[iOS] Fix AdaptiveTrigger not working as expected

src/Controls/tests/TestCases.HostApp/Issues/Issue19197.xaml

@@ -0,0 +1,40 @@
+<?xml version="1.0" encoding="utf-8" ?>
+<ContentPage xmlns="http://schemas.microsoft.com/dotnet/2021/maui"
+              xmlns:x="http://schemas.microsoft.com/winfx/2009/xaml"
+              x:Class="Maui.Controls.Sample.Issues.Issue19197">
+  <ContentPage.Resources>
+    <ResourceDictionary>
+
+      <Style TargetType="Label">
+        <Setter Property="VisualStateManager.VisualStateGroups">
+          <VisualStateGroupList>
+            <VisualStateGroup>
+              <VisualState x:Name="Vertical">
+                <VisualState.StateTriggers>
+                  <AdaptiveTrigger MinWindowWidth="0" />
+                </VisualState.StateTriggers>
+                <VisualState.Setters>
+                  <Setter Property="Text" Value="Vertical" />
+                </VisualState.Setters>
+              </VisualState>
+              <VisualState x:Name="Horizontal">
+                <VisualState.StateTriggers>
+                  <AdaptiveTrigger MinWindowWidth="800" />
+                </VisualState.StateTriggers>
+                <VisualState.Setters>
+                  <Setter Property="Text" Value="Horizontal" />
+                </VisualState.Setters>
+              </VisualState>
+            </VisualStateGroup>
+          </VisualStateGroupList>
+        </Setter>
+      </Style>
+    </ResourceDictionary>
+  </ContentPage.Resources>
+  <Grid>
+    <Label
+       AutomationId="WaitForStubControl"
+       HorizontalOptions="Center"
+       VerticalOptions="Center" />
+  </Grid>
+</ContentPage> 

src/Controls/tests/TestCases.HostApp/Issues/Issue19197.xaml.cs

@@ -0,0 +1,15 @@
+using Microsoft.Maui.Controls;
+using Microsoft.Maui.Controls.Xaml;
+
+namespace Maui.Controls.Sample.Issues
+{
+	[XamlCompilation(XamlCompilationOptions.Compile)]
+	[Issue(IssueTracker.Github, 19197, "AdaptiveTrigger does not work", PlatformAffected.iOS)]
+	public partial class Issue19197 : ContentPage
+	{
+		public Issue19197()
+		{
+			InitializeComponent();
+		}
+	}
+}

src/Controls/tests/TestCases.Shared.Tests/Tests/Issues/Issue19197.cs

@@ -0,0 +1,30 @@
+#if TEST_FAILS_ON_ANDROID && TEST_FAILS_ON_CATALYST && TEST_FAILS_ON_WINDOWS 
+// Test failing on Android.
+// The test fails on Windows and MacCatalyst because the SetOrientation method, which is intended to change the device orientation, is only supported on mobile platforms Android and iOS.
+using NUnit.Framework;
+using UITest.Appium;
+using UITest.Core;
+
+namespace Microsoft.Maui.TestCases.Tests.Issues
+{
+	public class Issue19197 : _IssuesUITest
+	{
+		public Issue19197(TestDevice device) : base(device)
+		{
+		}
+
+		public override string Issue => "AdaptiveTrigger does not work";
+
+		[Test]
+		[Category(UITestCategories.Page)]
+		public void AdaptiveTriggerWorks()
+		{
+			App.WaitForElement("WaitForStubControl");
+			App.SetOrientationLandscape();
+			var text = App.FindElement("WaitForStubControl").GetText();
+			Assert.That(text, Is.EqualTo("Horizontal"));
+			App.SetOrientationPortrait();
+		}
+	}
+}
+#endif

src/Core/src/Handlers/Window/WindowHandler.iOS.cs

@@ -6,16 +6,19 @@ namespace Microsoft.Maui.Handlers
 {
 	public partial class WindowHandler : ElementHandler<IWindow, UIWindow>
 	{
-		readonly WindowProxy _proxy = new();
+		readonly WindowProxy _windowProxy = new();
+		readonly FrameObserverProxy _frameObserverProxy = new();
 
 		protected override void ConnectHandler(UIWindow platformView)
 		{
 			base.ConnectHandler(platformView);
 
+			_frameObserverProxy.Connect(VirtualView, platformView);
+
 			// For newer Mac Catalyst versions, we want to wait until we get effective window dimensions from the platform.
 			if (OperatingSystem.IsMacCatalystVersionAtLeast(16))
 			{
-				_proxy.Connect(VirtualView, platformView);
+				_windowProxy.Connect(VirtualView, platformView);
 			}
 			else
 			{
@@ -27,7 +30,8 @@ protected override void DisconnectHandler(UIWindow platformView)
 		{
 			if (OperatingSystem.IsMacCatalystVersionAtLeast(16))
 			{
-				_proxy.Disconnect();
+				_windowProxy.Disconnect();
+				_frameObserverProxy.Disconnect(platformView);
 			}
 
 			base.DisconnectHandler(platformView);
@@ -167,5 +171,43 @@ void HandleEffectiveGeometryObserved(NSObservedChange obj)
 				}
 			}
 		}
+
+		class FrameObserverProxy
+		{
+			WeakReference<IWindow>? _virtualView;
+			WeakReference<UIWindow>? _platformView;
+
+			IDisposable? _frameObserver;
+
+			IWindow? VirtualView => _virtualView is not null && _virtualView.TryGetTarget(out var v) ? v : null;
+
+			UIWindow? PlatformView => _platformView is not null && _platformView.TryGetTarget(out var v) ? v : null;
+
+			public void Connect(IWindow virtualView, UIWindow platformView)
+			{
+				_virtualView = new(virtualView);
+				_platformView = new(platformView);
+
+				_frameObserver = platformView.AddObserver("frame", Foundation.NSKeyValueObservingOptions.New, FrameAction);
+			}
+
+			public void Disconnect(UIWindow platformView)
+			{
+				_virtualView = null;
+				_platformView = null;
+
+				_frameObserver?.Dispose();
+			}
+
+			public void Update()
+			{
+				if (VirtualView is IWindow virtualView && PlatformView is UIWindow platformView)
+				{
+					virtualView.FrameChanged(platformView.Frame.ToRectangle());
+				}
+			}
+
+			void FrameAction(Foundation.NSObservedChange obj) => Update();
+		}
 	}
 }