Improve property mapper performance

Author: albyrock87

src/Core/src/Handlers/FlyoutView/FlyoutViewHandler.Android.cs

@@ -118,16 +118,6 @@ void UpdateDetail()
 		void UpdateFlyout()
 		{
 			_ = MauiContext ?? throw new InvalidOperationException($"{nameof(MauiContext)} should have been set by base class.");
-
-			// Once this issue has been taken care of
-			// https://github.com/dotnet/maui/issues/8456
-			// we can remove this code
-			if (VirtualView.Flyout.Handler?.MauiContext != null &&
-				VirtualView.Flyout.Handler.MauiContext != MauiContext)
-			{
-				VirtualView.Flyout.Handler.DisconnectHandler();
-			}
-
 			_ = VirtualView.Flyout.ToPlatform(MauiContext);
 
 			var newFlyoutView = VirtualView.Flyout.ToPlatform();

src/Core/src/Handlers/FlyoutView/FlyoutViewHandler.cs

@@ -16,11 +16,19 @@ namespace Microsoft.Maui.Handlers
 {
 	public partial class FlyoutViewHandler : IFlyoutViewHandler
 	{
-		public static IPropertyMapper<IFlyoutView, IFlyoutViewHandler> Mapper = new PropertyMapper<IFlyoutView, IFlyoutViewHandler>(ViewHandler.ViewMapper)
+		// Like IViewHandler.ContainerView, those properties should be set with priority because other mappers depend on them (like IToolbarElement.Toolbar).
+		// So we have a separate mapper for them.
+		private static readonly IPropertyMapper<IFlyoutView, IFlyoutViewHandler> FlyoutLayoutMapper = new PropertyMapper<IFlyoutView, IFlyoutViewHandler>()
 		{
 #if ANDROID || WINDOWS || TIZEN
 			[nameof(IFlyoutView.Flyout)] = MapFlyout,
 			[nameof(IFlyoutView.Detail)] = MapDetail,
+#endif
+		};
+
+		public static IPropertyMapper<IFlyoutView, IFlyoutViewHandler> Mapper = new PropertyMapper<IFlyoutView, IFlyoutViewHandler>(ViewHandler.ViewMapper, FlyoutLayoutMapper)
+		{
+#if ANDROID || WINDOWS || TIZEN
 			[nameof(IFlyoutView.IsPresented)] = MapIsPresented,
 			[nameof(IFlyoutView.FlyoutBehavior)] = MapFlyoutBehavior,
 			[nameof(IFlyoutView.FlyoutWidth)] = MapFlyoutWidth,

src/Core/src/Handlers/View/AndroidBatchPropertyMapper.cs

@@ -1,13 +1,13 @@
-using System;
+using System;
 using System.Collections.Generic;
 
 namespace Microsoft.Maui.Handlers
 {
 #if ANDROID
-	class AndroidBatchPropertyMapper<TVirtualView, TViewHandler> : PropertyMapper<TVirtualView, TViewHandler>
-		where TVirtualView : IElement
-		where TViewHandler : IElementHandler
+	class AndroidBatchPropertyMapper
 	{
+		public const string InitializeBatchedPropertiesKey = "_InitializeBatchedProperties";
+
 		// During mass property updates, this list of properties will be skipped
 		public static HashSet<string> SkipList = new(StringComparer.Ordinal)
 		{ 
@@ -27,30 +27,48 @@ class AndroidBatchPropertyMapper<TVirtualView, TViewHandler> : PropertyMapper<TV
 			nameof(IView.AnchorX),
 			nameof(IView.AnchorY),
 		};
+	}
+
+	class AndroidBatchPropertyMapper<TVirtualView, TViewHandler> : PropertyMapper<TVirtualView, TViewHandler>
+		where TVirtualView : IElement
+		where TViewHandler : IElementHandler
+	{
 
 		public AndroidBatchPropertyMapper(params IPropertyMapper[] chained) : base(chained) { }
 
 		public override IEnumerable<string> GetKeys()
 		{
-			foreach (var key in _mapper.Keys)
+			var skipList = AndroidBatchPropertyMapper.SkipList;
+
+			// We want to retain the initial order of the keys to avoid race conditions
+			// when a property mapping is overridden by a new instance of property mapper.
+			// As an example, the container view mapper should always run first.
+			// Siblings mapper should not have keys intersection.
+			var chainedPropertyMappers = Chained;
+			if (chainedPropertyMappers is not null)
 			{
-				// When reporting the key list for mass updates up the chain, ignore properties in SkipList.
-				// These will be handled by ViewHandler.SetVirtualView() instead.
-				if (SkipList.Contains(key))
+				for (int i = chainedPropertyMappers.Length - 1; i >= 0; i--)
 				{
-					continue;
+					foreach (var key in chainedPropertyMappers[i].GetKeys())
+					{
+						yield return key;
+					}
 				}
-
-				yield return key;
 			}
 
-			if (Chained is not null)
+			// Enqueue keys from this mapper.
+			foreach (var mapper in _mapper)
 			{
-				foreach (var chain in Chained)
-					foreach (var key in chain.GetKeys())
-						yield return key;
+				var key = mapper.Key;
+
+				// When reporting the key list for mass updates up the chain, ignore properties in SkipList.
+				// These will be handled by ViewHandler.SetVirtualView() instead.
+				if (!skipList.Contains(key))
+				{
+					yield return key;
+				}
 			}
 		}
 	}
 #endif
-}
+}

src/Core/src/Handlers/View/ViewHandler.cs

@@ -26,11 +26,17 @@ public abstract partial class ViewHandler : ElementHandler, IViewHandler
 		public static IPropertyMapper<IView, IViewHandler> ViewMapper =
 #if ANDROID
 			// Use a custom mapper for Android which knows how to batch the initial property sets
-			new AndroidBatchPropertyMapper<IView, IViewHandler>(ElementMapper)
+			new AndroidBatchPropertyMapper<IView, IViewHandler>(ElementHandler.ElementMapper)
 #else
 			new PropertyMapper<IView, IViewHandler>(ElementHandler.ElementMapper)
 #endif
 			{
+				// This property is a special one and needs to be set before other properties.
+				[nameof(IViewHandler.ContainerView)] = MapContainerView,
+#if ANDROID
+				[AndroidBatchPropertyMapper.InitializeBatchedPropertiesKey] = MapInitializeBatchedProperties,
+#endif
+
 				[nameof(IView.AutomationId)] = MapAutomationId,
 				[nameof(IView.Clip)] = MapClip,
 				[nameof(IView.Shadow)] = MapShadow,
@@ -56,7 +62,6 @@ public abstract partial class ViewHandler : ElementHandler, IViewHandler
 				[nameof(IView.RotationY)] = MapRotationY,
 				[nameof(IView.AnchorX)] = MapAnchorX,
 				[nameof(IView.AnchorY)] = MapAnchorY,
-				[nameof(IViewHandler.ContainerView)] = MapContainerView,
 #pragma warning disable CS0618 // Type or member is obsolete
 				[nameof(IBorder.Border)] = MapBorderView,
 #pragma warning restore CS0618 // Type or member is obsolete
@@ -68,10 +73,6 @@ public abstract partial class ViewHandler : ElementHandler, IViewHandler
 #if WINDOWS || MACCATALYST
 				[nameof(IContextFlyoutElement.ContextFlyout)] = MapContextFlyout,
 #endif
-
-#if ANDROID
-				["_InitializeBatchedProperties"] = MapInitializeBatchedProperties
-#endif
 			};
 
 		/// <summary>

src/Core/src/Platform/iOS/ContainerViewController.cs

@@ -68,7 +68,10 @@ public override void LoadView()
 
 		void LoadPlatformView(IElement view)
 		{
-			currentPlatformView = _pendingLoadedView ?? CreatePlatformView(view);
+			var platformView = _pendingLoadedView ?? CreatePlatformView(view);
+			platformView = platformView.Superview as WrapperView ?? platformView;
+
+			currentPlatformView = platformView;
 			_pendingLoadedView = null;
 
 			View!.AddSubview(currentPlatformView);