anchor.diff:        ..onDragEnd.listen((_) async {
         li.classes.remove('dragging');
         var new_index = li.parent.children.indexOf(li);
  -      if(index == new_index){
  +      if (index == new_index) {
           return;
         }
         _activeList.classes.add('blur');
  
positive.code:       ..addHandler(_activeDragHandler)
        ..addUpdater(_updater)
        ..onAdd.listen((_) => _moveEmptyLast(list));
    }
  
    _show_page(Page page, LIElement li) {
  
negative.code:   }
  
    _create_active_generator(UListElement list, [parent=null]) {
      var generator = new ElementChildrenGenerator<Page, LIElement>(
              (Page p) => _active_element.clone(true),
          list,
          _pageSelector)
  