anchor.diff:    (multiple-value-bind (right top left bottom) (label-pane-margins pane)
       (declare (ignorable right top left bottom))
       (when (sheet-children pane)
  -      (with-bounding-rectangle* (x1 y1 x2 y2) (sheet-region pane);seems bogus
  +      (with-bounding-rectangle* (x1 y1 x2 y2) (values 0 0 width height)
           (move-sheet (first (sheet-children pane))
                       (+ x1 left) (+ y1 top))
           (allocate-space (first (sheet-children pane))
  
positive.code:               (scroll-bar-thumb-size vscrollbar) (bounding-rectangle-height (sheet-region viewport)))))))
  
  (defmethod initialize-instance :after ((pane scroller-pane) &key contents &allow-other-keys)
    (declare (ignore args))
    (sheet-adopt-child pane (first contents))
    (with-slots (scroll-bar viewport vscrollbar hscrollbar) pane
      (setq viewport (first (sheet-children pane)))
  
negative.code:         (height (window-configuration-event-height event)))
      (with-bounding-rectangle* (old-x1 old-y1 old-x2 old-y2) (sheet-region pane)
        (let ((old-width  (- old-x2 old-x1))
              (old-height (- old-y2 old-y1)))
          ;; avoid going into an infinite loop by not using (setf sheet-transformation)
          (setf (slot-value pane 'transformation)
  	      (make-translation-transformation x y))
  