TreeView drag and drop

[Grant McLean <grant mclean net nz>]

Hi All

I'm implementing a menu editor around a TreeView which presents the user
with a structure something like this:

  Item One
 +Menu One
    Item Two
    Item Three
 +Menu Two
    Item Four
    Item Five
  Item Six

I have enabled reordering of items via drag-n-drop with this line:

  $view->set_reorderable(TRUE);

The problem is that I want to control what happens when an item is
dropped.  If it's dropped on a Menu then the item should go 'into' the
menu, but if it's dropped on another Item then it should go 'after' the
item.

The Gtk2::TreeViewDropPosition enum seems related to what I want to
achieve.  

Is there any way to hook into the signals and affect the default drag
behaviour?  Or do I have to turn off reorderable and do it all myself if
I want something slightly non-standard?

Cheers
Grant