Specify link targets for index entries made with hyperref

Question

I have code for creating an index that refers readers to a page number and an example number. (The code is included in this answer, reproduced below for convenience. I happen to be using expex, but it could just as well be an equation number, for example.) I would like to use hyperref to generate links to the specific example, rather than just the page. Is there a way to do this? I am using xindy as an index processor.

\documentclass{book}
\usepackage{expex,lipsum,index}
\newcommand{\PageExample}{\thepage-\the\excnt}
\newindex[PageExample]{my-index}{idx}{ind}{My Custom Index}
\makeindex
\begin{document}
\ex \lipsum[1]\index[my-index]{First example} \xe

\ex \lipsum[2] \index[my-index]{Second example}\xe

\ex \lipsum[3] \index[my-index]{Third example}\xe

\ex \lipsum[4] \index[my-index]{Fourth example}\xe

\ex \lipsum[5] \index[my-index]{Fifth example}\xe

\ex \lipsum[6] \index[my-index]{Sixth example}\xe

\ex \lipsum[6] \index[my-index]{Seventh example}\xe

\printindex[my-index]
\end{document}

Answer 1

Here is the solution, based on this answer.

\documentclass{book}
\usepackage{expex,lipsum,index}
\newindex[PageExample]{my-index}{idx}{ind}{My Custom Index}
\usepackage[hyperindex=false]{hyperref} % has to be after makeidx
\newcommand{\PageExample}{\thepage-\the\excnt}
\makeindex

\def\xindex#1#2{%
  \edef\doindexentry{\noexpand\index[#1]
    {#2|indexanchor{example:\the\excnt}}}%
    \doindexentry}

\def\indexanchor#1#2{\hyperlink{#1}{#2}}

\begin{document}

\xindex{my-index}{First example}
\ex 
    \raisebox{\baselineskip}{\hypertarget{example:\the\excnt}{}}\ignorespaces%
    \lipsum[1] 
\xe

% now make the code prettier:
\def\iex#1{%
    \xindex{my-index}{#1}%
    \ex %
    \raisebox{\baselineskip}{\hypertarget{example:\the\excnt}{}}\ignorespaces}

\iex{Second example} \lipsum[2] \xe

\iex{Third example} \lipsum[3] \xe

\iex{Fourth example} \lipsum[4] \xe

\iex{Fifth example} \lipsum[5] \xe

\iex{Sixth example} \lipsum[6] \xe

\iex{Seventh example} \lipsum[7] \xe

\printindex[my-index]
\end{document}

There are two "tricks" to it. The first is that the a macro that creates a hyperlink is passed to \index as if it were a formatting command (e.g., \index{Joe|indexanchor} instead of \index{Joe|textit}).

The second trick is to use \edef to expand all of the needed macros before then calling it to call the \index macro. If \xindex had a call to \index outside of \edef, then it would write something like this to the .idx file: \indexentry {First example|indexanchor{example: \the \excnt}}{1-1}.