anchor.diff:      if (value != _headless) {
         _headless = value;
         
  +      if (_headerBounds != null) _headerBounds.visible = _headerBounds.includeInLayout = !value;
         if (_headerContainer != null) _headerContainer.visible = _headerContainer.includeInLayout = !value;
   
         if (_headerItemRenderers != null) {
  
positive.code:       
        if (_autoManageScrollBars) _list.horizontalScrollPolicy = (tw > _width) ? ScrollPolicy.AUTO : ScrollPolicy.NONE;
        else _list.horizontalScrollPolicy = _horizontalScrollPolicy;
  
        if (_headerContainer != null) {
          _headerContainer.width = w;
  
negative.code:   List<IHeaderItemRenderer> get headerItemRenderers => _headerItemRenderers;
  
    VGroup _gridContainer;
    HGroup _headerBounds, _headerContainer;
    ListRenderer _list;
    
    ListRenderer get list => _list;
  