retrace_count - Retrace count simulator. Allegro game programming library.
#include <allegro.h>
extern volatile int retrace_count;
If the retrace simulator is installed, this count is incremented on each
vertical retrace; otherwise, if the refresh rate is known, the count is
incremented at the same rate (ignoring retraces); otherwise, it is incremented
70 times a second. This provides a way of controlling the speed of your
program without installing user timer functions.
ex3d(3), exblend(3), exdbuf(3), exflip(3),
exlights(3)