anchor.diff:    return box.show();
   }
   
  -class MessageBox{
  +class MessageBox{ 
     DivElement _box;
     var _key_handler;
     StringBuffer html = new StringBuffer();
     Completer<String> _ready;
  -  
  +  NodeValidatorBuilder _validator = new NodeValidatorBuilder.common();
  +   
     static DivElement _modality;
     static void modality(bool mode){
       if (MessageBox._modality == null){
  
positive.code:     if (html != null){
        //finalize html initialization
        html.write("</div>");
        _box.innerHtml = html.toString();
        html = null;
      }
         
      //just ignore second show call, if any
      if (_ready != null)
        return;
      
      document.body.children.add(_box);
      _position_box();
  
negative.code:       html.write("<div class='dhtmlx_popup_title'>$header</div>");
      html.write("<div class='dhtmlx_popup_text'><span>$text</span></div>");
      html.write("<div class='dhtmlx_popup_controls'>");
      
      //Custom html validator
      _validator.allowElement("div", attributes: ["result"]);
    }
    
    String addButton(String text, String result){
  