Add Window.FromPoint API

src/Eto.Gtk/Forms/WindowHandler.cs

@@ -0,0 +1,49 @@
+using Eto.Drawing;
+using Eto.Forms;
+using System.Linq;
+
+namespace Eto.GtkSharp.Forms
+{
+	public class WindowHandler : Window.IWindowHandler
+	{
+		public Window FromPoint(PointF point)
+		{
+			var screenWindowStackWorks = false;
+			var windowStack = Gdk.Screen.Default.WindowStack;
+			// doesn't work on Mac.. can't figure out if it works on windows 🤔
+			if (windowStack != null)
+			{
+				foreach (var gdkWindow in windowStack.Reverse())
+				{
+					screenWindowStackWorks = true;
+					if (!gdkWindow.FrameExtents.Contains((int)point.X, (int)point.Y))
+						continue;
+
+					foreach (var window in Application.Instance.Windows)
+					{
+						if (window.Handler is IGtkWindow handler && handler.Control.Window?.Handle == gdkWindow.Handle)
+						{
+							return window;
+						}
+					}
+				}
+			}
+
+			if (!screenWindowStackWorks)
+			{
+				// fallback to looking at all windows in no particular order.
+				// TODO: this needs a proper implementation for Mac and possibly also for Windows,
+				// depending on whether Screen.WindowStack actually works there.
+				var pt = Point.Round(point);
+				foreach (var window in Application.Instance.Windows)
+				{
+					if (window.Bounds.Contains(pt))
+					{
+						return window;
+					}
+				}
+			}
+			return null;
+		}
+	}
+}

src/Eto.Gtk/Platform.cs

@@ -222,6 +222,7 @@ public static void AddTo(Eto.Platform p)
 			p.Add<FixedMaskedTextProvider.IHandler>(() => new FixedMaskedTextProviderHandler());
 			p.Add<DataObject.IHandler>(() => new DataObjectHandler());
 			p.Add<DataFormats.IHandler>(() => new DataFormatsHandler());
+			p.Add<Window.IWindowHandler>(() => new WindowHandler());
 			if (EtoEnvironment.Platform.IsLinux)
 			{
 				p.Add<TrayIndicator.IHandler>(() => new LinuxTrayIndicatorHandler());

src/Eto.Mac/Forms/WindowHandler.cs

@@ -0,0 +1,37 @@
+using Eto.Drawing;
+using Eto.Forms;
+using System.Linq;
+#if XAMMAC2
+using AppKit;
+using Foundation;
+using CoreGraphics;
+using ObjCRuntime;
+using CoreAnimation;
+#else
+using MonoMac.AppKit;
+using MonoMac.Foundation;
+using MonoMac.CoreGraphics;
+using MonoMac.ObjCRuntime;
+using MonoMac.CoreAnimation;
+#endif
+
+namespace Eto.Mac.Forms
+{
+	public class WindowHandler : Window.IWindowHandler
+	{
+		public Window FromPoint(PointF point)
+		{
+			var mainFrame = NSScreen.Screens[0].Frame;
+			var nspoint = new CGPoint(point.X, mainFrame.Height - point.Y);
+			var windowNumber = NSWindow.WindowNumberAtPoint(nspoint, 0);
+			foreach (var window in Application.Instance.Windows)
+			{
+				if (window.Handler is IMacWindow handler && handler.Control.WindowNumber == windowNumber)
+				{
+					return window;
+				}
+			}
+			return null;
+		}
+	}
+}

src/Eto.Mac/Platform.cs

@@ -287,6 +287,7 @@ public static void AddTo(Eto.Platform p)
 			p.Add<TrayIndicator.IHandler>(() => new TrayIndicatorHandler());
 			p.Add<DataFormats.IHandler>(() => new DataFormatsHandler());
 			p.Add<Taskbar.IHandler>(() => new TaskbarHandler());
+			p.Add<Window.IWindowHandler>(() => new WindowHandler());
 
 			// IO
 			p.Add<SystemIcons.IHandler>(() => new SystemIconsHandler());

src/Eto.WinForms/Forms/WindowHandler.cs

@@ -16,9 +16,27 @@ public interface IWindowHandler
 		swf.IWin32Window Win32Window { get; }
 	}
 
-	static class WindowHandler
+	public class WindowHandler : Window.IWindowHandler
 	{
 		internal static readonly object MovableByWindowBackground_Key = new object();
+
+		public Window FromPoint(PointF point)
+		{
+			var screenPoint = point.LogicalToScreen();
+			var windowHandle = Win32.WindowFromPoint(new Win32.POINT(screenPoint.X, screenPoint.Y));
+			if (windowHandle == IntPtr.Zero)
+				return null;
+			windowHandle = Win32.GetAncestor(windowHandle, Win32.GA.GA_ROOT);
+
+			foreach (var window in Application.Instance.Windows)
+			{
+				if (window.NativeHandle == windowHandle)
+				{
+					return window;
+				}
+			}
+			return null;
+		}
 	}
 
 	public abstract class WindowHandler<TControl, TWidget, TCallback> : WindowsPanel<TControl, TWidget, TCallback>, Window.IHandler, IWindowHandler

src/Eto.WinForms/Platform.cs

@@ -173,6 +173,7 @@ public static void AddTo(Eto.Platform p)
 			p.Add<DataObject.IHandler>(() => new DataObjectHandler());
 			p.Add<DataFormats.IHandler>(() => new DataFormatsHandler());
 			p.Add<Taskbar.IHandler>(() => new TaskbarHandler());
+			p.Add<Window.IWindowHandler>(() => new WindowHandler());
 
 			// IO
 			p.Add<SystemIcons.IHandler>(() => new SystemIconsHandler());

src/Eto.WinForms/Win32.cs

@@ -492,5 +492,8 @@ public static IntPtr GetThreadFocusWindow(uint? threadId = null)
 
 		[DllImport("gdi32.dll")]
 		public static extern bool OffsetWindowOrgEx(IntPtr hdc, int nXOffset, int nYOffset, ref POINT lpPoint);
+
+		[DllImport("user32.dll")]
+		public static extern IntPtr WindowFromPoint(POINT lpPoint);
 	}
 }

src/Eto.Wpf/Forms/WindowHandler.cs

@@ -0,0 +1,30 @@
+using System;
+using Eto.Drawing;
+using Eto.Forms;
+
+namespace Eto.Wpf.Forms
+{
+
+	public class WindowHandler : Window.IWindowHandler
+	{
+		internal static readonly object MovableByWindowBackground_Key = new object();
+
+		public Window FromPoint(PointF point)
+		{
+			var screenPoint = point.LogicalToScreen();
+			var windowHandle = Win32.WindowFromPoint(new Win32.POINT(screenPoint.X, screenPoint.Y));
+			if (windowHandle == IntPtr.Zero)
+				return null;
+			windowHandle = Win32.GetAncestor(windowHandle, Win32.GA.GA_ROOT);
+
+			foreach (var window in Application.Instance.Windows)
+			{
+				if (window.NativeHandle == windowHandle)
+				{
+					return window;
+				}
+			}
+			return null;
+		}
+	}
+}

src/Eto.Wpf/Platform.cs

@@ -192,6 +192,7 @@ public static void AddTo(Eto.Platform p)
 			p.Add<DataObject.IHandler>(() => new DataObjectHandler());
 			p.Add<DataFormats.IHandler>(() => new DataFormatsHandler());
 			p.Add<Taskbar.IHandler>(() => new TaskbarHandler());
+			p.Add<Window.IWindowHandler>(() => new WindowHandler());
 
 			// IO
 			p.Add<SystemIcons.IHandler>(() => new SystemIconsHandler());

src/Eto/Forms/Window.cs

@@ -51,7 +51,7 @@ public enum WindowStyle
 	/// </summary>
 	public abstract class Window : Panel
 	{
-		new IHandler Handler { get { return (IHandler)base.Handler; } }
+		new IHandler Handler => (IHandler)base.Handler;
 
 		#region Events
 
@@ -204,6 +204,19 @@ static Window()
 			EventLookup.Register<Window>(c => c.OnWindowStateChanged(null), WindowStateChangedEvent);
 			EventLookup.Register<Window>(c => c.OnLogicalPixelSizeChanged(null), LogicalPixelSizeChangedEvent);
 		}
+
+		/// <summary>
+		/// Gets the window at the specified logical screen point.
+		/// </summary>
+		/// <remarks>
+		/// This should get the first Eto window directly underneath the specified point.
+		/// </remarks>
+		/// <param name="point">Point to find the window at</param>
+		/// <returns>Instance of a Window (Form or Dialog) underneath the specified point, or null if none found</returns>
+		public static Window FromPoint(PointF point)
+		{
+			return Platform.Instance.CreateShared<IWindowHandler>().FromPoint(point);
+		}
 
 		/// <summary>
 		/// Initializes a new instance of the <see cref="Eto.Forms.Window"/> class.
@@ -846,6 +859,22 @@ public void OnLogicalPixelSizeChanged(Window widget, EventArgs e)
 			/// <value><c>true</c> to auto size the window when its content changes, <c>false</c> to only auto size when first created</value>
 			bool AutoSize { get; set; }
 		}
+
+		/// <summary>
+		/// Handler interface for static methods of <see cref="Window"/>
+		/// </summary>
+		public interface IWindowHandler
+		{
+			/// <summary>
+			/// Gets the window at the specified logical screen point.
+			/// </summary>
+			/// <remarks>
+			/// This should get the first Eto window directly underneath the specified point.
+			/// </remarks>
+			/// <param name="point">Point to find the window at</param>
+			/// <returns>Instance of a Window (Form or Dialog) underneath the specified point, or null if none found</returns>
+			Window FromPoint(PointF point);
+		}
 
 		#endregion
 	}

test/Eto.Test/UnitTests/Forms/WindowTests.cs

@@ -7,6 +7,7 @@
 using System.Collections.Specialized;
 using Eto.Drawing;
 using System.Threading;
+using System.Threading.Tasks;
 
 namespace Eto.Test.UnitTests.Forms
 {
@@ -251,6 +252,27 @@ Label CreateLabel()
 				return layout;
 			});
 		}
+
+		[Test, ManualTest]
+		public void WindowFromPointShouldReturnWindowUnderPoint()
+		{
+			ManualForm("Move your mouse, it should show the title of the window under the mouse pointer",
+			form => {
+				var content = new Panel { MinimumSize = new Size(100, 100) };
+				var timer = new UITimer { Interval = 0.5 };
+				timer.Elapsed += (sender, e) => {
+					var window = Window.FromPoint(Mouse.Position);
+					content.Content = $"Window: {window?.Title}";
+				};
+				timer.Start();
+				form.Closed += (sender, e) => {
+					timer.Stop();	
+				};
+				form.Title = "Test Form";
+				return content;
+			}
+			);
+		}
 	}
 }