anchor.diff:  ;;;
   ;;;
   ;;;
  -(defclass combo-box (layout widget)
  +(defclass combo-box (%layout widget)
     ((label :initarg :label :initform "")
      (color :initarg :color :initform nil)
      (height :initarg :height :initform 400f0)))
  
positive.code: ;;;
  ;;; CUSTOM LAYOUT
  ;;;
  (defclass custom-layout (layout) ())
  
  
  ;;;
  
negative.code: ;;;
  ;;;
  ;;;
  (defclass stacking-layout (expandable panel %layout) ())
  
  
  (defun default-row-height (child-height)
  