Patch \part to do something with optional and mandatory argument

Question

I am basically trying to patch \part of scrreprt to do something with the optional argument (if present) or the mandatory argument instead. In the example below the short caption would be added in red to the TOC and the long caption in blue (underneath its respective part).

But my code below basically doesn't do anything. This seems very related to this problem, and I have tried something similar with regexpatch, but without success. I am trying to get to a solution where \part can be used by other packages, e.g. hyperref without interference.

\documentclass{scrreprt}

\usepackage{xcolor}
\usepackage{xpatch}

\makeatletter

\catcode`\#=12

\xapptocmd{\@part}%
    {#1}%
    {\addcontentsline{toc}{chapter}{\textcolor{red}{#1}}}%  
    {}%

\xapptocmd{\@part}%
    {#2}%
    {\addcontentsline{toc}{chapter}{\textcolor{blue}{#2}}}% 
    {}%

\catcode`\#=6

\makeatother

\begin{document}

\tableofcontents

\part{Only Long Caption}

\part[Short Caption]{Long Caption}

\end{document}

You've got things mixed up somewhat, obviously. What do you want to happen with the content already written to the ToC? You still want that written, or not? — Werner, Nov 13 '14 at 22:33
Yes, still written. I want to use the short and long caption in addition to their normal behaviour. (and yes, I got things mixed up :-) ) — Jörg, Nov 13 '14 at 22:34
Your first instruction says: “Add #1 at the end of \@part and execute \addcontentsline... if the patch succeeds”. I guess you want \xpatchcmd instead. — egreg, Nov 13 '14 at 22:41
I've tried many things, something like \xpatchcmd{\@part}{##1}{\addcontentsline{toc}{chapter}{\textcolor{red}{##1}}}{}, but clearly I am not quite understanding it — Jörg, Nov 13 '14 at 22:41
@cfr Every macro is defined with \def (and \edef is \def under cover). — egreg, Nov 13 '14 at 22:54
@cfr TeX doesn't know what high level command defined a certain macro; all it does is storing the macro name, the parameter text and the replacement text. The high level functions are just interfaces to \def; once their job has ended, it's like a suitable \def had been executed. In other words, once \newcommand{\foo}{bar} has been issued, as far as TeX is concerned you could as well have used \long\def\foo{bar}. — egreg, Nov 13 '14 at 22:59
@egreg OK. Thanks. I guess in that case I'll just consider the documentation misleading. (Misleading to me, anyhow.) — cfr, Nov 13 '14 at 23:01

Werner · Accepted Answer · 2014-11-14T00:22:23.863

In order for the patching to work as expected, you need to understand how the function you're patching is constructed. Here is \@part as it's defined in scrreprt.cls:

\def\@part[#1]#2{%
  \ifnum \scr@osectarg=\z@
    \@scr@tempswafalse
  \else
    \scr@istest#1=\@nil
  \fi
  \if@scr@tempswa
    \setkeys{KOMAarg.section}{tocentry={#2},head={#2},#1}%
  \else
    \ifcase \scr@osectarg\relax
      \setkeys{KOMAarg.section}{tocentry={#1},head={#1}}%
    \or
      \setkeys{KOMAarg.section}{tocentry={#2},head={#1}}%
    \or
      \setkeys{KOMAarg.section}{tocentry={#1},head={#2}}%
    \or
      \setkeys{KOMAarg.section}{tocentry={#1},head={#1}}%
    \fi
  \fi
  \ifnumbered{part}{%
    \refstepcounter{part}%
    \@maybeautodot\thepart%
    \ifx\scr@ds@tocentry\@empty\else
      \addparttocentry{\thepart}{\scr@ds@tocentry}%
    \fi
  }{%
    \ifx\scr@ds@tocentry\@empty\else
      \addparttocentry{}{\scr@ds@tocentry}%
    \fi
  }%
  \begingroup
    \setparsizes{\z@}{\z@}{\z@\@plus 1fil}\par@updaterelative
    \raggedpart
    \interlinepenalty \@M
    \normalfont\sectfont\nobreak
    \ifnumbered{part}{%
      \size@partnumber{\partformat}%
      \partheadmidvskip
    }{}%
    \size@part{#2}\strut
    \ifx\partmark\@gobble
      \@mkboth{}{}\par
    \else
      \expandafter\partmark\expandafter{\scr@ds@head}\par
    \fi
  \endgroup
  \@endpart
}

It seems best to insert new ToC-related entries at the point where \@part issues \begingroup. For this we only need etoolbox to patch in the following way:

\usepackage{etoolbox}
\makeatletter
% \pdfstrcmp{<string1>}{<string2>}
% \pdfstrcmp compares two strings and expands to 0 if the strings are equal, to -1 if the first string
%   ranks before the second, and to 1 otherwise
\patchcmd{\@part}% <cmd>
    {\begingroup}% <search>
    {\ifnum\pdfstrcmp{#1}{#2}=0
       \addcontentsline{toc}{chapter}{\protect\textcolor{blue}{#2}}%
     \else
       \addcontentsline{toc}{chapter}{\protect\textcolor{red}{#1}}%
     \fi%
     \begingroup}%  
    {}{}%

\makeatother

The above inserts two \addcontentsline macros immediately before \begingroup. They are conditional on whether #1 matches #2 or not (using e-TeX's \pdfstrcmp). If they're the same, it means the user didn't supply an optional argument.

Note how content written to the ToC is \protected in order to avoid expansion. This is typical when writing to files to ensure things don't go horribly wrong.

Here is a complete minimal example:

enter image description here

\documentclass{scrreprt}

\usepackage{etoolbox,xcolor}

\makeatletter
% \pdfstrcmp{<string1>}{<string2>}
% \pdfstrcmp compares two strings and expands to 0 if the strings are equal, to -1 if the first string
%   ranks before the second, and to 1 otherwise
\patchcmd{\@part}% <cmd>
    {\begingroup}% <search>
    {\ifnum\pdfstrcmp{#1}{#2}=0
       \addcontentsline{toc}{chapter}{\protect\textcolor{blue}{#2}}%
     \else
       \addcontentsline{toc}{chapter}{\protect\textcolor{red}{#1}}%
     \fi%
     \begingroup}%  
    {}{}%

\makeatother

\begin{document}

\tableofcontents

\part{Only Long Caption}

\part[Short Caption]{Long Caption}

\end{document}

If you want the above to work with hyperref, you need to patch \H@old@part instead of \@part.

Thanks! Sorry, I probably wasn't clear, but when "short caption" is given it should only return "short caption". So under Part 2 there should be only "Short Caption" — Jörg, Nov 13 '14 at 22:50
Suggestion: Use \addchaptertocentry to use the internal addxcontentsline by package tocbasic. — Johannes_B, Nov 14 '14 at 08:32
@Jörg addchaptertocentry is explained in the documentation, and it is just substituting the \addcontentsline. Nothing to show really. But i have the feeling that you are trying to achieve something that my be very very easy to handle. — Johannes_B, Nov 16 '14 at 15:55
KOMA has an option to align all unnumbered chapters in the toc with the numbred chapters. This function will only work if the toc entry is done with the lower level addxcontentsline. — Johannes_B, Nov 16 '14 at 16:04

Patch \part to do something with optional and mandatory argument

1 Answers1