NAME

       al_get_backbuffer - Allegro 5 API

SYNOPSIS

              #include <allegro5/allegro.h>

              ALLEGRO_BITMAP *al_get_backbuffer(ALLEGRO_DISPLAY *display)

DESCRIPTION

       Return a special bitmap representing the back-buffer of the display.

       Care  should be taken when using the backbuffer bitmap (and its sub-bitmaps) as the source bitmap (e.g as
       the bitmap argument to al_draw_bitmap(3alleg5)).  Only untransformed operations are hardware accelerated.
       These consist of al_draw_bitmap(3alleg5) and al_draw_bitmap_region(3alleg5) when the current  transforma‐
       tion  is  the  identity.   If  the transformation is not the identity, or some other drawing operation is
       used, the call will be routed through the memory bitmap routines, which are slow.  If you need those  op‐
       erations  to  be accelerated, then first copy a region of the backbuffer into a temporary bitmap (via the
       al_draw_bitmap(3alleg5) and al_draw_bitmap_region(3alleg5)), and then use that temporary  bitmap  as  the
       source bitmap.

Allegro reference manual                                                              al_get_backbuffer(3alleg5)