anchor.diff:      :accessor event-root-y
       :initarg :root-y
       :type double-float))
  +  (:metaclass event-class))
  +
  +(defclass button-press-event (button-event)
  +  ()
     (:metaclass event-class)
     (:type :button-press))
   
  
positive.code:   (:type :no-expose))
    
  (defclass scroll-event (timed-event)
    ()
    (:metaclass event-class)
    (:type :scroll))
  
  (defclass setting-event (timed-event)
    ()
    (:metaclass event-class)
    (:type :setting))
  
negative.code:   (:metaclass event-class)
    (:type :expose))
  
  (defclass input-event (timed-event)
    ((x
      :allocation :alien
      :accessor event-x
  