Add reusable WebGPU scene resource arena

Author: JimBobSquarePants

src/ImageSharp.Drawing.WebGPU/WebGPUDrawingBackend.cs

@@ -39,6 +39,7 @@ public sealed unsafe partial class WebGPUDrawingBackend : IDrawingBackend, IDisp
     // Cached arenas for cross-flush buffer reuse. Rented via Interlocked.Exchange at flush
     // start and returned at flush end so parallel flushes on different threads don't contend.
     private WebGPUSceneSchedulingArena? cachedSchedulingArena;
+    private WebGPUSceneResourceArena? cachedResourceArena;
     private bool isDisposed;
 
     private static readonly Dictionary<Type, CompositePixelRegistration> CompositePixelHandlers = CreateCompositePixelHandlers();
@@ -258,6 +259,7 @@ public void FlushCompositions<TPixel>(
         // Rent the cached scheduling arena. Null on first flush or if another thread has it.
         // Returned in the finally block for the next flush to reuse.
         WebGPUSceneSchedulingArena? schedulingArena = Interlocked.Exchange(ref this.cachedSchedulingArena, null);
+        WebGPUSceneResourceArena? resourceArena = Interlocked.Exchange(ref this.cachedResourceArena, null);
         try
         {
             // Retry loop: bump allocators start small (Vello defaults) and the GPU discovers
@@ -268,7 +270,7 @@ public void FlushCompositions<TPixel>(
             // because successful sizes are persisted in this.bumpSizes.
             for (int attempt = 0; attempt < MaxDynamicGrowthAttempts; attempt++)
             {
-                if (!WebGPUSceneDispatch.TryCreateStagedScene(configuration, target, compositionScene, currentBumpSizes, out bool exceedsBindingLimit, out WebGPUSceneDispatch.BindingLimitFailure bindingLimitFailure, out WebGPUStagedScene stagedScene, out string? error))
+                if (!WebGPUSceneDispatch.TryCreateStagedScene(configuration, target, compositionScene, currentBumpSizes, ref resourceArena, out bool exceedsBindingLimit, out WebGPUSceneDispatch.BindingLimitFailure bindingLimitFailure, out WebGPUStagedScene stagedScene, out string? error))
                 {
                     this.TestingLastGPUInitializationFailure = exceedsBindingLimit
                         ? error ?? "The staged WebGPU scene exceeded the current binding limits."
@@ -319,10 +321,10 @@ public void FlushCompositions<TPixel>(
         }
         finally
         {
-            // Return the arena for the next flush. If another thread already returned one,
+            // Return arenas for the next flush. If another thread already returned one,
             // dispose the displaced arena (at most one survives in the cache).
-            WebGPUSceneSchedulingArena? prev = Interlocked.Exchange(ref this.cachedSchedulingArena, schedulingArena);
-            WebGPUSceneDispatch.DisposeSchedulingArena(prev);
+            WebGPUSceneDispatch.DisposeSchedulingArena(Interlocked.Exchange(ref this.cachedSchedulingArena, schedulingArena));
+            WebGPUSceneResourceArena.Dispose(Interlocked.Exchange(ref this.cachedResourceArena, resourceArena));
         }
     }
 
@@ -582,6 +584,7 @@ public void Dispose()
         this.TestingLastFlushUsedGPU = false;
         this.TestingLastGPUInitializationFailure = null;
         WebGPUSceneDispatch.DisposeSchedulingArena(this.cachedSchedulingArena);
+        WebGPUSceneResourceArena.Dispose(this.cachedResourceArena);
         this.isDisposed = true;
     }
 

src/ImageSharp.Drawing.WebGPU/WebGPUSceneDispatch.cs

@@ -98,6 +98,7 @@ public readonly record struct BindingLimitFailure(BindingLimitBuffer Buffer, nui
     /// <param name="target">The flush target that exposes the native WebGPU surface.</param>
     /// <param name="scene">The prepared composition scene to stage.</param>
     /// <param name="bumpSizes">The current dynamic scratch capacities to use for this attempt.</param>
+    /// <param name="resourceArena">Cross-flush cached scene resource buffers.</param>
     /// <param name="stagedScene">Receives the flush-scoped staged scene on success.</param>
     /// <param name="error">Receives the staging failure reason when creation fails.</param>
     /// <typeparam name="TPixel">The pixel type of the target surface.</typeparam>
@@ -107,10 +108,11 @@ public static bool TryCreateStagedScene<TPixel>(
         ICanvasFrame<TPixel> target,
         CompositionScene scene,
         WebGPUSceneBumpSizes bumpSizes,
+        ref WebGPUSceneResourceArena? resourceArena,
         out WebGPUStagedScene stagedScene,
         out string? error)
         where TPixel : unmanaged, IPixel<TPixel>
-        => TryCreateStagedScene(configuration, target, scene, bumpSizes, out _, out _, out stagedScene, out error);
+        => TryCreateStagedScene(configuration, target, scene, bumpSizes, ref resourceArena, out _, out _, out stagedScene, out error);
 
     /// <summary>
     /// Builds the flush-scoped encoded scene and uploads its GPU resources.
@@ -119,6 +121,7 @@ public static bool TryCreateStagedScene<TPixel>(
     /// <param name="target">The flush target that exposes the native WebGPU surface.</param>
     /// <param name="scene">The prepared composition scene for this flush.</param>
     /// <param name="bumpSizes">The current dynamic scratch capacities to use for this attempt.</param>
+    /// <param name="resourceArena">Cross-flush cached scene resource buffers.</param>
     /// <param name="exceedsBindingLimit">Receives whether creation failed because a single WebGPU binding would be too large.</param>
     /// <param name="bindingLimitFailure">Receives the exact binding-limit failure when <paramref name="exceedsBindingLimit"/> is <see langword="true"/>.</param>
     /// <param name="stagedScene">Receives the flush-scoped staged scene on success.</param>
@@ -130,6 +133,7 @@ public static bool TryCreateStagedScene<TPixel>(
         ICanvasFrame<TPixel> target,
         CompositionScene scene,
         WebGPUSceneBumpSizes bumpSizes,
+        ref WebGPUSceneResourceArena? resourceArena,
         out bool exceedsBindingLimit,
         out BindingLimitFailure bindingLimitFailure,
         out WebGPUStagedScene stagedScene,
@@ -199,7 +203,7 @@ public static bool TryCreateStagedScene<TPixel>(
                 return true;
             }
 
-            if (!WebGPUSceneResources.TryCreate<TPixel>(flushContext, encodedScene, config, baseColor, out WebGPUSceneResourceSet resources, out error))
+            if (!WebGPUSceneResources.TryCreate<TPixel>(flushContext, encodedScene, config, baseColor, ref resourceArena, out WebGPUSceneResourceSet resources, out error))
             {
                 encodedScene.Dispose();
                 flushContext.Dispose();