Fix for [iOS] Use non-overridden traits in AppInfoImplementation.RequestTheme

src/Controls/tests/TestCases.HostApp/Issues/Issue23411.xaml

@@ -0,0 +1,38 @@
+<?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.Issue23411">
+
+  <ScrollView AutomationId="ThemePage">
+    <VerticalStackLayout
+            Padding="30,0"
+            Spacing="25">
+      <Image
+                Source="dotnet_bot.png"
+                HeightRequest="185"
+                Aspect="AspectFit"
+                SemanticProperties.Description="dot net bot in a race car number eight" />
+
+      <Label  AutomationId="ThemeLabel" x:Name="ThemeLabelText"
+                Text="Hello, World!"
+                SemanticProperties.HeadingLevel="Level1" />
+
+      <Label
+                Text="Welcome to &#10;.NET Multi-platform App UI"
+                SemanticProperties.HeadingLevel="Level2"
+                SemanticProperties.Description="Welcome to dot net Multi platform App U I" />
+
+      <Button   AutomationId="ModalPageButton"
+                x:Name="ModalPageBtn"
+                Text="Open modal page"
+                Clicked="OnModalPage"
+                HorizontalOptions="Fill" />
+
+      <Button AutomationId="ResetThemeButton"
+                x:Name="ResetThemeBtn"
+                Text="Reset theme"
+                Clicked="OnResetTheme"
+                HorizontalOptions="Fill" />
+    </VerticalStackLayout>
+  </ScrollView>
+</ContentPage>

src/Controls/tests/TestCases.HostApp/Issues/Issue23411.xaml.cs

@@ -0,0 +1,86 @@
+using Microsoft.Maui.Controls;
+using Microsoft.Maui.Controls.PlatformConfiguration;
+using Microsoft.Maui.Controls.PlatformConfiguration.iOSSpecific;
+using Application = Microsoft.Maui.Controls.Application;
+using NavigationPage = Microsoft.Maui.Controls.NavigationPage;
+
+namespace Maui.Controls.Sample.Issues
+{
+	[Issue(IssueTracker.Github, 23411, "[iOS]Use non-overridden traits in AppInfoImplementation.RequestTheme",
+		PlatformAffected.iOS)]
+   public partial class Issue23411 : ContentPage
+    {
+        public Issue23411()
+        {
+            InitializeComponent();
+        }
+
+        protected override async void OnAppearing()
+        {
+            Application.Current.UserAppTheme = AppTheme.Dark;
+            await Task.Delay(500);
+            base.OnAppearing();
+        }
+        private void OnModalPage(object sender, EventArgs e)
+        {
+#if IOS
+            var modalPage = new Microsoft.Maui.Controls.NavigationPage(new Issue23411Pagesheet() { Title = "Modal Page" ,AutomationId = "PageSheetModalPage" });
+            modalPage.On<iOS>().SetModalPresentationStyle(UIModalPresentationStyle.PageSheet);
+            Navigation.PushModalAsync(modalPage);
+#endif
+        }
+
+        private  void OnResetTheme(object sender, EventArgs e)
+        {
+            Application.Current.UserAppTheme = AppTheme.Unspecified;
+        }
+    }
+
+    public partial class Issue23411Pagesheet : ContentPage
+    {
+        private Label ThemeLabelText;
+        private Button ResetThemeButton;
+
+        public Issue23411Pagesheet()
+        {
+            InitializeComponents();
+        }
+
+        private void InitializeComponents()
+        {
+            // Create Label
+            ThemeLabelText = new Label
+            {
+                Text = "Current Theme",
+                AutomationId = "ThemePageLabel",
+                HorizontalOptions = LayoutOptions.Center,
+                VerticalOptions = LayoutOptions.CenterAndExpand
+            };
+
+            // Create Button
+            ResetThemeButton = new Button
+            {
+                Text = "Reset Theme",
+                AutomationId = "ResetThemePageButton",
+                HorizontalOptions = LayoutOptions.Center,
+                VerticalOptions = LayoutOptions.CenterAndExpand
+            };
+            ResetThemeButton.Clicked += OnResetTheme;
+
+            // Create Layout
+            var stackLayout = new StackLayout
+            {
+                Children = { ThemeLabelText, ResetThemeButton },
+            };
+
+            // Set the page content to the layout
+            Content = stackLayout;
+        }
+
+        private void OnResetTheme(object sender, EventArgs e)
+        {
+            Application.Current.UserAppTheme = AppTheme.Unspecified;
+            ThemeLabelText.Text = "Theme reset to Unspecified";
+        }
+    }
+}

src/Controls/tests/TestCases.Shared.Tests/Tests/Issues/Issue23411.cs

@@ -0,0 +1,31 @@
+#if IOS
+using NUnit.Framework.Legacy;
+using NUnit.Framework;
+using UITest.Appium;
+using UITest.Core;
+
+namespace Microsoft.Maui.TestCases.Tests.Issues
+{
+    internal class Issue23411 : _IssuesUITest
+	{
+		public override string Issue => "[iOS]Use non-overridden traits in AppInfoImplementation.RequestTheme";
+
+		public Issue23411(TestDevice device) : base(device)
+		{
+		}
+
+		[Test]
+		[Category(UITestCategories.Page)]
+		public void ThemeUnspecifiedDoesNotAffectModalPageSheet()
+		{
+			// Is a iOS issue; see https://github.com/dotnet/maui/issues/23411
+			App.WaitForElement("ModalPageButton");
+			App.Tap("ModalPageButton");
+			App.WaitForElement("PageSheetModalPage");
+			App.WaitForElement("ResetThemePageButton");
+			App.Tap("ResetThemePageButton");
+			VerifyScreenshot();
+		}
+	}
+}
+#endif

src/Essentials/src/AppInfo/AppInfo.ios.tvos.watchos.macos.cs

@@ -54,9 +54,9 @@ public AppTheme RequestedTheme
 				if ((OperatingSystem.IsIOS() && !OperatingSystem.IsIOSVersionAtLeast(13, 0)) || (OperatingSystem.IsTvOS() && !OperatingSystem.IsTvOSVersionAtLeast(13, 0)))
 					return AppTheme.Unspecified;
 
-				var traits =
-					MainThread.InvokeOnMainThread(() => WindowStateManager.Default.GetCurrentUIViewController()?.TraitCollection) ??
-					UITraitCollection.CurrentTraitCollection;
+			    // This always returns the non-overridden trais which allows restoring the
+				// application back to the system theme.
+				var traits = UIScreen.MainScreen.TraitCollection;
 
 				var uiStyle = traits.UserInterfaceStyle;