Workaround for iOS material entry application freeze (#12316)

* Repro Issue 12246; UI test for 12246

* Subtly adjust entry colors on iOS 14 for material; fixes #12246

* Fix typo

* Forgot to add automation ids

fixes #12246

Author: hartez

Xamarin.Forms.Controls.Issues/Xamarin.Forms.Controls.Issues.Shared/Issue12246.cs

@@ -0,0 +1,80 @@
+using System.Collections.ObjectModel;
+using System.Threading.Tasks;
+using Xamarin.Forms.CustomAttributes;
+using Xamarin.Forms.Internals;
+
+#if UITEST
+using Xamarin.Forms.Core.UITests;
+using Xamarin.UITest;
+using NUnit.Framework;
+#endif
+
+namespace Xamarin.Forms.Controls.Issues
+{
+#if UITEST
+	[Category(UITestCategories.Entry)]
+	[Category(UITestCategories.Visual)]
+#endif
+	[Preserve(AllMembers = true)]
+	[Issue(IssueTracker.Github, 12246, "[Bug] iOS 14 App freezes when password is entered after email", PlatformAffected.iOS)]
+	public class Issue12246 : TestContentPage
+	{
+		const string Entry = "Entry";
+		const string Password = "Password";
+		const string Success = "Success";
+
+		protected override void Init()
+		{
+			var layout = new StackLayout() { Margin = 40, Spacing = 10, VerticalOptions = LayoutOptions.Center };
+
+			var instructions = new Label { Text = $"Focus the 'Email' Entry. Type in some text. Then focus the 'Password' Entry." +
+				$" Type in some text. Now focus the 'Email' Entry again. The '{Success}' Label should appear. " +
+				$"If the '{Success}' Label does not appear or the application hangs, this test has failed." };
+
+			var result = new Label { Text = Success, IsVisible = false };
+
+			var entry = new Entry() { Visual = VisualMarker.Material, Keyboard = Keyboard.Email, Placeholder = "Email", 
+				TextColor = Color.Purple, AutomationId = Entry };
+
+			var password = new Entry { Visual = VisualMarker.Material, IsPassword = true, Placeholder = "Password", 
+				TextColor = Color.Purple, AutomationId = Password };
+
+			var passwordConfirmation = new Entry
+			{
+				Visual = VisualMarker.Material,
+				IsPassword = true,
+				Placeholder = "Confirm Password",
+				TextColor = Color.Purple
+			};
+
+			password.Unfocused += (sender, args) => {
+				result.IsVisible = true;
+			};
+
+			layout.Children.Add(instructions);
+			layout.Children.Add(entry);
+			layout.Children.Add(password);
+			layout.Children.Add(passwordConfirmation);
+			layout.Children.Add(result);
+
+			Content = layout;
+		}
+
+#if UITEST
+		[Test]
+		public void UnfocusingPasswordDoesNotHang()
+		{
+			RunningApp.WaitForElement(Entry);
+			RunningApp.Tap(Entry);
+			RunningApp.EnterText("test");
+
+			RunningApp.WaitForElement(Password);
+			RunningApp.Tap(Password);
+			RunningApp.EnterText("test");
+
+			RunningApp.Tap(Entry);
+			RunningApp.WaitForElement(Success);
+		}
+#endif
+	}
+}

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

@@ -29,6 +29,7 @@
     <Compile Include="$(MSBuildThisFileDirectory)Issue10744.cs" />
     <Compile Include="$(MSBuildThisFileDirectory)Issue10909.cs" />
     <Compile Include="$(MSBuildThisFileDirectory)Issue11769.cs" />
+    <Compile Include="$(MSBuildThisFileDirectory)Issue12246.cs" />
     <Compile Include="$(MSBuildThisFileDirectory)Issue8613.cs" />
     <Compile Include="$(MSBuildThisFileDirectory)Issue9137.cs" />
     <Compile Include="$(MSBuildThisFileDirectory)Issue8691.cs" />

Xamarin.Forms.Material.iOS/MaterialTextManager.cs

@@ -10,6 +10,8 @@ namespace Xamarin.Forms.Material.iOS
 {
 	internal static class MaterialTextManager
 	{
+		static double AlphaAdjustment = 0.0;
+
 		public static void Init(IMaterialEntryRenderer element, IMaterialTextField textField, IFontElement fontElement)
 		{
 			var containerScheme = textField.ContainerScheme;
@@ -49,8 +51,10 @@ public static void ApplyTheme(IMaterialTextField textField, IMaterialEntryRender
 			textField.ContainerScheme.ColorScheme = (SemanticColorScheme)CreateColorScheme();
 			ApplyContainerTheme(textField);
 
-			var textColor = MaterialColors.GetEntryTextColor(element.TextColor);
-			var placeHolderColors = MaterialColors.GetPlaceHolderColor(element.PlaceholderColor, element.TextColor);
+			var adjustedTextColor = AdjustTextColor(element);
+
+			var textColor = MaterialColors.GetEntryTextColor(adjustedTextColor);
+			var placeHolderColors = MaterialColors.GetPlaceHolderColor(element.PlaceholderColor, adjustedTextColor);
 			var underlineColors = MaterialColors.GetUnderlineColor(element.PlaceholderColor);
 
 			textField.TextInput.TextColor = textColor;
@@ -63,7 +67,7 @@ public static void ApplyTheme(IMaterialTextField textField, IMaterialEntryRender
 			if (Brush.IsNullOrEmpty(brush))
 			{
 				// BackgroundColor
-				textField.ActiveTextInputController.BorderFillColor = MaterialColors.CreateEntryFilledInputBackgroundColor(element.BackgroundColor, element.TextColor);
+				textField.ActiveTextInputController.BorderFillColor = MaterialColors.CreateEntryFilledInputBackgroundColor(element.BackgroundColor, adjustedTextColor);
 			}
 			else
 			{
@@ -114,11 +118,45 @@ public static void UpdatePlaceholder(IMaterialTextField textField, IMaterialEntr
 
 		public static void UpdateTextColor(IMaterialTextField textField, IMaterialEntryRenderer element)
 		{
-			var uIColor = MaterialColors.GetEntryTextColor(element.TextColor);
+			var adjustedTextColor = AdjustTextColor(element);
+
+			var uIColor = MaterialColors.GetEntryTextColor(adjustedTextColor);
 			textField.ContainerScheme.ColorScheme.OnSurfaceColor = uIColor;
 			textField.ContainerScheme.ColorScheme.PrimaryColor = uIColor;
 		}
 
+		static Color AdjustTextColor(IMaterialEntryRenderer element) 
+		{
+			if (Forms.IsiOS14OrNewer)
+			{
+				// This is a workaround for an iOS/Material bug; https://github.com/xamarin/Xamarin.Forms/issues/12246
+				// If we are on iOS 14, and we have multiple material text entry fields of the same color,
+				// and any of them are password fields, setting them to the same TextColor value will cause the application
+				// to hang when a password field loses focus. 
+
+				// So to work around this, we make an imperceptible adjustment to the alpha value of the color each time
+				// we set it; that way, none of the text entry fields have _exactly_ the same color and we avoid the bug
+
+				// Obviously this will start to become noticeable after the first 20 million or so text entry fields are displayed.
+				// We apologize for the inconvenience.
+
+				var elementTextColor = element.TextColor;
+				AlphaAdjustment += 0.0000001;
+
+				var adjustedAlpha = elementTextColor.A - AlphaAdjustment;
+				if (adjustedAlpha < 0)
+				{
+					// Below an alpha of 0.01 stuff on iOS doesn't show up in hit tests anyway, so it seems unlikely
+					// that the entry will get focus and cause the issue. 
+					adjustedAlpha = 0;
+				}
+
+				return new Color(elementTextColor.R, elementTextColor.G, elementTextColor.B, adjustedAlpha);
+			}
+
+			return element.TextColor;
+		}
+
 		static IColorScheming CreateColorScheme()
 		{
 			var returnValue = MaterialColors.Light.CreateColorScheme();