anchor.diff:     (%category :initarg :category :reader category)))
   
   (defun subscribe-notification (window category)
  -  (mezzano.supervisor:fifo-push (make-instance 'subscribe-event
  -                                               :window window
  -                                               :category category)
  -                                *event-queue*))
  +  (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))
  
positive.code:   (recompose-windows (redisplay-time-event-fullp event)))
  
  (defun force-redisplay (&optional full)
    (mezzano.supervisor:fifo-push (make-instance 'redisplay-time-event :full full)
                                  *event-queue*))
  
  ;;;; Notifications.
  
  
negative.code: 
  (defvar *event-queue* (mezzano.supervisor:make-fifo 50)
    "Internal FIFO used to submit events to the compositor.")
  
  (defun submit-compositor-event (event)
    (mezzano.supervisor:fifo-push event *event-queue*))
  
  (defclass window ()
    ((%x :initarg :x :accessor window-x)
  