Merge pull request #9831 from AvaloniaUI/fixes/ignore-opacity-for-hittesting

Ignore Opacity for hit-testing purposes

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

@@ -175,8 +175,14 @@ namespace Avalonia.Rendering.Composition.Server
             
             EffectiveOpacity = Opacity * (Parent?.EffectiveOpacity ?? 1);
 
-            IsVisibleInFrame = _parent?.IsVisibleInFrame != false && Visible && EffectiveOpacity > 0.04 && !_isBackface &&
-                               !_combinedTransformedClipBounds.IsDefault;
+            IsHitTestVisibleInFrame = _parent?.IsHitTestVisibleInFrame != false
+                                      && Visible
+                                      && !_isBackface
+                                      && !_combinedTransformedClipBounds.IsDefault;
+
+            IsVisibleInFrame = IsHitTestVisibleInFrame
+                               && _parent?.IsVisibleInFrame != false
+                               && EffectiveOpacity > 0.04;
 
             if (wasVisible != IsVisibleInFrame || positionChanged)
             {
@@ -200,7 +206,7 @@ namespace Avalonia.Rendering.Composition.Server
             readback.Revision = root.Revision;
             readback.Matrix = GlobalTransformMatrix;
             readback.TargetId = Root.Id;
-            readback.Visible = IsVisibleInFrame;
+            readback.Visible = IsHitTestVisibleInFrame;
         }
 
         void AddDirtyRect(Rect rc)
@@ -261,6 +267,7 @@ namespace Avalonia.Rendering.Composition.Server
         }
 
         public bool IsVisibleInFrame { get; set; }
+        public bool IsHitTestVisibleInFrame { get; set; }
         public double EffectiveOpacity { get; set; }
         public Rect TransformedOwnContentBounds { get; set; }
         public virtual Rect OwnContentBounds => new Rect(0, 0, Size.X, Size.Y);

tests/Avalonia.Base.UnitTests/Rendering/CompositorHitTestingTests.cs

@@ -82,6 +82,39 @@ public class CompositorHitTestingTests : CompositorTestsBase
         }
     }
     
+    [Theory,
+        InlineData(false, false),
+        InlineData(true, false),
+        InlineData(false, true),
+        InlineData(true, true),
+    ]
+    public void HitTest_Should_Find_Zero_Opacity_Controls_At_Point(bool parent, bool child)
+    {
+        
+        using (var s = new CompositorServices(new Size(200, 200)))
+        {
+            Border visible, border;
+            s.TopLevel.Content = border = new Border
+            {
+                Width = 100,
+                Height = 100,
+                Background = Brushes.Red,
+                HorizontalAlignment = HorizontalAlignment.Center,
+                VerticalAlignment = VerticalAlignment.Center,
+                Opacity = parent ? 0 : 1,
+                Child = visible = new Border
+                {
+                    Opacity = child ? 0 : 1,
+                    Background = Brushes.Red,
+                    HorizontalAlignment = HorizontalAlignment.Stretch,
+                    VerticalAlignment = VerticalAlignment.Stretch,
+                }
+            };
+
+            s.AssertHitTest(new Point(100, 100), null, visible, border);
+        }
+    }
+    
     [Fact]
     public void HitTest_Should_Not_Find_Control_Outside_Point()
     {