Allegro 5 api
#include <allegro5/allegro.h> bool al_mouse_button_down(const ALLEGRO_MOUSE_STATE *state, int button)
Return true if the mouse button specified was held down in the state specified. Unlike most things, the first mouse button is numbered 1.
ALLEGRO_MOUSE_STATE(3alleg5), al_get_mouse_state(3alleg5), al_get_mouse_state_axis(3alleg5)