Fix visual snapshot on headless

src/Avalonia.Base/Rendering/Composition/Compositor.cs

@@ -294,7 +294,7 @@ public async Task<Bitmap> CreateCompositionVisualSnapshot(CompositionVisual visu
                 throw new InvalidOperationException();
             if (visual.Root == null)
                 throw new InvalidOperationException();
-            var impl = await InvokeServerJobAsync(() => _server.CreateCompositionVisualSnapshot(visual.Server, scaling), true);
+            var impl = await InvokeServerJobAsync(() => _server.CreateCompositionVisualSnapshot(visual.Server, scaling, true), true);
             return new Bitmap(RefCountable.Create(impl));
         }
 

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

@@ -20,9 +20,12 @@ protected override void RenderCore(ServerVisualRenderContext context, LtrbRect c
         {
             base.RenderCore(context, currentTransformedClip);
 
-            foreach (var ch in Children)
+            if (context.RenderChildren)
             {
-                ch.Render(context, currentTransformedClip);
+                foreach (var ch in Children)
+                {
+                    ch.Render(context, currentTransformedClip);
+                }
             }
         }
 

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

@@ -215,7 +215,7 @@ void RenderRootToContextWithClip(IDrawingContextImpl context, ServerCompositionV
 
                 using (var proxy = new CompositorDrawingContextProxy(context))
                 {
-                    var ctx = new ServerVisualRenderContext(proxy, DirtyRects, false);
+                    var ctx = new ServerVisualRenderContext(proxy, DirtyRects, false, true);
                     root.Render(ctx, null);
                 }
 

src/Avalonia.Base/Rendering/Composition/Server/ServerCompositor.UserApis.cs

@@ -49,7 +49,7 @@ public IReadOnlyDictionary<Type, object> RT_GetRenderInterfaceFeatures()
     }
 
     public IBitmapImpl CreateCompositionVisualSnapshot(ServerCompositionVisual visual,
-        double scaling)
+        double scaling, bool renderChildren)
     {
         using (RenderInterface.EnsureCurrent())
         {
@@ -69,11 +69,12 @@ public IBitmapImpl CreateCompositionVisualSnapshot(ServerCompositionVisual visua
                         PostTransform = invertRootTransform * scaleTransform,
                         Transform = Matrix.Identity
                     };
-                    var ctx = new ServerVisualRenderContext(proxy, null, true);
+                    var ctx = new ServerVisualRenderContext(proxy, null, true, renderChildren);
                     visual.Render(ctx, null);
                 }
 
-                if (target is IDrawingContextLayerWithRenderContextAffinityImpl affined)
+                if (target is IDrawingContextLayerWithRenderContextAffinityImpl affined
+                    && affined.HasRenderContextAffinity)
                     return affined.CreateNonAffinedSnapshot();
 
                 // We are returning the original target, so prevent it from being disposed
@@ -87,4 +88,4 @@ public IBitmapImpl CreateCompositionVisualSnapshot(ServerCompositionVisual visua
             }
         }
     }
-}
+}

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

@@ -8,15 +8,17 @@ internal class ServerVisualRenderContext
 {
     public IDirtyRectTracker? DirtyRects { get; }
     public bool DetachedRendering { get; }
+    public bool RenderChildren { get; }
     public CompositorDrawingContextProxy Canvas { get; }
     private readonly Stack<Matrix>? _transformStack;
 
     public ServerVisualRenderContext(CompositorDrawingContextProxy canvas, IDirtyRectTracker? dirtyRects,
-        bool detachedRendering)
+        bool detachedRendering, bool renderChildren)
     {
         Canvas = canvas;
         DirtyRects = dirtyRects;
         DetachedRendering = detachedRendering;
+        RenderChildren = renderChildren;
         if (detachedRendering)
         {
             _transformStack = new();
@@ -72,4 +74,4 @@ public void Dispose()
         }
     }
 
-}
+}

tests/Avalonia.Headless.UnitTests/RenderingTests.cs

@@ -1,8 +1,10 @@
 using System.Collections.ObjectModel;
+using System.Threading.Tasks;
 using Avalonia.Controls;
 using Avalonia.Controls.Shapes;
 using Avalonia.Layout;
 using Avalonia.Media;
+using Avalonia.Rendering.Composition;
 using Avalonia.Threading;
 
 namespace Avalonia.Headless.UnitTests;
@@ -37,7 +39,7 @@ public void Should_Render_Last_Frame_To_Bitmap()
 
         Assert.NotNull(frame);
     }
-    
+
 #if NUNIT
     [AvaloniaTest, Timeout(10000)]
 #elif XUNIT
@@ -136,4 +138,36 @@ public void Should_Not_Hang_With_Non_Trivial_Layout()
         var frame = window.CaptureRenderedFrame();
         Assert.NotNull(frame);
     }
+
+#if NUNIT
+    [AvaloniaTest, Timeout(10000)]
+#elif XUNIT
+    [AvaloniaFact(Timeout = 10000)]
+#endif
+    public async Task Should_Render_To_A_Compositor_Snapshot_Capture()
+    {
+        var window = new Window
+        {
+            Content = new ContentControl
+            {
+                HorizontalAlignment = HorizontalAlignment.Stretch,
+                VerticalAlignment = VerticalAlignment.Stretch,
+                Width = 100,
+                Height = 100,
+                Background = Brushes.Green
+            },
+            SizeToContent = SizeToContent.WidthAndHeight
+        };
+
+        window.Show();
+
+        var compositionVisual = ElementComposition.GetElementVisual(window)!;
+        var snapshot = await compositionVisual.Compositor.CreateCompositionVisualSnapshot(compositionVisual, 1);
+
+        Assert.NotNull(snapshot);
+        // ReSharper disable CompareOfFloatsByEqualityOperator
+        Assert.True(100 == snapshot.Size.Width);
+        Assert.True(100 == snapshot.Size.Height);
+        // ReSharper restore CompareOfFloatsByEqualityOperator
+    }
 }