Nested Tree View

[Alejandro Serrano <trupill yahoo es>]

Hi,
I'm trying to write a custom widget to represent some data in a way
similar to this image: http://www.threatofchaos.com/imagenes/hsl2.PNG
What I need is to "nest" items in a TreeView, but changing the set of
columns that are represented. I mean, I need to have

- Item 1
- Item 2
   * SubItem 2.1
   * SubItem 2.2
- Item 3
   * SubItem 3.1

All Item 1, 2 and 3 would have the same set of columns. SubItems 2.1 and
2.2 would have another set of columns, and SubItem 3.1 another different
one.

I have been trying to use a combination of Expanders and TreeViews, but
I feel that it's very inefficient, and I haven't found the way to have
all the columns in the same set correctly aligned yet.
Other option I was considering was creating some kind of new Cell
Renderer that would include the SubItems. Is there any way to make a
renderer that spans multiple columns and with a widget inside it?

Thanks very much in advance,
Alejandro Serrano