anchor.diff:           (d (text-style-descent (pane-text-style pane) pane))
            (m0 2)
            (h (+ a d m0 m0)))
  -    (cond ((slot-value pane 'contents)
  -           (let ((sr2 (compose-space (content-pane (first (slot-value pane 'contents))))))
  +    (cond ((sheet-children pane)
  +           (let ((sr2 (compose-space (first (sheet-children pane)))))
                (multiple-value-bind (right top left bottom) (label-pane-margins pane)
                  (make-space-requirement
                   ;; label!
  
positive.code: (defmethod allocate-space ((pane label-pane) width height)
    (multiple-value-bind (right top left bottom) (label-pane-margins pane)
      (declare (ignorable right top left bottom))
      (when (slot-value pane 'contents)
        (with-bounding-rectangle* (x1 y1 x2 y2) (sheet-region pane)
          (move-sheet (content-pane (first (slot-value pane 'contents)))
                      (+ x1 left) (+ y1 top))
          (allocate-space (content-pane (first (slot-value pane 'contents)))
                          (- (- x2 right) (+ x1 left))
                          (- (- y2 bottom) (+ y1 top)))))))
  
  
negative.code: 		(stream-replay pane (make-bounding-rectangle x1 (+ y2 dy) x2 y2)))
  	       (t
  		(draw-rectangle* (sheet-medium pane) x1 y1 x2 (+ y1 dy) :ink +background-ink+)
  		(stream-replay pane (make-bounding-rectangle x1 y1 x2 (+ y1 dy))))) )
  	     ((and (zerop dy)
  		   (< (abs dx) (- x2 x1)))
  	      (copy-area pane 0 0 (- x2 x1) (- y2 y1) dx 0)
  