Merge pull request #7372 from AvaloniaUI/feature/new-weak-events-for-visual

AffectsRender subscription optimization

src/Avalonia.Base/Media/Pen.cs

@@ -7,7 +7,7 @@ namespace Avalonia.Media
     /// <summary>
     /// Describes how a stroke is drawn.
     /// </summary>
-    public sealed class Pen : AvaloniaObject, IPen, IWeakEventSubscriber<EventArgs>
+    public sealed class Pen : AvaloniaObject, IPen
     {
         /// <summary>
         /// Defines the <see cref="Brush"/> property.
@@ -48,7 +48,8 @@ namespace Avalonia.Media
         private EventHandler? _invalidated;
         private IAffectsRender? _subscribedToBrush;
         private IAffectsRender? _subscribedToDashes;
-        
+        private TargetWeakEventSubscriber<Pen, EventArgs>? _weakSubscriber;
+
         /// <summary>
         /// Initializes a new instance of the <see cref="Pen"/> class.
         /// </summary>
@@ -207,13 +208,24 @@ namespace Avalonia.Media
         {
             if ((_invalidated == null || field != value) && field != null)
             {
-                InvalidatedWeakEvent.Unsubscribe(field, this);
+                if (_weakSubscriber != null)
+                    InvalidatedWeakEvent.Unsubscribe(field, _weakSubscriber);
                 field = null;
             }
 
             if (_invalidated != null && field != value && value is IAffectsRender affectsRender)
             {
-                InvalidatedWeakEvent.Subscribe(affectsRender, this);
+                if (_weakSubscriber == null)
+                {
+                    _weakSubscriber = new TargetWeakEventSubscriber<Pen, EventArgs>(
+                        this, static (target, _, ev, _) =>
+                        {
+                            if (ev == InvalidatedWeakEvent)
+                                target._invalidated?.Invoke(target, EventArgs.Empty);
+                        });
+                }
+
+                InvalidatedWeakEvent.Subscribe(affectsRender, _weakSubscriber);
                 field = affectsRender;
             }
         }
@@ -223,11 +235,5 @@ namespace Avalonia.Media
             UpdateSubscription(ref _subscribedToBrush, Brush);
             UpdateSubscription(ref _subscribedToDashes, DashStyle);
         }
-        
-        void IWeakEventSubscriber<EventArgs>.OnEvent(object? sender, WeakEvent ev, EventArgs e)
-        {
-            if (ev == InvalidatedWeakEvent) 
-                _invalidated?.Invoke(this, EventArgs.Empty);
-        }
     }
 }

src/Avalonia.Base/Utilities/IWeakEventSubscriber.cs

@@ -9,4 +9,31 @@ namespace Avalonia.Utilities;
 public interface IWeakEventSubscriber<in TEventArgs> where TEventArgs : EventArgs
 {
     void OnEvent(object? sender, WeakEvent ev, TEventArgs e);
-}
+}
+
+public sealed class WeakEventSubscriber<TEventArgs> : IWeakEventSubscriber<TEventArgs> where TEventArgs : EventArgs 
+{
+    public event Action<object?, WeakEvent, TEventArgs>? Event;
+
+    void IWeakEventSubscriber<TEventArgs>.OnEvent(object? sender, WeakEvent ev, TEventArgs e)
+    {
+        Event?.Invoke(sender, ev, e);
+    }
+}
+
+public sealed class TargetWeakEventSubscriber<TTarget, TEventArgs> : IWeakEventSubscriber<TEventArgs> where TEventArgs : EventArgs
+{
+    private readonly TTarget _target;
+    private readonly Action<TTarget, object?, WeakEvent, TEventArgs> _dispatchFunc;
+
+    public TargetWeakEventSubscriber(TTarget target, Action<TTarget, object?, WeakEvent, TEventArgs> dispatchFunc)
+    {
+        _target = target;
+        _dispatchFunc = dispatchFunc;
+    }
+
+    void IWeakEventSubscriber<TEventArgs>.OnEvent(object? sender, WeakEvent ev, TEventArgs e)
+    {
+        _dispatchFunc(_target, sender, ev, e);
+    }
+}

src/Avalonia.Base/Utilities/WeakEvent.cs

@@ -1,5 +1,6 @@
 using System;
 using System.Collections.Generic;
+using System.Diagnostics.CodeAnalysis;
 using System.Linq;
 using System.Reflection;
 using System.Runtime.CompilerServices;
@@ -36,7 +37,7 @@ public class WeakEvent<TSender, TEventArgs> : WeakEvent where TEventArgs : Event
     {
         if (!_subscriptions.TryGetValue(target, out var subscription))
             _subscriptions.Add(target, subscription = new Subscription(this, target));
-        subscription.Add(new WeakReference<IWeakEventSubscriber<TEventArgs>>(subscriber));
+        subscription.Add(subscriber);
     }
 
     public void Unsubscribe(TSender target, IWeakEventSubscriber<TEventArgs> subscriber)
@@ -51,11 +52,59 @@ public class WeakEvent<TSender, TEventArgs> : WeakEvent where TEventArgs : Event
         private readonly TSender _target;
         private readonly Action _compact;
 
-        private WeakReference<IWeakEventSubscriber<TEventArgs>>?[] _data =
+        struct Entry
-            new WeakReference<IWeakEventSubscriber<TEventArgs>>[16];
+        {
-        private int _count;
+            WeakReference<IWeakEventSubscriber<TEventArgs>>? _reference;
+            int _hashCode;
+
+            public Entry(IWeakEventSubscriber<TEventArgs> r)
+            {
+                if (r == null)
+                {
+                    _reference = null;
+                    _hashCode = 0;
+                    return;
+                }
+
+                _hashCode = r.GetHashCode();
+                _reference = new WeakReference<IWeakEventSubscriber<TEventArgs>>(r);
+            }
+
+            public bool IsEmpty
+            {
+                get
+                {
+                    if (_reference == null)
+                        return true;
+                    if (_reference.TryGetTarget(out _))
+                        return false;
+                    _reference = null;
+                    return true;
+                }
+            }
+
+            public bool TryGetTarget([MaybeNullWhen(false)]out IWeakEventSubscriber<TEventArgs> target)
+            {
+                if (_reference == null)
+                {
+                    target = null!;
+                    return false;
+                }
+                return _reference.TryGetTarget(out target);
+            }
+
+            public bool Equals(IWeakEventSubscriber<TEventArgs> r)
+            {
+                if (_reference == null || r.GetHashCode() != _hashCode)
+                    return false;
+                return _reference.TryGetTarget(out var target) && target == r;
+            }
+        }
+
         private readonly Action _unsubscribe;
+        private readonly WeakHashList<IWeakEventSubscriber<TEventArgs>> _list = new();
         private bool _compactScheduled;
+        private bool _destroyed;
 
         public Subscription(WeakEvent<TSender, TEventArgs> ev, TSender target)
         {
@@ -67,48 +116,27 @@ public class WeakEvent<TSender, TEventArgs> : WeakEvent where TEventArgs : Event
 
         void Destroy()
         {
+            if(_destroyed)
+                return;
+            _destroyed = true;
             _unsubscribe();
             _ev._subscriptions.Remove(_target);
         }
 
-        public void Add(WeakReference<IWeakEventSubscriber<TEventArgs>> s)
+        public void Add(IWeakEventSubscriber<TEventArgs> s) => _list.Add(s);
-        {
-            if (_count == _data.Length)
-            {
-                //Extend capacity
-                var extendedData = new WeakReference<IWeakEventSubscriber<TEventArgs>>?[_data.Length * 2];
-                Array.Copy(_data, extendedData, _data.Length);
-                _data = extendedData;
-            }
-
-            _data[_count] = s;
-            _count++;
-        }
 
         public void Remove(IWeakEventSubscriber<TEventArgs> s)
         {
-            var removed = false;
+            _list.Remove(s);
-
+            if(_list.IsEmpty)
-            for (int c = 0; c < _count; ++c)
+                Destroy();
-            {
+            else if(_list.NeedCompact && _compactScheduled)
-                var reference = _data[c];
-
-                if (reference != null && reference.TryGetTarget(out var instance) && instance == s)
-                {
-                    _data[c] = null;
-                    removed = true;
-                }
-            }
-
-            if (removed)
-            {
                 ScheduleCompact();
-            }
         }
 
         void ScheduleCompact()
         {
-            if(_compactScheduled)
+            if(_compactScheduled || _destroyed)
                 return;
             _compactScheduled = true;
             Dispatcher.UIThread.Post(_compact, DispatcherPriority.Background);
@@ -116,43 +144,27 @@ public class WeakEvent<TSender, TEventArgs> : WeakEvent where TEventArgs : Event
         
         void Compact()
         {
+            if(!_compactScheduled)
+                return;
             _compactScheduled = false;
-            int empty = -1;
+            _list.Compact();
-            for (var c = 0; c < _count; c++)
+            if (_list.IsEmpty)
-            {
-                var r = _data[c];
-                //Mark current index as first empty
-                if (r == null && empty == -1)
-                    empty = c;
-                //If current element isn't null and we have an empty one
-                if (r != null && empty != -1)
-                {
-                    _data[c] = null;
-                    _data[empty] = r;
-                    empty++;
-                }
-            }
-
-            if (empty != -1)
-                _count = empty;
-            if (_count == 0)
                 Destroy();
         }
 
         void OnEvent(object? sender, TEventArgs eventArgs)
         {
-            var needCompact = false;
+            var alive = _list.GetAlive();
-            for (var c = 0; c < _count; c++)
+            if(alive == null)
+                Destroy();
+            else
             {
-                var r = _data[c];
+                foreach(var item in alive.Span)
-                if (r?.TryGetTarget(out var sub) == true)
+                    item.OnEvent(_target, _ev, eventArgs);
-                    sub!.OnEvent(_target, _ev, eventArgs);
+                WeakHashList<IWeakEventSubscriber<TEventArgs>>.ReturnToSharedPool(alive);
-                else
+                if(_list.NeedCompact && !_compactScheduled)
-                    needCompact = true;
+                    ScheduleCompact();
             }
-
-            if (needCompact)
-                ScheduleCompact();
         }
     }
 

src/Avalonia.Base/Utilities/WeakHashList.cs

@@ -0,0 +1,236 @@
+using System;
+using System.Collections.Generic;
+using Avalonia.Collections.Pooled;
+
+namespace Avalonia.Utilities;
+
+internal class WeakHashList<T> where T : class
+{
+    private struct Key
+    {
+        public WeakReference<T>? Weak;
+        public T? Strong;
+        public int HashCode;
+
+        public static Key MakeStrong(T r) => new()
+        {
+            HashCode = r.GetHashCode(),
+            Strong = r
+        };
+
+        public static Key MakeWeak(T r) => new()
+        {
+            HashCode = r.GetHashCode(),
+            Weak = new WeakReference<T>(r)
+        };
+
+        public override int GetHashCode() => HashCode;
+    }
+
+    class KeyComparer : IEqualityComparer<Key>
+    {
+        public bool Equals(Key x, Key y)
+        {
+            if (x.HashCode != y.HashCode)
+                return false;
+            if (x.Strong != null)
+            {
+                if (y.Strong != null)
+                    return x.Strong == y.Strong;
+                if (y.Weak == null)
+                    return false;
+                return y.Weak.TryGetTarget(out var weakTarget) && weakTarget == x.Strong;
+            }
+            else if (y.Strong != null)
+            {
+                if (x.Weak == null)
+                    return false;
+                return x.Weak.TryGetTarget(out var weakTarget) && weakTarget == y.Strong;
+            }
+            else
+            {
+                if (x.Weak == null || x.Weak.TryGetTarget(out var xTarget) == false)
+                    return y.Weak?.TryGetTarget(out _) != true;
+                return y.Weak?.TryGetTarget(out var yTarget) == true && xTarget == yTarget;
+            }
+        }
+
+        public int GetHashCode(Key obj) => obj.HashCode;
+        public static KeyComparer Instance = new();
+    }
+
+    Dictionary<Key, int>? _dic;
+    WeakReference<T>?[]? _arr;
+    int _arrCount;
+    
+    public bool IsEmpty => _dic == null || _dic.Count == 0;
+    public bool NeedCompact { get; private set; }
+    
+    public void Add(T item)
+    {
+        if (_dic != null)
+        {
+            var strongKey = Key.MakeStrong(item);
+            if (_dic.TryGetValue(strongKey, out var cnt))
+                _dic[strongKey] = cnt + 1;
+            else
+                _dic[Key.MakeWeak(item)] = 1;
+            return;
+        }
+
+        if (_arr == null)
+            _arr = new WeakReference<T>[8];
+
+        if (_arrCount < _arr.Length)
+        {
+            _arr[_arrCount] = new WeakReference<T>(item);
+            _arrCount++;
+            return;
+        }
+
+        // Check if something is dead
+        for (var c = 0; c < _arrCount; c++)
+        {
+            if (_arr[c]!.TryGetTarget(out _) == false)
+            {
+                _arr[c] = new WeakReference<T>(item);
+                return;
+            }
+        }
+
+        _dic = new Dictionary<Key, int>(KeyComparer.Instance);
+        foreach (var existing in _arr)
+        {
+            if (existing!.TryGetTarget(out var target))
+                Add(target);
+        }
+        _arr = null;
+        
+    }
+
+    public void Remove(T item)
+    {
+        if (_arr != null)
+        {
+            for (var c = 0; c < _arr.Length; c++)
+            {
+                if (_arr[c]?.TryGetTarget(out var target) == true && target == item)
+                {
+                    _arr[c] = null;
+                    Compact();
+                    return;
+                }
+            }
+        }
+        else if (_dic != null)
+        {
+            var strongKey = Key.MakeStrong(item);
+            
+            if (_dic.TryGetValue(strongKey, out var cnt))
+            {
+                if (cnt > 1)
+                {
+                    _dic[strongKey] = cnt - 1;
+                    return;
+                }
+            }
+
+            _dic.Remove(strongKey);
+        }
+    }
+
+    private void ArrCompact()
+    {
+        if (_arr != null)
+        {
+            int empty = -1;
+            for (var c = 0; c < _arrCount; c++)
+            {
+                var r = _arr[c];
+                //Mark current index as first empty
+                if (r == null && empty == -1)
+                    empty = c;
+                //If current element isn't null and we have an empty one
+                if (r != null && empty != -1)
+                {
+                    _arr[c] = null;
+                    _arr[empty] = r;
+                    empty++;
+                }
+            }
+
+            if (empty != -1)
+                _arrCount = empty;
+        }
+    }
+    
+    public void Compact()
+    {
+        if (_dic != null)
+        {
+            PooledList<Key>? toRemove = null;
+            foreach (var kvp in _dic)
+            {
+                if (kvp.Key.Weak?.TryGetTarget(out _) != true)
+                    (toRemove ??= new PooledList<Key>()).Add(kvp.Key);
+            }
+
+            if (toRemove != null)
+            {
+                foreach (var k in toRemove)
+                    _dic.Remove(k);
+                toRemove.Dispose();
+            }
+        }
+    }
+
+    private static readonly Stack<PooledList<T>> s_listPool = new();
+
+    public static void ReturnToSharedPool(PooledList<T> list)
+    {
+        list.Clear();
+        s_listPool.Push(list);
+    }
+    
+    public PooledList<T>? GetAlive(Func<PooledList<T>>? factory = null)
+    {
+        PooledList<T>? pooled = null;
+        if (_arr != null)
+        {
+            bool needCompact = false;
+            for (var c = 0; c < _arrCount; c++)
+            {
+                if (_arr[c]?.TryGetTarget(out var target) == true)
+                    (pooled ??= factory?.Invoke()
+                                ?? (s_listPool.Count > 0
+                                    ? s_listPool.Pop()
+                                    : new PooledList<T>())).Add(target!);
+                else
+                {
+                    _arr[c] = null;
+                    needCompact = true;
+                }
+            }
+            if(needCompact)
+                ArrCompact();
+            return pooled;
+        }
+        if (_dic != null)
+        {
+            
+            foreach (var kvp in _dic)
+            {
+                if (kvp.Key.Weak?.TryGetTarget(out var target) == true)
+                    (pooled ??= factory?.Invoke()
+                                ?? (s_listPool.Count > 0
+                                    ? s_listPool.Pop()
+                                    : new PooledList<T>()))
+                        .Add(target!);
+                else
+                    NeedCompact = true;
+            }
+        }
+
+        return pooled;
+    }
+}

src/Avalonia.Base/Visual.cs

@@ -97,12 +97,18 @@ namespace Avalonia
         /// </summary>
         public static readonly StyledProperty<int> ZIndexProperty =
             AvaloniaProperty.Register<Visual, int>(nameof(ZIndex));
+        
+        private static readonly WeakEvent<IAffectsRender, EventArgs> InvalidatedWeakEvent =
+            WeakEvent.Register<IAffectsRender>(
+                (s, h) => s.Invalidated += h,
+                (s, h) => s.Invalidated -= h);
 
         private Rect _bounds;
         private TransformedBounds? _transformedBounds;
         private IRenderRoot? _visualRoot;
         private IVisual? _visualParent;
         private bool _hasMirrorTransform;
+        private TargetWeakEventSubscriber<Visual, EventArgs>? _affectsRenderWeakSubscriber;
 
         /// <summary>
         /// Initializes static members of the <see cref="Visual"/> class.
@@ -369,12 +375,21 @@ namespace Avalonia
                 {
                     if (e.OldValue is IAffectsRender oldValue)
                     {
-                        WeakEventHandlerManager.Unsubscribe<EventArgs, T>(oldValue, nameof(oldValue.Invalidated), sender.AffectsRenderInvalidated);
+                        if (sender._affectsRenderWeakSubscriber != null)
+                            InvalidatedWeakEvent.Unsubscribe(oldValue, sender._affectsRenderWeakSubscriber);
                     }
 
                     if (e.NewValue is IAffectsRender newValue)
                     {
-                        WeakEventHandlerManager.Subscribe<IAffectsRender, EventArgs, T>(newValue, nameof(newValue.Invalidated), sender.AffectsRenderInvalidated);
+                        if (sender._affectsRenderWeakSubscriber == null)
+                        {
+                            sender._affectsRenderWeakSubscriber = new TargetWeakEventSubscriber<Visual, EventArgs>(
+                                sender, static (target, _, _, _) =>
+                                {
+                                    target.InvalidateVisual();
+                                });
+                        }
+                        InvalidatedWeakEvent.Subscribe(newValue, sender._affectsRenderWeakSubscriber);
                     }
 
                     sender.InvalidateVisual();
@@ -625,8 +640,6 @@ namespace Avalonia
             OnVisualParentChanged(old, value);
         }
 
-        private void AffectsRenderInvalidated(object? sender, EventArgs e) => InvalidateVisual();
-
         /// <summary>
         /// Called when the <see cref="VisualChildren"/> collection changes.
         /// </summary>

src/Avalonia.Controls/Repeater/ItemsRepeater.cs

@@ -20,7 +20,7 @@ namespace Avalonia.Controls
     /// Represents a data-driven collection control that incorporates a flexible layout system,
     /// custom views, and virtualization.
     /// </summary>
-    public class ItemsRepeater : Panel, IChildIndexProvider, IWeakEventSubscriber<EventArgs>
+    public class ItemsRepeater : Panel, IChildIndexProvider
     {
         /// <summary>
         /// Defines the <see cref="HorizontalCacheLength"/> property.
@@ -60,6 +60,7 @@ namespace Avalonia.Controls
 
         private readonly ViewManager _viewManager;
         private readonly ViewportManager _viewportManager;
+        private readonly TargetWeakEventSubscriber<ItemsRepeater, EventArgs> _layoutWeakSubscriber;
         private IEnumerable? _items;
         private VirtualizingLayoutContext? _layoutContext;
         private EventHandler<ChildIndexChangedEventArgs>? _childIndexChanged;
@@ -74,6 +75,15 @@ namespace Avalonia.Controls
         /// </summary>
         public ItemsRepeater()
         {
+            _layoutWeakSubscriber = new TargetWeakEventSubscriber<ItemsRepeater, EventArgs>(
+                this, static (target, _, ev, _) =>
+                {
+                    if (ev == AttachedLayout.ArrangeInvalidatedWeakEvent)
+                        target.InvalidateArrange();
+                    else if (ev == AttachedLayout.MeasureInvalidatedWeakEvent)
+                        target.InvalidateMeasure();
+                });
+
             _viewManager = new ViewManager(this);
             _viewportManager = new ViewportManager(this);
             KeyboardNavigation.SetTabNavigation(this, KeyboardNavigationMode.Once);
@@ -728,8 +738,8 @@ namespace Avalonia.Controls
             {
                 oldValue.UninitializeForContext(LayoutContext);
 
-                AttachedLayout.MeasureInvalidatedWeakEvent.Unsubscribe(oldValue, this);
+                AttachedLayout.MeasureInvalidatedWeakEvent.Unsubscribe(oldValue, _layoutWeakSubscriber);
-                AttachedLayout.ArrangeInvalidatedWeakEvent.Unsubscribe(oldValue, this);
+                AttachedLayout.ArrangeInvalidatedWeakEvent.Unsubscribe(oldValue, _layoutWeakSubscriber);
 
                 // Walk through all the elements and make sure they are cleared
                 foreach (var element in Children)
@@ -747,8 +757,8 @@ namespace Avalonia.Controls
             {
                 newValue.InitializeForContext(LayoutContext);
 
-                AttachedLayout.MeasureInvalidatedWeakEvent.Subscribe(newValue, this);
+                AttachedLayout.MeasureInvalidatedWeakEvent.Subscribe(newValue, _layoutWeakSubscriber);
-                AttachedLayout.ArrangeInvalidatedWeakEvent.Subscribe(newValue, this);
+                AttachedLayout.ArrangeInvalidatedWeakEvent.Subscribe(newValue, _layoutWeakSubscriber);
             }
 
             bool isVirtualizingLayout = newValue != null && newValue is VirtualizingLayout;
@@ -798,15 +808,7 @@ namespace Avalonia.Controls
         {
             _viewportManager.OnBringIntoViewRequested(e);
         }
-
+        
-        void IWeakEventSubscriber<EventArgs>.OnEvent(object? sender, WeakEvent ev, EventArgs e)
-        {
-            if(ev == AttachedLayout.ArrangeInvalidatedWeakEvent)
-                InvalidateArrange();
-            else if (ev == AttachedLayout.MeasureInvalidatedWeakEvent)
-                InvalidateMeasure();
-        }
-
         private VirtualizingLayoutContext GetLayoutContext()
         {
             if (_layoutContext == null)

src/Avalonia.Controls/TopLevel.cs

@@ -34,8 +34,7 @@ namespace Avalonia.Controls
         ICloseable,
         IStyleHost,
         ILogicalRoot,
-        ITextInputMethodRoot,
+        ITextInputMethodRoot
-        IWeakEventSubscriber<ResourcesChangedEventArgs>
     {
         /// <summary>
         /// Defines the <see cref="ClientSize"/> property.
@@ -93,6 +92,7 @@ namespace Avalonia.Controls
         private WindowTransparencyLevel _actualTransparencyLevel;
         private ILayoutManager? _layoutManager;
         private Border? _transparencyFallbackBorder;
+        private TargetWeakEventSubscriber<TopLevel, ResourcesChangedEventArgs>? _resourcesChangesSubscriber;
 
         /// <summary>
         /// Initializes static members of the <see cref="TopLevel"/> class.
@@ -192,7 +192,13 @@ namespace Avalonia.Controls
 
             if (((IStyleHost)this).StylingParent is IResourceHost applicationResources)
             {
-                ResourcesChangedWeakEvent.Subscribe(applicationResources, this);
+                _resourcesChangesSubscriber = new TargetWeakEventSubscriber<TopLevel, ResourcesChangedEventArgs>(
+                    this, static (target, _, _, e) =>
+                    {
+                        ((ILogical)target).NotifyResourcesChanged(e);
+                    });
+
+                ResourcesChangedWeakEvent.Subscribe(applicationResources, _resourcesChangesSubscriber);
             }
 
             impl.LostFocus += PlatformImpl_LostFocus;
@@ -297,11 +303,6 @@ namespace Avalonia.Controls
         /// <inheritdoc/>
         IMouseDevice? IInputRoot.MouseDevice => PlatformImpl?.MouseDevice;
 
-        void IWeakEventSubscriber<ResourcesChangedEventArgs>.OnEvent(object? sender, WeakEvent ev, ResourcesChangedEventArgs e)
-        {
-            ((ILogical)this).NotifyResourcesChanged(e);
-        }
-
         /// <summary>
         /// Gets or sets a value indicating whether access keys are shown in the window.
         /// </summary>

tests/Avalonia.Benchmarks/Visuals/VisualAffectsRenderBenchmarks.cs

@@ -0,0 +1,45 @@
+using Avalonia.Controls;
+using Avalonia.Media;
+using BenchmarkDotNet.Attributes;
+
+namespace Avalonia.Benchmarks.Visuals;
+
+[MemoryDiagnoser]
+public class VisualAffectsRenderBenchmarks
+{
+    private readonly TestVisual _target;
+    private readonly IPen _pen;
+        
+    public VisualAffectsRenderBenchmarks()
+    {
+        _target = new TestVisual();
+        _pen = new Pen(Brushes.Black);
+    }
+        
+    [Benchmark]
+    public void SetPropertyThatAffectsRender()
+    {
+        _target.Pen = _pen;
+        _target.Pen = null;
+    }
+
+    private class TestVisual : Visual
+    {
+        /// <summary>
+        /// Defines the <see cref="Pen"/> property.
+        /// </summary>
+        public static readonly StyledProperty<IPen> PenProperty =
+            AvaloniaProperty.Register<Border, IPen>(nameof(Pen));
+            
+        public IPen Pen
+        {
+            get => GetValue(PenProperty);
+            set => SetValue(PenProperty, value);
+        }
+
+        static TestVisual()
+        {
+            AffectsRender<TestVisual>(PenProperty);
+        }
+    }
+}