# [luatex] sub and superscripts in Lua(La)TeX with tfm/otf

Arno Trautmann Arno.Trautmann at gmx.de
Mon Jun 13 11:35:11 CEST 2016

Hi all,

I encountered some strange behaviour regarding the subscript and
superscripts in LuaLaTeX compared to pdfLaTeX. Consider the following
small example:

%\RequirePackage{luatex85}
\documentclass{scrartcl}
%\usepackage{subdepth}
%\usepackage{unicode-math}

\begin{document}
$a_ia_i^+a^+a_i^\dagger$
$M_n M_n^\dagger M_n^+$
\end{document}

Compilation with pdfLaTeX results in shifted positions for the sub and
super scripts according to the TeXbook. The package subdepth equalizes
them, which in this case looks nicer.
With LuaLaTeX, the subdepth package does not work, and has no effect on
the positioning whatsoever. David suggested to ask for a reason for this
behaviour on the luatex-list.
Making things more complicated: If I load unicode-math and thus
lm-math.otf, the subdepth package still has no effect. BUT: The
positions of the subscrips is plain wrong in my opinion in the second
line, as in M_n^\dagger the subscript is placed *higher* than in the
other cases. Which does not happen for the a_i^\dagger.

In total, I see a lot of different placements of the sub/superscripts
and I am a bit lost which one is the right one, which one might be a bug
and which one is intendedly different – the placement depends on the
engine, the font, the size of the nucleus and the size of the
superscript. Can anybody help me figure this one out?
(What I *want* is the behaviour of pdfLaTeX + subdepth to work in
LuaLaTeX + unicode-math)

Best,
Arno