al_set_new_display_adapter - Allegro 5 API

       Sets  the  adapter  to  use  for  new  displays created by the calling thread.  The adapter has a monitor
       attached to it.  Information about the monitor can be gotten using al_get_num_video_adapters(3alleg5) and
       al_get_monitor_info(3alleg5).

       To return to the default behaviour, pass ALLEGRO_DEFAULT_DISPLAY_ADAPTER.

       al_set_new_display_adapter - Allegro 5 API

al_get_num_video_adapters(3alleg5), al_get_monitor_info(3alleg5)

Allegro reference manual                                                     al_set_new_display_adapter(3alleg5)

              #include <allegro5/allegro.h>

              void al_set_new_display_adapter(int adapter)