anchor.diff:      :initform 0
       :accessor tabbar-prev-display-width)))
   
  -(defvar *use-tabbar* nil)
   (defvar *tabbar* nil)
   
   (defun tabbar-init ()
  
positive.code:     (let ((button (button-at p)))
        (when button
          (button-action button)))))
  
negative.code:   (:use :cl :lem :lem.button)
    (:export :tabbar-active-tab-attribute
             :tabbar-attribute
             :tabbar-background-attribute
             :tabbar))
  (in-package :lem.tabbar)
  
  (define-attribute tabbar-active-tab-attribute
  