Merge branch 'master' into fixes/vmem-optimizations

src/Avalonia.Controls/Repeater/ItemsRepeater.cs

@@ -7,10 +7,10 @@ using System;
 using System.Collections;
 using System.Collections.Specialized;
 using Avalonia.Controls.Templates;
-using Avalonia.Data;
 using Avalonia.Input;
 using Avalonia.Layout;
 using Avalonia.Logging;
+using Avalonia.Utilities;
 using Avalonia.VisualTree;
 
 namespace Avalonia.Controls
@@ -681,8 +681,15 @@ namespace Avalonia.Controls
             if (oldValue != null)
             {
                 oldValue.UninitializeForContext(LayoutContext);
-                oldValue.MeasureInvalidated -= InvalidateMeasureForLayout;
-                oldValue.ArrangeInvalidated -= InvalidateArrangeForLayout;
+
+                WeakEventHandlerManager.Unsubscribe<EventArgs, ItemsRepeater>(
+                    oldValue,
+                    nameof(AttachedLayout.MeasureInvalidated),
+                    InvalidateMeasureForLayout);
+                WeakEventHandlerManager.Unsubscribe<EventArgs, ItemsRepeater>(
+                    oldValue,
+                    nameof(AttachedLayout.ArrangeInvalidated),
+                    InvalidateArrangeForLayout);
 
                 // Walk through all the elements and make sure they are cleared
                 foreach (var element in Children)
@@ -699,8 +706,15 @@ namespace Avalonia.Controls
             if (newValue != null)
             {
                 newValue.InitializeForContext(LayoutContext);
-                newValue.MeasureInvalidated += InvalidateMeasureForLayout;
-                newValue.ArrangeInvalidated += InvalidateArrangeForLayout;
+
+                WeakEventHandlerManager.Subscribe<AttachedLayout, EventArgs, ItemsRepeater>(
+                    newValue,
+                    nameof(AttachedLayout.MeasureInvalidated),
+                    InvalidateMeasureForLayout);
+                WeakEventHandlerManager.Subscribe<AttachedLayout, EventArgs, ItemsRepeater>(
+                    newValue,
+                    nameof(AttachedLayout.ArrangeInvalidated),
+                    InvalidateArrangeForLayout);
             }
 
             bool isVirtualizingLayout = newValue != null && newValue is VirtualizingLayout;

src/Avalonia.Layout/Layoutable.cs

@@ -758,8 +758,6 @@ namespace Avalonia.Layout
 
         protected override void OnDetachedFromVisualTreeCore(VisualTreeAttachmentEventArgs e)
         {
-            base.OnDetachedFromVisualTreeCore(e);
-
             if (e.Root is ILayoutRoot r)
             {
                 if (_layoutUpdated is object)
@@ -772,6 +770,8 @@ namespace Avalonia.Layout
                     r.LayoutManager.UnregisterEffectiveViewportListener(this);
                 }
             }
+
+            base.OnDetachedFromVisualTreeCore(e);
         }
 
         /// <summary>

tests/Avalonia.LeakTests/ControlTests.cs

@@ -552,6 +552,37 @@ namespace Avalonia.LeakTests
             }
         }
 
+        [Fact]
+        public void ItemsRepeater_Is_Freed()
+        {
+            using (Start())
+            {
+                Func<Window> run = () =>
+                {
+                    var window = new Window
+                    {
+                        Content = new ItemsRepeater(),
+                    };
+
+                    window.Show();
+
+                    window.LayoutManager.ExecuteInitialLayoutPass();
+                    Assert.IsType<ItemsRepeater>(window.Presenter.Child);
+
+                    window.Content = null;
+                    window.LayoutManager.ExecuteLayoutPass();
+                    Assert.Null(window.Presenter.Child);
+
+                    return window;
+                };
+
+                var result = run();
+
+                dotMemory.Check(memory =>
+                    Assert.Equal(0, memory.GetObjects(where => where.Type.Is<ItemsRepeater>()).ObjectsCount));
+            }
+        }
+
         private IDisposable Start()
         {
             return UnitTestApplication.Start(TestServices.StyledWindow.With(