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

        # So we can't use TexitEditor::getCursorBufferPosition(), fotunately,
        # symbols-view serialize buffer state initaially, we use this.
        onShow: =>
          editor = @getEditor()
          point  = panel.getItem().initialState?.bufferRanges[0].start
          {editor, point}
        onHide: =>
          editor = @getEditor()
          point  = editor.getCursorBufferPosition()
          {editor, point}

      {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"
      console.log "lock?: #{@isLocked()}: #{@_locker}"

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