[Mac] Fix Titlebar content is not aligned to left on fullscreen

src/Controls/src/Core/TitleBar/TitleBar.cs

@@ -54,6 +54,40 @@ public partial class TitleBar : TemplatedView, ITitleBar, ISafeAreaView
 #if MACCATALYST
 		static int GetMacCatalystLeadingMargin() =>
 			OperatingSystem.IsMacCatalystVersionAtLeast(26) ? MacCatalystMarginLiquidGlass : MacCatalystMargin;
+
+		bool IsMacCatalystFullScreen()
+		{
+			if (OperatingSystem.IsMacCatalystVersionAtLeast(16)
+				&& Window?.Handler?.PlatformView is UIKit.UIWindow uiwindow)
+			{
+				return uiwindow.WindowScene?.FullScreen ?? false;
+			}
+
+			return false;
+		}
+
+		void ApplyMacCatalystMargin()
+		{
+			if (!_isDefaultControlTemplate)
+			{
+				return;
+			}
+
+			if (_templateRoot is not Grid contentGrid)
+			{
+				return;
+			}
+
+			if (IsMacCatalystFullScreen())
+			{
+				contentGrid.Margin = new Thickness(0);
+				return;
+			}
+
+			contentGrid.Margin = FlowDirection == FlowDirection.RightToLeft
+				? new Thickness(0, 0, GetMacCatalystLeadingMargin(), 0)
+				: new Thickness(GetMacCatalystLeadingMargin(), 0, 0, 0);
+		}
 #endif
 
 		// Margin space (150px) required for Windows title bar system buttons
@@ -313,21 +347,40 @@ public Color ForegroundColor
 
 		static ControlTemplate? _defaultTemplate;
 		View? _templateRoot;
+#if MACCATALYST
+		bool _isDefaultControlTemplate;
+#endif
 
 		public TitleBar()
 		{
 			PassthroughElements = new List<IView>();
 			PropertyChanged += TitleBar_PropertyChanged;
 
+#if MACCATALYST
+			SizeChanged += OnSizeChanged;
+#endif
+
 			if (ControlTemplate is null)
 			{
 				ControlTemplate = DefaultTemplate;
 			}
 		}
 
+#if MACCATALYST
+		void OnSizeChanged(object? sender, EventArgs e)
+		{
+			ApplyMacCatalystMargin();
+		}
+#endif
+
 		internal void Cleanup()
 		{
 			PropertyChanged -= TitleBar_PropertyChanged;
+
+#if MACCATALYST
+			SizeChanged -= OnSizeChanged;
+#endif
+
 			if (Window is not null)
 			{
 				Window.Activated -= Window_Activated;
@@ -358,6 +411,11 @@ void UpdateFlowDirectionState()
 				: TitleBarLTRState;
 
 			ApplyVisibleState(flowDirectionState);
+
+#if MACCATALYST
+			ApplyMacCatalystMargin();
+#endif
+
 		}
 
 		internal void ApplyVisibleState(string stateGroup)
@@ -391,6 +449,10 @@ protected override void OnApplyTemplate()
 
 			_templateRoot = controlTemplate?.TemplateRoot as View;
 
+#if MACCATALYST
+			_isDefaultControlTemplate = ReferenceEquals(ControlTemplate, DefaultTemplate);
+#endif
+
 			if (controlTemplate?.GetTemplateChild(TitleBarLeading) is IView leadingContent)
 			{
 				PassthroughElements.Add(leadingContent);
@@ -428,7 +490,7 @@ static View BuildDefaultTemplate()
 			var contentGrid = new Grid()
 			{
 #if MACCATALYST
-				Margin = new Thickness(GetMacCatalystLeadingMargin(), 0, 0, 0),
+				Margin = new Thickness(0),
 #endif
 				HorizontalOptions = LayoutOptions.Fill,
 				ColumnDefinitions =
@@ -630,30 +692,30 @@ static View BuildDefaultTemplate()
 
 			// Left-to-Right state (default)
 			var ltrState = new VisualState() { Name = TitleBarLTRState };
+
+#if !MACCATALYST
 			ltrState.Setters.Add(new Setter()
 			{
 				Property = MarginProperty,
 				TargetName = TemplateRootName,
-#if MACCATALYST
-				Value = new Thickness(GetMacCatalystLeadingMargin(), 0, 0, 0)  // System buttons on left in macOS
-#else
 				Value = new Thickness(0, 0, WindowsMargin, 0)  // System buttons on right in Windows
-#endif
 			});
+#endif
+
 			flowDirectionGroup.States.Add(ltrState);
 
 			// Right-to-Left state
 			var rtlState = new VisualState() { Name = TitleBarRTLState };
+
+#if !MACCATALYST
 			rtlState.Setters.Add(new Setter()
 			{
 				Property = MarginProperty,
 				TargetName = TemplateRootName,
-#if MACCATALYST
-				Value = new Thickness(0, 0, GetMacCatalystLeadingMargin(), 0)  // System buttons on right in macOS RTL
-#else
 				Value = new Thickness(WindowsMargin, 0, 0, 0)  // System buttons on left in Windows RTL
-#endif
 			});
+#endif
+
 			flowDirectionGroup.States.Add(rtlState);
 
 			visualStateGroups.Add(flowDirectionGroup);

src/Controls/tests/TestCases.HostApp/Issues/Issue30248.cs

@@ -0,0 +1,56 @@
+namespace Maui.Controls.Sample.Issues;
+
+[Issue(IssueTracker.Github, 30248, "TitleBar, MacCatalyst - content is not aligned to left on fullscreen", PlatformAffected.macOS)]
+
+public class Issue30248 : ContentPage
+{
+	public Issue30248()
+	{
+		Title = "Issue 30248";
+
+		// Create TitleBar
+		var titleBar = new TitleBar
+		{
+			Title = "Maui App",
+			Subtitle = "Hello, World!",
+			ForegroundColor = Colors.Red,
+			HeightRequest = 48
+		};
+
+		titleBar.LeadingContent = new Image {Source = "dotnet_bot.png", HeightRequest = 24};
+
+		// Set the TitleBar on the current Window when this page appears
+		this.Loaded += (sender, e) =>
+		{
+			if (Window != null)
+			{
+				Window.TitleBar = titleBar;
+			}
+		};
+
+		// Create the page content with a Label
+		Content = new VerticalStackLayout
+		{
+			Spacing = 25,
+			Padding = new Thickness(30),
+			VerticalOptions = LayoutOptions.Center,
+			Children =
+				{
+					new Label
+					{
+						Text = "TitleBar should be aligned to the left in fullscreen mode",
+						AutomationId = "TitleBarAlignmentLabel",
+						FontSize = 32,
+						HorizontalOptions = LayoutOptions.Center
+					},
+					new Button
+					{
+						Text = "Empty Button",
+						AutomationId = "EmptyButton",
+						HorizontalOptions = LayoutOptions.Center
+					}
+				}
+		};
+	}
+}
+

src/Controls/tests/TestCases.Shared.Tests/Tests/Issues/Issue30248.cs

@@ -0,0 +1,34 @@
+#if MACCATALYST    //This is the Mac Specific issue, so restricting other platforms
+using NUnit.Framework;
+using UITest.Appium;
+using UITest.Core;
+
+namespace Microsoft.Maui.TestCases.Tests.Issues;
+
+public class Issue30248 : _IssuesUITest
+{
+	public override string Issue => "TitleBar, MacCatalyst - content is not aligned to left on fullscreen";
+
+	public Issue30248(TestDevice device)
+	: base(device)
+	{ }
+
+	[Test]
+	[Category(UITestCategories.Window)]
+	public void VerifyTitleBarContentinFullScreenmode()
+	{
+		App.WaitForElement("TitleBarAlignmentLabel");
+		try
+		{
+			App.EnterFullScreen();
+			App.WaitForElement("TitleBarAlignmentLabel");
+			App.Tap("EmptyButton");
+			VerifyScreenshot(includeTitleBar: true);
+		}
+		finally
+		{
+			App.ExitFullScreen();
+		}
+	}
+}
+#endif