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