al_flip_display - Allegro 5 API

       Copies  or  updates  the  front  and back buffers so that what has been drawn previously on the currently
       selected display becomes visible on screen.  Pointers to the special back buffer bitmap remain valid  and
       retain their semantics as the back buffer, although the contents may have changed.

              Note:  If  not using the ALLEGRO_SINGLE_BUFFER option, you typically want to redraw every pixel of
              the backbuffer bitmap to avoid uninitialized memory artifacts.

       Several display options change how this function behaves:

       • With ALLEGRO_SINGLE_BUFFER, no flipping is done.  You still have  to  call  this  function  to  display
         graphics, depending on how the used graphics system works.

       • The  ALLEGRO_SWAP_METHOD  option  may  have additional information about what kind of operation is used
         internally to flip the front and back buffers.

       • If ALLEGRO_VSYNC is 1, this function will force  waiting  for  vsync.   If  ALLEGRO_VSYNC  is  2,  this
         function  will  not wait for vsync.  With many drivers the vsync behavior is controlled by the user and
         not the application, and ALLEGRO_VSYNC will not be set; in this case al_flip_display(3alleg5) will wait
         for vsync depending on the settings set in the system’s graphics preferences.

       al_flip_display - Allegro 5 API

al_set_new_display_flags(3alleg5), al_set_new_display_option(3alleg5)

Allegro reference manual                                                                al_flip_display(3alleg5)

              #include <allegro5/allegro.h>

              void al_flip_display(void)