anchor.diff:      :initarg :root-y
       :type double-float))
     (:metaclass event-class)
  -  (:type :motion-notify))
  +  (:event-type :motion-notify))
     
   (defclass button-event (input-event)
     ((button
  
positive.code: (defclass delete-event (event)
    ()
    (:metaclass event-class)
    (:type :delete))
  
  
  (defclass destroy-event (event)
    ()
    (:metaclass event-class)
    (:type :destroy))
  
  (defclass expose-event (event)
    ((x
  
negative.code:     :initarg :new-window-state
      :type window-state))
    (:metaclass event-class)
    (:event-type :window-state))
    
  (defclass owner-change-event (event)
    ()
    (:metaclass event-class)
    (:event-type :owner-change))
  
  