Improve effect render performance by providing Skia with information about subscene bounds (#20191)

* Improve effect render performance by providing Skia with information about subscene bounds

* Fixed test

* apidiff

* Update API diff

---------

Co-authored-by: Julien Lebosquain <julien@lebosquain.net>

api/Avalonia.nupkg.xml

@@ -187,4 +187,4 @@
     <Left>baseline/netstandard2.0/Avalonia.Controls.dll</Left>
     <Right>target/netstandard2.0/Avalonia.Controls.dll</Right>
   </Suppression>
-</Suppressions>
+</Suppressions>

src/Avalonia.Base/Platform/IDrawingContextImpl.cs

@@ -201,9 +201,10 @@ namespace Avalonia.Platform
         object? GetFeature(Type t);
     }
 
-    public interface IDrawingContextImplWithEffects
+    [PrivateApi]
+    public interface IDrawingContextImplWithEffects : IDrawingContextImpl
     {
-        void PushEffect(IEffect effect);
+        void PushEffect(Rect? clipRect, IEffect effect);
         void PopEffect();
     }
 

src/Avalonia.Base/Rendering/Composition/Server/DrawingContextProxy.PendingCommands.cs

@@ -48,6 +48,10 @@ internal partial class CompositorDrawingContextProxy
         [FieldOffset(0)] public bool IsRoundRect;
         [FieldOffset(4)] public RoundedRect RoundRect;
         [FieldOffset(4)] public Rect NormalRect;
+        
+        // PushEffect
+        [FieldOffset(0)]
+        public Rect? EffectClipRect;
     }
 
     struct PendingCommand
@@ -140,7 +144,7 @@ internal partial class CompositorDrawingContextProxy
         else if (cmd.Type == PendingCommandType.PushEffect)
         {
             if (_impl is IDrawingContextImplWithEffects effects)
-                effects.PushEffect(cmd.ObjectUnion.Effect!);
+                effects.PushEffect(cmd.DataUnion.EffectClipRect, cmd.ObjectUnion.Effect!);
         }
         else if (cmd.Type == PendingCommandType.PushRenderOptions)
             _impl.PushRenderOptions(cmd.DataUnion.RenderOptions);

src/Avalonia.Base/Rendering/Composition/Server/DrawingContextProxy.cs

@@ -285,14 +285,18 @@ internal partial class CompositorDrawingContextProxy : IDrawingContextImpl,
             _impl.DrawRectangle(new ImmutableSolidColorBrush(material.FallbackColor), null, rect);
     }
 
-    public void PushEffect(IEffect effect)
+    public void PushEffect(Rect? clipRect, IEffect effect)
     {
         AddCommand(new()
         {
             Type = PendingCommandType.PushEffect,
             ObjectUnion =
             {
-                Effect = effect
+                Effect = effect,
+            },
+            DataUnion =
+            {
+                EffectClipRect = clipRect
             }
         });
     }

src/Avalonia.Base/Rendering/Composition/Server/ServerCompositionContainerVisual.cs

@@ -65,6 +65,8 @@ namespace Avalonia.Rendering.Composition.Server
             return new(_transformedContentBounds, oldInvalidated, newInvalidated);
         }
 
+        protected override LtrbRect GetEffectBounds() => _transformedContentBounds ?? default;
+
         void AddEffectPaddedDirtyRect(IImmutableEffect effect, LtrbRect transformedBounds)
         {
             var padding = effect.GetEffectOutputPadding();

src/Avalonia.Base/Rendering/Composition/Server/ServerCompositionVisual.cs

@@ -62,9 +62,8 @@ namespace Avalonia.Rendering.Composition.Server
 
             if (applyRenderOptions)
                 canvas.PushRenderOptions(RenderOptions);
-            if (Effect != null)
-                canvas.PushEffect(Effect);
-            
+            var needPopEffect = PushEffect(canvas);
+
             if (Opacity != 1)
                 canvas.PushOpacity(Opacity, ClipToBounds ? boundsRect : null);
             if (ClipToBounds && !HandlesClipToBounds)
@@ -87,12 +86,28 @@ namespace Avalonia.Rendering.Composition.Server
             if (Opacity != 1)
                 canvas.PopOpacity();
             
-            if (Effect != null)
+            if (needPopEffect)
                 canvas.PopEffect();
             if(applyRenderOptions)
                 canvas.PopRenderOptions();
         }
 
+        protected virtual LtrbRect GetEffectBounds() => TransformedOwnContentBounds;
+        
+        private bool PushEffect(CompositorDrawingContextProxy canvas)
+        {
+            if (Effect == null)
+                return false;
+            var clip = GetEffectBounds();
+            if (clip.IsZeroSize)
+                return false;
+            var oldMatrix = canvas.Transform;
+            canvas.Transform = Matrix.Identity;
+            canvas.PushEffect(GetEffectBounds().ToRect(), Effect!);
+            canvas.Transform = oldMatrix;
+            return true;
+        }
+
         protected virtual bool HandlesClipToBounds => false;
 
         private ReadbackData _readback0, _readback1, _readback2;

src/Skia/Avalonia.Skia/DrawingContextImpl.Effects.cs

@@ -7,13 +7,16 @@ namespace Avalonia.Skia;
 partial class DrawingContextImpl
 {
     
-    public void PushEffect(IEffect effect)
+    public void PushEffect(Rect? effectClipRect, IEffect effect)
     {
         CheckLease();
         using var filter = CreateEffect(effect);
         var paint = SKPaintCache.Shared.Get();
         paint.ImageFilter = filter;
-        Canvas.SaveLayer(paint);
+        if (effectClipRect.HasValue)
+            Canvas.SaveLayer(effectClipRect.Value.ToSKRect(), paint);
+        else
+            Canvas.SaveLayer(paint);
         SKPaintCache.Shared.ReturnReset(paint);
     }