How do I get references in subscripts to be the right size when compiling to dvi with hyperref?

Question

(Having investigated the original question, I'm taking the liberty of re-writing it as I've found a MWE and so isolated the problem, but I don't know a solution. Andrew Stacey.)

The scenario is as follows: a LaTeX document uses hyperref and, for some reason, has references as subscripts in some equation. When compiling to PDF, these are the correct size. When compiling to DVI, they come out normal size. They are still typeset in mathematics mode, just not in the right size. Here's a MWE. I'm using roman labels to better show that they are typeset in mathematics.

\documentclass{article}
\usepackage{hyperref}

\begin{document}

\begin{enumerate}
\renewcommand{\theenumi}{\roman{enumi}}
\item \label{ab} First
\item \label{cd} Second
\end{enumerate}

\[
  M_{\ref{ab}} + M_i + M_{\mathrm{i}} + N_{\ref{cd}} + N_{ii} + N_{\mathrm{ii}}
\]

\end{document}

This is from the DVI:

This is from the PDF:

This would appear to be a bug in the hdvips driver and so the obvious answer is to fix this. However, the difficulty with that is that the problem was spotted with an upload to the arXiv which, according to the logs, uses TL2009. (The document above still exhibits the fault with TL2011, by the way.) So the questions:

1. Is there some way to fix this from within the main document?
2. If not, and the driver needs fixing, is there a simple fix, and how could that be applied to a file uploaded to the arXiv without getting the arXiv to do anything? (For those who don't know how the arXiv works, it is possible to upload auxilliary files with the submission.)

---

As this is a major rewrite of the question, the original question now follows.

When I compile my LaTeX, the size of all subscripts are smaller than the normal size of text (including reference subscripts), as expected.

However, when the arXiv compiles my LaTeX, reference subscripts are the same size as normal text.

When the subscript is not also a reference, the correct font size is used.

I include

• \usepackage{subfig}
• \usepackage{graphicx}
• \usepackage{hyperref}
• \usepackage{tikz}
• \usetikzlibrary{arrows,backgrounds,calc,fit}
• \usepackage{multirow}
• \usepackage{tyson.sty} % my personal style file

while the packages included by the arXiv LaTeX can be found in their log file from compiling my LaTeX.

Question: How can I force the arXiv to typeset reference subscripts in the correct font size?

Answer 1

I've tracked the problem down to the file pdfmark.def which gets included by the hdvips.def driver. The reference link is typeset in a box and so if the external environment is mathematical, it needs to restore the mathematics mode inside the box. Unfortunately, as I found out in my question Is there a test for the different styles inside maths mode? there isn't a way for TeX to know absolutely which maths mode it is in.

One could include a \mathchoice macro here to sort this out, but that would be quite complicated and a smaller hack is to allow the user to specify whether or not the link is in a subscript or whatever.

This involves hacking pdfmark.def a little to add a style selection macro. Against the version in TL2010, the patch file is:

=== modified file 'pdfmark.def'
--- pdfmark.def 2011-08-18 19:15:22 +0000
+++ pdfmark.def 2011-08-18 19:15:44 +0000
@@ -223,6 +223,7 @@
     \hbox\bgroup
     \Hy@RestoreSpaceFactor
     \Hy@LinkMath
+        \Hy@mathstyle
   \fi
   \expandafter\Hy@colorlink\csname @#1color\endcsname
   \literalps@out{H.S}%
@@ -517,6 +518,13 @@
 \providecommand*{\Hy@setouterhbox}{\sbox}
 \providecommand*{\Hy@breaklinksunhbox}{\unhbox}
 \def\Hy@DEST{/DEST}
+\def\Hy@mathstyle{%
+\ifmmode
+\csname \Hy@currentmstyle\endcsname
+\fi
+}%
+\def\setmathstyle#1{\def\Hy@currentmstyle{#1style}}%
+\def\Hy@currentmstyle{textstyle}%
 \def\pdf@rect#1{%
   \begingroup
     \chardef\x=1 %
@@ -548,6 +556,7 @@
       \Hy@setouterhbox\pdf@box{%
         \Hy@RestoreSpaceFactor
         \Hy@LinkMath
+        \Hy@mathstyle
         \Hy@AllowHyphens#1\Hy@xspace@end
         \Hy@LinkMath
         \Hy@SaveSpaceFactor
@@ -556,6 +565,7 @@
       \sbox\pdf@box{%
         \Hy@RestoreSpaceFactor
         \Hy@LinkMath
+        \Hy@mathstyle
         #1\Hy@xspace@end
         \Hy@LinkMath
         \Hy@SaveSpaceFactor

We define a new command \Hy@mathstyle which is a hook to select a maths style based on a macro \Hy@currentmstyle. So if we set that macro accordingly, the hyperlink will be typeset in the corresponding style.

Then in the document itself, we define a command \subref which sets the default style to be script and then calls \ref. We check to see if the setmathstyle command is defined so that if run with pdflatex, for example, this just calls \ref.

\makeatletter
\def\subref{%
  \@ifundefined{setmathstyle}{}{\setmathstyle{script}}\ref}
\makeatother

So the total document is:

\documentclass{article}
\usepackage{hyperref}

% hdvips: hdvips.def, pdfmark.def
% hpdftex: hpdftex.def

\makeatletter
\def\subref{%
  \@ifundefined{setmathstyle}{}{\setmathstyle{script}}\ref}
\makeatother
\begin{document}

\begin{enumerate}
\renewcommand{\theenumi}{\roman{enumi}}
\item \label{ab} First
\item \label{cd} Second
\end{enumerate}

\[
  M_{\subref{ab}} + M_i + M_{\mathrm{i}} + N_{\subref{cd}} + N_{ii} + N_{\mathrm{ii}}
\]

\end{document}

with result from the DVI:

To make this work with the arXiv, you'd have to include the modified pdfmark.def with the submission. You should probably also get the pdfmark.def file from TL2009 and modify that since the hyperref files check for the right version.

Answer 2

From arXiv help:

You can ensure pdflatex processing by setting \pdfoutput=1 within the first 5 lines of the preamble of the main pdflatex file.

There is more important information on the arXiv help page about this setting so be sure to read it.