Using listings' escapebegin/escapeend with short commands

Question

I'm building beamer slides with code set using listings and I want to draw arrows to parts of the code. To achieve that I have a zero width command that defines a named PGF coordinate (given as the argument), here called libraryCommand.

Now the problem: I want to have a pretty syntax, so I use escapeinside, which should allow me to write QhereW to create a coordinate called here. Instead of writing the full command.

The argument that's passed to libraryCommand has to be wrapped between two commands, I use the environment for that. It works outside the lstlisting. But inside, I get Missing \endcsname inserted: \end{^lstlisting}.

\documentclass{scrartcl}
\usepackage{listings}
\lstset{
    % escapeinside={Q}{W}, % uncommenting this fails.
    escapebegin=\begin{wrapThat},
    escapeend=\end{wrapThat}
}
\newcommand{\libraryCommand}[1]{((#1))}
\newenvironment{wrapThat}{\wrapToEnd}{}
\long\def\wrapToEnd#1\end{\libraryCommand{#1}\end}
\begin{document}
  foo \begin{wrapThat}bar\end{wrapThat} baz
  \begin{lstlisting}
    foo QbarW baz
  \end{lstlisting}
\end{document}

So, how could I get this to work? I can't see what special thing they do in the DTX...

Answer 1

And with plainTeX environments like \def\wrapThat#1\endWrapThat{\libraryCommand{#1}} it fails with File ended while scanning use of \wrapThat.

It seems that the endmarker is not inserted directly by listings. Rather the Q and W are probably active and expand to the escapebegin and escapeend codes. Therefore \wrapThat never finds \endWrapThat because W isn't expanded yet. With your initial code the \end it finds would be then the \end{lstlisting}!

You need to define a macro which scannes for an active W instead:

\begingroup
\catcode`W=\active
\gdef\wrapThat#1W{\libraryCommand{#1}}%
\endgroup

If you need the endmarker for any other escapeend code, then you can readd the active W after your command:

\gdef\wrapThat#1W{\libraryCommand{#1}W}%

Answer 2

Solution from Martin Scharrer's comment:

\documentclass{scrartcl}
\usepackage{listings}
\lstset{
  escapeinside={Q}{W},
  escapebegin=\wrapThat,
  escapeend=%
}
\newcommand{\libraryCommand}[1]{((#1))}
\begingroup%
  \catcode`W=\active%
  \gdef\wrapThat#1W{\libraryCommand{#1}W}%
\endgroup
\begin{document}
  \begin{lstlisting}
    foo QbarW baz
  \end{lstlisting}
\end{document}