mouse_callback - User specified mouse callback. Allegro game programming
library.
#include <allegro.h>
extern void (*mouse_callback)(int flags);
Called by the interrupt handler whenever the mouse moves or one of the buttons
changes state. This function must be in locked memory, and must execute _very_
quickly! It is passed the event flags that triggered the call, which is a
bitmask containing any of the values MOUSE_FLAG_MOVE, MOUSE_FLAG_LEFT_DOWN,
MOUSE_FLAG_LEFT_UP, MOUSE_FLAG_RIGHT_DOWN, MOUSE_FLAG_RIGHT_UP,
MOUSE_FLAG_MIDDLE_DOWN, MOUSE_FLAG_MIDDLE_UP, and MOUSE_FLAG_MOVE_Z. Note that
even if the mouse has more than three buttons, only the first three can be
trapped using a callback.