poll_scroll man page
poll_scroll — Checks the status of a scroll request with triple buffering. Allegro game programming library.
This function is used for triple buffering. It checks the status of a hardware scroll previously initiated by the request_scroll() routine.
Returns non-zero if it is still waiting to take place, and zero if the requested scroll has already happened.
request_scroll(3), request_video_bitmap(3), ex3buf(3), exupdate(3)
ex3buf(3), exupdate(3), request_scroll(3), request_video_bitmap(3).