I've been googling for quite a long time and I just can't find any information on how to get screen_number for every screen connected to computer. Here I found a list of macros and some of them (like for example ScreenOfDisplay(display, screen_number) ) use argument screen_number. However there is no such macro that could give me a list of those numbers (one for every connected screen). I know how to get number of default screen (DefaultScreen() ) and count of all screens ( ScreenCount() ) but what about other screens? I noticed that screen_number of default screen is 0, although I have only one screen connected to my computer so I can't really test what happens when there are more of them. I think that screen_number could be assigned in a very simple way which is screen_number=0 for first screen,screen_number=1 for second,screen_number=2 for third and so on but as I said... I can't test wheather it's true and even if I had multiple screens how could I be sure that it works like this for all computers .Please ,if anyone of you has more experience with X11 and knows all details about how it works,tell me if I am right.
The ScreenCount(dpy) macro and int XScreenCount(Display*) function both return the number of screens connected to the display. Valid screen numbers are 0 to ScreenCount(dpy)-1. Macros in Xlib.h confirm:
#define ScreenCount(dpy) (((_XPrivDisplay)dpy)->nscreens)
#define ScreenOfDisplay(dpy, scr) (&((_XPrivDisplay)dpy)->screens[scr])