// If we are currently resizing a column then we shouldn't initiate a drag action
if (header.getResizingColumn() == null) {
TableColumnModel model = header.getColumnModel();
TypeExpr listElementType = getListElementType();
if (listElementType.rootRecordType() != null) {
// A list of values which are records.
if (getListElementType().isTupleType()) {
int xPos = ((MouseEvent)dge.getTriggerEvent()).getX();
dragFromListOfTuples(dge, model.getColumnIndexAtX(xPos));