[gtkmm] My own TreeModel

[David Vest <davve674 student liu se>]

Hello everyone!

I'm thinking about implementing my own TreeModel for a TreeView. The 
reason for this is that I already have lots of data in memory, that I 
don't want to duplicate in the model if I can avoid it. The concept is 
tried and works well by the windows version of the program.

I have read all a can find on the net, but havn't found anything about 
what I would really do to make my TreeView be able to access my data. 
On to my questions:

- Have this been done before in any OSS project?
- I find overridable functions in gtkmm/treemodel.h, is that what I am 
supposed to do?
- In the same file it says that it is not easy, why?

Thanks

David