fix: Align Popup light-dismiss with WinUI

Handle pointer events exclusively on PopupPanel (not quite PopupRoot, but close). Rather than bounds-checking and adding handlers to the child content, just check the OriginalSource of the event, as WinUI does, to exclude events that are 'blocked' by the Popup content. This aligns Uno with WinUI in terms of hit-transparent areas of the content.

src/Uno.UI/UI/Xaml/Controls/Popup/Popup.Base.cs

@@ -122,23 +122,6 @@ partial void OnChildChangedPartial(UIElement oldChild, UIElement newChild)
 			UpdateDataContext(null);
 			UpdateTemplatedParent();
 			PropagateFocusProperties();
-
-			if (oldChild is FrameworkElement ocfe)
-			{
-				ocfe.PointerPressed -= HandlePointerEvent;
-				ocfe.PointerReleased -= HandlePointerEvent;
-			}
-
-			if (newChild is FrameworkElement ncfe)
-			{
-				ncfe.PointerPressed += HandlePointerEvent;
-				ncfe.PointerReleased += HandlePointerEvent;
-			}
-		}
-
-		private void HandlePointerEvent(object sender, PointerRoutedEventArgs e)
-		{
-			e.Handled = true;
 		}
 
 		protected internal override void OnDataContextChanged(DependencyPropertyChangedEventArgs e)

src/Uno.UI/UI/Xaml/Controls/Popup/Popup.cs

@@ -86,36 +86,6 @@ internal PopupPanel PopupPanel
 
 		private void OnPopupPanelChanged(PopupPanel oldHost, PopupPanel newHost)
 		{
-			// Note: On UWP if the popup is light dismissable, the popup is closed as soon as we get a PointerPressed
-			//		 Controls under the popup does not receive any Pointer event while the popup is open,
-			//		 and when light dismissed they receive the PointerReleased but not the pressed
-
-			if (oldHost != null)
-			{
-				oldHost.PointerPressed -= _handleIfOpenedAndTryDismiss; // Cf. comment about child pressed below
-
-				oldHost.PointerEntered -= _handleIfOpened;
-				oldHost.PointerExited -= _handleIfOpened;
-				oldHost.PointerMoved -= _handleIfOpened;
-				oldHost.PointerReleased -= _handleIfOpened;
-				oldHost.PointerCanceled -= _handleIfOpened;
-				oldHost.PointerCaptureLost -= _handleIfOpened;
-				oldHost.PointerWheelChanged -= _handleIfOpened;
-			}
-
-			if (newHost != null)
-			{
-				newHost.PointerPressed += _handleIfOpenedAndTryDismiss; // Cf. comment about child pressed below
-
-				newHost.PointerEntered += _handleIfOpened;
-				newHost.PointerExited += _handleIfOpened;
-				newHost.PointerMoved += _handleIfOpened;
-				newHost.PointerReleased += _handleIfOpened;
-				newHost.PointerCanceled += _handleIfOpened;
-				newHost.PointerCaptureLost += _handleIfOpened;
-				newHost.PointerWheelChanged += _handleIfOpened;
-			}
-
 			OnPopupPanelChangedPartial(oldHost, newHost);
 
 			ApplyLightDismissOverlayMode();
@@ -129,50 +99,6 @@ partial void OnVerticalOffsetChangedPartial(double oldVerticalOffset, double new
 		partial void OnHorizontalOffsetChangedPartial(double oldHorizontalOffset, double newHorizontalOffset)
 			=> PopupPanel?.InvalidateMeasure();
 
-		private static readonly PointerEventHandler _handleIfOpened = (snd, e) =>
-		{
-			var popup = ((PopupPanel)snd).Popup;
-			if (!popup.IsOpen || !popup.IsLightDismissEnabled)
-			{
-				return;
-			}
-
-			e.Handled = true;
-		};
-		private static readonly PointerEventHandler _handleIfOpenedAndTryDismiss = (snd, e) =>
-		{
-			var popup = ((PopupPanel)snd).Popup;
-			if (!popup.IsOpen || !popup.IsLightDismissEnabled)
-			{
-				return;
-			}
-
-			e.Handled = true;
-
-			if (popup.Child is FrameworkElement content)
-			{
-				var position = e.GetCurrentPoint(content).Position;
-				if (
-					position.X < 0 || position.X > content.ActualWidth
-								   || position.Y < 0 || position.Y > content.ActualHeight)
-				{
-					popup.IsOpen = false;
-				}
-			}
-			else if (popup.Child == null)
-			{
-				popup.Log().Warn($"Dismiss is not supported if the 'Child' is null.");
-			}
-			else
-			{
-				popup.Log().Warn($"Dismiss is not supported if the 'Child' ({popup.Child?.GetType()}) of the 'Popup' is not a 'FrameworkElement'.");
-			}
-
-			// Note: This is not the right way: we should instead listen for the PointerPressed directly on the Child
-			//		 so we should be able to still dismiss the Popup if the background if the Child is `null`.
-			//		 But this would require us to refactor more deeply the Popup which is not the purpose of the current work.
-		};
-
 		internal override void UpdateThemeBindings(Data.ResourceUpdateReason updateReason)
 		{
 			base.UpdateThemeBindings(updateReason);

src/Uno.UI/UI/Xaml/Controls/Popup/PopupPanel.cs

@@ -11,6 +11,7 @@
 using Windows.UI.Xaml.Media;
 using Uno.UI.DataBinding;
 using Uno.Foundation.Logging;
+using Windows.UI.Xaml.Input;
 
 #if XAMARIN_IOS
 using UIKit;
@@ -38,6 +39,7 @@ public PopupPanel(Popup popup)
 		{
 			Popup = popup ?? throw new ArgumentNullException(nameof(popup));
 			Visibility = Visibility.Collapsed;
+			PointerPressed += OnPointerPressed;
 		}
 
 		protected Size _lastMeasuredSize;
@@ -188,5 +190,18 @@ private protected override void OnUnloaded()
 			base.OnUnloaded();
 			this.SetLogicalParent(null);
 		}
+
+		// TODO: pointer handling should really go on PopupRoot. For now it's easier to put here because PopupRoot doesn't track open popups, and also we
+		// need to support native popups on Android that don't use PopupRoot.
+		private void OnPointerPressed(object sender, PointerRoutedEventArgs args)
+		{
+			// Make sure we are the original source.  We do not want to handle PointerPressed on the Popup itself.
+			if (args.OriginalSource == this && Popup is { } popup)
+			{
+				popup.IsOpen = false;
+			}
+		}
+
+		internal override bool IsViewHit() => Popup?.IsLightDismissEnabled ?? false;
 	}
 }