anchor.diff:                                            t)))
           (setf (lem:frame-window-tree frame) new-window
                 (lem:frame-current-window frame) new-window
  -              (virtual-frame-current vf) %frame)
  -        (allocate-frame vf %frame)
  +              (virtual-frame-current vf) frame)
  +        (allocate-frame vf frame)
           (lem:map-frame (implementation) frame))
         (setf (virtual-frame-changed vf) t))))
   
  
positive.code:     :for impl :in (list (implementation))  ; for multi-frame support in the future...
      :do (let ((vf (make-virtual-frame impl (lem:get-frame impl))))
            (setf (gethash impl *virtual-frame-map*) vf)
            (lem:map-frame (implementation) (%frame-frame (virtual-frame-current vf))))))
  
  (defun enabled-frame-multiplexer-p ()
    (variable-value 'frame-multiplexer :global))
  
negative.code: (defun make-virtual-frame (impl frame)
    (declare (type frame frame))
    (let* ((buffer (make-buffer "*fm*" :enable-undo-p nil :temporary t))
           (id/frame-table (make-array +fm-max-number-of-frames+ :initial-element nil)))
      (setf (aref id/frame-table 0) frame)
      (setf (lem:variable-value 'truncate-lines :buffer buffer) nil)
      (let ((vf (make-instance 'virtual-frame
                               :impl impl
  