emacs and fallback fonts

[Francesco Mazzoli]

Hi list,

I am trying to get emacs to fallback nicely when my font of choice 
(Terminus) doesn't have a symbol.

Using something like

(set-fontset-font "fontset-default" 'unicode "DejaVu Sans Mono-10")

works, but then *every* unicode symbol is displayed using DejaVu.

I couldn't find a way to configure the fallback font only (without even 
caring about unicode, I just want the missing symbols to be displayed 
with a font that I choose).

This message seems to ask the same question: 
http://lists.gnu.org/archive/html/help-gnu-emacs/2011-03/msg00154.html , 
but there was no answer, so I am asking again.

Francesco.