[gtkmm] treeview iterator

[Erwan Ancel <eancel amadeus net>]

Hi,
I would like to know how to get an iterator to the row before the selected
one. I know that I can parse the whole list, but this is not efficient at
all.
This corresponds to a -- operator for the iterator (I can easily get the
next one with the ++ operator)
Does anyone know a way to get an iterator to the previous row efficiently ?

      Thanks.

            Erwan