Add ViewHandler Mapper docs

src/Core/src/Handlers/ActivityIndicator/ActivityIndicatorHandler.Android.cs

@@ -6,12 +6,12 @@ public partial class ActivityIndicatorHandler : ViewHandler<IActivityIndicator,
 	{
 		protected override ProgressBar CreatePlatformView() => new ProgressBar(Context) { Indeterminate = true };
 
-		public static void MapIsRunning(IActivityIndicatorHandler handler, IActivityIndicator activityIndicator)
+		public static partial void MapIsRunning(IActivityIndicatorHandler handler, IActivityIndicator activityIndicator)
 		{
 			handler.PlatformView?.UpdateIsRunning(activityIndicator);
 		}
 
-		public static void MapColor(IActivityIndicatorHandler handler, IActivityIndicator activityIndicator)
+		public static partial void MapColor(IActivityIndicatorHandler handler, IActivityIndicator activityIndicator)
 		{
 			handler.PlatformView?.UpdateColor(activityIndicator);
 		}

src/Core/src/Handlers/ActivityIndicator/ActivityIndicatorHandler.Standard.cs

@@ -6,7 +6,7 @@ public partial class ActivityIndicatorHandler : ViewHandler<IActivityIndicator,
 	{
 		protected override object CreatePlatformView() => throw new NotImplementedException();
 
-		public static void MapIsRunning(IActivityIndicatorHandler handler, IActivityIndicator activityIndicator) { }
-		public static void MapColor(IActivityIndicatorHandler handler, IActivityIndicator activityIndicator) { }
+		public static partial void MapIsRunning(IActivityIndicatorHandler handler, IActivityIndicator activityIndicator) { }
+		public static partial void MapColor(IActivityIndicatorHandler handler, IActivityIndicator activityIndicator) { }
 	}
 }

src/Core/src/Handlers/ActivityIndicator/ActivityIndicatorHandler.Tizen.cs

@@ -6,12 +6,12 @@ public partial class ActivityIndicatorHandler : ViewHandler<IActivityIndicator,
 	{
 		protected override ActivityIndicator CreatePlatformView() => new ActivityIndicator();
 
-		public static void MapIsRunning(IActivityIndicatorHandler handler, IActivityIndicator activityIndicator)
+		public static partial void MapIsRunning(IActivityIndicatorHandler handler, IActivityIndicator activityIndicator)
 		{
 			handler.PlatformView?.UpdateIsRunning(activityIndicator);
 		}
 
-		public static void MapColor(IActivityIndicatorHandler handler, IActivityIndicator activityIndicator)
+		public static partial void MapColor(IActivityIndicatorHandler handler, IActivityIndicator activityIndicator)
 		{
 			handler.PlatformView?.UpdateColor(activityIndicator);
 		}

src/Core/src/Handlers/ActivityIndicator/ActivityIndicatorHandler.Windows.cs

@@ -15,31 +15,31 @@ public partial class ActivityIndicatorHandler : ViewHandler<IActivityIndicator,
 			IsIndeterminate = true
 		};
 
-		public static void MapBackground(IActivityIndicatorHandler handler, IActivityIndicator activityIndicator)
+		public static partial void MapBackground(IActivityIndicatorHandler handler, IActivityIndicator activityIndicator)
 		{
 			handler.UpdateValue(nameof(IViewHandler.ContainerView));
 			handler.ToPlatform().UpdateBackground(activityIndicator);
 		}
 
-		public static void MapIsRunning(IActivityIndicatorHandler handler, IActivityIndicator activityIndicator)
+		public static partial void MapIsRunning(IActivityIndicatorHandler handler, IActivityIndicator activityIndicator)
 		{
 			handler.PlatformView?.UpdateIsRunning(activityIndicator);
 		}
 
-		public static void MapColor(IActivityIndicatorHandler handler, IActivityIndicator activityIndicator)
+		public static partial void MapColor(IActivityIndicatorHandler handler, IActivityIndicator activityIndicator)
 		{
 			handler.PlatformView?.UpdateColor(activityIndicator);
 		}
 
-		public static void MapWidth(IActivityIndicatorHandler handler, IActivityIndicator activityIndicator)
+		public static partial void MapWidth(IActivityIndicatorHandler handler, IActivityIndicator activityIndicator)
 		{
 			if (handler.PlatformView is ProgressRing platformView)
 			{
 				platformView.UpdateWidth(activityIndicator);
 			}
 		}
 
-		public static void MapHeight(IActivityIndicatorHandler handler, IActivityIndicator activityIndicator)
+		public static partial void MapHeight(IActivityIndicatorHandler handler, IActivityIndicator activityIndicator)
 		{
 			if (handler.PlatformView is ProgressRing platformView)
 			{

src/Core/src/Handlers/ActivityIndicator/ActivityIndicatorHandler.cs

@@ -12,6 +12,10 @@
 
 namespace Microsoft.Maui.Handlers
 {
+	/// <summary>
+	/// Represents the view handler for the abstract <see cref="IActivityIndicator"/> view and its platform-specific implementation.
+	/// </summary>
+	/// <seealso href="https://learn.microsoft.com/dotnet/maui/user-interface/handlers/">Conceptual documentation on handlers</seealso>
 	public partial class ActivityIndicatorHandler : IActivityIndicatorHandler
 	{
 		public static IPropertyMapper<IActivityIndicator, IActivityIndicatorHandler> Mapper = new PropertyMapper<IActivityIndicator, IActivityIndicatorHandler>(ViewHandler.ViewMapper)
@@ -49,5 +53,42 @@ public ActivityIndicatorHandler(IPropertyMapper? mapper, CommandMapper? commandM
 		IActivityIndicator IActivityIndicatorHandler.VirtualView => VirtualView;
 
 		PlatformView IActivityIndicatorHandler.PlatformView => PlatformView;
+
+		/// <summary>
+		/// Maps the abstract <see cref="IActivityIndicator.IsRunning"/> property to the platform-specific implementations.
+		/// </summary>
+		/// <param name="handler">The associated handler.</param>
+		/// <param name="activityIndicator">The associated <see cref="IActivityIndicator"/> instance.</param>
+		public static partial void MapIsRunning(IActivityIndicatorHandler handler, IActivityIndicator activityIndicator);
+
+		/// <summary>
+		/// Maps the abstract <see cref="IActivityIndicator.Color"/> property to the platform-specific implementations.
+		/// </summary>
+		/// <param name="handler">The associated handler.</param>
+		/// <param name="activityIndicator">The associated <see cref="IActivityIndicator"/> instance.</param>
+		public static partial void MapColor(IActivityIndicatorHandler handler, IActivityIndicator activityIndicator);
+
+#if WINDOWS
+		/// <summary>
+		/// Maps the abstract <see cref="IView.Width"/> property to the platform-specific implementations.
+		/// </summary>
+		/// <param name="handler">The associated handler.</param>
+		/// <param name="activityIndicator">The associated <see cref="IActivityIndicator"/> instance.</param>
+		public static partial void MapWidth(IActivityIndicatorHandler handler, IActivityIndicator activityIndicator);
+
+		/// <summary>
+		/// Maps the abstract <see cref="IView.Height"/> property to the platform-specific implementations.
+		/// </summary>
+		/// <param name="handler">The associated handler.</param>
+		/// <param name="activityIndicator">The associated <see cref="IActivityIndicator"/> instance.</param>
+		public static partial void MapHeight(IActivityIndicatorHandler handler, IActivityIndicator activityIndicator);
+
+		/// <summary>
+		/// Maps the abstract <see cref="IView.Background"/> property to the platform-specific implementations.
+		/// </summary>
+		/// <param name="handler">The associated handler.</param>
+		/// <param name="activityIndicator">The associated <see cref="IActivityIndicator"/> instance.</param>
+		public static partial void MapBackground(IActivityIndicatorHandler handler, IActivityIndicator activityIndicator);
+#endif
 	}
 }

src/Core/src/Handlers/ActivityIndicator/ActivityIndicatorHandler.iOS.cs

@@ -19,12 +19,12 @@ protected override MauiActivityIndicator CreatePlatformView()
 			return platformView;
 		}
 
-		public static void MapIsRunning(IActivityIndicatorHandler handler, IActivityIndicator activityIndicator)
+		public static partial void MapIsRunning(IActivityIndicatorHandler handler, IActivityIndicator activityIndicator)
 		{
 			handler.PlatformView?.UpdateIsRunning(activityIndicator);
 		}
 
-		public static void MapColor(IActivityIndicatorHandler handler, IActivityIndicator activityIndicator)
+		public static partial void MapColor(IActivityIndicatorHandler handler, IActivityIndicator activityIndicator)
 		{
 			handler.PlatformView?.UpdateColor(activityIndicator);
 		}

src/Core/src/Handlers/Application/ApplicationHandler.Android.cs

@@ -5,7 +5,7 @@ namespace Microsoft.Maui.Handlers
 {
 	public partial class ApplicationHandler : ElementHandler<IApplication, Application>
 	{
-		public static void MapTerminate(ApplicationHandler handler, IApplication application, object? args)
+		public static partial void MapTerminate(ApplicationHandler handler, IApplication application, object? args)
 		{
 			var currentActivity = ApplicationModel.Platform.CurrentActivity;
 
@@ -17,12 +17,12 @@ public static void MapTerminate(ApplicationHandler handler, IApplication applica
 			}
 		}
 
-		public static void MapOpenWindow(ApplicationHandler handler, IApplication application, object? args)
+		public static partial void MapOpenWindow(ApplicationHandler handler, IApplication application, object? args)
 		{
 			handler.PlatformView?.RequestNewWindow(application, args as OpenWindowRequest);
 		}
 
-		public static void MapCloseWindow(ApplicationHandler handler, IApplication application, object? args)
+		public static partial void MapCloseWindow(ApplicationHandler handler, IApplication application, object? args)
 		{
 			if (args is IWindow window)
 			{

src/Core/src/Handlers/Application/ApplicationHandler.Standard.cs

@@ -6,8 +6,8 @@ public partial class ApplicationHandler : ElementHandler<IApplication, object>
 	{
 		protected override object CreatePlatformElement() => throw new NotImplementedException();
 
-		public static void MapTerminate(ApplicationHandler handler, IApplication application, object? args) { }
-		public static void MapOpenWindow(ApplicationHandler handler, IApplication application, object? args) { }
-		public static void MapCloseWindow(ApplicationHandler handler, IApplication application, object? args) { }
+		public static partial void MapTerminate(ApplicationHandler handler, IApplication application, object? args) { }
+		public static partial void MapOpenWindow(ApplicationHandler handler, IApplication application, object? args) { }
+		public static partial void MapCloseWindow(ApplicationHandler handler, IApplication application, object? args) { }
 	}
 }

src/Core/src/Handlers/Application/ApplicationHandler.Tizen.cs

@@ -5,17 +5,17 @@ namespace Microsoft.Maui.Handlers
 {
 	public partial class ApplicationHandler : ElementHandler<IApplication, CoreApplication>
 	{
-		public static void MapTerminate(ApplicationHandler handler, IApplication application, object? args)
+		public static partial void MapTerminate(ApplicationHandler handler, IApplication application, object? args)
 		{
 			handler.PlatformView.Exit();
 		}
 
-		public static void MapOpenWindow(ApplicationHandler handler, IApplication application, object? args)
+		public static partial void MapOpenWindow(ApplicationHandler handler, IApplication application, object? args)
 		{
 			handler.PlatformView?.RequestNewWindow(application, args as OpenWindowRequest);
 		}
 
-		public static void MapCloseWindow(ApplicationHandler handler, IApplication application, object? args)
+		public static partial void MapCloseWindow(ApplicationHandler handler, IApplication application, object? args)
 		{
 			if (args is IWindow window)
 			{

src/Core/src/Handlers/Application/ApplicationHandler.Windows.cs

@@ -5,17 +5,17 @@ namespace Microsoft.Maui.Handlers
 {
 	public partial class ApplicationHandler : ElementHandler<IApplication, UI.Xaml.Application>
 	{
-		public static void MapTerminate(ApplicationHandler handler, IApplication application, object? args)
+		public static partial void MapTerminate(ApplicationHandler handler, IApplication application, object? args)
 		{
 			handler.PlatformView.Exit();
 		}
 
-		public static void MapOpenWindow(ApplicationHandler handler, IApplication application, object? args)
+		public static partial void MapOpenWindow(ApplicationHandler handler, IApplication application, object? args)
 		{
 			handler.PlatformView?.CreatePlatformWindow(application, args as OpenWindowRequest);
 		}
 
-		public static void MapCloseWindow(ApplicationHandler handler, IApplication application, object? args)
+		public static partial void MapCloseWindow(ApplicationHandler handler, IApplication application, object? args)
 		{
 			if (args is IWindow window)
 			{

src/Core/src/Handlers/Application/ApplicationHandler.cs

@@ -14,6 +14,10 @@
 
 namespace Microsoft.Maui.Handlers
 {
+	/// <summary>
+	/// Represents the view handler for the abstract <see cref="IApplication"/> view and its platform-specific implementation.
+	/// </summary>
+	/// <seealso href="https://learn.microsoft.com/dotnet/maui/user-interface/handlers/">Conceptual documentation on handlers</seealso>
 	public partial class ApplicationHandler
 	{
 		internal const string TerminateCommandKey = "Terminate";
@@ -55,5 +59,29 @@ public ApplicationHandler(IPropertyMapper? mapper, CommandMapper? commandMapper)
 		protected override PlatformView CreatePlatformElement() =>
 			MauiContext?.Services.GetService<PlatformView>() ?? throw new InvalidOperationException($"MauiContext did not have a valid application.");
 #endif
+
+		/// <summary>
+		/// Maps the abstract "Terminate" command to the platform-specific implementations.
+		/// </summary>
+		/// <param name="handler">The associated handler.</param>
+		/// <param name="application">The associated <see cref="IApplication"/> instance.</param>
+		/// <param name="args">The associated command arguments.</param>
+		public static partial void MapTerminate(ApplicationHandler handler, IApplication application, object? args);
+
+		/// <summary>
+		/// Maps the abstract <see cref="IApplication.OpenWindow"/> command to the platform-specific implementations.
+		/// </summary>
+		/// <param name="handler">The associated handler.</param>
+		/// <param name="application">The associated <see cref="IApplication"/> instance.</param>
+		/// <param name="args">The associated command arguments.</param>
+		public static partial void MapOpenWindow(ApplicationHandler handler, IApplication application, object? args);
+
+		/// <summary>
+		/// Maps the abstract <see cref="IApplication.CloseWindow"/> command to the platform-specific implementations.
+		/// </summary>
+		/// <param name="handler">The associated handler.</param>
+		/// <param name="application">The associated <see cref="IApplication"/> instance.</param>
+		/// <param name="args">The associated command arguments.</param>
+		public static partial void MapCloseWindow(ApplicationHandler handler, IApplication application, object? args);
 	}
 }

src/Core/src/Handlers/Application/ApplicationHandler.iOS.cs

@@ -10,7 +10,7 @@ namespace Microsoft.Maui.Handlers
 {
 	public partial class ApplicationHandler : ElementHandler<IApplication, IUIApplicationDelegate>
 	{
-		public static void MapTerminate(ApplicationHandler handler, IApplication application, object? args)
+		public static partial void MapTerminate(ApplicationHandler handler, IApplication application, object? args)
 		{
 #if __MACCATALYST__
 			NSApplication.SharedApplication.Terminate();
@@ -21,14 +21,14 @@ public static void MapTerminate(ApplicationHandler handler, IApplication applica
 
 		[SupportedOSPlatform("ios13.0")]
 		[SupportedOSPlatform("tvos13.0")]
-		public static void MapOpenWindow(ApplicationHandler handler, IApplication application, object? args)
+		public static partial void MapOpenWindow(ApplicationHandler handler, IApplication application, object? args)
 		{
 			handler.PlatformView?.RequestNewWindow(application, args as OpenWindowRequest);
 		}
 
 		[SupportedOSPlatform("ios13.0")]
 		[SupportedOSPlatform("tvos13.0")]
-		public static void MapCloseWindow(ApplicationHandler handler, IApplication application, object? args)
+		public static partial void MapCloseWindow(ApplicationHandler handler, IApplication application, object? args)
 		{
 			if (args is IWindow window)
 			{

src/Core/src/Handlers/Border/BorderHandler.Android.cs

@@ -26,13 +26,14 @@ protected override ContentViewGroup CreatePlatformView()
 		public override void SetVirtualView(IView view)
 		{
 			base.SetVirtualView(view);
+
 			_ = VirtualView ?? throw new InvalidOperationException($"{nameof(VirtualView)} should have been set by base class.");
 			_ = PlatformView ?? throw new InvalidOperationException($"{nameof(PlatformView)} should have been set by base class.");
 
 			PlatformView.CrossPlatformLayout = VirtualView;
 		}
 
-		static void UpdateContent(IBorderHandler handler)
+		static partial void UpdateContent(IBorderHandler handler)
 		{
 			_ = handler.PlatformView ?? throw new InvalidOperationException($"{nameof(PlatformView)} should have been set by base class.");
 			_ = handler.MauiContext ?? throw new InvalidOperationException($"{nameof(MauiContext)} should have been set by base class.");
@@ -44,23 +45,18 @@ static void UpdateContent(IBorderHandler handler)
 				handler.PlatformView.AddView(view.ToPlatform(handler.MauiContext));
 		}
 
-		public static void MapHeight(IBorderHandler handler, IBorderView border)
+		public static partial void MapHeight(IBorderHandler handler, IBorderView border)
 		{
 			handler.PlatformView?.UpdateHeight(border);
 			handler.PlatformView?.InvalidateBorderStrokeBounds();
 		}
 
-		public static void MapWidth(IBorderHandler handler, IBorderView border)
+		public static partial void MapWidth(IBorderHandler handler, IBorderView border)
 		{
 			handler.PlatformView?.UpdateWidth(border);
 			handler.PlatformView?.InvalidateBorderStrokeBounds();
 		}
 
-		public static void MapContent(IBorderHandler handler, IBorderView border)
-		{
-			UpdateContent(handler);
-		}
-
 		protected override void DisconnectHandler(ContentViewGroup platformView)
 		{
 			// If we're being disconnected from the xplat element, then we should no longer be managing its children

src/Core/src/Handlers/Border/BorderHandler.Standard.cs

@@ -5,9 +5,5 @@ namespace Microsoft.Maui.Handlers
 	public partial class BorderHandler : ViewHandler<IBorderView, object>
 	{
 		protected override object CreatePlatformView() => throw new NotImplementedException();
-
-		public static void MapContent(IBorderHandler handler, IBorderView border)
-		{
-		}
 	}
 }

src/Core/src/Handlers/Border/BorderHandler.Tizen.cs

@@ -29,35 +29,33 @@ protected override void SetupContainer()
 		public override void SetVirtualView(IView view)
 		{
 			base.SetVirtualView(view);
+
 			_ = VirtualView ?? throw new InvalidOperationException($"{nameof(VirtualView)} should have been set by base class.");
 			_ = PlatformView ?? throw new InvalidOperationException($"{nameof(PlatformView)} should have been set by base class.");
 
 			PlatformView.CrossPlatformMeasure = VirtualView.CrossPlatformMeasure;
 			PlatformView.CrossPlatformArrange = VirtualView.CrossPlatformArrange;
 		}
 
-		public static void MapContent(IBorderHandler handler, IBorderView border)
-		{
-			if (handler is BorderHandler borderHandler)
-				borderHandler.UpdateContent();
-		}
-
-		void UpdateContent()
+		static partial void UpdateContent(IBorderHandler handler)
 		{
-			_ = PlatformView ?? throw new InvalidOperationException($"{nameof(PlatformView)} should have been set by base class.");
-			_ = VirtualView ?? throw new InvalidOperationException($"{nameof(VirtualView)} should have been set by base class.");
-			_ = MauiContext ?? throw new InvalidOperationException($"{nameof(MauiContext)} should have been set by base class.");
+			_ = handler.PlatformView ?? throw new InvalidOperationException($"{nameof(PlatformView)} should have been set by base class.");
+			_ = handler.VirtualView ?? throw new InvalidOperationException($"{nameof(VirtualView)} should have been set by base class.");
+			_ = handler.MauiContext ?? throw new InvalidOperationException($"{nameof(MauiContext)} should have been set by base class.");
 
-			PlatformView.Children.Clear();
-			_contentHandler?.Dispose();
-			_contentHandler = null;
+			handler.PlatformView.Children.Clear();
+			if (handler is BorderHandler borderHandler)
+			{
+				borderHandler._contentHandler?.Dispose();
+				borderHandler._contentHandler = null;
+			}
 
-			if (VirtualView.PresentedContent is IView view)
+			if (handler.VirtualView.PresentedContent is IView view)
 			{
-				PlatformView.Children.Add(view.ToPlatform(MauiContext));
-				if (view.Handler is IPlatformViewHandler thandler)
+				handler.PlatformView.Children.Add(view.ToPlatform(handler.MauiContext));
+				if (view.Handler is IPlatformViewHandler thandler && handler is BorderHandler alsoBorderHandler)
 				{
-					_contentHandler = thandler;
+					alsoBorderHandler._contentHandler = thandler;
 				}
 			}
 		}