rotatebox symbol in caption generates error

Question

Following minimal example doesn't work and generates an error

\documentclass{article}
\usepackage{graphicx}
\usepackage{amssymb}
\begin{document}
\begin{figure}
  FIGURE
\caption{$\blacksquare$ result of; \rotatebox[origin=c]{45}{$\blacksquare$}}%
\end{figure}
\rotatebox[origin=c]{45}{$\blacksquare$}
\end{document}

The error message says:

rotatebox-in-caption.tex|7| Argument of \@caption has an extra }.
|| <inserted text> 
||                 \par 
|| l.7 ...; \rotatebox[origin=c]{45}{$\blacksquare$}}

Do I have to wrap the \rotatebox in a certain box to make it work?

You can read for the underlying cause http://tex.stackexchange.com/questions/12698/what-is-the-purpose-of-protect — percusse, Jun 19 '13 at 15:20
It'll probably come down to using \caption[Stuff for the list of figures goes here]{$\blacksquare$ result of; \rotatebox[origin=c]{45}{$\blacksquare$}}. You might be able to \protect some of it if you really want it in the lof — cmhughes, Jun 19 '13 at 15:21
Just add \protect in front of \rotatebox, that is, \protect\rotatebox[origin=c]{45}{...}, when it's in the argument of \caption. — egreg, Jun 19 '13 at 15:26
using \protect solves the problem. @percusse I checked your link. What does \protect actually do to allow the fragile(?) command \rotatebox within a moving env. such as the \caption. What does it have to do with the lof what cmhughes was mentioning (there is no list of figures)? — Hotschke, Jun 19 '13 at 15:39

score 10 · Accepted Answer · edited Sep 29 '22 at 23:07

\rotatebox is fragile, see also: What is the difference between Fragile and Robust commands?

Inside "moving arguments" as in the argument of \caption fragile macros can be protected by prefixing them with \protect:

\documentclass{article}
\usepackage{graphicx}
\usepackage{amssymb}
\begin{document}
\listoffigures
\begin{figure}
  FIGURE
\caption{$\blacksquare$ result of;
 \protect\rotatebox[origin=c]{45}{$\blacksquare$}}%
\end{figure}
Text: \rotatebox[origin=c]{45}{$\blacksquare$}
\end{document}

Making fragile macros robust

Package makerobust defines macro \MakeRobustCommand. It adds the LaTeX's protection layer for the macro in the same way as LaTeX's \DeclareRobustCommand:
```
  \usepackage{graphicx}
  \usepackage{makerobust}
  \MakeRobustCommand\rotatebox
  ...
  \caption{... \rotatebox ...}
```
\rotatebox is no longer fragile and can be used without \protect.
Package etoolbox defines \robustify that redefines a macro with e-TeX's \protected:
```
  \usepackage{graphicx}
  \usepackage{etoolbox}
  \robustify\rotatebox
  ...
  \caption{... \rotatebox ...}
```
This also makes \rotatebox robust without the need of \protect for this macro.

an update some years later.... \rotatebox is robust in current releases so the original document will run without error. — David Carlisle, May 06 '21 at 08:46

rotatebox symbol in caption generates error

1 Answers1

Making fragile macros robust

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