fix(GTK): pointer events in wrong locations using Wayland

For GTK applications using Wayland the title bar is rendered by the
window itself and not by the composer. And it seems to me that GTK
counts the title bar as part of the window and uses it to trigger the
window events, leading to erroneous considerations about the size and
location of pointers in the area where it is used to draw the
components.

The fix adds a GtkEventBox in the window, instead of use the window
events we will be based on the events of the GtkEventBox which we can
assure that the GTK will take into account the title bar.

Related-to: #5706
Signed-off-by: Matheus Castello <matheus@castello.eng.br>

src/Uno.UI.Runtime.Skia.Gtk/GtkCoreWindowExtension.cs

@@ -49,19 +49,23 @@ public void SetPointerCapture()
 		public GtkCoreWindowExtension(object owner)
 		{
 			_owner = (CoreWindow)owner;
-			_ownerEvents = (ICoreWindowEvents)owner;
-
-			GtkHost.Window.AddEvents((int)RequestedEvents);
-
-			GtkHost.Window.EnterNotifyEvent += OnWindowEnterEvent;
-			GtkHost.Window.LeaveNotifyEvent += OnWindowLeaveEvent;
-			GtkHost.Window.ButtonPressEvent += OnWindowButtonPressEvent;
-			GtkHost.Window.ButtonReleaseEvent += OnWindowButtonReleaseEvent;
-			GtkHost.Window.MotionNotifyEvent += OnWindowMotionEvent;
-			GtkHost.Window.ScrollEvent += OnWindowScrollEvent;
-			GtkHost.Window.TouchEvent += OnWindowTouchEvent;
-			GtkHost.Window.ProximityInEvent += OnWindowProximityInEvent;
-			GtkHost.Window.ProximityOutEvent += OnWindowProximityOutEvent;
+			_ownerEvents = (ICoreWindowEvents)owner;
+
+			// even though we are not going to use events directly in the window here maintain the masks
+			GtkHost.Window.AddEvents((int)RequestedEvents);
+			// add masks for the GtkEventBox
+			GtkHost.EventBox.AddEvents((int)RequestedEvents);
+
+			// Use GtkEventBox to fix Wayland titlebar events
+			GtkHost.EventBox.EnterNotifyEvent += OnWindowEnterEvent;
+			GtkHost.EventBox.LeaveNotifyEvent += OnWindowLeaveEvent;
+			GtkHost.EventBox.ButtonPressEvent += OnWindowButtonPressEvent;
+			GtkHost.EventBox.ButtonReleaseEvent += OnWindowButtonReleaseEvent;
+			GtkHost.EventBox.MotionNotifyEvent += OnWindowMotionEvent;
+			GtkHost.EventBox.ScrollEvent += OnWindowScrollEvent;
+			GtkHost.EventBox.TouchEvent += OnWindowTouchEvent;
+			GtkHost.EventBox.ProximityInEvent += OnWindowProximityInEvent;
+			GtkHost.EventBox.ProximityOutEvent += OnWindowProximityOutEvent;
 
 			InitializeKeyboard();
 		}

src/Uno.UI.Runtime.Skia.Gtk/GtkHost.cs

@@ -26,11 +26,13 @@ public class GtkHost : ISkiaHost
 		private readonly string[] _args;
 		private readonly Func<WUX.Application> _appBuilder;
 		private static Gtk.Window _window;
+		private static Gtk.EventBox _eventBox;
 		private UnoDrawingArea _area;
 		private Fixed _fix;
 		private GtkDisplayInformationExtension _displayInformationExtension;
 
 		public static Gtk.Window Window => _window;
+		public static Gtk.EventBox EventBox => _eventBox;
 
 		public GtkHost(Func<WUX.Application> appBuilder, string[] args)
 		{
@@ -108,13 +110,15 @@ void Dispatch(System.Action d)
 				WUX.Window.Current.OnNativeSizeChanged(new Windows.Foundation.Size(e.Allocation.Width, e.Allocation.Height));
 			};
 
-			var overlay = new Overlay();			
-
-			_area = new UnoDrawingArea();
+			var overlay = new Overlay();
+
+			_eventBox = new EventBox();
+			_area = new UnoDrawingArea();
 			_fix = new Fixed();
 			overlay.Add(_area);
 			overlay.AddOverlay(_fix);
-			_window.Add(overlay);
+			_eventBox.Add(overlay);
+			_window.Add(_eventBox);
 
 			/* avoids double invokes at window level */
 			_area.AddEvents((int)GtkCoreWindowExtension.RequestedEvents);

src/Uno.UI.Runtime.Skia.Gtk/UI/Xaml/Controls/TextBoxViewExtension.cs

@@ -36,7 +36,8 @@ public TextBoxViewExtension(TextBoxView owner, GtkWindow window)
 
 		private Fixed GetWindowTextInputLayer()
 		{
-			var overlay = (Overlay)_window.Child;
+			// now we have the GtkEventBox
+			var overlay = (Overlay)((EventBox) _window.Child).Child;
 			return overlay.Children.OfType<Fixed>().First();
 		}