void gtk_custom_sorter_set_sort_func ( GtkCustomSorter* self, GCompareDataFunc sort_func, gpointer user_data, GDestroyNotify user_destroy )
Sets (or unsets) the function used for sorting items.
NULL, all items are considered equal.
If the sort func changes its sorting behavior,
gtk_sorter_changed() needs to be called.
If a previous function was set, its
user_destroy will be