Optimize resetting gesture recognizers

src/Controls/src/Core/View/View.cs

@@ -1,10 +1,10 @@
 #nullable disable
 using System;
+using System.Collections;
 using System.Collections.Generic;
 using System.Collections.ObjectModel;
 using System.Collections.Specialized;
 using System.Linq;
-using Microsoft.Maui;
 using Microsoft.Maui.Controls.Internals;
 using Microsoft.Maui.Controls.Platform;
 using Microsoft.Maui.Graphics;
@@ -96,19 +96,20 @@ protected internal View()
 			_gestureManager = new GestureManager(this);
 			_gestureRecognizers.CollectionChanged += (sender, args) =>
 			{
-				void AddItems(IEnumerable<IElementDefinition> elements)
+				void AddItems(IList newItems)
 				{
-					foreach (IElementDefinition item in elements)
+					foreach (IElementDefinition item in newItems)
 					{
-						ValidateGesture(item as IGestureRecognizer);
+						var gestureRecognizer = item as IGestureRecognizer;
+						ValidateGesture(gestureRecognizer);
 						item.Parent = this;
-						GestureController.CompositeGestureRecognizers.Add(item as IGestureRecognizer);
+						GestureController.CompositeGestureRecognizers.Add(gestureRecognizer);
 					}
 				}
 
-				void RemoveItems(IEnumerable<IElementDefinition> elements)
+				void RemoveItems(IList oldItems)
 				{
-					foreach (IElementDefinition item in elements)
+					foreach (IElementDefinition item in oldItems)
 					{
 						item.Parent = null;
 						GestureController.CompositeGestureRecognizers.Remove(item as IGestureRecognizer);
@@ -118,41 +119,46 @@ void RemoveItems(IEnumerable<IElementDefinition> elements)
 				switch (args.Action)
 				{
 					case NotifyCollectionChangedAction.Add:
-						AddItems(args.NewItems.OfType<IElementDefinition>());
+						AddItems(args.NewItems);
 						break;
 					case NotifyCollectionChangedAction.Remove:
-						RemoveItems(args.OldItems.OfType<IElementDefinition>());
+						RemoveItems(args.OldItems);
 						break;
 					case NotifyCollectionChangedAction.Replace:
-						AddItems(args.NewItems.OfType<IElementDefinition>());
-						RemoveItems(args.OldItems.OfType<IElementDefinition>());
+						AddItems(args.NewItems);
+						RemoveItems(args.OldItems);
 						break;
 					case NotifyCollectionChangedAction.Reset:
 
-						List<IElementDefinition> remove = new List<IElementDefinition>();
-						List<IElementDefinition> add = new List<IElementDefinition>();
-
-						foreach (IElementDefinition item in _gestureRecognizers.OfType<IElementDefinition>())
+						foreach (IGestureRecognizer gestureRecognizer in _gestureRecognizers)
 						{
-							if (!_gestureRecognizers.Contains((IGestureRecognizer)item))
-								add.Add(item);
-							item.Parent = this;
+							if (gestureRecognizer is IElementDefinition item)
+							{
+								item.Parent = this;
+							}
 						}
 
-						foreach (IElementDefinition item in GestureController.CompositeGestureRecognizers.OfType<IElementDefinition>())
-						{
-							if (item == _recognizerForPointerOverState)
-								continue;
+						HashSet<IGestureRecognizer> compositeGestureRecognizers = new(GestureController.CompositeGestureRecognizers);
 
-							if (_gestureRecognizers.Contains((IGestureRecognizer)item))
-								item.Parent = this;
-							else
-								remove.Add(item);
+						foreach (IGestureRecognizer gestureRecognizer in compositeGestureRecognizers)
+						{
+							if (gestureRecognizer is IElementDefinition item)
+							{
+								if (item == _recognizerForPointerOverState)
+									continue;
+
+								if (_gestureRecognizers.Contains(gestureRecognizer))
+								{
+									item.Parent = this;
+								}
+								else
+								{
+									item.Parent = null;
+									GestureController.CompositeGestureRecognizers.Remove(gestureRecognizer);
+								}
+							}
 						}
 
-						AddItems(add);
-						RemoveItems(remove);
-
 						break;
 				}
 			};

src/Core/tests/Benchmarks/Benchmarks/GestureRecognizerBenchmarker.cs

@@ -0,0 +1,123 @@
+using BenchmarkDotNet.Attributes;
+using Microsoft.Maui.Controls;
+
+namespace Microsoft.Maui.Handlers.Benchmarks;
+
+[MemoryDiagnoser]
+public class GestureRecognizerBenchmarker
+{
+	View[] _views = null;
+	IGestureRecognizer[] _gestureRecognizers = null;
+
+	[GlobalSetup]
+	public void Setup()
+	{
+		_views = [
+			new Border(), new BoxView(), new CarouselView(), new Grid(), new Entry(), new Picker(), new CollectionView(),
+			new CheckBox(), new DatePicker(), new Stepper(), new Slider(), new ActivityIndicator(), new Frame(),
+			new ContentView(), new ProgressBar(), new SearchBar(), new Switch(), new TimePicker(), new WebView(), new Button(),
+		];
+
+		_gestureRecognizers = [
+			new PointerGestureRecognizer(), new TapGestureRecognizer(), new PanGestureRecognizer(),
+			new SwipeGestureRecognizer(), new DragGestureRecognizer(), new DropGestureRecognizer(),
+		];
+	}
+
+	[Benchmark]
+	public void AddLotsOfGestureRecognizers()
+	{
+		var layout = new VerticalStackLayout();
+
+		AddGestureRecognizers(layout, _gestureRecognizers);
+
+		for (int i = 0; i < 100; i++)
+		{
+			var childLayout = new VerticalStackLayout();
+
+			AddGestureRecognizers(childLayout, _gestureRecognizers);
+
+			foreach (var view in _views)
+			{
+				AddGestureRecognizers(view, _gestureRecognizers);
+
+				childLayout.Add(view);
+			}
+
+			layout.Add(childLayout);
+		}
+	}
+
+
+	[Benchmark]
+	public void ClearLotsOfGestureRecognizers()
+	{
+		var layout = new VerticalStackLayout();
+
+		for (int i = 0; i < 1000; i++)
+		{
+			AddGestureRecognizers(layout, _gestureRecognizers);
+		}
+
+		layout.GestureRecognizers.Clear();
+	}
+
+
+	[Benchmark]
+	public void RemoveLotsOfGestureRecognizers()
+	{
+		var layout = new VerticalStackLayout();
+
+		foreach (var gestureRecognizer in _gestureRecognizers)
+		{
+			for (int i = 0; i < 1000; i++)
+			{
+				layout.GestureRecognizers.Remove(gestureRecognizer);
+			}
+		}
+	}
+
+	[Benchmark]
+	public void AddOneGestureRecognizer()
+	{
+		var gestureRecognizer = new PointerGestureRecognizer();
+
+		for (int i = 0; i < 1000; i++)
+		{
+			var button = new Button();
+			button.GestureRecognizers.Add(gestureRecognizer);
+		}
+	}
+
+	[Benchmark]
+	public void RemoveOneGestureRecognizer()
+	{
+		var gestureRecognizer = new PointerGestureRecognizer();
+
+		for (int i = 0; i < 1000; i++)
+		{
+			var button = new Button();
+			button.GestureRecognizers.Remove(gestureRecognizer);
+		}
+	}
+
+	[Benchmark]
+	public void ClearOneGestureRecognizer()
+	{
+		for (int i = 0; i < 1000; i++)
+		{
+			var button = new Button();
+			var gestureRecognizer = new PointerGestureRecognizer();
+			button.GestureRecognizers.Add(gestureRecognizer);
+			button.GestureRecognizers.Clear();
+		}
+	}
+
+	private static void AddGestureRecognizers(View view, params IGestureRecognizer[] gestureRecognizers)
+	{
+		foreach (var gestureRecognizer in gestureRecognizers)
+		{
+			view.GestureRecognizers.Add(gestureRecognizer);
+		}
+	}
+}