anchor.diff:                .toString() +
             "px"
         ..top =
  -          (_domElement.offsetTop - _REPEAT_BUTTON_SIZE / 2).toString() + "px"
  +          (_getOffsetTop(_domElement) - _REPEAT_BUTTON_SIZE / 2).toString() + "px"
         ..display = "block";
   
       _moveDownDomElement.style
  
positive.code:                 .toString() +
              "px"
          ..top =
              (_domElement.offsetTop - _REPEAT_BUTTON_SIZE / 2).toString() + "px"
          ..display = "block";
      }
  
  
negative.code:     html.document.body.children.add(_moveDownDomElement);
    }
  
    int _getOffsetTop(html.Element el) {
      int res = 0;
  
      while(el != null) {
        res += el.offsetTop;
        el = el.offsetParent;
      }
  
      return res;
    }
  
    void show() {
      _isShown = true;
  
  