Treeview dnd with sorted treestore

[Jef Driesen <jefdriesen hotmail com>]

For my application I would like to change the default drag and drop 
(dnd) behaviour of the treeview. I need a behaviour that is similar to 
the nautilus file treeview. This treeview can be sorted by clicking on 
the column headers and you can only drop a row into another one (but not 
between two rows), and the inserted row is automatically sorted.

But by default, the treeview disables dnd if the model is sorted and it 
also allows to drop rows between two other rows (and thus specifying the 
exact drop location, which is of course mutually exclusive with the 
sorting). How can I allow only dropping into another row?

Can this be done with the high level dnd api? Or is the low level api 
the only way to do this? But I don't want to loose all the features like 
hover-to-open and auto-scroll.