al_get_monitor_info - Allegro 5 API

       Get   information  about  a  monitor’s  position  on  the  desktop.   adapter  is  a  number  from  0  to
       al_get_num_video_adapters()-1.

       On Windows, use al_set_new_display_flags(3alleg5) to switch between Direct3D and OpenGL  backends,  which
       will often have different adapters available.

       Returns true on success, false on failure.

       al_get_monitor_info - Allegro 5 API

ALLEGRO_MONITOR_INFO(3alleg5), al_get_num_video_adapters(3alleg5)

Allegro reference manual                                                            al_get_monitor_info(3alleg5)

              #include <allegro5/allegro.h>

              bool al_get_monitor_info(int adapter, ALLEGRO_MONITOR_INFO *info)