Fixed shell pages with top bar

src/Controls/samples/Controls.Sample.UITests/Issues/Issue19159.xaml

@@ -0,0 +1,17 @@
+<?xml version="1.0" encoding="utf-8" ?>
+<Shell xmlns="http://schemas.microsoft.com/dotnet/2021/maui"
+             xmlns:x="http://schemas.microsoft.com/winfx/2009/xaml"
+            xmlns:local="clr-namespace:Maui.Controls.Sample.Issues"
+             x:Class="Maui.Controls.Sample.Issues.Issue19159">
+       <TabBar>
+           <Tab>
+             <ShellContent
+                 Title="Page 1"
+                 ContentTemplate="{x:DataTemplate local:Issue19159ContentPage}">
+             </ShellContent>
+             <ShellContent
+                 Title="Page 2"
+                 ContentTemplate="{x:DataTemplate local:Issue19159ContentPage}"/>
+            </Tab>
+        </TabBar>
+</Shell>

src/Controls/samples/Controls.Sample.UITests/Issues/Issue19159.xaml.cs

@@ -0,0 +1,30 @@
+using Microsoft.Maui.Controls;
+using Microsoft.Maui.Controls.Xaml;
+
+namespace Maui.Controls.Sample.Issues
+{
+	[XamlCompilation(XamlCompilationOptions.Compile)]
+	[Issue(IssueTracker.Github, 19159, "Top tab bar on Shell hides content", PlatformAffected.iOS)]
+	public partial class Issue19159 : Shell
+	{
+		public Issue19159()
+		{
+			InitializeComponent();
+		}
+	}
+
+	public class Issue19159ContentPage : ContentPage
+	{
+		public Issue19159ContentPage()
+		{
+			Content = new StackLayout()
+			{
+				AutomationId = "page",
+				HorizontalOptions = LayoutOptions.Fill,
+				VerticalOptions = LayoutOptions.Fill,
+				BackgroundColor = new Microsoft.Maui.Graphics.Color(255, 0, 0),
+				Margin = new Microsoft.Maui.Thickness(10)
+			};
+		}
+	}
+}

src/Controls/src/Core/Page/Page.cs

@@ -18,7 +18,7 @@ namespace Microsoft.Maui.Controls
 	/// </summary>
 	/// <remarks><see cref = "Page" /> is primarily a base class for more useful derived types. Objects that are derived from the <see cref="Page"/> class are most prominently used as the top level UI element in .NET MAUI applications. In addition to their role as the main pages of applications, <see cref="Page"/> objects and their descendants can be used with navigation classes, such as <see cref="NavigationPage"/> or <see cref="FlyoutPage"/>, among others, to provide rich user experiences that conform to the expected behaviors on each platform.
 	/// </remarks>
-	public partial class Page : VisualElement, ILayout, IPageController, IElementConfiguration<Page>, IPaddingElement, ISafeAreaView, ISafeAreaView2, IView, ITitledElement, IToolbarElement
+	public partial class Page : VisualElement, ILayout, IPageController, IElementConfiguration<Page>, IPaddingElement, ISafeAreaView, ISafeAreaView2, IView, ITitledElement, IToolbarElement, IShellContentInsetObserver
 	{
 		/// <summary>
 		/// The identifier used by the internal messaging system to set <see cref="IsBusy"/>.
@@ -73,6 +73,8 @@ public partial class Page : VisualElement, ILayout, IPageController, IElementCon
 
 		View _titleView;
 
+		ShellSection _shellSection;
+
 		List<Action> _pendingActions = new List<Action>();
 
 		/// <summary>
@@ -486,6 +488,20 @@ protected override void OnParentSet()
 		{
 			if (!Application.IsApplicationOrWindowOrNull(RealParent) && !(RealParent is Page) && !(RealParent is BaseShellItem))
 				throw new InvalidOperationException("Parent of a Page must also be a Page");
+
+			var parent = Parent;
+			while (!Application.IsApplicationOrWindowOrNull(parent))
+			{
+				if (parent is ShellSection shellSection)
+				{
+					_shellSection = shellSection;
+					((IShellSectionController)shellSection).AddContentInsetObserver(this);
+					break;
+				}
+
+				parent = parent.Parent;
+			}
+
 			base.OnParentSet();
 		}
 
@@ -644,6 +660,12 @@ public void SendDisappearing()
 			var pageContainer = this as IPageContainer<Page>;
 			pageContainer?.CurrentPage?.SendDisappearing();
 
+			if (_shellSection != null)
+			{
+				((IShellSectionController)_shellSection).RemoveContentInsetObserver(this);
+				_shellSection = null;
+			}
+
 			OnDisappearing();
 			Disappearing?.Invoke(this, EventArgs.Empty);
 
@@ -853,5 +875,13 @@ protected virtual void OnNavigatedFrom(NavigatedFromEventArgs args) { }
 		/// <returns>The <see cref="Window"/> instance that parents the page.</returns>
 		public virtual Window GetParentWindow()
 			=> this.FindParentOfType<Window>();
+
+		/// <summary>
+		/// Adds inset to the page if the page is a part of a shell
+		/// </summary>
+		void IShellContentInsetObserver.OnInsetChanged(Thickness inset, double tabThickness)
+		{
+			Padding = new Thickness(inset.Left, inset.Top + tabThickness, inset.Right, inset.Bottom);
+		}
 	}
 }

src/Controls/tests/UITests/Tests/Issues/Issue19159.cs

@@ -0,0 +1,25 @@
+using NUnit.Framework;
+using UITest.Appium;
+using UITest.Core;
+
+namespace Microsoft.Maui.AppiumTests.Issues
+{
+	public class Issue19159 : _IssuesUITest
+	{
+		public Issue19159(TestDevice device) : base(device)
+		{
+		}
+
+		public override string Issue => "Top tab bar on Shell hides content";
+
+		[Test]
+		public void ContentShouldNotBeOverlaidByTopBar()
+		{
+			this.IgnoreIfPlatforms(new TestDevice[] { TestDevice.Mac, TestDevice.Windows | TestDevice.Android });
+			_ = App.WaitForElement("page1");
+
+			// The content should not be overlaid by top bar
+			VerifyScreenshot();
+		}
+	}
+}