GtkCTree: Getting all top-level nodes?

["M Razhov" <mrazhov mail ru>]

Hi,

How do I enumerate all top-level nodes in a GtkCTree?
For example, if I had a tree with nodes 1 and 2, stemming
from root (no parent), and 1 had two children, 1.1 and 1.2,
like this:
  |
  +--1
  |  +--1.1
  |  +--1.2
  |
  +--2
I would like to programmatically ask the CTree about its
root nodes and get 1 and 2.  (I suspect this may be non-
trivial and possibly require ugly code, I'm just looking
to do it).