GtkComboBox submenus

[Carlos Pereira <jose carlos pereira ist utl pt>]

Is there a way to create GtkComboBox menus with submenus?

The logical way to achieve this would be to use a GtkTreeStore model, 
and indeed it works as expected,
except that each first level item appears also as a second level title, 
that can be selected...

disabling a first level item disables the whole subtree, so this cannot 
be used to disable the second level titles...

Or the only solution is to use
gtk_combo_box_set_wrap_width (GTK_COMBO_BOX (combo), width)
with width > 1? My data has some nice structure, so the submenus 
approach looks slightly better...

Cheers,
Carlos