Sets the current sort column to be @sort_column_id. The @sortable will
resort itself to reflect this change, after emitting a
#GtkTreeSortable::sort-column-changed signal. @sort_column_id may either be
a regular column id, or one of the following special values:
- %GTK_TREE_SORTABLE_DEFAULT_SORT_COLUMN_ID: the default sort function
will be used, if it is set
- %GTK_TREE_SORTABLE_UNSORTED_SORT_COLUMN_ID: no sorting will occur
Sets the current sort column to be @sort_column_id. The @sortable will resort itself to reflect this change, after emitting a #GtkTreeSortable::sort-column-changed signal. @sort_column_id may either be a regular column id, or one of the following special values:
- %GTK_TREE_SORTABLE_DEFAULT_SORT_COLUMN_ID: the default sort function will be used, if it is set
- %GTK_TREE_SORTABLE_UNSORTED_SORT_COLUMN_ID: no sorting will occur