Firefox ignores the setting of $LC_MESSAGES=C and shows the UI in german, just because I set $LANG to german. Firefox should honour $LC_MESSAGES properly, just like any other good program.
looks like the problem is the Fedora script used to launch firefox, it does check that the language extension is installed using the LANG. That script is RH specific, I removed the offending line and let firefox select the language by itself, With LANG=ja_JP I saw the UI in Japanese., with both LC_MESSAGES=en_US LANG=ja_JP everything was shown on English. Related lines on /usr/bin/firefox: # Try without a local variant first, then with a local variant # So that pt-BR doesn't try to use pt for example SHORTMOZLOCALE=`echo $LANG | sed "s|_\([^.]*\).*||g"` [ -f $MOZ_EXTENSIONS_DIR/langpack-${SHORTMOZLOCALE}@firefox.mozilla.org/chrome/$SHORTMOZLOCALE.jar ] && MOZARGS="-UILocale $SHORTMOZLOCALE" MOZLOCALE=`echo $LANG | sed "s|_\([^.]*\).*|-\1|g"` [ -f $MOZ_EXTENSIONS_DIR/langpack-${MOZLOCALE}@firefox.mozilla.org/chrome/$MOZLOCALE.jar ] && MOZARGS="-UILocale $MOZLOCALE"
Perfectly reproducable.
Changing version to '9' as part of upcoming Fedora 9 GA. More information and reason for this action is here: http://fedoraproject.org/wiki/BugZappers/HouseKeeping
Taking this one...
Commit to CVS and fixed in next release.