How can I change the default behavior of grid.js::_setSort() in order to correctly display the sort criteria (up/down arrow) in the header of all the columns involved in a sort? Currently, _setSort() only deals with the first column of the array passed to grid.set("sort"). For example, after setting the sort criteria with the following command, only the header of col1 will contain an arrow (up arrow in this case).
grid.set("sort", [{attribute: col1, descending: false}, {attribute: col2, descending: true}]);
I could override _setSort() but the underscore tells me it's a private function...