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