How to get a GtkSizeGroup?

[Jaap Haitsma <jaap haitsma org>]

Hi,

I have a number of comboboxes that I want to have exactly the same size, 
and also I want them to align vertically. I can't use a table because in 
the dialog I want to use them there will be some text in between. 
Somebody on this list pointed me to use GtkSizeGroup.

However using that I still can't get it right. I attached a very simple 
project, where I try and do it. I'm hoping that somebody can take a took 
at it and tell me what I do wrong.

Thanks

Jaap