Here is an example of a simple, but typical use of a GtkCombo:

GtkWidget *combo;
GList *items = NULL;

items = g_list_append (items, "First Item");
items = g_list_append (items, "Second Item");
items = g_list_append (items, "Third Item");

combo = gtk_combo_new ();
gtk_combo_set_popdown_strings (GTK_COMBO (combo), items);
      

In order to react to the user's selection, connect to the "changed" signal on the combo and use gtk_entry_get_text (GTK_ENTRY (combo->entry)) to retrieve the selected text.

And here is how it would be done using GtkComboBoxEntry:

combo_box = gtk_combo_box_entry_new_text ();

gtk_combo_box_append_text (GTK_COMBO_BOX (combo_box), "First Item");
gtk_combo_box_append_text (GTK_COMBO_BOX (combo_box), "Second Item");
gtk_combo_box_append_text (GTK_COMBO_BOX (combo_box), "Third Item");
      

In order to react to the user's selection, connect to the "changed" signal on the combo and use gtk_entry_get_text (GTK_ENTRY (GTK_BIN (combo_box)->child)) to retrieve the selected text.