assert tableRenderer != null;
ArrayList/*<String>*/ styleClasses = new ArrayList/*<String>*/();
/* todo: refactor. add a chain of style decorators here; easier to extend this way. */
FilterModel filterModel = dataGridModel.getState().getFilterModel();
if(filterModel.isFiltered(_headerCellModel.getFilterExpression()))
styleClasses.add(dataGridModel.getStyleModel().getHeaderCellFilteredClass());
SortModel sortModel = dataGridModel.getState().getSortModel();
if(sortModel.isSorted(_headerCellModel.getSortExpression()))
styleClasses.add(dataGridModel.getStyleModel().getHeaderCellSortedClass());