Is it possible to use the verbatim environment in an XY-pic node?

Question

Is it possible to use the verbatim environment (i.e. \begin{verbatim}...\end{verbatim}) in an XY-pic node? If so, please could you provide a MWE (Minimal Working Example)?

---

Update for those who want example code.

This (which is based on the LaTeX Wikibook examples) renders without errors:

\documentclass[class=minimal,border=0pt]{standalone}
\usepackage[all]{xy}
\usepackage{varwidth}
\renewcommand{\familydefault}{\sfdefault}

\begin{document}
\begin{displaymath}
  \xymatrix{
    *+[F:<3pt>]\txt{START}\ar[d] \\
    *+[F:<3pt>]\txt{\begin{varwidth}{30em}We'll assume that Git is to be used for source control; so as a precaution against accidentally checking in temporary files used by Vim, enter the following at the command prompt:\end{varwidth}} \\
  }
\end{displaymath}
\end{document}

but this, by contrast

\documentclass[class=minimal,border=0pt]{standalone}
\usepackage[all]{xy}
\usepackage{varwidth}
\usepackage{verbatim}
\renewcommand{\familydefault}{\sfdefault}

\begin{document}
\begin{displaymath}
  \xymatrix{
    *+[F:<3pt>]\txt{START}\ar[d] \\
    *+[F:<3pt>]\txt{\begin{varwidth}{30em}We'll assume that Git is to be used for source control; so as a precaution against accidentally checking in temporary files used by Vim, enter the following at the command prompt: \begin{verbatim}echo '*.swp' >> .gitignore\end{verbatim}\end{varwidth}} \\
  }
\end{displaymath}
\end{document}

causes pdflatex to halt with the following:

<xymatrix
! Argument of \verbatim@ has an extra }.
<inserted text> 
                \par 
l.12   }

?

Answer 1

You can never use verbatim commands in a macro argument. You can however always save it in a box and use that box.

%in preamble
\newsavebox\mybox
....
% where you want the text
\begin{lrbox}{\mybox}%
\begin{minipage}{5cm}
\begin{verbatim}
....
\foo
\end{verbatim}
\end{minipage}%
\end{lrbox}
\begin{xy....        \usebox{\mybox}......

---

Firstly it's worth noting that for the text shown in your edited question verbatim isn't needed at all, a simple font change like \texttt can be used as shown in the first fragment below. verbatim is needed for multi-line text that included TeX-special characters such as \ and { as in the second example. Which is more or less a direct application of my original answer to your edited question.

I switched to article as my copy of standalone can't cope with the display math, I think it's too old.

\documentclass{article}
\usepackage[all]{xy}
\usepackage{varwidth}
\usepackage{verbatim}
\renewcommand{\familydefault}{\sfdefault}
\newsavebox\mybox
\begin{document}



\begin{displaymath}
  \xymatrix{
    *+[F:<3pt>]\txt{START}\ar[d] \\
    *+[F:<3pt>]\txt{\begin{varwidth}{30em}We'll assume that Git is to be used for source control; so as a precaution against accidentally checking in temporary files used by Vim, enter the following at the command prompt:
\newline
\texttt{echo '*.swp' >> .gitignore}\end{varwidth}} \\
  }
\end{displaymath}

\begin{lrbox}{\mybox}%
\begin{minipage}{.75\textwidth}
\begin{verbatim}
multi-line
stuff
with \backslash
and {
\end{verbatim}
\end{minipage}
\end{lrbox}

\begin{displaymath}
  \xymatrix{
    *+[F:<3pt>]\txt{START}\ar[d] \\
    *+[F:<3pt>]\txt{\begin{varwidth}{30em}We'll assume that Git is to be used for source control; so as a precaution against accidentally checking in temporary files used by Vim, enter the following at the command prompt:
\usebox\mybox
\end{varwidth}} \\
  }
\end{displaymath}


\end{document}

Answer 2

Here is the minimal example, expanded from David Carlisle's answer above. Note that \end{verbatim} must appear on it own line.

\documentclass{minimal}
\usepackage[all]{xy}
\usepackage{verbatim}

\newsavebox\mybox

\begin{document}
\begin{lrbox}{\mybox}%
\begin{minipage}{5cm}
\begin{verbatim}
% echo '*.swp' >> .gitignore
\end{verbatim}
\end{minipage}%
\end{lrbox}

\begin{displaymath}
  \xymatrix{
    *+[F:<3pt>]\txt{START}\ar[d] \\
    *+[F:<3pt>]\txt{command prompt: \usebox{\mybox}} \\
  }
\end{displaymath}
\end{document}