anchor.diff:  	      :initarg :enabled-p
                 :initform t
                 :accessor sheet-enabled-p)))
  -; Native region is volatile, and is only computed at the first request when it's equal to nil.
  -; Invalidate-cached-region method sets the native-region to nil.
  +
  +;;; Native region is volatile, and is only computed at the first
  +;;; request when it's equal to nil.
  +;;;
  +;;; Invalidate-cached-region method sets the native-region to nil.
   
   (defmethod sheet-parent ((sheet basic-sheet))
     nil)
  
positive.code: 
  (defmethod note-sheet-grafted :before ((sheet mirrored-sheet-mixin))
    (unless (port sheet)
      (error "~S called on sheet ~S, which has no port?!" 'note-sheet-grafted sheet))
    (realize-mirror (port sheet) sheet))
  
  (defmethod note-sheet-degrafted :after ((sheet mirrored-sheet-mixin))
  
negative.code:                                (port-set-mirror-region port mirror MR)
                                 (port-set-mirror-transformation port mirror MT)))
                             (return-from update-mirror-geometry nil) ))))
  		   ;; FIXME: There is a quote character on a line by
  		   ;; itself here.  It looks like someone tried to
  		   ;; avoid evaluation, but WHY?  Certainly not the
  		   ;; right method to do that, especially without
  		   ;; explanation.
  		   ;;
                     ;; Try reusing the mirror transformation:
                     '
                     (let ((MT (%sheet-mirror-transformation sheet)))
                       (when MT
  