al_get_mouse_state_axis - Allegro 5 API

       Extract  the mouse axis value from the saved state.  The axes are numbered from 0, in this order: x-axis,
       y-axis, z-axis, w-axis.

       al_get_mouse_state_axis - Allegro 5 API

ALLEGRO_MOUSE_STATE(3alleg5), al_get_mouse_state(3alleg5), al_mouse_button_down(3alleg5)

Allegro reference manual                                                        al_get_mouse_state_axis(3alleg5)

              #include <allegro5/allegro.h>

              int al_get_mouse_state_axis(const ALLEGRO_MOUSE_STATE *state, int axis)