[Fullscreen] Fullscreen alt-tab behavior

Hello,
Recently I had to implement a D3D12 rendering backend at work. I used the fullscreen sample to implement fullscreen behavior and I had a few issues. Most notably some users were complaining that Alt-tabbing did not work properly in fullscreen (e.g You cannot switch to a window on the same screen as the fullscreen window)

After a bit of debugging I found the culprit: https://github.com/microsoft/DirectX-Graphics-Samples/blob/master/Samples/Desktop/D3D12Fullscreen/src/Win32Application.cpp#L155

The sample uses HWND_TOPMOST when switching to fullscreen. As stated in the documentation (https://learn.microsoft.com/en-us/windows/win32/api/winuser/nf-winuser-setwindowpos), it breaks standard alt-tab behavior ("The window maintains its topmost position even when it is deactivated. "). I believe it should be HWND_TOP instead?

If the original intent is to have a topmost window, it would be great to have a comment explaining the difference between HWND_TOP and HWND_TOPMOST.

Start in Samples/Desktop/D3D12Fullscreen/src/Win32Application.cpp around line 155 and inspect the SetWindowPos call that uses HWND_TOPMOST. Compare the documented behavior of HWND_TOPMOST and HWND_TOP, then update the fullscreen window handling or add the requested explanatory comment. Verify that standard Alt-tab behavior is preserved.