Windows: Ensure layouts without background participate in hit testing

src/Controls/tests/TestCases.HostApp/Issues/Issue32279.cs

@@ -0,0 +1,81 @@
+namespace Maui.Controls.Sample.Issues;
+
+[Issue(IssueTracker.Github, 32279, "TapGestureRecognizer does not work on layouts without a Background on Windows", PlatformAffected.UWP)]
+public class Issue32279 : TestContentPage
+{
+	const string TapAnchorNoBackground = "TapAnchorNoBackground";
+	const string TapAnchorWithBackground = "TapAnchorWithBackground";
+	const string ResultLabelNoBackground = "ResultLabelNoBackground";
+	const string ResultLabelWithBackground = "ResultLabelWithBackground";
+
+	protected override void Init()
+	{
+		var layout = new StackLayout
+		{
+			Spacing = 20,
+			Padding = new Thickness(20)
+		};
+
+		// ContentView with NO background
+		var resultLabelNoBackground = new Label
+		{
+			AutomationId = ResultLabelNoBackground,
+			Text = "Waiting",
+			FontSize = 18,
+		};
+
+		var contentViewNoBackground = new ContentView
+		{
+			HeightRequest = 200,
+			WidthRequest = 300,
+			Content = new Label
+			{
+				Text = "Tap below me (no background)",
+				AutomationId = TapAnchorNoBackground,
+				VerticalOptions = LayoutOptions.Start,
+				HorizontalOptions = LayoutOptions.Fill,
+				HorizontalTextAlignment = TextAlignment.Center,
+			}
+		};
+
+		contentViewNoBackground.GestureRecognizers.Add(new TapGestureRecognizer
+		{
+			Command = new Command(() => resultLabelNoBackground.Text = "Tapped"),
+		});
+
+		// ContentView WITH explicit background
+		var resultLabelWithBackground = new Label
+		{
+			AutomationId = ResultLabelWithBackground,
+			Text = "Waiting",
+			FontSize = 18,
+		};
+
+		var contentViewWithBackground = new ContentView
+		{
+			HeightRequest = 200,
+			WidthRequest = 300,
+			BackgroundColor = Colors.LightGray,
+			Content = new Label
+			{
+				Text = "Tap below me (with background)",
+				AutomationId = TapAnchorWithBackground,
+				VerticalOptions = LayoutOptions.Start,
+				HorizontalOptions = LayoutOptions.Fill,
+				HorizontalTextAlignment = TextAlignment.Center,
+			}
+		};
+
+		contentViewWithBackground.GestureRecognizers.Add(new TapGestureRecognizer
+		{
+			Command = new Command(() => resultLabelWithBackground.Text = "Tapped"),
+		});
+
+		layout.Children.Add(contentViewNoBackground);
+		layout.Children.Add(resultLabelNoBackground);
+		layout.Children.Add(contentViewWithBackground);
+		layout.Children.Add(resultLabelWithBackground);
+
+		Content = layout;
+	}
+}

src/Controls/tests/TestCases.Shared.Tests/Tests/Issues/Issue32279.cs

@@ -0,0 +1,45 @@
+using NUnit.Framework;
+using UITest.Appium;
+using UITest.Core;
+
+namespace Microsoft.Maui.TestCases.Tests.Issues;
+
+public class Issue32279 : _IssuesUITest
+{
+	const string TapAnchorNoBackground = "TapAnchorNoBackground";
+	const string TapAnchorWithBackground = "TapAnchorWithBackground";
+	const string ResultLabelNoBackground = "ResultLabelNoBackground";
+	const string ResultLabelWithBackground = "ResultLabelWithBackground";
+
+	public Issue32279(TestDevice device) : base(device) { }
+
+	public override string Issue => "TapGestureRecognizer does not work on layouts without a Background on Windows";
+
+	[Test]
+	[Category(UITestCategories.Gestures)]
+	public void TapOnLayoutWithNoBackgroundShouldWork()
+	{
+		var anchor = App.WaitForElement(TapAnchorNoBackground).GetRect();
+
+		// Tap below the label, inside the ContentView surface
+		App.TapCoordinates(anchor.CenterX(), anchor.Y + anchor.Height + 50);
+
+		var result = App.FindElement(ResultLabelNoBackground).GetText();
+
+		Assert.That(result, Is.EqualTo("Tapped"));
+	}
+
+	[Test]
+	[Category(UITestCategories.Gestures)]
+	public void TapOnLayoutWithBackgroundShouldWork()
+	{
+		var anchor = App.WaitForElement(TapAnchorWithBackground).GetRect();
+
+		// Tap below the label, inside the ContentView surface
+		App.TapCoordinates(anchor.CenterX(), anchor.Y + anchor.Height + 50);
+
+		var result = App.FindElement(ResultLabelWithBackground).GetText();
+
+		Assert.That(result, Is.EqualTo("Tapped"));
+	}
+}

src/Core/src/Platform/Windows/ContentPanel.cs

@@ -11,6 +11,7 @@
 using Microsoft.UI.Xaml;
 using Microsoft.UI.Xaml.Hosting;
 using Microsoft.UI.Xaml.Shapes;
+using Microsoft.UI.Xaml.Media;
 
 namespace Microsoft.Maui.Platform
 {
@@ -71,6 +72,9 @@ public ContentPanel()
 			EnsureBorderPath(containsCheck: false);
 
 			SizeChanged += ContentPanelSizeChanged;
+
+			RegisterPropertyChangedCallback(BackgroundProperty, OnBackgroundPropertyChanged);
+			EnsureHitTestBackground();
 		}
 
 		void ContentPanelSizeChanged(object sender, SizeChangedEventArgs e)
@@ -109,6 +113,22 @@ internal void EnsureBorderPath(bool containsCheck = true)
 			}
 		}
 
+		static void OnBackgroundPropertyChanged(DependencyObject dependencyObject, DependencyProperty dependencyProperty)
+		{
+			if (dependencyObject is ContentPanel contentPanel)
+			{
+				contentPanel.EnsureHitTestBackground();
+			}
+		}
+
+		void EnsureHitTestBackground()
+		{
+			if (Background == null)
+			{
+				Background = new SolidColorBrush(UI.Colors.Transparent);
+			}
+		}
+
 		public void UpdateBackground(Paint? background)
 		{
 			if (_borderPath is null)