osx man page for install_mouse

install_mouse(3alleg4)						  Allegro manual					    install_mouse(3alleg4)

NAME

       install_mouse - Installs the Allegro mouse handler.

SYNOPSIS

       #include <allegro.h>

       int install_mouse();

DESCRIPTION

       Installs the Allegro mouse handler. You must do this before using any other mouse functions.

RETURN VALUE

       Returns	-1 on failure, zero if the mouse handler is already installed (in which case this function does nothing) and the number of buttons
       on the mouse if the mouse handler has successfully been installed (ie. this is the first time a handler is installed or	you  have  removed
       the previous one).

       Note  that  the number of mouse buttons returned by this function is more an indication than a physical reality. With most devices there is
       no way of telling how many buttons there are, and any user can override the number of mouse buttons returned by this function with a custom
       configuration file and the variable num_buttons. Even if this value is overridden by the user, the global mouse variables will still report
       whatever the hardware is sending.

SEE ALSO

       remove_mouse(3alleg4), poll_mouse(3alleg4),  mouse_x(3alleg4),  show_mouse(3alleg4),  get_mouse_mickeys(3alleg4),  position_mouse(3alleg4),
       set_mouse_range(3alleg4), set_mouse_speed(3alleg4)

Allegro 							   version 4.4.2					    install_mouse(3alleg4)