The #GtkTreeModelSort is a model which implements the #GtkTreeSortable interface. It does not hold any data itself, but rather is created with a child model and proxies its data. It has identical column types to this child model, and the changes in the child are propagated. The primary purpose of this model is to provide a way to sort a different model without modifying it. Note that the sort function used by #GtkTreeModelSort is not guaranteed to be stable.