mouse_on_screen - Man Page

#include <allegro.h>

int mouse_on_screen();

This function can be useful to prevent having two mouse pointers on the  screen at the same time when running your program in windowed mode and  drawing the mouse pointer yourself. Other possible uses include the  ability to pause your game when the mouse goes off of the window, or  only scrolling the view when the pointer is near the edge of the window, but not while off of the window.

Example :

   if (mouse_on_screen()) {draw_sprite(buffer , mouse_sprite , mouse_x , mouse_y);}

Returns 0 if the mouse pointer is off of the screen, or non-zero otherwise.