GtkCombo list elements

[Mateusz Z.ó?tak <zozlak staszic waw pl>]

I have created a GtkCombo widget and I have added a GtkList to it by
using a gtk_combo_set_popdown_strings() function.
Now I want to get a text of an element of that list and I don't know how
to do that.
I can access to elements of the list using a gtk_container_foreach()
function but it is passing a GtkWidget pointer to the handle function
and I don't know what can I do with such argument - is it a GtkHBox,
GtkLable, or somethnk else widget.
How can I check what widget it is or how can I access to the texts of
the GtkList elements?

Have you any advice?
Thank for help
Mateusz Z.ó?tak