func (win *Window) GetHandle() unsafe.Pointer {
	p := C.cvGetWindowHandle(win.name_c)
	return unsafe.Pointer(p)
}
func (win *Window) GetHandle() unsafe.Pointer {
	p := C.cvGetWindowHandle(win.name_c)
	return unsafe.Pointer(p)
}
/* get native window handle (HWND in case of Win32 and Widget in case of X Window) */