add_clip_rect (3) - Linux Manuals
add_clip_rect: Intersects a bitmap's clipping rectangle with the given area. Allegro game programming library.
NAME
add_clip_rect - Intersects a bitmap's clipping rectangle with the given area. Allegro game programming library.SYNOPSIS
#include <allegro.h>
void add_clip_rect(BITMAP *bitmap, int x1, int y1, int x2, int y2);