Allegro 5 api
#include <allegro5/allegro.h> int al_get_new_display_adapter(void)
Gets the video adapter index where new displays will be created by the calling thread, if previously set with al_set_new_display_adapter(3alleg5). Otherwise returns ALLEGRO_DEFAULT_DISPLAY_ADAPTER.
al_set_new_display_adapter(3alleg5)