Bool DMXGetScreenCount(Display *dpy, int *screen_count);
returns the number of back-end screens that a
server controls. Since a DMX screen usually fills all of the available
area on a back-end server, there is usually a one-to-one correspondence
between DMX screens and backend servers. However, it is also possible
for a DMX screen to cover only part of the available area on a back-end
server, and for more than one DMX screens to occupy different parts of
the visible area on the same back-end server.
A DMX screen may be managed as a regular X screen in the
server or may be joined with other DMX screens using Xinerama.
unless there is a protocol error.
If Xinerama is active, only one logical screen will be available to
clients of the
server. However, this call will accurately reflect the number of
composite back-end screens that the
server is using.