anchor.diff:  ;; on-event based dispatching test
   (defmethod glop:on-event (window (event glop:key-event))
     (format t "Key ~:[released~;pressed~]: ~S~%" (glop:event-pressed event) (glop:event-key event))
  -  (when (eql (glop:event-key event) #\Escape)
  +  (when (= (glop:event-key event) 9)    ;ESC
         (glop:push-close-event window))
  -  (when (and (glop:event-pressed event) (eql (glop:event-key event) #\f))
  +  (when (and (glop:event-pressed event) (= (glop:event-key event) 41)) ;F
       (glop:set-fullscreen window)))
   
   (defmethod glop:on-event (window (event glop:button-event))
  
positive.code:          if evt
           do (typecase evt
                (glop:key-press-event
                 (when (eql (glop:event-key evt) #\Escape)
                   (glop:push-close-event win)))
                (glop:close-event (setf running nil))
                (t (format t "Unhandled event: ~A~%" evt)))
  
negative.code:   (if pressed
        (format t "Key pressed: ~D (~S)~%" key string)
        (format t "Key released: ~D (~S) ~%" key string))
    (when (= key 9)                       ;ESC
      (glop:push-close-event window))
    (when (and pressed (= key 41))        ;F
      (glop::toggle-fullscreen window)))
  
  (defmethod glop:on-button (window pressed button)
  