Comment # 27 on bug 1209594 from Stefan Dirsch

(In reply to Stefan Dirsch from comment #26)
> > If it is to just provide sensible defaults in case some settings are
> > missing, 
> > maybe this logic might do the trick:
> > 
> > if KEYMAP and XKBLAYOUT are defined 
> >   do nothing (and preserve user settings)
> > 
> > else if KEYMAP is defined but not XKBLAYOUT
> >   set-keymap KEYMAP (which will also implicitly set XKB*)
> > 
> > else
> >   do nothing (current behavior)
> > fi
> 
> Yes, that may work. Haven't tested this though.

Implemented this now. Will attach it in a minute.