[XeTeX] strande behavior of Linux Libertine fonts with optio Fractions=On

[mskala at ansuz.sooke.bc.ca]

On Thu, 13 Jan 2011, François Patte wrote:
> > You should only turn the fractions option on where you actually want

> So no other solution that:
> {\addfontfeature{Fractions=On} 1/2}
>
> Or a macro doing the same job?

As far as I know, that's what must be done.

Fr. Michael said that Latin Modern Roman and Junicode don't have this
effect, and that's very interesting because I thought (for the reasons
described) that it was impossible to avoid at the level of OpenType
substitution.  I couldn't find the source code for the OpenType features
in Latin Modern Roman; in the case of Junicode, it appears to me that it
just doesn't do fraction substitution at all.  If it seems to, in XeTeX,
I wonder if XeTeX is implementing it rather than the font using OpenType
substitution.

It would be possible for an OpenType font to do substitution for fractions
without disturbing non-fraction digit sequences, if it put a fixed limit
on the maximum length of sequences it could handle.  That is what I'm
implementing in one of my own font projects.  It's not much help if you
have a specific font you want to use that's doing the arbitrary-length
thing.
-- 
Matthew Skala
mskala at ansuz.sooke.bc.ca                 People before principles.
http://ansuz.sooke.bc.ca/