[luatex] "Proper" use of \Udelimiterover &c

[Khaled Hosny]

On Thu, Jul 29, 2010 at 10:17:20AM +0300, Khaled Hosny wrote:
> On Wed, Jul 14, 2010 at 01:03:55PM +0200, Taco Hoekwater wrote:
> > On 07/14/2010 12:13 PM, ulrik.vieth at arcor.de wrote:
> > >>Ulrik, can you try this overbrace stuff in Word to see how it looks?
> > >
> > >Enclosed is a PDF from Word 2007 using CambriaMath.
> > >
> > >In Word, the overbrace stuff is hidden in the accents palette.
> > >You can choose between a simple overbrace or and overbrace
> > >with an extra group (which TeX typesets as \mathop\limits).
> > >
> > >Hope this helps to clarify your issues.
> > 
> > Thanks. It sure looks like I am misinterpreting something in
> > the luatex implementation.
> 
> Also, the over and under delimeters are taken from the scriptfont, the
> attached example shows:

Now reading the MAPS article on LuaTeX math, it is clear that this is
what it is supposed to do:

  ... and the complementary \Udelimiterunder and \Udelimiterover
  primitives allow the placement of an extensible item as a subscript or
  superscript on a nucleus.

So I'm wondering if those are the right primitives for \over/underbrace,
since in plain TeX both text style. In this case \Umathaccent and
\Umathbotaccent seems to be a better match.

Regards,
 Khaled

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