[Tex/LaTex] Is it safe to redefine \@starttoc

multicoltable of contentstocloft

I'm using tocloft and would like to produce a two-column table of contents. While it's easy to just wrap the whole toc in a multicol-environment, I don't like the look of that, because the title gets wrapped into that as well, which makes the second column start above the title.

As tocloft redefines \tableofcontents using \AtBeginDocument, I thought instead of overwriting that definition at a later point I might just redefine \@starttoc to produce what I want, like this:

\documentclass{scrbook}
\usepackage{multicol}
\usepackage{tocloft}
\makeatletter
% tocloft redefines \tableofcontents \AtBeginDocument
% As I don't want the title to be part of the two column layout,
% it seems easiest to just add the multicols to \@starttoc.
\let\@starttocorg\@starttoc
\def\@starttoc#1{%
    \begin{multicols*}{2}%
        \@starttocorg{#1}%
    \end{multicols*}}%
\makeatother
\begin{document}
\tableofcontents
\part{part}
\chapter{chapter}
\section{section}
\section{section}
\chapter{chapter}
\section{section}
\section{section}
\chapter{chapter}
\section{section}
\section{section}
\chapter{chapter}
\section{section}
\section{section}
\chapter{chapter}
\section{section}
\section{section}
\part{part}
\chapter{chapter}
\section{section}
\section{section}
\chapter{chapter}
\section{section}
\section{section}
\chapter{chapter}
\section{section}
\section{section}
\chapter{chapter}
\section{section}
\section{section}
\chapter{chapter}
\section{section}
\section{section}
\part{part}
\chapter{chapter}
\section{section}
\section{section}
\chapter{chapter}
\section{section}
\section{section}
\chapter{chapter}
\section{section}
\section{section}
\chapter{chapter}
\section{section}
\section{section}
\chapter{chapter}
\section{section}
\section{section}
\end{document}

Which produces:

enter image description here

But as I don't know what \@starttoc does internally, I'm not sure if it's safe to do that. Are there any implications I don't see? (I suppose I could also re-phrase the question as Can it really be that easy?)

Best Answer

Each of the KOMA-Script classes scrartcl, scrreprt and scrbook load and use package tocbasic for the ToC and the Lists. tocbasic uses \tocbasic@starttoc based on \@starttoc. \tocbasic@starttoc and \@starttoc both are internal commands and should not be redefined by users. But tocbasic provides two hooks to execute code before (\BeforeStartingTOC) and after (\AfterStartingTOC) @starttoc.

Note that \BeforeStartingTOC and \AfterStartingTOC are at the same group level (inside the same group), so you can use:

\BeforeStartingTOC[toc]{\begin{multicols}{2}}
\AfterStartingTOC[toc]{\end{multicols}}

enter image description here

Code:

\documentclass{scrbook}
\usepackage{multicol}

\BeforeStartingTOC[toc]{\begin{multicols}{2}}
\AfterStartingTOC[toc]{\end{multicols}}

\begin{document}
\tableofcontents

\part{part}
\chapter{chapter}
\section{section}
\section{section}
\chapter{chapter}
\section{section}
\section{section}
\chapter{chapter}
\section{section}
\section{section}
\chapter{chapter}
\section{section}
\section{section}
\chapter{chapter}
\section{section}
\section{section}
\part{part}
\chapter{chapter}
\section{section}
\section{section}
\chapter{chapter}
\section{section}
\section{section}
\chapter{chapter}
\section{section}
\section{section}
\chapter{chapter}
\section{section}
\section{section}
\chapter{chapter}
\section{section}
\section{section}
\end{document}

Or with the starred version of multicols:

\BeforeStartingTOC[toc]{\begin{multicols*}{2}}
\AfterStartingTOC[toc]{\end{multicols*}}

enter image description here

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