Use weak CompositionVisual reference in server-side

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

@@ -52,10 +52,13 @@ namespace Avalonia.Rendering.Composition
             return res;
         }
 
-        private static void ProcessHitTestReadbackUpdates(IReadOnlyList<CompositionVisual> readbackUpdates)
+        private static void ProcessHitTestReadbackUpdates(IReadOnlyList<WeakReference<CompositionVisual>> readbackUpdates)
         {
-            foreach (var visual in readbackUpdates)
+            foreach (var weakVisual in readbackUpdates)
             {
+                if (!weakVisual.TryGetTarget(out var visual))
+                    continue;
+
                 if (visual.Parent is CompositionContainerVisual parent)
                     parent.UpdateHitTestChildBounds(visual);
             }

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

@@ -1,3 +1,4 @@
+using System;
 using System.Collections.Generic;
 using System.Threading;
 
@@ -16,11 +17,11 @@ namespace Avalonia.Rendering.Composition.Server
         private ulong _nextWriteRevision = 1;
         public ulong WriteRevision { get; private set; }
         public ulong LastCompletedWrite { get; private set; }
-        private readonly HashSet<CompositionVisual> _pendingHitTestUpdateSet = new();
+        private readonly HashSet<WeakReference<CompositionVisual>> _pendingHitTestUpdateSet = new();
-        private List<CompositionVisual> _pendingHitTestUpdates = new();
+        private List<WeakReference<CompositionVisual>> _pendingHitTestUpdates = new();
-        private List<CompositionVisual> _readHitTestUpdates = new();
+        private List<WeakReference<CompositionVisual>> _readHitTestUpdates = new();
 
-        public IReadOnlyList<CompositionVisual> NextRead()
+        public IReadOnlyList<WeakReference<CompositionVisual>> NextRead()
         {
             lock (_lock)
             {
@@ -49,7 +50,7 @@ namespace Avalonia.Rendering.Composition.Server
             Monitor.Exit(_lock);
         }
 
-        internal void AddHitTestUpdate(CompositionVisual? visual)
+        internal void AddHitTestUpdate(WeakReference<CompositionVisual>? visual)
         {
             if (visual != null && _pendingHitTestUpdateSet.Add(visual))
                 _pendingHitTestUpdates.Add(visual);

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

@@ -20,7 +20,7 @@ namespace Avalonia.Rendering.Composition.Server
     {
         public ServerCompositionVisualCollection? Children { get; private set; } = null!;
         public ServerCompositionVisualCache? Cache { get; private set; }
-        internal CompositionVisual? Client { get; set; }
+        internal WeakReference<CompositionVisual>? Client { get; set; }
 
         partial void OnRootChanging()
         {

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

@@ -22,7 +22,7 @@ namespace Avalonia.Rendering.Composition
 
         partial void InitializeDefaultsExtra()
         {
-            Server.Client = this;
+            Server.Client = new WeakReference<CompositionVisual>(this);
         }
 
         partial void OnRootChanged() => OnRootChangedCore();