Man pages matching name al_get_joystick_num_buttons in section 3alleg5:

al_get_joystick_num_buttons.3alleg5.en	debian 10 / allegro5-doc
al_get_joystick_num_buttons.3alleg5.en	debian 11 / allegro5-doc
al_get_joystick_num_buttons.3alleg5.en	debian 12 / allegro5-doc