anchor.diff:    (let* ((vf (gethash (implementation) *virtual-frame-map*))
            (frame (search-next-frame vf (virtual-frame-current vf))))
       (when frame
  -      (setf (virtual-frame-current vf) frame)
  -      (map-frame (implementation) frame))
  +      (switch-current-frame vf frame))
       (lem::change-display-size-hook)
       (setf (virtual-frame-changed vf) t)))
   
  
positive.code:                              :id/frame-table id/frame-table
                               :current frame)))
        vf)))
  
  (defun find-unused-frame-id (virtual-frame)
    (position-if #'null (virtual-frame-id/frame-table virtual-frame)))
  
negative.code:       (editor-error "it's full of frames in virtual frame"))
      (let ((frame (make-frame (current-frame))))
        (setup-frame frame (primordial-buffer))
        (allocate-frame vf frame)
        (switch-current-frame vf frame)
        (setf (virtual-frame-changed vf) t))))
  
  (define-key *global-keymap* "C-z d" 'frame-multiplexer-delete)
  