anchor.diff:     options."
     (let* ((sr           (compose-space child))
            ;; The child's dimension is clamped within its min/max space requirement
  -         (child-width  (clamp width  (space-requirement-min-width sr)  (space-requirement-max-width sr)))
  -         (child-height (clamp height (space-requirement-min-height sr) (space-requirement-max-height sr)))
  +         (child-width  (clamp width
  +                              (space-requirement-min-width sr)
  +                              (space-requirement-max-width sr)))
  +         (child-height (clamp height
  +                              (space-requirement-min-height sr)
  +                              (space-requirement-max-height sr)))
            ;; Align the child within the available area
            (child-x      (ecase align-x
                            ((:left)   x)
  
positive.code:             (c (stack-space-requirements-horizontally csrs)))
          (let ((res
                 (make-space-requirement
                  :width (space-requirement-width r)
                  :min-width (space-requirement-min-width r)
                  :max-width (space-requirement-max-width r)
                  :height (space-requirement-height c)
                  :min-height (space-requirement-min-height c)
                  :max-height (space-requirement-max-height c))))
            #+NIL
  
negative.code:                       (t
                         max-foo))))))
      (make-space-requirement
        :width      width
        :min-width  min-width
        :max-width  max-width
        :height     height
        :min-height min-height
        :max-height max-height)))
  
  (defmethod merge-user-specified-options ((pane border-space-requirement-options-mixin) sr)
    (with-slots (user-width user-min-width user-max-width
                 user-height user-min-height user-max-height) pane
      (let* ((min-width  (or user-min-width  2))
             (max-width  (or user-max-width  +fill+))
             (min-height (or user-min-height 2))
             (max-height (or user-max-height +fill+)))
        (space-requirement+* sr
                             :width      (clamp (or user-width 2) min-width max-width)
                             :min-width  min-width
                             :max-width  max-width
                             :height     (clamp (or user-height 2) min-height max-height)
                             :min-height min-height
                             :max-height max-height))))
  
  (defmethod compose-space :around ((pane space-requirement-options-mixin)
                                    &key width height)
  