Pff, mais la doc, ca sert a ca non ?
http://developer.gnome.org/doc/API/2.0/gtk/
gtk_combo_box_new ()
GtkWidget* gtk_combo_box_new (void);
Creates a new empty GtkComboBox.
<col align=\"left\" valign=\"top\" />----
Returns :, A new GtkComboBox.
gtk_combo_box_new_text ()
GtkWidget* gtk_combo_box_new_text (void);
Convenience function which constructs a new text combo box, which is a
GtkComboBox just displaying strings. If you use this function to create
a text combo box, you should only manipulate its data source with the
following convenience functions: gtk_combo_box_append_text()
,
gtk_combo_box_insert_text()
, gtk_combo_box_prepend_text()
and
gtk_combo_box_remove_text()
.
<col align=\"left\" valign=\"top\" />----
Returns :, A new text combo box.