debian man page for fli_bmp_dirty_to

fli_bmp_dirty_from(3alleg4)					  Allegro manual				       fli_bmp_dirty_from(3alleg4)

NAME
       fli_bmp_dirty_from, fli_bmp_dirty_to - Indicate which parts of the image have changed. Allegro game programming library.

SYNOPSIS
       #include <allegro.h>

       extern int fli_bmp_dirty_from;

       extern int fli_bmp_dirty_to;

DESCRIPTION
       These  variables  are  set  by next_fli_frame() to indicate which part of the fli_bitmap has changed since the last call to reset_fli_vari-
       ables(). If fli_bmp_dirty_from is greater than fli_bmp_dirty_to,  the  bitmap  has  not	changed,  otherwise  lines  fli_bmp_dirty_from	to
       fli_bmp_dirty_to  (inclusive) have altered. You can use these when copying the fli_bitmap onto the screen, to avoid moving data unnecessar-
       ily. Example:

	  if (fli_bmp_dirty_from <= fli_bmp_dirty_to)
	     blit(fli_bitmap, screen, 0, fli_bmp_dirty_from,
		  0, fli_bmp_dirty_from, fli_bitmap->w,
		  fli_bmp_dirty_to - fli_bmp_dirty_from + 1);

SEE ALSO
       fli_bitmap(3alleg4), reset_fli_variables(3alleg4)

Allegro 							   version 4.4.2				       fli_bmp_dirty_from(3alleg4)