int createOverlayWindow () {
int gdevice = OS.GetMainDevice ();
int [] ptr = new int [1];
OS.memcpy (ptr, gdevice, 4);
GDevice device = new GDevice ();
OS.memcpy (device, ptr [0], GDevice.sizeof);
Rect rect = new Rect ();
OS.SetRect (rect, device.left, device.top, device.right, device.bottom);
int [] outWindow = new int [1];
OS.CreateNewWindow (OS.kOverlayWindowClass, 0, rect, outWindow);