ice is
locked by the caller, but locking the device prevents the Ghostscript DLL
from closing the device or changing its size or depth.

<p>
Under OS/2, Windows 95/98 and Windows NT, this lock is implemented using a
mutual exclusion semaphore (mutex).  The return value is the lock count,
which is either 0 ("unlocked") or 1 ("locked").  The function blocks until
the device is locked by the caller.

<p>
Under Win16 or Win32s, <b><tt>gsdll_lock_device()</tt></b> always returns
immediately with a lock count as 