How to strip a string of all formatting

Question

I'm using XeLaTeX with Polyglossia.

I have a string like this

Three \emph{blind} Mice, Émile.

saved in a macro, thus:

\gdef\foobar{Three \emph{blind} Mice, Émile.}

and I want to send the text in \foobar into the metadata of a PDF using \pdfinfo{}, thus:

\pdfinfo{/Title (\foobar)}

It doesn't work, because the text in \foobar is sent into the PDF with messy expansion. And the Unicode chars are also messed up.

I've tried some ideas using \noexpand, \expandafter, \toks, but without any success.

Any ideas?

PS don't tell me to use \hyperref's "pdfauthor={}"mechanism, because that clashes with the pdfx package and I can't use it. And I don't want to use pdfx's xmpdata method either. I'm after a solution to the specific issue mentioned, how to change "Three \emph{blind} Mice, Émile."into "Three blind Mice, Emile." Even "Three blind Mice, Émile." would be an improvement.

Answer 1

Using \pdfinfo is not recommended, if package hyperref is used:

• \pdfinfo is a low-level driver-specific command, only supported in pdfTeX and LuaTeX.

• The extracting of markup, the right encoding, the escaping of unmatched parentheses, ... must be done manually.

Package hyperref provides options for setting the metadata. The string is automatically processed by \pdfstringdef.

\documentclass{article}
\usepackage[utf8]{inputenc}
\usepackage[pdfencoding=auto]{hyperref}

\hypersetup{
  pdftitle={Three \emph{blind} Mice, Émile.},
}

\begin{document}
  Lorem ipsum.
\end{document}

Option pdfencoding=auto takes care of the encoding of bookmark strings and information meta data. The PDF format supports two encodings:

• PDFDocEncoding (8-bit)
• Unicode (UTF-16BE)

with auto the string is encoded in PDFDocEncoding, if it fits there, otherwise Unicode is used.

Answer 2

I've just discovered \pdfstringdef, documented in the hyperref manual. It does exactly what I need.

Answer 3

\pdfstringdef turns accented characters into octal escape sequence.

Turns : LIPSUM ÉÈÇÀÙÎÏ éèçàùîï 231

Into : LIPSUM \311\310\307\300\331\316\317 \351\350\347\340 231

From How to make a glowing text?

\documentclass{article}
\usepackage{tikz}
\usepackage[outline]{contour}
\usepackage{hyperref}
\begin{document}
\Huge
Assume pdf\TeX
\def\exText{LIPSUM ÉÈÇÀÙÎÏ éèçàùîï 231}
\makeatletter
Reverse engineer the contour package.

Here is an MWE\\
\leavevmode
\begingroup
    \color{green}%
    \con@coloroff
    \pdfliteral{%
        q % enter a scope
        1 j % Set line join style
        1 J % Set line cap style
        1 Tr % Set text rendering mode
        2.5 w % Set line width (in PostScript Point)
    }%
    \rlap{\exText}%
    \pdfliteral{%
        Q % leave the scope
    }%
\endgroup
\mbox{\exText}


Now use TikZ.\\
\pdfstringdef\plainstr{\exText} % Extraction chaine 'nettoyée'
\leavevmode
\pgfsys@beginscope% = pdf literal q
\pgfsetroundjoin% = 1 J
\pgfsetroundcap% = 1 j
\pdfliteral{1 Tr}% no pgf alternative
\foreach\ind in{10,...,1}{%
    \pgfmathsetmacro\per{(11-\ind)*5}%
    \color{green!\per}%
    \pgfsetlinewidth{\ind/2}%
    \rlap{\plainstr}%
}%
\pgfsys@endscope % = pdf literal Q
\plainstr


\makeatother
\end{document}