[iOS] Add legacy Done accessory compatibility switch

src/Core/src/Platform/iOS/MauiDoneAccessoryView.cs

@@ -11,6 +11,7 @@ internal class MauiDoneAccessoryView : UIView
 		const double AccessoryHeight = 44;
 		const double GlassButtonBottomSpacing = 4;
 		const string DoneAccessoryIdentifier = "DoneAccessory";
+		internal const string UseLegacyDoneAccessorySwitch = "Microsoft.Maui.Platform.iOS.UseLegacyDoneAccessory";
 
 		// UIKit's localized "Done" label, matching UIBarButtonSystemItem.Done so VoiceOver keeps reading
 		// the affordance in the user's language on the iOS 26+ glass button path.
@@ -20,12 +21,16 @@ internal class MauiDoneAccessoryView : UIView
 		// iOS 26 gives bars a translucent Liquid Glass background, so a full-width accessory looks empty
 		// and appears to let taps through to the field behind it (dotnet/maui#36412). On those versions
 		// we replace the bar with a floating, pass-through close button. Earlier iOS keeps the original
-		// full-width touch-blocking Done toolbar, so the accessory already blocks taps behind it.
-		static bool UseGlassButton => OperatingSystem.IsIOSVersionAtLeast(26);
+		// full-width touch-blocking Done toolbar. Apps can temporarily restore that toolbar on iOS 26+
+		// by setting the UseLegacyDoneAccessory AppContext switch to true before creating controls.
+		static bool UseGlassButton =>
+			OperatingSystem.IsIOSVersionAtLeast(26) &&
+			!(AppContext.TryGetSwitch(UseLegacyDoneAccessorySwitch, out var useLegacyDoneAccessory) && useLegacyDoneAccessory);
 
 		readonly BarButtonItemProxy _proxy;
+		readonly bool _useGlassButton;
 
-		// Cache the discovered button so hit-testing (iOS 26+) doesn't walk the subview tree on every
+		// Cache the discovered button so glass-path hit-testing doesn't walk the subview tree on every
 		// touch. It's held weakly because the button is already retained by the native Subviews array,
 		// so a strong managed field here would trip the MEM0002 memory-leak analyzer for NSObject
 		// subclasses. The weak reference effectively always resolves while the button is a subview.
@@ -34,12 +39,14 @@ internal class MauiDoneAccessoryView : UIView
 		public MauiDoneAccessoryView() : base(InitialFrame())
 		{
 			_proxy = new BarButtonItemProxy();
+			_useGlassButton = UseGlassButton;
 			Initialize(_proxy.OnDataClicked);
 		}
 
 		public MauiDoneAccessoryView(Action doneClicked) : base(InitialFrame())
 		{
 			_proxy = new BarButtonItemProxy(doneClicked);
+			_useGlassButton = UseGlassButton;
 			Initialize(_proxy.OnClicked);
 		}
 
@@ -62,7 +69,7 @@ internal UIButton? DoneButton
 
 		internal void SendDoneClicked()
 		{
-			if (UseGlassButton && DoneButton is UIButton button)
+			if (_useGlassButton && DoneButton is UIButton button)
 				button.SendActionForControlEvents(UIControlEvent.TouchUpInside);
 			else
 				_proxy.Invoke();
@@ -72,11 +79,11 @@ internal void SendDoneClicked()
 		{
 			var hitView = base.HitTest(point, uievent);
 
-			// The classic toolbar (iOS < 26) keeps its original full-width touch-blocking behavior.
-			if (!UseGlassButton)
+			// The classic toolbar keeps its original full-width touch-blocking behavior.
+			if (!_useGlassButton)
 				return hitView;
 
-			// The floating glass button (iOS 26+) lets taps pass through everywhere except the button
+			// The floating glass button lets taps pass through everywhere except the button
 			// itself, so the field showing behind the accessory stays tappable.
 			if (hitView is null || Equals(hitView))
 				return null;
@@ -94,14 +101,14 @@ void Initialize(EventHandler doneClicked)
 		{
 			AccessibilityIdentifier = DoneAccessoryIdentifier;
 
-			if (UseGlassButton)
+			if (_useGlassButton)
 				InitializeGlassButton(doneClicked);
 			else
 				InitializeToolbar(doneClicked);
 		}
 
-		// iOS < 26: the original translucent toolbar with the system Done item. It sizes itself and is
-		// already localized, so there are no hard-coded metrics here.
+		// Legacy path: the original translucent toolbar with the system Done item. It sizes itself and
+		// is already localized, so there are no hard-coded metrics here.
 		void InitializeToolbar(EventHandler doneClicked)
 		{
 			var toolbar = new UIToolbar(Bounds)
@@ -118,9 +125,9 @@ void InitializeToolbar(EventHandler doneClicked)
 			AddSubview(toolbar);
 		}
 
-		// iOS 26+: a floating Liquid Glass close button pinned to the trailing layout margin and lifted
-		// above the keyboard. Keep the original accessory height so UIKit continues scrolling focused
-		// input above the keyboard.
+		// Default iOS 26+ path: a floating Liquid Glass close button pinned to the trailing layout margin
+		// and lifted above the keyboard. Keep the original accessory height so UIKit continues scrolling
+		// focused input above the keyboard.
 		void InitializeGlassButton(EventHandler doneClicked)
 		{
 			ClipsToBounds = false;

src/Core/tests/DeviceTests/Platform/iOS/MauiDoneAccessoryViewTests.iOS.cs

@@ -8,12 +8,65 @@
 
 namespace Microsoft.Maui.DeviceTests
 {
+	[CollectionDefinition(MauiDoneAccessoryViewAppContextSwitchCollection.Name, DisableParallelization = true)]
+	public class MauiDoneAccessoryViewAppContextSwitchCollection
+	{
+		public const string Name = "MauiDoneAccessoryView AppContext switch";
+	}
+
 	[Category(TestCategory.Entry)]
+	[Collection(MauiDoneAccessoryViewAppContextSwitchCollection.Name)]
 	public class MauiDoneAccessoryViewTests : TestBase
 	{
-		// iOS 26+ shows the floating, pass-through Liquid Glass close button; earlier versions keep the
-		// original full-width touch-blocking Done toolbar. The expected behavior differs by path.
-		static bool UsesGlassButton => OperatingSystem.IsIOSVersionAtLeast(26);
+		// iOS 26+ shows the floating, pass-through Liquid Glass close button by default; earlier versions
+		// and apps using the compatibility switch keep the original full-width touch-blocking Done toolbar.
+		static bool UsesGlassButton =>
+			OperatingSystem.IsIOSVersionAtLeast(26) &&
+			!(AppContext.TryGetSwitch(MauiDoneAccessoryView.UseLegacyDoneAccessorySwitch, out var useLegacyDoneAccessory) && useLegacyDoneAccessory);
+
+		[Fact]
+		public async Task LegacyDoneAccessorySwitchSelectsExpectedImplementation()
+		{
+			var wasConfigured = AppContext.TryGetSwitch(
+				MauiDoneAccessoryView.UseLegacyDoneAccessorySwitch,
+				out var previousValue);
+
+			try
+			{
+				await InvokeOnMainThreadAsync(() =>
+				{
+					if (!wasConfigured)
+					{
+						using var defaultAccessoryView = CreateLaidOutAccessoryView();
+						AssertUsesGlassButton(defaultAccessoryView, OperatingSystem.IsIOSVersionAtLeast(26));
+					}
+
+					AppContext.SetSwitch(MauiDoneAccessoryView.UseLegacyDoneAccessorySwitch, false);
+					using var modernAccessoryView = CreateLaidOutAccessoryView();
+
+					AssertUsesGlassButton(modernAccessoryView, OperatingSystem.IsIOSVersionAtLeast(26));
+
+					var wasClicked = false;
+					AppContext.SetSwitch(MauiDoneAccessoryView.UseLegacyDoneAccessorySwitch, true);
+					using var legacyAccessoryView = CreateLaidOutAccessoryView(() => wasClicked = true);
+
+					AssertUsesGlassButton(modernAccessoryView, OperatingSystem.IsIOSVersionAtLeast(26));
+					AssertUsesGlassButton(legacyAccessoryView, false);
+
+					legacyAccessoryView.SendDoneClicked();
+					Assert.True(wasClicked);
+
+					AppContext.SetSwitch(MauiDoneAccessoryView.UseLegacyDoneAccessorySwitch, false);
+					AssertUsesGlassButton(legacyAccessoryView, false);
+				});
+			}
+			finally
+			{
+				AppContext.SetSwitch(
+					MauiDoneAccessoryView.UseLegacyDoneAccessorySwitch,
+					wasConfigured && previousValue);
+			}
+		}
 
 		[Theory]
 		[InlineData(UISemanticContentAttribute.ForceLeftToRight, false)]
@@ -30,7 +83,7 @@ await InvokeOnMainThreadAsync(() =>
 				var hitView = accessoryView.HitTest(new CGPoint(transparentHitX, accessoryView.Bounds.GetMidY()), null);
 
 				if (UsesGlassButton)
-					Assert.Null(hitView); // iOS 26+ floating button lets taps pass through to the field behind
+					Assert.Null(hitView); // floating button lets taps pass through to the field behind
 				else
 					Assert.NotNull(hitView); // classic toolbar keeps blocking taps across its full width
 			});
@@ -117,16 +170,16 @@ await InvokeOnMainThreadAsync(() =>
 
 				if (UsesGlassButton)
 				{
-					// iOS 26+: our floating close button supplies the localized "Done" label explicitly.
+					// The floating close button supplies the localized "Done" label explicitly.
 					var expected = Foundation.NSBundle.FromIdentifier("com.apple.UIKit").GetLocalizedString("Done");
 
 					Assert.False(string.IsNullOrEmpty(accessoryView.DoneButton?.AccessibilityLabel));
 					Assert.Equal(expected, accessoryView.DoneButton?.AccessibilityLabel);
 				}
 				else
 				{
-					// iOS < 26: the classic UIToolbar hosts a UIBarButtonSystemItem.Done, which UIKit
-					// localizes for us — so the accessory is a translucent toolbar and needs no manual label.
+					// The classic UIToolbar hosts a UIBarButtonSystemItem.Done, which UIKit localizes
+					// for us, so the accessory is a translucent toolbar and needs no manual label.
 					var toolbar = Assert.IsType<UIToolbar>(Assert.Single(accessoryView.Subviews));
 					Assert.True(toolbar.Translucent);
 				}
@@ -150,6 +203,22 @@ static MauiDoneAccessoryView CreateLaidOutAccessoryView(
 			return accessoryView;
 		}
 
+		static void AssertUsesGlassButton(MauiDoneAccessoryView accessoryView, bool expected)
+		{
+			var backgroundPoint = new CGPoint(accessoryView.Bounds.GetMinX() + 1, accessoryView.Bounds.GetMidY());
+
+			if (expected)
+			{
+				Assert.IsType<UIButton>(Assert.Single(accessoryView.Subviews));
+				Assert.Null(accessoryView.HitTest(backgroundPoint, null));
+			}
+			else
+			{
+				Assert.IsType<UIToolbar>(Assert.Single(accessoryView.Subviews));
+				Assert.NotNull(accessoryView.HitTest(backgroundPoint, null));
+			}
+		}
+
 		static CGPoint FindDoneButtonHitPoint(MauiDoneAccessoryView accessoryView, bool doneButtonIsLeading)
 		{
 			var y = accessoryView.Bounds.GetMidY();