Fixed Incorrect Window.Y and Window.Height values when closing a maximized window

src/Controls/tests/DeviceTests/Elements/Window/WindowTests.Windows.cs

@@ -154,6 +154,67 @@ await CreateHandlerAndAddToWindow<IWindowHandler>(mainPage, async (handler) =>
 			});
 		}
 
+		[Fact]
+		public async Task WindowsBoundsWhenMaximized()
+		{
+			SetupBuilder();
+			var mainPage = new NavigationPage(new ContentPage());
+
+			await CreateHandlerAndAddToWindow<IWindowHandler>(mainPage, async (handler) =>
+			{
+				var appWindowPlatform = handler.PlatformView.GetAppWindow();
+				Assert.NotNull(appWindowPlatform?.Presenter);
+				var presenter = Assert.IsType<OverlappedPresenter>(appWindowPlatform.Presenter);
+
+				// maximize window
+				presenter.Maximize();
+				var appWindow = handler.PlatformView.GetWindow();
+				await AssertEventually(() => appWindow.X == 0);
+				await AssertEventually(() => appWindow.Y == 0);
+				// Verify width and height are non-zero (regression: Height was reported as 0 when maximized)
+				await AssertEventually(() => appWindow.Width > 0);
+				await AssertEventually(() => appWindow.Height > 0);
+			});
+		}
+
+		[Fact]
+		public async Task WindowsYAndHeightCorrectWhenClosingMaximizedWindow()
+		{
+			SetupBuilder();
+			var mainPage = new NavigationPage(new ContentPage());
+
+			double destroyingY = double.NaN;
+			double destroyingHeight = double.NaN;
+
+			await CreateHandlerAndAddToWindow<IWindowHandler>(mainPage, async (handler) =>
+			{
+				var window = handler.VirtualView as Window;
+				Assert.NotNull(window);
+
+				var appWindowPlatform = handler.PlatformView.GetAppWindow();
+				Assert.NotNull(appWindowPlatform?.Presenter);
+				var presenter = Assert.IsType<OverlappedPresenter>(appWindowPlatform.Presenter);
+
+				// Capture the frame values at destroy time so we can verify them after cleanup
+				window.Destroying += (s, e) =>
+	   {
+				 destroyingY = window.Y;
+				 destroyingHeight = window.Height;
+			 };
+
+				// Maximize the window and wait until the frame update reflects the maximized bounds
+				presenter.Maximize();
+				await AssertEventually(() => window.Y == 0);
+				await AssertEventually(() => window.Height > 0);
+			});
+
+			// The window is destroyed during CreateHandlerAndAddToWindow cleanup.
+			// Verify that the Y and Height values at Destroying time were non-negative / non-zero.
+			Assert.False(double.IsNaN(destroyingHeight), "Window.Destroying event was not raised");
+			Assert.True(destroyingHeight > 0, $"Height should be > 0 when closing a maximized window, but was {destroyingHeight}");
+			Assert.True(destroyingY >= 0, $"Y should be >= 0 when closing a maximized window, but was {destroyingY}");
+		}
+
 		[Fact]
 		public async Task ToggleFullscreenTitleBarWorks()
 		{

src/Core/src/Handlers/Window/WindowHandler.Windows.cs

@@ -199,12 +199,32 @@ void OnWindowChanged(AppWindow sender, AppWindowChangedEventArgs args)
 
 			UpdateVirtualViewFrame(sender);
 		}
-
 		void UpdateVirtualViewFrame(AppWindow appWindow)
 		{
+			var hwnd = PlatformView.GetWindowHandle();
+			if (hwnd == IntPtr.Zero)
+			{
+				return;
+			}
+
+			var bounds = hwnd.GetExtendedFrameBounds();
+
 			var size = appWindow.Size;
 			var pos = appWindow.Position;
 
+			if (appWindow.Presenter is OverlappedPresenter presenter &&
+			 presenter.IsMaximizable &&
+			 presenter.State == OverlappedPresenterState.Maximized &&
+			 bounds.Width > 0 && bounds.Height > 0)
+			{
+				// If the window is maximized, we need to use the bounds of the window
+				// instead of the size and position of the app window.
+				// Only apply when GetExtendedFrameBounds returned a valid (non-empty) rect;
+				// if DWM failed (returned EmptyRect), keep the AppWindow values as fallback.
+				size = new SizeInt32((int)bounds.Width, (int)bounds.Height);
+				pos = new PointInt32((int)bounds.X, (int)bounds.Y);
+			}
+
 			var density = PlatformView.GetDisplayDensity();
 
 			VirtualView.FrameChanged(new Rect(

src/Core/src/Platform/Windows/WindowExtensions.cs

@@ -1,6 +1,7 @@
 using System;
 using System.Collections.Generic;
 using System.Linq;
+using System.Runtime.InteropServices;
 using Microsoft.Maui.ApplicationModel;
 using Microsoft.Maui.Devices;
 using Microsoft.Maui.Graphics;
@@ -14,6 +15,43 @@ namespace Microsoft.Maui.Platform
 {
 	public static partial class WindowExtensions
 	{
+		const int DWMWA_EXTENDED_FRAME_BOUNDS = 9;
+
+		[DllImport("dwmapi.dll", PreserveSig = true)]
+		 static extern int DwmGetWindowAttribute(
+			IntPtr hwnd,
+			int dwAttribute,
+			out PlatformMethods.RECT pvAttribute,
+			int cbAttribute);
+
+		static readonly Rect EmptyRect = new(0, 0, 0, 0);
+
+		internal static Rect GetExtendedFrameBounds(this IntPtr hwnd)
+		{
+			if (hwnd == IntPtr.Zero)
+			{
+				return EmptyRect;
+			}
+
+			try
+			{
+				PlatformMethods.RECT rect = default;
+				int result = DwmGetWindowAttribute(
+				hwnd,
+				DWMWA_EXTENDED_FRAME_BOUNDS,
+				out rect,
+				Marshal.SizeOf<PlatformMethods.RECT>());
+
+				return result == 0
+				? new Rect(rect.Left, rect.Top, rect.Right - rect.Left, rect.Bottom - rect.Top)
+				: EmptyRect;
+			}
+			catch
+			{
+				return EmptyRect;
+			}
+		}
+
 		internal static Rect[]? GetDefaultTitleBarDragRectangles(this UI.Xaml.Window platformWindow, IWindow window)
 		{
 			if (window?.Handler?.MauiContext is IMauiContext mauiContext)