php man page for retrace_count

retrace_count(3alleg4)						  Allegro manual					    retrace_count(3alleg4)

NAME
       retrace_count - Retrace count simulator. Allegro game programming library.

SYNOPSIS
       #include <allegro.h>

       extern volatile int retrace_count;

DESCRIPTION
       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  control-
       ling the speed of your program without installing user timer functions.

SEE ALSO
       ex3d(3alleg4), exblend(3alleg4), exdbuf(3alleg4), exflip(3alleg4), exlights(3alleg4)

Allegro 							   version 4.4.2					    retrace_count(3alleg4)