SMART datagrid v.1 > Classes > DataSet
It will be fired when Undo stack of data set is changed, that is, when a new change call is added or undo, redo is run.
ds.onUndoStateChanged = function (grid, canUndo, canRedo) {
document.getElementById('btnUndo').disabled = !canUndo;
document.getElementById('btnRedo').disabled = !canRedo;
};