     App.TicketArticle.unsubscribe(@subscribeId)
 
   setHighlighter: =>
-    return if !@el.is(':visible')
+    return if @el.is(':hidden')
     # use delay do no ui blocking
     #@highligher.loadHighlights(@ticket_article_id)
     d = =>

    @article = App.TicketArticle.fullLocal( @ticket_article_id )

    # set @el attributes
    @el.addClass("ticket-article-item #{@article.sender.name.toLowerCase()}")
    if @article.internal is true
      @el.addClass('is-internal')
    else
      @el.removeClass('is-internal')
    @el.attr('data-id',  @article.id)
    @el.attr('id', "article-#{@article.id}")

    # check if rerender is needed
    return if !@hasChanged(@article)

    # prepare html body
    if @article.content_type is 'text/html'

  hasChanged: (article) =>

    # if no last article exists, remember it and return true
    if !@articleAttributesLastUpdate
      @articleAttributesLastUpdate = {}
      for item in @hasChangedAttributes
        @articleAttributesLastUpdate[item] = article[item]
      return true

    # compare last and current article attributes
    articleAttributesLastUpdateCheck = {}
    for item in @hasChangedAttributes
      articleAttributesLastUpdateCheck[item] = article[item]
    diff = difference(@articleAttributesLastUpdate, articleAttributesLastUpdateCheck)
    return false if !diff || _.isEmpty( diff )
    @articleAttributesLastUpdate = articleAttributesLastUpdateCheck
    true

  render: (article) =>
