anchor.diff:     (columns :initform nil :initarg :columns)))
   
   
  -(defun make-dynamic-row-layout (height &optional columns)
  -  (make-instance 'dynamic-row :height height :columns columns))
  +(defun make-dynamic-row-layout (height &key columns name)
  +  (make-instance 'dynamic-row :height height :columns columns :name name))
   
   
   (defmethod compose ((this dynamic-row))
  
positive.code:     (compose element)))
  
  
  (defclass layout (parent) ())
  
  
  (defmethod name-of ((this layout))
    nil)
  
  
  (defmethod compose ((this layout))
  
negative.code: (defgeneric show-widget (widget))
  
  
  (defclass widget (named)
    ((hidden :initform nil :reader hiddenp)))
  
  
  (defmethod children-of ((this widget))
  