[XeTeX] Bug with underbrace

[Khaled Hosny]

On Thu, Nov 04, 2010 at 03:59:53PM +0100, Ulrike Fischer wrote:
> Am Wed, 03 Nov 2010 07:44:07 +0100 schrieb Tobias Schoel:
> 
> > Hi,
> > 
> > \underbrace is doing strange things. Minimal example:
> > 
> > \documentclass{minimal}
> > \usepackage{fontspec}
> > \usepackage{unicode-math}
> > \setmainfont{TeX Gyre Pagella}
> > \setmathfont{Asana Math}
> > \begin{document}
> > \[\underbrace{123}_{456}\]
> > \end{document}
> > 
> > Why is that and how to help?
> 
> With xetex \underbrace use internally the commands \bracelu,
> \braceld and they simply don't give the correct glyphs with a
> unicode-math font. That's certainly a problem unicode-math should
> correct somehow (I don't know if the needed glyphs exists in the
> fonts).

I think this worked before since family 1 and 2 were kept using CM, now
since unicode-math are using those two families (to fix the other bug)
this no longer works, and this would also affect any other symbol that
would fallback to CM because unicode-math does not define.

> With luatex \underbrace seems to use \luatexUdelimiterunder, but I
> don't know if the fact that the brace is above instead of below the
> numbers indicates a luatex bug or wrong use of the luatex command on
> the side of unicode-math.

IMO, \Udelimiter* was wrong here, because it also sets the symbol in
\scriptstyle, \Umathaccent* should be used instead (there is an open
unicode-math issue for that IIRC).

Regards,
 Khaled

-- 
 Khaled Hosny
 Arabic localiser and member of Arabeyes.org team
 Free font developer