Track IsEffectivelyVisible state

src/Avalonia.Base/Visual.cs

@@ -104,7 +104,7 @@ public partial class Visual : StyledElement
         /// </summary>
         public static readonly DirectProperty<Visual, Visual?> VisualParentProperty =
             AvaloniaProperty.RegisterDirect<Visual, Visual?>(nameof(VisualParent), o => o._visualParent);
-
+        
         /// <summary>
         /// Defines the <see cref="ZIndex"/> property.
         /// </summary>
@@ -120,6 +120,7 @@ public partial class Visual : StyledElement
         private IRenderRoot? _visualRoot;
         private Visual? _visualParent;
         private bool _hasMirrorTransform;
+
         private TargetWeakEventSubscriber<Visual, EventArgs>? _affectsRenderWeakSubscriber;
 
         /// <summary>
@@ -147,7 +148,7 @@ public Visual()
         {
             // Disable transitions until we're added to the visual tree.
             DisableTransitions();
-
+            
             var visualChildren = new AvaloniaList<Visual>();
             visualChildren.ResetBehavior = ResetBehavior.Remove;
             visualChildren.Validate = visual => ValidateVisualChild(visual);
@@ -195,26 +196,36 @@ public Geometry? Clip
         /// <summary>
         /// Gets a value indicating whether this control and all its parents are visible.
         /// </summary>
-        public bool IsEffectivelyVisible
+        public bool IsEffectivelyVisible { get; private set; } = true;
+
+        /// <summary>
+        /// Updates the <see cref="IsEffectivelyVisible"/> property based on the parent's
+        /// <see cref="IsEffectivelyVisible"/>.
+        /// </summary>
+        /// <param name="parent">The parent control.</param>
+        private void UpdateIsEffectivelyEnabled(bool state)
         {
-            get
-            {
-                Visual? node = this;
+            IsEffectivelyVisible = state;
 
-                while (node != null)
-                {
-                    if (!node.IsVisible)
-                    {
-                        return false;
-                    }
+            // PERF-SENSITIVE: This is called on entire hierarchy and using foreach or LINQ
+            // will cause extra allocations and overhead.
+
+            var children = VisualChildren;
 
-                    node = node.VisualParent;
-                }
+            // ReSharper disable once ForCanBeConvertedToForeach
+            for (int i = 0; i < children.Count; ++i)
+            {
+                var child = children[i];
 
-                return true;
+                child?.UpdateIsEffectivelyEnabled(state);
             }
         }
 
+        private static void IsVisibleChanged(AvaloniaPropertyChangedEventArgs e)
+        {
+            ((Visual)e.Sender).UpdateIsEffectivelyEnabled(e.GetNewValue<bool>());
+        }
+
         /// <summary>
         /// Gets or sets a value indicating whether this control is visible.
         /// </summary>
@@ -453,7 +464,11 @@ protected override void OnPropertyChanged(AvaloniaPropertyChangedEventArgs chang
         {
             base.OnPropertyChanged(change);
 
-            if (change.Property == FlowDirectionProperty)
+            if (change.Property == IsVisibleProperty)
+            {
+                IsVisibleChanged(change);
+            } 
+            else if (change.Property == FlowDirectionProperty)
             {
                 InvalidateMirrorTransform();
 
@@ -463,7 +478,7 @@ protected override void OnPropertyChanged(AvaloniaPropertyChangedEventArgs chang
                 }
             }
         }
-
+ 
         protected override void LogicalChildrenCollectionChanged(object? sender, NotifyCollectionChangedEventArgs e)
         {
             base.LogicalChildrenCollectionChanged(sender, e);
@@ -495,10 +510,13 @@ protected virtual void OnAttachedToVisualTreeCore(VisualTreeAttachmentEventArgs
             OnAttachedToVisualTree(e);
             AttachedToVisualTree?.Invoke(this, e);
             InvalidateVisual();
+
             _visualRoot.Renderer.RecalculateChildren(_visualParent!);
-
-            if (ZIndex != 0 && VisualParent is Visual parent)
-                parent.HasNonUniformZIndexChildren = true;
+
+            if (ZIndex != 0 && _visualParent is { })
+                _visualParent.HasNonUniformZIndexChildren = true;
+
+            SyncIsEffectivelyEnabledFromParent(_visualParent);
 
             var visualChildren = VisualChildren;
             var visualChildrenCount = visualChildren.Count;
@@ -512,6 +530,13 @@ protected virtual void OnAttachedToVisualTreeCore(VisualTreeAttachmentEventArgs
             }
         }
 
+        private void SyncIsEffectivelyEnabledFromParent(Visual? parent)
+        {
+            var vis = (parent?.IsVisible ?? false) && IsVisible;
+
+            UpdateIsEffectivelyEnabled(vis);
+        }
+
         /// <summary>
         /// Calls the <see cref="OnDetachedFromVisualTree(VisualTreeAttachmentEventArgs)"/> method 
         /// for this control and all of its visual descendants.
@@ -535,6 +560,8 @@ protected virtual void OnDetachedFromVisualTreeCore(VisualTreeAttachmentEventArg
             DetachedFromVisualTree?.Invoke(this, e);
             e.Root.Renderer.AddDirty(this);
 
+            SyncIsEffectivelyEnabledFromParent(_visualParent);
+
             var visualChildren = VisualChildren;
             var visualChildrenCount = visualChildren.Count;
 

tests/Avalonia.Base.UnitTests/VisualTests.cs

@@ -349,5 +349,20 @@ public void Changing_ZIndex_Should_Recalculate_Parent_Children()
 
             renderer.Verify(x => x.RecalculateChildren(stackPanel));
         }
+
+        [Fact]
+        public void IsEffectivelyVisible_Propagates_To_Visual_Children()
+        {
+            var child2 = new Decorator();
+            var child1 = new Decorator { Child = child2 };
+            var root = new TestRoot { Child = child1 };
+
+            Assert.True(child2.IsEffectivelyVisible);
+
+            root.IsVisible = false;
+
+            Assert.False(child2.IsEffectivelyVisible);
+        }
+
     }
 }