Adding content boxes around TOC

Question

How does one customize the layout of the table of contents? I don't mean customize the style of the nodes of the TOC (chapter name, page number, etc) as here. Rather, I want to add text boxes with arbitrary text (not taken from the contents of the book) to the side of it. Something like this arrangement (the colours are merely for illustration of the structure I'm after):

Here's sample code:

\documentclass{book}
\usepackage{lipsum,titletoc}
\begin{document}

% TOC CONTENT
%% Right column:
\tableofcontents

%%  Left column
%%% Box 1:
\textbf{Authors:}
\begin{itemize}
    \item[] Barry
    \item[] Betty
    \item[] Berty
\end{itemize}
%%% Box 2:
This is a rather good cookbook, I'm sure you'll agree.

% ACTUAL CONTENT
\chapter{Vegetables}
\lipsum
\chapter{Fruit}
\lipsum
\chapter{Seaweed}
\lipsum

\end{document}

Answer 1

Here is a possible way with tcolorbox, using TikZ nodes in underlays.

The outer box wraps around the \tableofcontents, being shifted to the right side, then two 'side' panels are drawn, each is a separate node. The dimensions of the side panels can be controlled with sidepanel xshift and bottom sidepanel yshift etc.

One underlay is for the unbroken box, the other one appears only for the first box if the box is broken.

If there's no page break for the ToC, tcbraster is easier, of course.

\documentclass{book}
\usepackage{lipsum}%,titletoc}

\usepackage[margin=2cm]{geometry}

\usepackage[most]{tcolorbox}
\usetikzlibrary{calc}

\makeatletter
\tcbset{%
  sidepanel xshift/.store in=\tocbox@sidepanel@xshift,
  sidepanel xshift=5cm,
  sidepanel width/.store in=\tocbox@sidepanel@width,
  sidepanel width=4cm,
  bottomsidepanel yshift/.store in=\tocbox@bottomsidepanel@yshift,
  bottomsidepanel yshift=1cm,
  tocback/.colorlet=tcbcol@tocback,
  tocback=gray!40!white,
  topsidepanel/.style={enhanced,sharp corners, frame hidden, colback=tcbcol@tocback},
  bottomsidepanel/.style={topsidepanel},
}




\DeclareTotalTColorBox{\tableofcontentsbox}{+O{}+m+m}{
  enhanced,
  breakable,
  colupper=white,
  left skip=\tocbox@sidepanel@xshift,
  sharp corners,
  colback=tcbcol@tocback,
  frame hidden,
  remember,
  underlay={%
    \coordinate (topsidepanel) at ($(frame.north west)+(-\tocbox@sidepanel@xshift,0pt)$);
    \node[below right,inner sep=0pt] (topsidepanelnode) at (topsidepanel) {
      \begin{tcolorbox}[topsidepanel,width=\tocbox@sidepanel@width,colupper=white,
        overlay={\node[inner sep=0pt, outer sep=0pt] (topsidepanelbottom) at (frame.south west) {};},#1]
        #2%
      \end{tcolorbox}};
    \node[below right,inner sep=0pt] (bottomsidepanelnode) at ($(topsidepanelbottom) + (0pt,-\tocbox@bottomsidepanel@yshift)$) {
      \begin{tcolorbox}[bottomsidepanel,width=\tocbox@sidepanel@width,colupper=white,#1]
        #3% 
        \end{tcolorbox}};
      },
    underlay first={%
\coordinate (topsidepanel) at ($(frame.north west)+(-\tocbox@sidepanel@xshift,0pt)$);
\node[below right,inner sep=0pt] (topsidepanelnode) at (topsidepanel) {
  \begin{tcolorbox}[topsidepanel,width=\tocbox@sidepanel@width,colupper=white,
    overlay={\node[inner sep=0pt, outer sep=0pt] (topsidepanelbottom) at (frame.south west) {};},#1]
    #2%
  \end{tcolorbox}};
\node[below right,inner sep=0pt] (bottomsidepanelnode) at ($(topsidepanelbottom) + (0pt,-\tocbox@bottomsidepanel@yshift)$) {
  \begin{tcolorbox}[bottomsidepanel,width=\tocbox@sidepanel@width,colupper=white,#1]
    #3% 
    \end{tcolorbox}};
  },
  #1}{%
  \tableofcontents
}
\makeatother

\begin{document}

% TOC CONTENT
%% Right column:
\tableofcontentsbox[fontupper=\large,bottomsidepanel yshift=0.5cm]{\textbf{Authors:}
\begin{itemize}
    \item[] Barry
    \item[] Betty
    \item[] Berty
\end{itemize}
}{
  This is a rather good cookbook, I'm sure you'll agree.%
}


% ACTUAL CONTENT
\chapter{Vegetables}
\lipsum
\chapter{Fruit}
\lipsum
\chapter{Seaweed}
\lipsum

\end{document}

Answer 2

In the end I deduced that the most stable way of customising the TOC was to place the other boxes as a background to the content of the TOC, so that it wouldn't be effected when it changed size.

First I created a new geometry for the TOC list, in order to push the toc to the right.

\newcommand{\tocgeometry}{
  \newgeometry{
    onecolumn,
    includefoot,
    top=3.2cm,
    width=17.5cm,
    height=27.2cm
  }
}

Then I created a background template using \AddToShipoutPictureFG, taking three options: content (#3), horizontal distance from bottom-left of page (#1) and vertical distance from bottom-left of page (#2). Starred version specifies to place on this page only, not on every page.

\newcommand{\placethis}[3]{
  \AddToShipoutPictureFG*{\put(#1,#2){#3}}}

I copied the \tableofcontents function from article.cls, so that I could customize it in my preamble.

\makeatletter
\renewcommand\tableofcontents{
   % Parbox allows for multi-line text. 
   \placethis{125}{450}{\parbox{15cm}{
        Authors:
        \begin{itemize}
          \item Barry
          \item Betty
          \item Berty
        \end{itemize}}}
    %
    \placethis{75}{257}{\parbox{15cm}{
        This is a rather good cookbook, I'm sure you'll agree.
        }
    \@starttoc{toc}
    }
\makeatother

This also allowed me to place images in place of the \parbox, simply with \includegraphics.

This allowed me to include the TOC in the body of my book like so:

\tocgeometry
\tableofcontents*
\addtocontents{toc}{\protect\thispagestyle{empty}}
\thispagestyle{empty}
\restoregeometry

That's all it took to customize my TOC :)