Gtk3 - treview - drag and drop

[Michal Hucik - ORDOZ <ordoz ordoz com>]

Hello,

I have a TreeView with data model which has two logical element types - 
Groups and Points. I would like preserve to the only records with a 
"GROUP" type could be parenting. Elements of a type "POINT" must be 
childless.

I want to let moving the Groups, Points or the branches by drag and 
drop. It is seamless.

But I need make a test of the destination type when the element is 
dropped, and abort the drag and drop action, if destinaton element is 
not a type "GROUP". How to achieve this?

The ideal would be if carried out evaluated targets before drop, and 
dissable dropping on not a GROUP type rows.

but it will suffice, if the drag and drop action will be evaluated after 
drop event  (before insert rows into data model) and eventually will be 
D'N'D canceled.

As a suitable place for such a test I try to connect handler to signal 
"drag-drop" on the GtkTreeView. Interrupting the D'N'D action I can make 
by a return code, but how do I find the target iter from this place? 
What better place for this?

Michal