al_set_display_option - Allegro 5 API

       Change  an  option  that  was previously set for a display.  After displays are created, they take on the
       options  set   with   al_set_new_display_option(3alleg5).    Calling   al_set_new_display_option(3alleg5)
       subsequently  only  changes  options for newly created displays, and doesn’t touch the options of already
       created displays.  al_set_display_option(3alleg5) allows changing some of these values.  Not all  display
       options  can  be  changed or changing them will have no effect.  Changing options other than those listed
       below is undefined.

       • ALLEGRO_SUPPORTED_ORIENTATIONS - This can be changed  to  allow  new  or  restrict  previously  enabled
         orientations of the screen/device.  See al_set_new_display_option(3alleg5) for more information on this
         option.

       al_set_display_option - Allegro 5 API

al_set_new_display_option(3alleg5)

Allegro reference manual                                                          al_set_display_option(3alleg5)

       5.1.5

              #include <allegro5/allegro.h>

              void al_set_display_option(ALLEGRO_DISPLAY *display, int option, int value)