Some optimizations

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

@@ -7,6 +7,11 @@ namespace Avalonia.Rendering.Composition;
 
 internal sealed class CompositionHitTestAabbTree
 {
+    internal interface IQueryHitTester
+    {
+        CompositionVisual? HitTest(CompositionVisual visual);
+    }
+
     private const int Null = -1;
     private const double FatBoundsPadding = 1;
     private static readonly CandidateComparer s_candidateComparer = new();
@@ -124,6 +129,56 @@ internal sealed class CompositionHitTestAabbTree
         _queryCandidates.Clear();
     }
 
+    public CompositionVisual? QueryFirst<T>(Point point, ref T hitTest)
+        where T : struct, IQueryHitTester
+    {
+        _queryCandidates.Clear();
+
+        if (_root != Null)
+        {
+            var stackCount = 0;
+            PushQueryNode(ref stackCount, _root);
+
+            while (stackCount > 0)
+            {
+                var nodeIndex = _queryStack[--stackCount];
+                var node = _nodes[nodeIndex];
+
+                if (!node.Bounds.Contains(point))
+                    continue;
+
+                if (node.IsLeaf)
+                {
+                    if (node.Visual != null)
+                        _queryCandidates.Add(new Candidate(node.Visual, node.Order));
+                }
+                else
+                {
+                    PushQueryNode(ref stackCount, node.Child1);
+                    PushQueryNode(ref stackCount, node.Child2);
+                }
+            }
+        }
+
+        foreach (var candidate in _unbounded)
+            _queryCandidates.Add(new Candidate(candidate.Key, candidate.Value));
+
+        _queryCandidates.Sort(s_candidateComparer);
+
+        foreach (var candidate in _queryCandidates)
+        {
+            var hit = hitTest.HitTest(candidate.Visual);
+            if (hit != null)
+            {
+                _queryCandidates.Clear();
+                return hit;
+            }
+        }
+
+        _queryCandidates.Clear();
+        return null;
+    }
+
     private void Add(CompositionVisual visual, int order)
     {
         var state = GetBoundsState(visual, out var bounds);

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

@@ -189,23 +189,12 @@ namespace Avalonia.Rendering.Composition
                 var queriedIndexedChildren = false;
                 if (cv.Children.Count >= CompositionContainerVisual.HitTestAabbTreeThreshold)
                 {
-                    var candidates = RentHitTestChildCandidates(out var releaseToField);
-                    try
+                    var query = new FirstHitTestQuery(this, point, filter, resultFilter);
+                    if (cv.TryQueryFirstHitTestChild(point, ref query, out var hit))
                     {
-                        if (cv.TryQueryHitTestChildren(point, candidates))
-                        {
-                            queriedIndexedChildren = true;
-                            foreach (var child in candidates)
-                            {
-                                var hit = HitTestFirstCore(child, point, filter, resultFilter);
-                                if (hit != null)
-                                    return hit;
-                            }
-                        }
-                    }
-                    finally
-                    {
-                        ReleaseHitTestChildCandidates(candidates, releaseToField);
+                        queriedIndexedChildren = true;
+                        if (hit != null)
+                            return hit;
                     }
                 }
 
@@ -223,6 +212,16 @@ namespace Avalonia.Rendering.Composition
             return visual.HitTest(point) && (resultFilter == null || resultFilter(visual)) ? visual : null;
         }
 
+        private readonly struct FirstHitTestQuery(
+            CompositionTarget target,
+            Point point,
+            Func<CompositionVisual, bool>? filter,
+            Func<CompositionVisual, bool>? resultFilter) : CompositionHitTestAabbTree.IQueryHitTester
+        {
+            public CompositionVisual? HitTest(CompositionVisual visual) =>
+                target.HitTestFirstCore(visual, point, filter, resultFilter);
+        }
+
         /// <summary>
         /// Registers the composition target for explicit redraw
         /// </summary>

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

@@ -8,7 +8,7 @@ namespace Avalonia.Rendering.Composition
     /// </summary>
     public partial class CompositionContainerVisual : CompositionVisual
     {
-        internal static readonly int HitTestAabbTreeThreshold = CompositionHitTestAabbTree.IsEnabled ? 1 : int.MaxValue;
+        internal static readonly int HitTestAabbTreeThreshold = CompositionHitTestAabbTree.IsEnabled ? 32 : int.MaxValue;
         private CompositionHitTestAabbTree? _hitTestChildren;
         private bool _hitTestChildrenDirty = true;
 
@@ -67,5 +67,28 @@ namespace Avalonia.Rendering.Composition
             _hitTestChildren.Query(point, results);
             return true;
         }
+
+        internal bool TryQueryFirstHitTestChild<T>(Point point, ref T hitTest, out CompositionVisual? hit)
+            where T : struct, CompositionHitTestAabbTree.IQueryHitTester
+        {
+            if (Children.Count < HitTestAabbTreeThreshold)
+            {
+                _hitTestChildren?.Clear();
+                _hitTestChildren = null;
+                hit = null;
+                return false;
+            }
+
+            _hitTestChildren ??= new CompositionHitTestAabbTree();
+
+            if (_hitTestChildrenDirty)
+            {
+                _hitTestChildren.Rebuild(Children);
+                _hitTestChildrenDirty = false;
+            }
+
+            hit = _hitTestChildren.QueryFirst(point, ref hitTest);
+            return true;
+        }
     }
 }