[Interest] Move window without borders on Win32

[Philipp Kursawe]

Hello,

the common trick to move a captionless window on Windows is to call
its DefWndProc like this:
if (msg->message == WM_LBUTTONDOWN) {
  *result = DefWindowProc(msg->hwnd, WM_NCLBUTTONDOWN, HTCAPTION, msg->lParam);
  return false;
}

I do that in my QMainWindow nativeEvent handler. However now no
control in the window gets mouseclicks anymore.How can I detect if a
click on that position would hit a vital control (that accepts mouse
activation/input)?