GtkTreeView: how to reduce size of cell

[Romain Liévin <roms lievin net>]

Hi,

I'm working on a debugger 
(http://www.lievin.net/downloads/lpg/vti_dock.png). As you can see, 
there is a lot of space between each line of the left upper frame.

How can I decrease space between lines or value of padding in cell?

I did not find any useful function in the GTK API which could do my job...

Romain.