anchor.diff:  
   (defmethod initialize-instance :after ((bp border-pane) &rest ignore)
     (declare (ignore ignore))
  +  #+NIL
     (with-slots (border-width) bp
       (let ((2*border-width (* 2 border-width)))
         (setf (slot-value bp 'margin-width) 2*border-width
  
positive.code:    )
    (:documentation ""))
  
  (defun panep (x)
    (typep x 'pane))
  
  (defun make-pane (type &rest args)
    (apply #'make-pane-1 *pane-realizer* *application-frame* type args))
  
  #||
  ;; dummy but useful
  (defmacro do-in (size min max)
    `(max ,min (min ,max ,size)))
  ;; moved as clamp into utils.lisp
  ||#
  
  (defun get-pane-width (pane)
    ;; Give the region size if already set, otherwise, give the space-requirement
    (let ((width (rectangle-width (sheet-region pane))))
      (if (or (not width) (zerop width)) (sr-width pane) width)))
  
  (defun get-pane-height (pane)
    ;; Give the region size if already set, otherwise, give the space-requirement
    (let ((height (rectangle-height (sheet-region pane))))
      (if (or (not height) (zerop height)) (sr-height pane) height)))
  
  (defun make-extremums-children-ratio-width (pane children)
    (with-slots (sorted-max-w-r sorted-min-w-r) pane
      (loop for child in children
  	  for max-width-ratio = (/ (sr-width child) (sr-max-width child))
  	  for min-width-ratio = (/ (sr-width child) (sr-min-width child))
  	  collect (cons max-width-ratio child) into max-w-ratios
  	  collect (cons min-width-ratio child) into min-w-ratios
  	  finally (setf sorted-max-w-r (sort max-w-ratios #'> :key #'car)
  			sorted-min-w-r (sort min-w-ratios #'< :key #'car)))))
  
  (defun make-extremums-children-ratio-height (pane children)
    (with-slots (sorted-max-h-r sorted-min-h-r) pane
      (loop for child in children
  	  for max-height-ratio = (/ (sr-height child) (sr-max-height child))
  	  for min-height-ratio = (/ (sr-height child) (sr-min-height child))
  	  collect (cons max-height-ratio child) into max-h-ratios
  	  collect (cons min-height-ratio child) into min-h-ratios
  	  finally (setf sorted-max-h-r (sort max-h-ratios #'> :key #'car)
  			sorted-min-h-r (sort min-h-ratios #'< :key #'car)))))
  
  (defun allocate-space-internal-width (pane size)
    (loop with sum = (slot-value pane 'sum-width)
  	and maxs = (slot-value pane 'sorted-max-w-r)
  	and mins = (slot-value pane 'sorted-min-w-r)
  	for (nil . child) in (if (>= size sum) maxs mins)
  	and box-size = sum then (- box-size (get-pane-width child))
  	for tmp = (round (/ (* size (get-pane-width child)) box-size))
  	for new-size = (clamp tmp (sr-min-width child) (sr-max-width child))
  	for new-sum = new-size then (+ new-sum new-size)
  	do (decf size new-size)
  	   (setf (slot-value child 'new-width) new-size)
  	finally
  	   (setf (slot-value pane 'sum-width) new-sum)))
  
  (defun allocate-space-internal-height (pane size)
    (loop with sum = (slot-value pane 'sum-height) 
  	and maxs = (slot-value pane 'sorted-max-h-r)
  	and mins = (slot-value pane 'sorted-min-h-r)
  	for (nil . child) in (if (>= size sum) maxs mins)
  	and box-size = sum then (- box-size (get-pane-height child))
  	for tmp = (round (/ (* size (get-pane-height child)) box-size))
  	for new-size = (clamp tmp (sr-min-height child) (sr-max-height child))
  	for new-sum = new-size then (+ new-sum new-size)
  	do (decf size new-size)
  	   (setf (slot-value child 'new-height) new-size)
  	finally
  	   (setf (slot-value pane 'sum-height) new-sum)))
  
  (defmethod medium-foreground ((pane pane))
    (medium-foreground (sheet-medium pane)))
  
negative.code:   `(make-pane 'border-pane ,@options :contents (list ,@contents)))
  
  (defmethod allocate-space ((bp border-pane) width height)
    (when (first (sheet-children bp))
      (let ((border-width (border-pane-width bp)))
        (setf (sheet-transformation (first (sheet-children bp)))
  