void mav_callbackKeyboardSet(MAV_window *w, MAV_class *c, MAV_callbackKeyboardFn fn);
int mav_callbackKeyboardExec(MAV_window *w, MAV_object *o,MAV_keyboardEvent *ke);
mav_callbackKeyboardSet sets the callback function for keyboard events for object class c in window w, to be fn.
When a keyboard event is detected by mav_eventsCheck, the system checks if the mouse is currently pointing at an object. If it is, and a keyboard callback has been registered for that class of object, the system calls mav_callbackKeyboardExec to execute fn, passing it the keyboard event data me.
Note: to cause fn to be executed regardless of the mouse position (to obtain a non-object specific action) specify object class o to be MAV_CLASS_WORLD.