GtkTreeView: Prevent drag and drop to a nested level

[Lars Paulsen <lars_paulsen web de>]

Hi All,

I am using a GTkTreeView with automatic DND enabled and I wonder if 
there is a simple way to prevent/suppress
that a toplevel item can be dragged to a child position of another 
toplevel item.

What I did so far was catch the "row-inserted" signal, check if the item 
has moved to a child position,
and if yes, move it back to become a sibling of the parent.

Is there any better way?
Thanks for all help in advance.

Greetings,
Lars