[texhax] quotation marks with babel in LuaLaTeX

[Arno Trautmann]

Herbert Voss wrote:
> Am 19.09.2011 13:46, schrieb Martin Schröder:
>> Am 19. September 2011 12:36 schrieb Herbert
>> Voss<Herbert.Voss at fu-berlin.de>:
>>> \documentclass[ngerman]{scrartcl}
>>> \usepackage{fontspec}
>>> \usepackage{babel}
>>> \usepackage{libertine}
>>> %\setmainfont{Linux Libertine O}
>>>
>>> \begin{document}
>>> „“ "` "'
>>> \end{document}
>>
>> (/opt/tex/texlive/2011/texmf-dist/tex/generic/babel/babel.sty
>>
>> ! Package babel Error: You haven't specified a language option.
>
> I do not get such a message ...

Me neither, it works for me, thanks. (Martin, you might have to remove 
your .aux file, too …)

However, Linux Libertine was only an example. What do I do if I want to 
use an arbitrary system font? In the libertine.sty, I find the line

\ProvideTextCommand{\glqq}{EU2}{\textormath{\quotedblbase}
   {\mbox{\quotedblbase}}}

So (I guess) babel maps "` to \glqq, and the libertine package 
re-defines that command. Now, in source2e, I find

\DeclareTextSymbol{\quotedblbase}{T1}{18}

I'm not sure why, but I have the feeling that this is awkward. Wouldn't 
it make much more sense if "` was mapped directly to the unicode point 
of „? If so, should this be in some package? I could imagine babel to 
check for luatex or xetex and then apply this definition. Or maybe 
fontspec to overwrite it.

What do you think?

cheers
Arno