Can't add \raisebox to ToC in XeTeX

Question

In XeLaTeX I've defined the following command:

\newcommand*{\PoETeX}{P\kern -.15em\raisebox{-0.21em}{O}\kern -.05em E\TeX}

as a simple (non-robust) way to create a silly logo styled after \LaTeX.

It works fine until I try to insert it into the table of contents with something like:

\addcontentsline{toc}{section}{\PoETeX}

at which point I get the following from xelatex:

! Argument of \reserved@a has an extra }. \par l.11 \addcontentsline{toc}{section}{\PoETeX}

The problem seems to be caused by\raisebox — taking out raisebox, or using \addcontentsline* gets rid of the error.

A minimal example can be found below:

\documentclass[a4paper,11pt]{article}

\begin{document}
\thispagestyle{empty}

\newcommand*{\PoETeX}{P\kern -.15em\raisebox{-0.21em}{O}\kern -.05em E\TeX}

\addcontentsline{toc}{section}{\PoETeX}
\section*{\PoETeX}

\begin{verse}

There once was a poem called \PoETeX\\
That's name sounded somewhat /pəˈθɛtɛk/.\\
\hspace*{2em}It was really quite sad,\\
\hspace*{2em}to see pronunciation so bad,\\
And to read such a terrible /ˈlɪme(ə)rɛk/!

\end{verse}
\end{document}

Answer 1

If you plan to often use \PoETeX in moving arguments, it's better to use

\DeclareRobustCommand*{\PoETeX}{%
  P\kern -.15em\raisebox{-0.21em}{O}\kern -.05em E\TeX}

so you won't have to put \protect before the command in many places.

Roughly speaking, defining a command with \DeclareRobustCommand is like having \protect before it whenever it's needed. Don't take the habit of defining all commands like this: use the technique only where it proves necessary.

---

Alternative definition:

\protected\def\PoETeX{%
  P\kern -.15em\raisebox{-0.21em}{O}\kern -.05em E\TeX}

This is actually more efficient than \DeclareRobustCommand, but has the disadvantage of using low level commands.

Answer 2

You need to protect the fragile command \PoETeX:

 \addcontentsline{toc}{section}{\protect\PoETeX}