Changing font of TreeView column header

[Hannes Mayr <hannes mayr indunet it>]

Hello,

I'm looking for a way to set font and font size for the treeview column 
header. Changing the font of the CellRenderer is no problem, but all 
attempts to change the font of the treeview header didn't work.

What I've tried is this, but without success:

PangoFontDescription *font_desc = pango_font_description_new();
pango_font_description_set_family(font_desc, "Arial");
pango_font_description_set_size(font_desc, 16);
gtk_widget_modify_font(treeview, font_desc);
pango_font_description_free(font_desc);

Can someone give me an advice how to set the font of the treeview header?

Thanks,
Hannes