man DMXGetScreenCount (Fonctions bibliothèques) - determine number of back-end screens
NAME
DMXGetScreenCount - determine number of back-end screens
SYNOPSIS
#include <X11/extensions/dmxext.h>
Bool DMXGetScreenCount(Display *dpy,
int *screen_count);
DESCRIPTION
DMXGetScreenCount() returns the number of back-end screens that a Xdmx(1) 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 Xdmx(1) server or may be joined with other DMX screens using Xinerama.
RETURN VALUE
DMXGetScreenCount() sets screen_count and returns True unless there is a protocol error.
NOTES
If Xinerama is active, only one logical screen will be available to clients of the Xdmx(1) server. However, this call will accurately reflect the number of composite back-end screens that the Xdmx(1) server is using.