anchor.diff:     (%category :initarg :category :reader category)))
   
   (defun unsubscribe-notification (window category)
  -  (mezzano.supervisor:fifo-push (make-instance 'unsubscribe-event
  -                                               :window window
  -                                               :category category)
  -                                *event-queue*))
  +  (submit-compositor-event (make-instance 'unsubscribe-event
  +                                          :window window
  +                                          :category category)))
   
   (defmethod process-event ((event unsubscribe-event))
     (setf (slot-value (window event) '%subscribed-notifications)
  
positive.code:      (when (or (not (eql *main-screen* (mezzano.supervisor:current-framebuffer)))
                 (and (not (zerop *clip-rect-width*))
                      (not (zerop *clip-rect-height*))))
         (mezzano.supervisor:fifo-push (make-instance 'redisplay-time-event)
                                       *event-queue*))))
  
  (when (not *compositor*)
    (setf *compositor* (mezzano.supervisor:make-thread 'compositor-thread
  
negative.code:    (%category :initarg :category :reader category)))
  
  (defun subscribe-notification (window category)
    (submit-compositor-event (make-instance 'subscribe-event
                                            :window window
                                            :category category)))
  
  (defmethod process-event ((event subscribe-event))
    (pushnew (category event) (slot-value (window event) '%subscribed-notifications))
  