[net10.0] Trimmable view handlers (#28357)

simonrozsival · web-flow · commit 368000a3171e · 2025-05-13T09:15:09.000-05:00
* Add ElementHandlerAttribute

* Add the attribute to Label and CheckBox

* Use the attribute in MauiHandlersFactory

* Add IRemappable and RemappingHelper

* Add implementation of IRemappable to Label and CheckBox

* Update app host builder

* Fix MAUI handlers factory

* Change TrySetValue from extension method to Element virtual method

* Move big switch from GesturePlatformManager to VisualHandler and subclasses

* Fix dereference of a possibly null reference

* Fix remapping

* Remove unnecessary changes

* Fix attribute inheritance

* Drop custom inheritance logic
diff --git a/src/Controls/src/Core/CheckBox/CheckBox.Mapper.cs b/src/Controls/src/Core/CheckBox/CheckBox.Mapper.cs
@@ -9,8 +9,12 @@ namespace Microsoft.Maui.Controls
 {
 	public partial class CheckBox
 	{
-		internal new static void RemapForControls()
+		static CheckBox() => RemapForControls();
+
+		private new static void RemapForControls()
 		{
+			VisualElement.RemapForControls();
+
 			CheckBoxHandler.Mapper.ReplaceMapping<ICheckBox, ICheckBoxHandler>(nameof(Color), MapColor);
 		}
 
diff --git a/src/Controls/src/Core/CheckBox/CheckBox.cs b/src/Controls/src/Core/CheckBox/CheckBox.cs
@@ -7,6 +7,7 @@ namespace Microsoft.Maui.Controls
 {
 	/// <include file="../../docs/Microsoft.Maui.Controls/CheckBox.xml" path="Type[@FullName='Microsoft.Maui.Controls.CheckBox']/Docs/*" />
 	[DebuggerDisplay("{GetDebuggerDisplay(), nq}")]
+	[ElementHandler<CheckBoxHandler>]
 	public partial class CheckBox : View, IElementConfiguration<CheckBox>, IBorderElement, IColorElement, ICheckBox
 	{
 		readonly Lazy<PlatformConfigurationRegistry<CheckBox>> _platformConfigurationRegistry;
@@ -116,5 +117,16 @@ private protected override string GetDebuggerDisplay()
 		{
 			return $"{base.GetDebuggerDisplay()}, IsChecked = {IsChecked}";
 		}
+
+		internal override bool TrySetValue(string text)
+		{
+			if (bool.TryParse(text, out bool result))
+			{
+				IsChecked = result;
+				return true;
+			}
+
+			return false;
+		}
 	}
 }
diff --git a/src/Controls/src/Core/Element/Element.Mapper.cs b/src/Controls/src/Core/Element/Element.Mapper.cs
@@ -8,6 +8,13 @@ namespace Microsoft.Maui.Controls
 {
 	public partial class Element
 	{
+		static Element() => RemapIfNeeded();
+
+		internal static void RemapIfNeeded()
+		{
+			RemappingHelper.RemapIfNeeded(typeof(Element), RemapForControls);
+		}
+
 		internal static void RemapForControls()
 		{
 			ViewHandler.ViewMapper.ReplaceMapping<Maui.IElement, IElementHandler>(AutomationProperties.IsInAccessibleTreeProperty.PropertyName, MapAutomationPropertiesIsInAccessibleTree);
diff --git a/src/Controls/src/Core/Element/Element.cs b/src/Controls/src/Core/Element/Element.cs
@@ -1072,6 +1072,47 @@ HandlerDisconnectPolicy IHandlerDisconnectPolicies.DisconnectPolicy
 			set => HandlerProperties.SetDisconnectPolicy(this, value);
 		}
 
+		internal virtual bool TrySetValue(string text)
+		{
+			if (this is Label label)
+			{
+				label.Text = text;
+				return true;
+			}
+			else if (this is Entry entry)
+			{
+				entry.Text = text;
+				return true;
+			}
+			else if (this is Editor editor)
+			{
+				editor.Text = text;
+				return true;
+			}
+			else if (this is Switch sw && bool.TryParse(text, out bool swResult))
+			{
+				sw.IsToggled = swResult;
+				return true;
+			}
+			else if (this is RadioButton rb && bool.TryParse(text, out bool rbResult))
+			{
+				rb.IsChecked = rbResult;
+				return true;
+			}
+			else if (this is TimePicker tp && TimeSpan.TryParse(text, out TimeSpan tpResult))
+			{
+				tp.Time = tpResult;
+				return true;
+			}
+			else if (this is DatePicker dp && DateTime.TryParse(text, out DateTime dpResult))
+			{
+				dp.Date = dpResult;
+				return true;
+			}
+
+			return false;
+		}
+
 		class TemporaryWrapper : IList<Element>
 		{
 			IReadOnlyList<Element> _inner;
diff --git a/src/Controls/src/Core/Hosting/AppHostBuilderExtensions.cs b/src/Controls/src/Core/Hosting/AppHostBuilderExtensions.cs
@@ -73,13 +73,11 @@ internal static IMauiHandlersCollection AddControlsHandlers(this IMauiHandlersCo
 		handlersCollection.AddHandler<ActivityIndicator, ActivityIndicatorHandler>();
 		handlersCollection.AddHandler<BoxView, BoxViewHandler>();
 		handlersCollection.AddHandler<Button, ButtonHandler>();
-		handlersCollection.AddHandler<CheckBox, CheckBoxHandler>();
 		handlersCollection.AddHandler<DatePicker, DatePickerHandler>();
 		handlersCollection.AddHandler<Editor, EditorHandler>();
 		handlersCollection.AddHandler<Entry, EntryHandler>();
 		handlersCollection.AddHandler<GraphicsView, GraphicsViewHandler>();
 		handlersCollection.AddHandler<Image, ImageHandler>();
-		handlersCollection.AddHandler<Label, LabelHandler>();
 		handlersCollection.AddHandler<Layout, LayoutHandler>();
 		handlersCollection.AddHandler<Picker, PickerHandler>();
 		handlersCollection.AddHandler<ProgressBar, ProgressBarHandler>();
@@ -263,12 +261,10 @@ static MauiAppBuilder ConfigureImageSourceHandlers(this MauiAppBuilder builder)
 	internal static MauiAppBuilder RemapForControls(this MauiAppBuilder builder)
 	{
 		// Update the mappings for IView/View to work specifically for Controls
-		Element.RemapForControls();
+		Element.RemapIfNeeded();
 		Application.RemapForControls();
-		VisualElement.RemapForControls();
-		Label.RemapForControls();
+		VisualElement.RemapIfNeeded();
 		Button.RemapForControls();
-		CheckBox.RemapForControls();
 		DatePicker.RemapForControls();
 		RadioButton.RemapForControls();
 		FlyoutPage.RemapForControls();
diff --git a/src/Controls/src/Core/Label/Label.Mapper.cs b/src/Controls/src/Core/Label/Label.Mapper.cs
@@ -9,8 +9,12 @@ namespace Microsoft.Maui.Controls
 	/// <include file="../../../docs/Microsoft.Maui.Controls/Label.xml" path="Type[@FullName='Microsoft.Maui.Controls.Label']/Docs/*" />
 	public partial class Label
 	{
-		internal static new void RemapForControls()
+		static Label() => RemapForControls();
+
+		private new static void RemapForControls()
 		{
+			VisualElement.RemapIfNeeded();
+
 			// Adjust the mappings to preserve Controls.Label legacy behaviors
 			// ILabel does not include the TextType property, so we map it here to handle HTML text
 			// And we map some of the other property handlers to Controls-specific versions that avoid stepping on HTML text settings
diff --git a/src/Controls/src/Core/Label/Label.cs b/src/Controls/src/Core/Label/Label.cs
@@ -15,6 +15,7 @@ namespace Microsoft.Maui.Controls
 	/// <include file="../../docs/Microsoft.Maui.Controls/Label.xml" path="Type[@FullName='Microsoft.Maui.Controls.Label']/Docs/*" />
 	[ContentProperty(nameof(Text))]
 	[DebuggerDisplay("{GetDebuggerDisplay(), nq}")]
+	[ElementHandler<LabelHandler>]
 	public partial class Label : View, IFontElement, ITextElement, ITextAlignmentElement, ILineHeightElement, IElementConfiguration<Label>, IDecorableTextElement, IPaddingElement, ILabel
 	{
 		/// <summary>Bindable property for <see cref="HorizontalTextAlignment"/>.</summary>
diff --git a/src/Controls/src/Core/Platform/GestureManager/GesturePlatformManager.Windows.cs b/src/Controls/src/Core/Platform/GestureManager/GesturePlatformManager.Windows.cs
@@ -88,25 +88,8 @@ public FrameworkElement? Container
 		// Do we need to provide a hook for this in the handlers?
 		// For now I just built this ugly matching statement
 		// to replicate our handlers where we are setting this to true
-		public bool PreventGestureBubbling
-		{
-			get
-			{
-				return Element switch
-				{
-					Button => true,
-					CheckBox => true,
-					DatePicker => true,
-					Stepper => true,
-					Slider => true,
-					Switch => true,
-					TimePicker => true,
-					ImageButton => true,
-					RadioButton => true,
-					_ => false,
-				};
-			}
-		}
+		public bool PreventGestureBubbling =>
+			(Element?.Handler as ViewHandler)?.PreventGestureBubbling ?? false;
 
 		public FrameworkElement? Control
 		{
diff --git a/src/Controls/src/Core/ViewExtensions.cs b/src/Controls/src/Core/ViewExtensions.cs
@@ -509,52 +509,6 @@ internal static List<Page> GetParentPages(this Page target)
 			return text;
 		}
 
-		internal static bool TrySetValue(this Element element, string text)
-		{
-			if (element is Label label)
-			{
-				label.Text = text;
-				return true;
-			}
-			else if (element is Entry entry)
-			{
-				entry.Text = text;
-				return true;
-			}
-			else if (element is Editor editor)
-			{
-				editor.Text = text;
-				return true;
-			}
-			else if (element is CheckBox cb && bool.TryParse(text, out bool result))
-			{
-				cb.IsChecked = result;
-				return true;
-			}
-			else if (element is Switch sw && bool.TryParse(text, out bool swResult))
-			{
-				sw.IsToggled = swResult;
-				return true;
-			}
-			else if (element is RadioButton rb && bool.TryParse(text, out bool rbResult))
-			{
-				rb.IsChecked = rbResult;
-				return true;
-			}
-			else if (element is TimePicker tp && TimeSpan.TryParse(text, out TimeSpan tpResult))
-			{
-				tp.Time = tpResult;
-				return true;
-			}
-			else if (element is DatePicker dp && DateTime.TryParse(text, out DateTime dpResult))
-			{
-				dp.Date = dpResult;
-				return true;
-			}
-
-			return false;
-		}
-
 		static internal bool RequestFocus(this VisualElement view)
 		{
 			// if there is an attached handler, we use that and we will end up in the MapFocus method below
diff --git a/src/Controls/src/Core/VisualElement/VisualElement.Mapper.cs b/src/Controls/src/Core/VisualElement/VisualElement.Mapper.cs
@@ -8,6 +8,13 @@ namespace Microsoft.Maui.Controls
 	/// <include file="../../../docs/Microsoft.Maui.Controls/VisualElement.xml" path="Type[@FullName='Microsoft.Maui.Controls.VisualElement']/Docs/*" />
 	public partial class VisualElement
 	{
+		static VisualElement() => RemapIfNeeded();
+
+		internal static new void RemapIfNeeded()
+		{
+			RemappingHelper.RemapIfNeeded(typeof(VisualElement), RemapForControls);
+		}
+
 		internal static new void RemapForControls()
 		{
 			RemapForControls(ViewHandler.ViewMapper, ViewHandler.ViewCommandMapper);
@@ -17,6 +24,8 @@ internal static void RemapForControls(
 			IPropertyMapper<IView, IViewHandler> viewMapper,
 			CommandMapper<IView, IViewHandler> commandMapper)
 		{
+			Element.RemapIfNeeded();
+
 #if WINDOWS
 			viewMapper.ReplaceMapping<IView, IViewHandler>(PlatformConfiguration.WindowsSpecific.VisualElement.AccessKeyHorizontalOffsetProperty.PropertyName, MapAccessKeyHorizontalOffset);
 			viewMapper.ReplaceMapping<IView, IViewHandler>(PlatformConfiguration.WindowsSpecific.VisualElement.AccessKeyPlacementProperty.PropertyName, MapAccessKeyPlacement);
diff --git a/src/Core/src/Handlers/CheckBox/CheckBoxHandler.Windows.cs b/src/Core/src/Handlers/CheckBox/CheckBoxHandler.Windows.cs
@@ -76,5 +76,7 @@ void OnChecked(object sender, RoutedEventArgs e)
 			if (sender is CheckBox platformView && VirtualView != null)
 				VirtualView.IsChecked = platformView.IsChecked == true;
 		}
+
+		internal override bool PreventGestureBubbling => true;
 	}
 }
diff --git a/src/Core/src/Handlers/Element/ElementHandlerAttribute.cs b/src/Core/src/Handlers/Element/ElementHandlerAttribute.cs
@@ -0,0 +1,17 @@
+using System;
+
+namespace Microsoft.Maui.Handlers;
+
+[AttributeUsage(AttributeTargets.Class, Inherited = true, AllowMultiple = false)]
+internal abstract class ElementHandlerAttribute : Attribute
+{
+	public abstract IElementHandler CreateHandler();
+	public abstract Type HandlerType { get; }
+}
+
+internal sealed class ElementHandlerAttribute<THandler> : ElementHandlerAttribute
+	where THandler : IElementHandler, new()
+{
+	public override IElementHandler CreateHandler() => new THandler();
+	public override Type HandlerType => typeof(THandler);
+}
diff --git a/src/Core/src/Handlers/Element/RemappingHelper.cs b/src/Core/src/Handlers/Element/RemappingHelper.cs
@@ -0,0 +1,26 @@
+using System;
+using System.Collections.Generic;
+using System.Threading;
+
+#if !NET9_0_OR_GREATER
+using Lock = object;
+#endif
+
+namespace Microsoft.Maui.Handlers;
+
+internal static class RemappingHelper
+{
+	private static readonly HashSet<Type> s_remappedTypes = new();
+	private static readonly Lock s_lock = new();
+
+	public static void RemapIfNeeded(Type handlerType, Action remapForControls)
+	{
+		lock (s_lock)
+		{
+			if (s_remappedTypes.Add(handlerType))
+			{
+				remapForControls();
+			}
+		}
+	}
+}
diff --git a/src/Core/src/Handlers/View/ViewHandler.Windows.cs b/src/Core/src/Handlers/View/ViewHandler.Windows.cs
@@ -169,5 +169,19 @@ private protected void UpdateIsFocused(bool isFocused)
 				virtualView.IsFocused = isFocused;
 			}
 		}
+
+		internal virtual bool PreventGestureBubbling
+			=> this switch
+			{
+				ButtonHandler => true,
+				DatePickerHandler => true,
+				StepperHandler => true,
+				SliderHandler => true,
+				SwitchHandler => true,
+				TimePickerHandler => true,
+				ImageButtonHandler => true,
+				RadioButtonHandler => true,
+				_ => false,
+			};
 	}
-}
+}
diff --git a/src/Core/src/Hosting/Internal/MauiHandlersFactory.cs b/src/Core/src/Hosting/Internal/MauiHandlersFactory.cs
diff --git a/src/Core/src/Hosting/Internal/RegisteredHandlerServiceTypeSet.cs b/src/Core/src/Hosting/Internal/RegisteredHandlerServiceTypeSet.cs
diff --git a/src/Core/tests/UnitTests/Hosting/RegisteredHandlerServiceTypeSetTests.cs b/src/Core/tests/UnitTests/Hosting/RegisteredHandlerServiceTypeSetTests.cs

Original file line number	Diff line number	Diff line change
`@@ -9,8 +9,12 @@ namespace Microsoft.Maui.Controls`
`9`	`9`	`{`
`10`	`10`	`public partial class CheckBox`
`11`	`11`	`{`
`12`		`- internal new static void RemapForControls()`
	`12`	`+ static CheckBox() => RemapForControls();`
	`13`	`+`
	`14`	`+ private new static void RemapForControls()`
`13`	`15`	`{`
	`16`	`+ VisualElement.RemapForControls();`
	`17`	`+`
`14`	`18`	`CheckBoxHandler.Mapper.ReplaceMapping<ICheckBox, ICheckBoxHandler>(nameof(Color), MapColor);`
`15`	`19`	`}`
`16`	`20`
Original file line number	Diff line number	Diff line change
`@@ -7,6 +7,7 @@ namespace Microsoft.Maui.Controls`
`7`	`7`	`{`
`8`	`8`	`/// <include file="../../docs/Microsoft.Maui.Controls/CheckBox.xml" path="Type[@FullName='Microsoft.Maui.Controls.CheckBox']/Docs/*" />`
`9`	`9`	`[DebuggerDisplay("{GetDebuggerDisplay(), nq}")]`
	`10`	`+ [ElementHandler<CheckBoxHandler>]`
`10`	`11`	`public partial class CheckBox : View, IElementConfiguration<CheckBox>, IBorderElement, IColorElement, ICheckBox`
`11`	`12`	`{`
`12`	`13`	`readonly Lazy<PlatformConfigurationRegistry<CheckBox>> _platformConfigurationRegistry;`
`@@ -116,5 +117,16 @@ private protected override string GetDebuggerDisplay()`
`116`	`117`	`{`
`117`	`118`	`return $"{base.GetDebuggerDisplay()}, IsChecked = {IsChecked}";`
`118`	`119`	`}`
	`120`	`+`
	`121`	`+ internal override bool TrySetValue(string text)`
	`122`	`+ {`
	`123`	`+ if (bool.TryParse(text, out bool result))`
	`124`	`+ {`
	`125`	`+ IsChecked = result;`
	`126`	`+ return true;`
	`127`	`+ }`
	`128`	`+`
	`129`	`+ return false;`
	`130`	`+ }`
`119`	`131`	`}`
`120`	`132`	`}`
Original file line number	Diff line number	Diff line change
`@@ -8,6 +8,13 @@ namespace Microsoft.Maui.Controls`
`8`	`8`	`{`
`9`	`9`	`public partial class Element`
`10`	`10`	`{`
	`11`	`+ static Element() => RemapIfNeeded();`
	`12`	`+`
	`13`	`+ internal static void RemapIfNeeded()`
	`14`	`+ {`
	`15`	`+ RemappingHelper.RemapIfNeeded(typeof(Element), RemapForControls);`
	`16`	`+ }`
	`17`	`+`
`11`	`18`	`internal static void RemapForControls()`
`12`	`19`	`{`
`13`	`20`	`ViewHandler.ViewMapper.ReplaceMapping<Maui.IElement, IElementHandler>(AutomationProperties.IsInAccessibleTreeProperty.PropertyName, MapAutomationPropertiesIsInAccessibleTree);`
Original file line number	Diff line number	Diff line change
`@@ -9,8 +9,12 @@ namespace Microsoft.Maui.Controls`
`9`	`9`	`/// <include file="../../../docs/Microsoft.Maui.Controls/Label.xml" path="Type[@FullName='Microsoft.Maui.Controls.Label']/Docs/*" />`
`10`	`10`	`public partial class Label`
`11`	`11`	`{`
`12`		`- internal static new void RemapForControls()`
	`12`	`+ static Label() => RemapForControls();`
	`13`	`+`
	`14`	`+ private new static void RemapForControls()`
`13`	`15`	`{`
	`16`	`+ VisualElement.RemapIfNeeded();`
	`17`	`+`
`14`	`18`	`// Adjust the mappings to preserve Controls.Label legacy behaviors`
`15`	`19`	`// ILabel does not include the TextType property, so we map it here to handle HTML text`
`16`	`20`	`// And we map some of the other property handlers to Controls-specific versions that avoid stepping on HTML text settings`
Original file line number	Diff line number	Diff line change
`@@ -15,6 +15,7 @@ namespace Microsoft.Maui.Controls`
`15`	`15`	`/// <include file="../../docs/Microsoft.Maui.Controls/Label.xml" path="Type[@FullName='Microsoft.Maui.Controls.Label']/Docs/*" />`
`16`	`16`	`[ContentProperty(nameof(Text))]`
`17`	`17`	`[DebuggerDisplay("{GetDebuggerDisplay(), nq}")]`
	`18`	`+ [ElementHandler<LabelHandler>]`
`18`	`19`	`public partial class Label : View, IFontElement, ITextElement, ITextAlignmentElement, ILineHeightElement, IElementConfiguration<Label>, IDecorableTextElement, IPaddingElement, ILabel`
`19`	`20`	`{`
`20`	`21`	`/// <summary>Bindable property for <see cref="HorizontalTextAlignment"/>.</summary>`