   editorSubscriptions: null
   lastEditor: null
   locked: false
+  _locker: null
 
   activate: ->
     History = require './history'

      {editor, point, URI: lastURI} = @lastEditor.getInfo()
      if not @isLocked() and (lastURI isnt item.getURI())
        @history.add editor, point, lastURI, dumpMessage: "[Pane item changed] save history"

      @lastEditor.set item
      @debug "set LastEditor #{path.basename(item.getURI())}"

    @subscriptions.add panel.onDidDestroy ->
      panelSubscription.dispose()

  lock: (locker) ->
    @_locker = locker
    @locked = true

  unLock:   -> @locked = false
  isLocked: -> @locked

