[Bug] Fix ClearButtonVisibility.Never does not take effect on UWP (#9250)

* Setup Issue Page

* Update VSM to remove delete button

Fixes #8836

Xamarin.Forms.Controls.Issues/Xamarin.Forms.Controls.Issues.Shared/Issue8836.cs

@@ -0,0 +1,48 @@
+using Xamarin.Forms.CustomAttributes;
+using Xamarin.Forms.Internals;
+
+namespace Xamarin.Forms.Controls.Issues
+{
+	[Preserve(AllMembers = true)]
+	[Issue(IssueTracker.Github, 8836, "[Bug] ClearButtonVisibility.Never does not take effect on UWP", PlatformAffected.UWP)]
+	public class Issue8836 : TestContentPage
+	{
+		protected override void Init()
+		{
+			var stack = new StackLayout();
+
+			stack.Children.Add(new Label {Text = "Click the button to toggle the clear button visibility."});
+
+			Entry = new Entry
+			{
+				Text = "Clear Button: While Editing",
+				ClearButtonVisibility = ClearButtonVisibility.WhileEditing
+			};
+			stack.Children.Add(Entry);
+
+			var button = new Button { Text = "Toggle Clear Button State" };
+			button.Clicked += Button_Clicked;
+			stack.Children.Add(button);
+
+			Content = stack;
+		}
+
+		private void Button_Clicked(object sender, System.EventArgs e)
+		{
+			if (Entry.ClearButtonVisibility == ClearButtonVisibility.Never)
+			{
+				Entry.ClearButtonVisibility = ClearButtonVisibility.WhileEditing;
+				Entry.Text = "Clear Button: While Editing";
+			}
+			else
+			{
+				Entry.ClearButtonVisibility = ClearButtonVisibility.Never;
+				Entry.Text = "Clear Button: Never";
+			}
+			Entry.Focus();
+		}
+
+		public Entry Entry { get; set; }
+
+	}
+}

Xamarin.Forms.Controls.Issues/Xamarin.Forms.Controls.Issues.Shared/Xamarin.Forms.Controls.Issues.Shared.projitems

@@ -44,6 +44,7 @@
     <Compile Include="$(MSBuildThisFileDirectory)Issue8262.cs" />
     <Compile Include="$(MSBuildThisFileDirectory)Issue8899.cs" />
     <Compile Include="$(MSBuildThisFileDirectory)Issue8551.cs" />
+    <Compile Include="$(MSBuildThisFileDirectory)Issue8836.cs" />
     <Compile Include="$(MSBuildThisFileDirectory)Issue8902.xaml.cs">
       <DependentUpon>Issue8902.xaml</DependentUpon>
       <SubType>Code</SubType>

Xamarin.Forms.Platform.UAP/EntryRenderer.cs

@@ -66,6 +66,9 @@ namespace Xamarin.Forms.Platform.UWP
 				UpdateReturnType();
 				UpdateIsReadOnly();
 				UpdateInputScope();
+				UpdateClearButtonVisibility();
+
+
 
 				if (_cursorPositionChangePending)
 					UpdateCursorPosition();
@@ -148,6 +151,8 @@ namespace Xamarin.Forms.Platform.UWP
 				UpdateSelectionLength();
 			else if (e.PropertyName == InputView.IsReadOnlyProperty.PropertyName)
 				UpdateIsReadOnly();
+			else if (e.PropertyName == Entry.ClearButtonVisibilityProperty.PropertyName)
+				UpdateClearButtonVisibility();
 		}
 
 		protected override void UpdateBackgroundColor()
@@ -236,6 +241,11 @@ namespace Xamarin.Forms.Platform.UWP
 			Control.CharacterSpacing = Element.CharacterSpacing.ToEm();
 		}
 
+		void UpdateClearButtonVisibility()
+		{
+			Control.ClearButtonVisible = Element.ClearButtonVisibility == ClearButtonVisibility.WhileEditing;
+		}
+
 		void UpdateInputScope()
 		{
 			Entry entry = Element;

Xamarin.Forms.Platform.UAP/FormsTextBox.cs

@@ -42,9 +42,15 @@ namespace Xamarin.Forms.Platform.UWP
 		public new static readonly DependencyProperty TextProperty = DependencyProperty.Register(nameof(Text),
 			typeof(string), typeof(FormsTextBox), new PropertyMetadata("", TextPropertyChanged));
 
+		public static readonly DependencyProperty ClearButtonVisibleProperty = DependencyProperty.Register(nameof(ClearButtonVisible),
+			typeof(bool), typeof(FormsTextBox), new PropertyMetadata(true, ClearButtonVisibleChanged));
+
 		InputScope _passwordInputScope;
 		InputScope _numericPasswordInputScope;
 		Border _borderElement;
+		Windows.UI.Xaml.Controls.Grid _rootGrid;
+		Windows.UI.Xaml.VisualState _DeleteButtonVisibleState;
+		Windows.UI.Xaml.VisualStateGroup _DeleteButtonVisibleStateGroups;
 		InputScope _cachedInputScope;
 		bool _cachedPredictionsSetting;
 		bool _cachedSpellCheckSetting;
@@ -64,6 +70,12 @@ namespace Xamarin.Forms.Platform.UWP
 			UpdateEnabled();
 		}
 
+		public bool ClearButtonVisible
+		{
+			get { return (bool)GetValue(ClearButtonVisibleProperty); }
+			set { SetValue(ClearButtonVisibleProperty, value);}
+		}
+
 		public Brush BackgroundFocusBrush
 		{
 			get { return (Brush)GetValue(BackgroundFocusBrushProperty); }
@@ -146,6 +158,15 @@ namespace Xamarin.Forms.Platform.UWP
 				// so we can manually handle its background when focused
 				_borderElement = (Border)GetTemplateChild("BorderElement");
 			}
+			
+			_rootGrid = (Windows.UI.Xaml.Controls.Grid)GetTemplateChild("RootGrid");
+			if (_rootGrid != null)
+			{
+				var stateGroups = WVisualStateManager.GetVisualStateGroups(_rootGrid).ToList();
+				_DeleteButtonVisibleStateGroups = stateGroups.SingleOrDefault(sg => sg.Name == "ButtonStates");
+				if (_DeleteButtonVisibleStateGroups != null)
+					_DeleteButtonVisibleState = _DeleteButtonVisibleStateGroups.States.SingleOrDefault(s => s.Name == "ButtonVisible");
+			}
 		}
 
 		void DelayObfuscation()
@@ -346,6 +367,21 @@ namespace Xamarin.Forms.Platform.UWP
 			SelectionStart = base.Text.Length;
 		}
 
+		static void ClearButtonVisibleChanged(DependencyObject dependencyObject, DependencyPropertyChangedEventArgs dependencyPropertyChangedEventArgs)
+		{
+			var textBox = (FormsTextBox)dependencyObject;
+			var visibleState = textBox._DeleteButtonVisibleState;
+			var states = textBox._DeleteButtonVisibleStateGroups?.States;
+
+			if (states != null && visibleState != null)
+			{
+				if (textBox.ClearButtonVisible && !states.Contains(visibleState))
+					states.Add(visibleState);
+				else
+					states.Remove(visibleState);
+			}
+		}
+
 		static void TextPropertyChanged(DependencyObject dependencyObject, DependencyPropertyChangedEventArgs dependencyPropertyChangedEventArgs)
 		{
 			var textBox = (FormsTextBox)dependencyObject;

Xamarin.Forms.Platform.UAP/FormsTextBoxStyle.xaml

@@ -26,7 +26,7 @@
 		<Setter Property="Template">
 			<Setter.Value>
 				<ControlTemplate TargetType="uwp:FormsTextBox">
-					<Grid>
+					<Grid x:Name="RootGrid">
 						<Grid.Resources>
 							<Style x:Name="DeleteButtonStyle" TargetType="Button">
 								<Setter Property="Template">