man rest_callback () - Like rest(), but calls the callback during the wait. Allegro game programming library.
NAME
rest_callback - Like rest(), but calls the callback during the wait. Allegro game programming library.
SYNOPSIS
#include <allegro.h>
void rest_callback(long time, void (*callback)())
DESCRIPTION
Like rest(), but for non-zero values continually calls the specified function while it is waiting for the required time to elapse. If the provided `callback' parameter is NULL, this function does exactly the same thing as calling rest().