I'm a recent user of the gtk package and I found troubles trying to change the font in a multiline widget. I've seen the documentation for modules TexTag  and TextTagTable , but I was not able to do it. No compilation error, no runtime error, but no changes in the font.
Can anyone give me some pointers?
 - http://hackage.haskell.org/packages/archive/gtk/0.12.0/doc/html/Graphics-UI-Gtk-Multiline-TextTag.html
 - http://hackage.haskell.org/packages/archive/gtk/0.12.0/doc/html/Graphics-UI-Gtk-Multiline-TextTagTable.html