anchor.diff:         :box-layout-orientation :xical))
   
    (defmethod initialize-instance :after ((pane xbox-pane) &key contents &allow-other-keys)
  -   (let ((children (mapcar (lambda (content)
  -                             ;; Note: if you extend the allowed
  -                             ;; "syntax" also update the XICALLY macro
  -                             ;; also. --GB
  -                             (cond ((panep content)
  -                                    content)
  -                                   ;;
  -                                   ((or (eql content +fill+) (eql content '+fill+))
  -                                    (let ((child (make-instance 'null-pane)))
  -                                      (setf (constraint-slot pane child 'fill-p) t)
  -                                      child))
  -                                   ;;
  -                                   ((and (consp content)
  -                                         (or (member (car content) '(+fill+ :fill))
  -                                             (eql (car content) +fill+)))
  -                                    (let ((child  (cadr content)))
  -                                      (setf (constraint-slot pane child 'fill-p) t)
  -                                      child))
  -                                   ;;
  -                                   ;; what about something like (30 :mm) ?
  -                                   ;;
  -                                   ((and (realp content) (>= content 0))
  -                                    (let ((child (make-instance 'null-pane)))
  -                                      (setf (constraint-slot pane child 'fixed-size) content)
  -                                      child))
  -                                   ;;
  -                                   ;; match (<n> <pane>)
  -                                   ;;
  -                                   ((and (consp content)
  -                                         (realp (car content))
  -                                         (>= (car content) 0)
  -                                         (consp (cdr content))
  -                                         (panep (cadr content))
  -                                         (null (cddr content)))
  -                                    (let ((number (car content))
  -                                          (child  (cadr content)))
  -                                      (if (< number 1)
  -                                          (setf (constraint-slot pane child 'proportion) number)
  -                                          (setf (constraint-slot pane child 'fixed-size) number))
  -                                      child))
  -                                   (t
  -                                    (error "~S is not a valid element in the ~S option of ~S."
  -                                           content :contents pane)) ))
  -                           contents)))
  -     (mapc (curry #'sheet-adopt-child pane) children)))
  +   ;;
  +   (labels ((parse-box-content (content)
  +              "Parses a box/rack content and returns a BOX-CLIENT instance."
  +              ;; ### we need to parse more
  +              (cond
  +                ;; <pane>
  +                ((panep content)
  +                 (make-instance 'box-client :pane content))
  +                ;; +fill+
  +                ((or (eql content +fill+)
  +                     (eql content '+fill+)
  +                     (eql content :fill))
  +                 (make-instance 'box-client
  +                                :pane nil
  +                                :fillp t))
  +                ;; (+fill+ <pane>)
  +                ((and (consp content)
  +                      (or (member (car content) '(+fill+ :fill))
  +                          (eql (car content) +fill+)))
  +                 (make-instance 'box-client
  +                                :pane nil
  +                                :fillp t))
  +                ;; <n>
  +                ;;
  +                ;; what about something like (30 :mm) ?
  +                ;;
  +                ((and (realp content) (>= content 0))
  +                 (make-instance 'box-client
  +                                :pane nil
  +                                :fixed-size content))
  +
  +                ;; (<n> pane)
  +                ((and (consp content)
  +                      (realp (car content))
  +                      (>= (car content) 0)
  +                      (consp (cdr content))
  +                      (panep (cadr content))
  +                      (null (cddr content)))
  +                 (let ((number (car content))
  +                       (child  (cadr content)))
  +                   (if (< number 1)
  +                       (make-instance 'box-client
  +                                      :pane pane
  +                                      :proportion number)
  +                       (make-instance 'box-client
  +                                      :pane pane
  +                                      :fixed-size number))))
  +
  +                (t
  +                 (error "~S is not a valid element in the ~S option of ~S."
  +                        content :contents pane)) )))
  +
  +     (let* ((clients  (mapcar #'parse-box-content contents))
  +            (children (remove nil (mapcar #'box-client-pane clients))))
  +       ;;
  +       (setf (box-layout-mixin-clients pane) clients)
  +       (mapc (curry #'sheet-adopt-child pane) children))))
   
    (defclass xrack-pane (rack-layout-mixin xbox-pane)
      ()
  
positive.code:    (declare (ignorable width height))
     (let ((children (reverse (sheet-enabled-children box))))
       (with-slots (major-spacing) box
         (let* ((content-srs (mapcar #'(lambda (c) (xically-content-sr** box c)) children))
                (allot       (mapcar #'ceiling (mapcar #'space-requirement-major content-srs)))
                (wanted      (reduce #'+ allot))
                (excess      (- major wanted
  
negative.code: 
  (defmethod handle-repaint ((pane lowered-pane) region)
    (declare (ignore region))
    (with-slots (border-width) pane
      (multiple-value-call #'draw-bordered-rectangle* pane (bounding-rectangle* (sheet-region pane))
                           :style :inset
                           :border-width border-width)))
  
  ;;; RESTRAINING PANE
  
  