anchor.diff:              (:inactive
                (draw-button :ink +grey+)
                (draw-button :ink +black+ :filled nil))
  +            (:highlighted
  +             (draw-button :ink +grey95+)
  +             (draw-button :ink +black+ :filled nil))
               (:selected
                (draw-button :ink +black+ :filled nil :closed nil))))
           ;; Draw label.
  
positive.code:     (object (type tab-page) stream (view tab-bar-view) &key)
    (let ((enabledp (sheet-enabled-p (tab-page-pane object))))
      (draw-tab-header stream object (if enabledp :selected :inactive))))
  
  (defclass tab-layout-pane (tab-layout)
    ((header-pane :accessor tab-layout-header-pane
  
negative.code: (defpackage #:clim-tab-layout
    (:use #:clim #:clim-lisp)
    (:import-from #:alexandria
                  #:when-let
                  #:first-elt)
    (:export #:tab-layout
             #:tab-layout-pane
             #:tab-layout-pages
  