Fix Windows 10 title bar borders

src/common/ManagedCommon/NativeMethods.cs

@@ -42,6 +42,9 @@ internal static class NativeMethods
         [DllImport("user32.dll")]
         internal static extern uint SendInput(uint nInputs, INPUT[] pInputs, int cbSize);
 
+        [DllImport("dwmapi")]
+        internal static extern IntPtr DwmExtendFrameIntoClientArea(IntPtr hWnd, ref MARGINS pMarInset);
+
         [StructLayout(LayoutKind.Sequential)]
         public struct INPUT
         {
@@ -100,5 +103,14 @@ internal enum INPUTTYPE : uint
             INPUT_KEYBOARD = 1,
             INPUT_HARDWARE = 2,
         }
+
+        [StructLayout(LayoutKind.Sequential)]
+        internal struct MARGINS
+        {
+            public int cxLeftWidth;
+            public int cxRightWidth;
+            public int cyTopHeight;
+            public int cyBottomHeight;
+        }
     }
 }

src/common/ManagedCommon/WindowHelpers.cs

@@ -35,5 +35,17 @@ public static void BringToForeground(IntPtr handle)
                 }
             }
         }
+
+        /// <summary>
+        /// Workaround for a WinUI bug on Windows 10 in which a window's top border is always
+        /// black. Calls <c>DwmExtendFrameIntoClientArea()</c> with a <c>cyTopHeight</c> of 2 to force
+        /// the window's top border to be visible.<br/><br/>
+        /// Has no visible effect on Windows 11.
+        /// </summary>
+        public static void ForceTopBorder1PixelInset(IntPtr handle)
+        {
+            var margins = new NativeMethods.MARGINS { cxLeftWidth = 0, cxRightWidth = 0, cyBottomHeight = 0, cyTopHeight = 2 };
+            NativeMethods.DwmExtendFrameIntoClientArea(handle, ref margins);
+        }
     }
 }

src/modules/AdvancedPaste/AdvancedPaste/AdvancedPasteXAML/MainWindow.xaml.cs

@@ -82,6 +82,7 @@ double GetHeight(int maxCustomActionCount) =>
             };
 
             WindowHelpers.BringToForeground(this.GetWindowHandle());
+            WindowHelpers.ForceTopBorder1PixelInset(this.GetWindowHandle());
         }
 
         private void OnActivated(object sender, WindowActivatedEventArgs args)

src/modules/EnvironmentVariables/EnvironmentVariables/EnvironmentVariablesXAML/MainWindow.xaml.cs

@@ -40,6 +40,7 @@ public MainWindow()
             var handle = this.GetWindowHandle();
             RegisterWindow(handle);
 
+            WindowHelpers.ForceTopBorder1PixelInset(handle);
             WindowHelpers.BringToForeground(handle);
 
             MainPage = App.GetService<EnvironmentVariablesMainPage>();

src/modules/FileLocksmith/FileLocksmithUI/FileLocksmithXAML/MainWindow.xaml.cs

@@ -3,7 +3,7 @@
 // See the LICENSE file in the project root for more information.
 
 using System;
-
+using ManagedCommon;
 using Microsoft.UI.Windowing;
 using Microsoft.UI.Xaml;
 using Microsoft.UI.Xaml.Media;
@@ -22,6 +22,7 @@ public MainWindow(bool isElevated)
             SetTitleBar(AppTitleBar);
             Activated += MainWindow_Activated;
             AppWindow.SetIcon("Assets/FileLocksmith/Icon.ico");
+            WindowHelpers.ForceTopBorder1PixelInset(this.GetWindowHandle());
 
             var loader = ResourceLoaderInstance.ResourceLoader;
             var title = isElevated ? loader.GetString("AppAdminTitle") : loader.GetString("AppTitle");

src/modules/Hosts/Hosts/HostsXAML/MainWindow.xaml.cs

@@ -39,6 +39,7 @@ public MainWindow()
 
             var handle = this.GetWindowHandle();
 
+            WindowHelpers.ForceTopBorder1PixelInset(handle);
             WindowHelpers.BringToForeground(handle);
             Activated += MainWindow_Activated;
 

src/modules/peek/Peek.UI/PeekXAML/MainWindow.xaml.cs

@@ -48,7 +48,8 @@ public MainWindow()
             ViewModel = Application.Current.GetService<MainWindowViewModel>();
 
             TitleBarControl.SetTitleBarToWindow(this);
-            AppWindow.TitleBar.ExtendsContentIntoTitleBar = true;
+            ExtendsContentIntoTitleBar = true;
+            WindowHelpers.ForceTopBorder1PixelInset(this.GetWindowHandle());
             AppWindow.TitleBar.PreferredHeightOption = TitleBarHeightOption.Tall;
             AppWindow.SetIcon("Assets/Peek/Icon.ico");
 

src/modules/peek/Peek.UI/PeekXAML/Views/TitleBar.xaml.cs

@@ -231,7 +231,7 @@ private void UpdateTitleBarCustomization(MainWindow mainWindow)
             if (AppWindowTitleBar.IsCustomizationSupported())
             {
                 AppWindow appWindow = mainWindow.AppWindow;
-                appWindow.TitleBar.ExtendsContentIntoTitleBar = true;
+                mainWindow.ExtendsContentIntoTitleBar = true;
                 appWindow.TitleBar.ButtonBackgroundColor = Colors.Transparent;
                 appWindow.TitleBar.ButtonInactiveBackgroundColor = Colors.Transparent;
                 appWindow.TitleBar.ButtonForegroundColor = ThemeHelpers.GetAppTheme() == AppTheme.Light ? Colors.DarkSlateGray : Colors.White;

src/modules/registrypreview/RegistryPreview/RegistryPreviewXAML/MainWindow.xaml.cs

@@ -38,8 +38,8 @@ internal MainWindow()
             OpenWindowPlacementFile(settingsFolder, windowPlacementFile);
 
             // Update the Win32 looking window with the correct icon (and grab the appWindow handle for later)
-            IntPtr windowHandle = WinRT.Interop.WindowNative.GetWindowHandle(this);
-            Microsoft.UI.WindowId windowId = Win32Interop.GetWindowIdFromWindow(windowHandle);
+            IntPtr windowHandle = this.GetWindowHandle();
+            WindowId windowId = Win32Interop.GetWindowIdFromWindow(windowHandle);
             appWindow = Microsoft.UI.Windowing.AppWindow.GetFromWindowId(windowId);
             appWindow.SetIcon("Assets\\RegistryPreview\\RegistryPreview.ico");
 
@@ -49,6 +49,7 @@ internal MainWindow()
 
             // Extend the canvas to include the title bar so the app can support theming
             ExtendsContentIntoTitleBar = true;
+            WindowHelpers.ForceTopBorder1PixelInset(windowHandle);
             SetTitleBar(titleBar);
 
             // if have settings, update the location of the window

src/settings-ui/Settings.UI/SettingsXAML/App.xaml.cs

@@ -241,6 +241,10 @@ private void OnLaunchedFromRunner(string[] cmdArgs)
                 // https://github.com/microsoft/microsoft-ui-xaml/issues/7595 - Activate doesn't bring window to the foreground
                 // Need to call SetForegroundWindow to actually gain focus.
                 WindowHelpers.BringToForeground(settingsWindow.GetWindowHandle());
+
+                // https://github.com/microsoft/microsoft-ui-xaml/issues/8948 - A window's top border incorrectly
+                // renders as black on Windows 10.
+                WindowHelpers.ForceTopBorder1PixelInset(WindowNative.GetWindowHandle(settingsWindow));
             }
             else
             {
@@ -255,6 +259,7 @@ private void OnLaunchedFromRunner(string[] cmdArgs)
                     OobeWindow oobeWindow = new OobeWindow(OOBE.Enums.PowerToysModules.Overview);
                     oobeWindow.Activate();
                     oobeWindow.ExtendsContentIntoTitleBar = true;
+                    WindowHelpers.ForceTopBorder1PixelInset(WindowNative.GetWindowHandle(settingsWindow));
                     SetOobeWindow(oobeWindow);
                 }
                 else if (ShowScoobe)
@@ -263,6 +268,7 @@ private void OnLaunchedFromRunner(string[] cmdArgs)
                     OobeWindow scoobeWindow = new OobeWindow(OOBE.Enums.PowerToysModules.WhatsNew);
                     scoobeWindow.Activate();
                     scoobeWindow.ExtendsContentIntoTitleBar = true;
+                    WindowHelpers.ForceTopBorder1PixelInset(WindowNative.GetWindowHandle(settingsWindow));
                     SetOobeWindow(scoobeWindow);
                 }
                 else if (ShowFlyout)
@@ -310,6 +316,7 @@ protected override void OnLaunched(Microsoft.UI.Xaml.LaunchActivatedEventArgs ar
                 // Window is also needed to show MessageDialog
                 settingsWindow = new MainWindow();
                 settingsWindow.ExtendsContentIntoTitleBar = true;
+                WindowHelpers.ForceTopBorder1PixelInset(WindowNative.GetWindowHandle(settingsWindow));
                 settingsWindow.Activate();
                 settingsWindow.NavigateToSection(StartupPage);
                 ShowMessageDialog("The application is running in Debug mode.", "DEBUG");

src/settings-ui/Settings.UI/SettingsXAML/OOBE/Views/OobeShellPage.xaml.cs

@@ -6,12 +6,13 @@
 using System.Collections.ObjectModel;
 using System.Globalization;
 
-using global::PowerToys.GPOWrapper;
+using ManagedCommon;
 using Microsoft.PowerToys.Settings.UI.Library;
 using Microsoft.PowerToys.Settings.UI.OOBE.Enums;
 using Microsoft.PowerToys.Settings.UI.OOBE.ViewModel;
 using Microsoft.UI.Xaml;
 using Microsoft.UI.Xaml.Controls;
+using WinRT.Interop;
 
 namespace Microsoft.PowerToys.Settings.UI.OOBE.Views
 {
@@ -306,6 +307,7 @@ private void SetTitleBar()
                 // A custom title bar is required for full window theme and Mica support.
                 // https://docs.microsoft.com/windows/apps/develop/title-bar?tabs=winui3#full-customization
                 u.ExtendsContentIntoTitleBar = true;
+                WindowHelpers.ForceTopBorder1PixelInset(WindowNative.GetWindowHandle(u));
                 u.SetTitleBar(AppTitleBar);
             }
         }

src/settings-ui/Settings.UI/SettingsXAML/Views/ShellPage.xaml.cs

@@ -14,6 +14,7 @@
 using Microsoft.UI.Xaml.Controls;
 using Windows.Data.Json;
 using Windows.System;
+using WinRT.Interop;
 
 namespace Microsoft.PowerToys.Settings.UI.Views
 {
@@ -421,6 +422,7 @@ private void SetTitleBar()
                 // A custom title bar is required for full window theme and Mica support.
                 // https://docs.microsoft.com/windows/apps/develop/title-bar?tabs=winui3#full-customization
                 u.ExtendsContentIntoTitleBar = true;
+                WindowHelpers.ForceTopBorder1PixelInset(WindowNative.GetWindowHandle(u));
                 u.SetTitleBar(AppTitleBar);
                 var loader = ResourceLoaderInstance.ResourceLoader;
                 AppTitleBarText.Text = App.IsElevated ? loader.GetString("SettingsWindow_AdminTitle") : loader.GetString("SettingsWindow_Title");