Code Quality: Defined manual SetWindowLongPtr (#16781)

Author: 0x5bfa

src/Files.App.CsWin32/NativeMethods.txt

@@ -98,7 +98,7 @@ FindWindow
 SendMessage
 IsWindowVisible
 COPYDATASTRUCT
-SetWindowLongPtr
+WINDOW_LONG_PTR_INDEX
 GetDpiForWindow
 CallWindowProc
 MINMAXINFO

src/Files.App.CsWin32/Windows.Win32.Extras.cs

@@ -3,6 +3,7 @@
 
 using System.Runtime.InteropServices;
 using Windows.Win32.Foundation;
+using Windows.Win32.UI.WindowsAndMessaging;
 
 namespace Windows.Win32
 {
@@ -17,4 +18,23 @@ namespace UI.WindowsAndMessaging
 		[UnmanagedFunctionPointer(CallingConvention.Winapi)]
 		public delegate LRESULT WNDPROC(HWND hWnd, uint msg, WPARAM wParam, LPARAM lParam);
 	}
+
+	public static partial class PInvoke
+	{
+		[DllImport("User32", EntryPoint = "SetWindowLongW", ExactSpelling = true)]
+		static extern int _SetWindowLong(HWND hWnd, int nIndex, int dwNewLong);
+
+		[DllImport("User32", EntryPoint = "SetWindowLongPtrW", ExactSpelling = true)]
+		static extern nint _SetWindowLongPtr(HWND hWnd, int nIndex, nint dwNewLong);
+
+		// NOTE:
+		//  CsWin32 doesn't generate SetWindowLong on other than x86 and vice versa.
+		//  For more info, visit https://github.com/microsoft/CsWin32/issues/882
+		public static unsafe nint SetWindowLongPtr(HWND hWnd, WINDOW_LONG_PTR_INDEX nIndex, nint dwNewLong)
+		{
+			return sizeof(nint) is 4
+				? (nint)_SetWindowLong(hWnd, (int)nIndex, (int)dwNewLong)
+				: _SetWindowLongPtr(hWnd, (int)nIndex, dwNewLong);
+		}
+	}
 }