anchor.diff:                                                    (- (bounding-rectangle-max-x (sheet-region scrollee))
                                                        (bounding-rectangle-width (sheet-region viewport)))
                                                     (bounding-rectangle-min-x (sheet-region scrollee)))
  -              (scroll-bar-thumb-size hscrollbar) (bounding-rectangle-width (sheet-region viewport))))
  +              (scroll-bar-thumb-size hscrollbar) (bounding-rectangle-width (sheet-region viewport))
  +              (gadget-value hscrollbar :invoke-callback nil)
  +              (- (nth-value 0 (transform-position (sheet-transformation scrollee) 0 0)))
  +              ))
         ;;
         (when vscrollbar
           (setf (gadget-min-value vscrollbar)      (bounding-rectangle-min-y (sheet-region scrollee))
  
positive.code:   (declare (ignore width height))
    (with-slots (viewport vscrollbar hscrollbar) pane
      (if viewport
          (let ((req (compose-space viewport)))
            (when vscrollbar
              (setq req (space-requirement+* req
                                             :height     *scrollbar-thickness*
  
negative.code:     (if viewport
  	(sheet-parent viewport))))
  
  (defmethod scroll-extent ((pane basic-pane) x y)
    (when (pane-viewport pane)
      (move-sheet pane (round (- x)) (round (- y)))
      (when (pane-scroller pane)
        (scroller-pane/update-scroll-bars (pane-scroller pane)))))
  
  ;;; LABEL PANE
  
  