man VIRTUAL_W () - Global define to obtain the virtual size of the screen. Allegro game programming library.
NAME
VIRTUAL_W, VIRTUAL_H - Global define to obtain the virtual size of the screen. Allegro game programming library.
SYNOPSIS
#include <allegro.h>
#define VIRTUAL_W;
#define VIRTUAL_H;
DESCRIPTION
Global defines that return the width and height of the virtual screen, or zero if the screen has not been initialised yet. Example:
char buf[100];
...
uszprintf(buf, sizeof(buf),
"The virtual screen size is %d x %d pixels",
SCREEN_W, SCREEN_H);