TitleBar Captions buttons automatically adjust WindowStyle to match flow direction

Author: Avid29

components/TitleBar/src/NativeMethods.cs

@@ -19,14 +19,21 @@ public enum WindowMessage : int
     [Flags]
     public enum WindowStyle : uint
     {
-        WS_SYSMENU = 0x80000
+        WS_SYSMENU = 0x80000,
+    }
+
+    [Flags]
+    public enum WindowStyleExtended : ulong
+    {
+        WS_EX_LAYOUTRTL= 0x00400000L,
     }
 
     [Flags]
     public enum WindowLongIndexFlags : int
     {
         GWL_WNDPROC = -4,
-        GWL_STYLE = -16
+        GWL_STYLE = -16,
+        GWL_EXSTYLE = -20,
     }
 
     [Flags]
@@ -44,43 +51,50 @@ public enum SystemCommand
         SC_KEYMENU = 0xF100
     }
 
+    // TODO: Check for typing online. IntPtr, int, or long?
+
     [DllImport("user32.dll", EntryPoint = "GetWindowLongW", SetLastError = false)]
-    public static extern int GetWindowLong(IntPtr hWnd, int nIndex);
+    public static extern int GetWindowLongW(IntPtr hWnd, int nIndex);
+
+    [DllImport("user32.dll", EntryPoint = "GetWindowLongPtr", SetLastError = false)]
+    public static extern IntPtr GetWindowLongPtr(IntPtr hWnd, int nIndex);
 
     [DllImport("user32.dll", EntryPoint = "GetWindowLongPtrW", SetLastError = false)]
-    public static extern int GetWindowLongPtr(IntPtr hWnd, int nIndex);
+    public static extern int GetWindowLongPtrW(IntPtr hWnd, int nIndex);
 
     public static int GetWindowLongAuto(IntPtr hWnd, int nIndex)
     {
         if (IntPtr.Size is 8)
         {
-            return GetWindowLongPtr(hWnd, nIndex);
+            return GetWindowLongPtrW(hWnd, nIndex);
         }
         else
         {
-            return GetWindowLong(hWnd, nIndex);
+            return GetWindowLongW(hWnd, nIndex);
         }
     }
 
     [DllImport("user32.dll", EntryPoint = "FindWindowExW", SetLastError = true, CharSet = CharSet.Unicode)]
     public static extern IntPtr FindWindowEx(IntPtr hWndParent, IntPtr hWndChildAfter, string lpszClass, string lpszWindow);
 
-
     [DllImport("user32.dll", EntryPoint = "SetWindowLongW", SetLastError = false)]
-    public static extern IntPtr SetWindowLong(IntPtr hWnd, int nIndex, IntPtr dwNewLong);
+    public static extern IntPtr SetWindowLongW(IntPtr hWnd, int nIndex, IntPtr dwNewLong);
 
-    [DllImport("user32.dll", EntryPoint = "SetWindowLongPtrW", SetLastError = false)]
+    [DllImport("user32.dll", EntryPoint = "SetWindowLongPtr", SetLastError = false)]
     public static extern IntPtr SetWindowLongPtr(IntPtr hWnd, int nIndex, IntPtr dwNewLong);
 
+    [DllImport("user32.dll", EntryPoint = "SetWindowLongPtrW", SetLastError = false)]
+    public static extern IntPtr SetWindowLongPtrW(IntPtr hWnd, int nIndex, IntPtr dwNewLong);
+
     public static IntPtr SetWindowLongAuto(IntPtr hWnd, int nIndex, IntPtr dwNewLong)
     {
         if (IntPtr.Size is 8)
         {
-            return SetWindowLongPtr(hWnd, nIndex, dwNewLong);
+            return SetWindowLongPtrW(hWnd, nIndex, dwNewLong);
         }
         else
         {
-            return SetWindowLong(hWnd, nIndex, dwNewLong);
+            return SetWindowLongW(hWnd, nIndex, dwNewLong);
         }
     }
 

components/TitleBar/src/TitleBar.WASDK.cs

@@ -3,11 +3,12 @@
 // See the LICENSE file in the project root for more information.
 
 #if WINDOWS_WINAPPSDK && !HAS_UNO
-using Windows.Graphics;
 using Microsoft.UI;
 using Microsoft.UI.Input;
 using Microsoft.UI.Windowing;
 using Microsoft.UI.Xaml.Media;
+using System.Runtime.InteropServices;
+using Windows.Graphics;
 
 namespace CommunityToolkit.WinUI.Controls;
 
@@ -100,6 +101,30 @@ private void UpdateCaptionButtons(FrameworkElement rootElement)
             Window.AppWindow.TitleBar.ButtonForegroundColor = Colors.Black;
             Window.AppWindow.TitleBar.ButtonInactiveForegroundColor = Colors.DarkGray;
         }
+
+        // Set the caption buttons to match the flow direction of the app
+        UpdateCaptionButtonsDirection(rootElement.FlowDirection);
+    }
+
+    private void UpdateCaptionButtonsDirection(FlowDirection direction)
+    {
+        var hwnd = WinRT.Interop.WindowNative.GetWindowHandle(this.Window);
+
+        if (hwnd != 0)
+        {
+            var exStyle = NativeMethods.GetWindowLongPtr(hwnd, (int)NativeMethods.WindowLongIndexFlags.GWL_EXSTYLE);
+
+            if (direction == FlowDirection.RightToLeft)
+            {
+                exStyle |= (nint)NativeMethods.WindowStyleExtended.WS_EX_LAYOUTRTL;
+            }
+            else
+            {
+                exStyle &= (nint)NativeMethods.WindowStyleExtended.WS_EX_LAYOUTRTL;
+            }
+
+            NativeMethods.SetWindowLongPtr(hwnd, (int)NativeMethods.WindowLongIndexFlags.GWL_EXSTYLE, exStyle);
+        }
     }
 
     private void ResetWASDKTitleBar()

components/TitleBar/src/WndProcHelper.cs

@@ -44,7 +44,7 @@ public void RegisterInputNonClientPointerSourceWndProc(WNDPROC wndProc)
 
         if (inputNonClientPointerSourceHandle != IntPtr.Zero)
         {
-            int style = NativeMethods.GetWindowLongAuto(Handle, (int)NativeMethods.WindowLongIndexFlags.GWL_STYLE);
+            IntPtr style = NativeMethods.GetWindowLongAuto(Handle, (int)NativeMethods.WindowLongIndexFlags.GWL_STYLE);
             NativeMethods.SetWindowLongAuto(Handle, (int)NativeMethods.WindowLongIndexFlags.GWL_STYLE, (IntPtr)(style & ~(int)NativeMethods.WindowStyle.WS_SYSMENU));
 
             newInputNonClientPointerSourceWndProc = wndProc;