I don't like placement of subsripts when using unicode math fonts under XeLaTeX. In contrast to CM fonts the subscripts are placed at different vertical positions obviously depending on the depth of preceding symbol. Here is an example:
It is produced with the following MWE:
\documentclass{article}
\usepackage{fontspec}
\defaultfontfeatures{Renderer=Basic,Ligatures={TeX}}
\setmainfont[Numbers={OldStyle}]{Minion Pro}
\usepackage[math-style=ISO,bold-style=ISO]{unicode-math}
\setmathfont[version=asana]{Asana Math}
\setmathfont[version=cambria]{Cambria Math}
\setmathfont[version=lm]{Latin Modern Math}
\setmathfont[version=stix]{STIXGeneral}
\setmathfont[version=xits]{XITS Math}
\begin{document}%
Asana Math \mathversion{asana}
\( \nabla_{\bot}p_{\bot} + \nabla_{\parallel}p_{\parallel} + d_{s}J_{s} \)
Cambria Math
\mathversion{cambria}
\( \nabla_{\bot}p_{\bot} + \nabla_{\parallel}p_{\parallel} + d_{s}J_{s} \)
STIXGeneral
\mathversion{stix}
\( \nabla_{\bot}p_{\bot} + \nabla_{\parallel}p_{\parallel} + d_{s}J_{s} \)
Latin Modern
\mathversion{lm}
\( \nabla_{\bot}p_{\bot} + \nabla_{\parallel}p_{\parallel} + d_{s}J_{s} \)
XITS Math
\mathversion{xits}
\( \nabla_{\bot}p_{\bot} + \nabla_{\parallel}p_{\parallel} + d_{s}J_{s} \)
\end{document}
And original PDFLaTeX with Computer Modern fonts yields subscript aligned at same vertical position:
UPDATE:
LuaLaTeX has no such "feature":
Q#1: Is it the XeLaTeX bug?
Q#2: Is it possible to instruct unicode-math
to align subscripts on same vertial position under XeLaTeX?
Best Answer
I experienced a similar problem with superscripts. Searching for a solution I encountered your question.
Problem Description: Just typeset
The alignment is wrong.
Further search, which might contribute to a solution, revealed that:
Q#1 It is not a
xelatex
bug, because typesetting witheulervm
as a math font and themathspec
package does not lead to this behavior. It is also not an error of opentype font metrics, because the above formulae appear correctly in Word 2010 using Cambria Math (this is embarrassing). Therefore, I am led to believe that there is something rotten in the code of theunicode-math
package.Q#2: Reading the documentation of the
unicode-math
package, I didn't find any way of correcting this behavior except for modifying the source code, which I don't know how to do.I think that this should be filed as an example of an unwanted behavior (or bug) to the maintainer of the
unicode-math
package, in order to be corrected in future versions.Compiling with
lualatex
cannot be a general solution, because (at least in my case) I needpolyglossia
's features, as my text involves English, Greek and some Russian text andpolyglossia
has its problems withlualatex
(or the other way around?).