[luatex] Wrong placement of \int\limits in Lua(La)TeX

[Simon May]

(Apologies for breaking the thread – I hadn't subscribed to the list
before.)

I agree that it's not trivial to decide where the limits should actually
be, but I guess many things in typesetting are a matter of taste.
However, I think anyone would agree that
– Using the same TeX input, the output of Lua(La)TeX and Xe(La)TeX
  should be (at least qualitatively) the same. If I decide that I want
  or need to use a different engine for a document, I want to change
  as little as possible (preferably nothing) in my document as a result.
  If a change of engine produces significantly different output, that's
  always a hint that there must be a bug somewhere.
– "\limits" should mean that the limits of the operator are placed above
  and below instead of to the sides. Whether one thinks that the
  placement with unicode-math looks good or not, the limits are so far
  to the side that it cannot really be said that they are placed above
  and below.

Moreover, I really do think that the current placement with unicode-math
looks just bad. The limits are floating somewhere to the upper
right/upper left with barely any attachment to the operator they belong
to. Originally, I thought that the placement and spacing demonstrated at
https://tex.stackexchange.com/a/103925
could universally agreed upon to be good-looking (and definitely better
than the same document typeset with LuaLaTeX).

Now that I'm looking more closely at some tests, it seems that there is
way too much space inserted after an integral sign with LuaLaTeX.
Looking at the following TeX source:

\documentclass{scrartcl}
\usepackage{unicode-math}
\begin{document}
\[
	A = \int f(x) \,\mathrm{d}x
\]
\end{document}

It seems like the amount of space between the integral sign and f(x) is
almost doubled compared to the version without unicode-math. It actually
looks really ugly. Perhaps this issue is related?


Ulrike Fischer wrote:
>Am Tue, 3 Mar 2015 20:03:33 +0100 schrieb Simon May:
>
>> Hello,
>>
>> with unicode-math and LuaLaTeX, the placement of the limits using
>> \int\limits is incorrect. The limits are placed too far to the
>> right. As
>> discussed in the comments at
>> https://tex.stackexchange.com/a/103925/51235
>> this issue does not occur with XeTeX. There is also a bug at
>> http://tracker.luatex.org/view.php?id=729
>> that might refer to this same issue. Is this indeed a bug in LuaTeX
>> and
>> are there perhaps any workarounds?
>> I'm using LuaTeX beta-0.79.1 (TeX Live 2014/Debian) (rev 4971).
>>
>> Below is a demonstration of this issue. Producing the document will
>> show
>> the incorrect placement of the limits. Removing the line
>> "\usepackage{unicode-math}" will show the expected output.
>>
>>
>> \documentclass{scrartcl}
>> \usepackage{unicode-math}
>> \begin{document}
>> \[
>> 	\int_a^b
>> 	\int\limits_a^b
>> \]
>> \end{document}
>
> The placement is certainly different than with xelatex or without
> unicode-math. But I do find it difficult to describe exactly where
> the symbol should placed and I often don't like the placement in
> pdflatex. It also depends a bit on the actual font. You can always
> move the subscripts a bit if you want:
>
> \documentclass{scrartcl}
> \usepackage{unicode-math}
> %\setmathfont{Cambria Math}
> \begin{document}
> \[
> 	\int_a^b
> 	\int\limits_{\!\!\!\!a}^{b}
>     \int\limits_{a}^{b}
>     \int\limits_{a}^{b=5}
>     \int\limits_{a=1}^{b}
>     \int\limits_{a=1}^{b=5}
> \]
> \end{document}
>
>
>> Out of interest: Using unicode-math (even without limits) does not
>> produce the same output in the example as the same document without
>> unicode-math. The the size of the integral sign and the spacing of
>> the limits changes slightly. Is this intended/expected?
>
> You are using different fonts. So differences are always possible.
>
>
> --
> Ulrike Fischer
> http://www.troubleshooting-tex.de/
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