# [XeTeX] Problems with thickness of \frac rule and width of accents (\hat) with XeLaTeX

ulrik.vieth at arcor.de ulrik.vieth at arcor.de
Mon Aug 16 11:46:34 CEST 2010

Hi,

the funny thing is: If you don't use anything special in your documents,
you don't have to learn anything if you want to switch.
You can use exactly the same input with both LuaLaTeX and XeLaTeX,
but the output may be slightly different due to implementation differences
(or due to the presence or absence of certain bugs).

In TeX Live 2010 (currently in pretest) both engines will be provided,
and both engines will be supported by the new version of unicode-math.
Unfortunately, I don't know when TeX Live 2010 will be released and
I don't known anything about what is currently provided in MikTeX.

Regards, Ulrik.

P.S: Just to make sure I won't be mistunderstood: I do not want to
advertise switching from one engine to another here. That's a decision
between XeTeX and LuaTeX everyone has to make for themselves.

I happen to know the authors of both engines and I respect their work.
Both engines follow different design philosophies and both have good
reasons to do so. If there weren't any bugs, both engines should be
equally well suited for the job, but there may be other reasons why
one might prefer one engine or the other for a particular type of job.

----- Original Nachricht ----
Von:     drgz drgz <syrehue at hotmail.com>
An:      xetex at tug.org
Datum:   16.08.2010 10:59
Betreff: Re: [XeTeX] Problems with thickness of \frac rule and width of
accents (\hat) with XeLaTeX

>
> Thanks for the detailed answer Ulrik, although it seems like there's not
> much I can do but learn LuaLaTeX in order to get the documents as I want
> them to be. :)
> Would it be possible to get the LuaLaTeX code you used in order to compile
> the document as a starting-point, as I've never seen or tried it before?
>
> Best regards,
> D.
>
> > Date: Mon, 16 Aug 2010 00:15:35 +0200
> > From: ulrik.vieth at arcor.de
> > To: xetex at tug.org
> > Subject: Re: [XeTeX] Problems with thickness of \frac rule and width of
> accents (\hat) with XeLaTeX
> >
> > Hi,
> >
> > I tested it with both XeLaTeX and LuaLaTeX (both from TL2010 pretest).
> > In short, the problem only occurs in XeLaTeX, but not in LuaLaTeX,
> > despite using the same macro packages and fonts for both engines.
> >
> > I do not really understand the problem with the fraction rule thickness.
> > It probably should be the same on both engines (despite conceptual
> > differences), as it should be based on the same OpenType parameter
> > RadicalRuleThickness, but it seems to be different nonetheless:
> >
> > XeLaTeX:
> > .......\kern4.7461
> > .......\rule(0.47998+0.0)x*
> > .......\kern2.97542
> >
> > LuaLaTeX:
> > .......\kern3.43199
> > .......\rule(0.79199+0.0)x*
> > .......\kern2.98799
> >
> > The LuaTeX value of 0.792pt at 12pt matches the scaled value of 0.66pt
> > at 10pt of the OpenType font parameter for XITS Math.
> >
> > The XeTeX value of 0.48pt at 12pt matches the scaled value of 0.4pt
> > at 10pt, which is suspiciously similar to the default rule thickness
> > of CM fonts. I don't know how this comes about. I'm not sure if this
> > is an engine bug or if it could be caused by a macro problem.
> >
> > As for the overly wide hat, this is obviously an engine bug in XeTeX.
> > The behavior is clearly wrong and the problem does not occur in LuaTeX.
> >
> > I believe I have seen a similar problem before in XeTeX, which had
> > been fixed by Jonathan during a lunch break at EuroTeX 2009 last year.
> > I wonder if an old bug has resurfaced now or if anything went wrong
> > merging the bug fixes (or if it was a different bug that was fixed).
> >
> > Regards, Ulrik
> >
> >
> > P.S: On second thought, I'm not sure any more if this was really
> > the same bug that was fixed or just a similar one. It could have been
> > about the positioning of math accents (e.g. centering \dot and \ddot)
> > rather than the width of wide math accents, but it also had to do
> > with an incorrect calculation of the size based on the subscripts.
> >
> >
> > On 08/15/2010 09:37 PM, drgz drgz wrote:
> > > Anyhow, I'm playing around with XeLaTeX (the newest version coming with
> > > MikTeX) trying to compile some documents. And almost everything is as
> it
> > > should be, except the thickness of the rule in \frac (does not get any
> > > thicker) and the width of the \hat accent (which gets wider than it
> should).
> > > I've attached a link to a compiled PDF which illustrates what I
> > > experience - see http://folk.ntnu.no/mitrevsk/temp/xelatex/ex.pdf
> > >
> > > No matter which OTF font with unicode-math support I select I
> experience
> > > this problem when I compile with XeLaTeX. Is there any way to fix this
> ?
> >
> >
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