As you may have noticed in the GtkCombo constructor example, it is not by any means essential that the items in a GtkList are GtkListItems. This method is intended to provide a way to give an alternative to the entry box, where only the string data type is allowed.

set_item_string() can be set regardless of whether there is already text in the list item, and in either case will provide the string that is compared against the entry's text content during search routines.