osx man page for set_clip_rect

set_clip_rect(3alleg4)						  Allegro manual					    set_clip_rect(3alleg4)

NAME

       set_clip_rect - Sets the clipping rectangle of a bitmap. Allegro game programming library.

SYNOPSIS

       #include <allegro.h>

       void set_clip_rect(BITMAP *bitmap, int x1, int y1, int x2, int y2);

DESCRIPTION

       Each bitmap has an associated clipping rectangle, which is the area of the image that it is OK to draw onto. Nothing will be drawn to posi-
       tions outside this space. This function sets the clipping rectangle for the specified bitmap. Pass the coordinates of the top-left and bot-
       tom-right  corners of the clipping rectangle in this order; these are both inclusive, i.e. set_clip_rect(bitmap, 16, 16, 32, 32) will allow
       drawing to (16, 16) and (32, 32), but not to (15, 15) and (33, 33).

       Drawing operations will be performed (at least partially) on the bitmap as long as the first coordinates of its clipping rectangle are  not
       greater	than the second coordinates and its intersection with the actual image is non-empty. If either condition is not fulfilled, drawing
       will be turned off for the bitmap, e.g.

	  set_clip_rect(bmp, 0, 0, -1, -1); /* disable drawing on bmp */

       Note that passing "out-of-bitmap" coordinates is allowed, but  they  are  likely  to  be  altered  (and	so  the  coordinates  returned	by
       get_clip_rect()	will  be different). However, such modifications are guaranteed to preserve the external effect of the clipping rectangle,
       that is not to modify the actual area of the image that it is OK to draw onto.

SEE ALSO

       get_clip_rect(3alleg4), add_clip_rect(3alleg4), set_clip_state(3alleg4), get_clip_state(3alleg4), ex12bit(3alleg4), excamera(3alleg4)

Allegro 							   version 4.4.2					    set_clip_rect(3alleg4)