this);
     }
 
+    public bool ShouldClose;
+
     public void Run()
     {
         while (!_disposed)
         {
-            ImGui.GetIO().DeltaTime = (float)(_timer.Elapsed - _time).TotalSeconds;
+            if (ImGui.GetIO().WantTextInput && !SDL.TextInputActive(Window))
-            _time = _timer.Elapsed;
+                SDL.StartTextInput(Window);
+            else if (!ImGui.GetIO().WantTextInput && SDL.TextInputActive(Window))
+                SDL.StopTextInput(Window);
 
-            PollEvents();
+            while (SDL.PollEvent(out SDL.Event ev))
+            {
+                ImGuiSDL3Platform.ProcessEvent(ev);
 
-            Update();
+                switch ((SDL.EventType)ev.Type)
+                {
+                    case SDL.EventType.Terminating:
+                    case SDL.EventType.WindowCloseRequested:
+                    case SDL.EventType.Quit:
+                        ShouldClose = true;
+                        break;
+                }
+            }
+
+            ImGuiSDL3Platform.NewFrame();
+            ImGuiSDL3Renderer.NewFrame();
+            ImGui.NewFrame();
 
             RenderCallback?.Invoke();
 
-            Render();
+            ImGuiIOPtr io = ImGui.GetIO();
+
+            ImGui.Render();
+
+            SDL.SetRenderScale(Renderer, io.DisplayFramebufferScale.X, io.DisplayFramebufferScale.Y);
+            SDL.SetRenderDrawColorFloat(Renderer, ClearColor.X, ClearColor.Y, ClearColor.Z, ClearColor.W);
+            SDL.RenderClear(Renderer);
+
+            ImGuiSDL3Renderer.RenderDrawData(ImGui.GetDrawData(), Renderer);
+
+            if ((io.ConfigFlags & ImGuiConfigFlags.ViewportsEnable) != 0)
+            {
+                ImGui.UpdatePlatformWindows();
+                ImGui.RenderPlatformWindowsDefault();
+            }
+
+            SDL.RenderPresent(Renderer);
 
             if (ShouldClose)
             {
@@ -122,56 +154,6 @@ public sealed unsafe class SDL3Window : IDisposable
             Dispose();
     }
 
-    public bool ShouldClose;
-
-    private void PollEvents()
-    {
-        if (ImGui.GetIO().WantTextInput && !SDL.TextInputActive(Window))
-            SDL.StartTextInput(Window);
-        else if (!ImGui.GetIO().WantTextInput && SDL.TextInputActive(Window))
-            SDL.StopTextInput(Window);
-
-        while (SDL.PollEvent(out SDL.Event ev))
-        {
-            ImGuiSDL3Platform.ProcessEvent(ev);
-
-            switch ((SDL.EventType)ev.Type)
-            {
-                case SDL.EventType.Terminating:
-                case SDL.EventType.WindowCloseRequested:
-                case SDL.EventType.Quit:
-                    ShouldClose = true;
-                    break;
-            }
-        }
-    }
-
-    private void Update()
-    {
-        ImGuiSDL3Platform.NewFrame();
-        ImGuiSDL3Renderer.NewFrame();
-        ImGui.NewFrame();
-    }
-
-    private void Render()
-    {
-        ImGuiIOPtr io = ImGui.GetIO();
-
-        ImGui.Render();
-        SDL.SetRenderScale(Renderer, io.DisplayFramebufferScale.X, io.DisplayFramebufferScale.Y);
-        SDL.SetRenderDrawColorFloat(Renderer, ClearColor.X, ClearColor.Y, ClearColor.Z, ClearColor.W);
-        SDL.RenderClear(Renderer);
-        ImGuiSDL3Renderer.RenderDrawData(ImGui.GetDrawData(), Renderer);
-
-        if ((io.ConfigFlags & ImGuiConfigFlags.ViewportsEnable) != 0)
-        {
-            ImGui.UpdatePlatformWindows();
-            ImGui.RenderPlatformWindowsDefault();
-        }
-
-        SDL.RenderPresent(Renderer);
-    }
-
     ~SDL3Window()
     {
         Dispose(false);
@@ -190,6 +172,19 @@ public sealed unsafe class SDL3Window : IDisposable
 
         if (disposing)
         {
+            if (_imGuiContext.Handle != null)
+            {
+                ImGui.SetCurrentContext(_imGuiContext);
+            }
+            if (_imPlotContext.Handle != null)
+            {
+                ImPlot.SetCurrentContext(_imPlotContext);
+            }
+            // if (_imPlot3DContext.Handle != null)
+            // {
+            //     ImPlot3D.SetCurrentContext(_imPlot3DContext);
+            // }
+
             ImGuiSDL3Renderer.Dispose();
             ImGuiSDL3Platform.Dispose();
 
@@ -202,6 +197,18 @@ public sealed unsafe class SDL3Window : IDisposable
             ImGui.DestroyContext(_imGuiContext);
             _imGuiContext = null;
         }
+        if (_imPlotContext.Handle != null)
+        {
+            ImPlot.SetCurrentContext(null);
+            ImPlot.DestroyContext(_imPlotContext);
+            _imPlotContext = null;
+        }
+        // if (_imPlot3DContext.Handle != null)
+        // {
+        //     ImPlot3D.SetCurrentContext(null);
+        //     ImPlot3D.DestroyContext(_imPlot3DContext);
+        //     _imPlot3DContext = null;
+        // }
 
         if (Renderer != nint.Zero)
         {