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

       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_variables().  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 unnecessarily.
       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);

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

fli_bitmap(3alleg4), reset_fli_variables(3alleg4)

Allegro                                           version 4.4.3                      fli_bmp_dirty_from(3alleg4)

#include<allegro.h>externintfli_bmp_dirty_from;externintfli_bmp_dirty_to;