These functions are declared in the main Allegro header file:

#include <allegro5/allegro.h>

ALLEGRO_MONITOR_INFO

typedef struct ALLEGRO_MONITOR_INFO

Describes a monitors size and position relative to other monitors. x1, y1 will be 0, 0 on the primary display. Other monitors can have negative values if they are to the left or above the primary display.

typedef struct ALLEGRO_MONITOR_INFO
{
   int x1;
   int y1;
   int x2;
   int y2;
} ALLEGRO_MONITOR_INFO;

al_get_new_display_adapter

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. Otherwise returns ALLEGRO_DEFAULT_DISPLAY_ADAPTER.

al_set_new_display_adapter

void al_set_new_display_adapter(int adapter)

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 and al_get_monitor_info.

To return to the default behaviour, pass ALLEGRO_DEFAULT_DISPLAY_ADAPTER.

al_get_monitor_info

bool al_get_monitor_info(int adapter, ALLEGRO_MONITOR_INFO *info)

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

Returns true on success, false on failure.

al_get_num_video_adapters

int al_get_num_video_adapters(void)

Get the number of video "adapters" attached to the computer. Each video card attached to the computer counts as one or more adapters. An adapter is thus really a video port that can have a monitor connected to it.

Monitors

ALLEGRO_MONITOR_INFO

al_get_new_display_adapter

al_set_new_display_adapter

al_get_monitor_info

al_get_num_video_adapters