TikZ – Customizing Table of Contents

Question

Are you aware of tentatives to customize the table of contents with TikZ? I am thinking of fancy graphical objects (coloured ovals, squares, rectangles…) coming with "chapter" or the numbering, for instance. That could obviously involve the titletoc package.

Edit 1: below is a try. Maybe the pfgpicture environment is more relevant for the TOC.

\documentclass{book}
\usepackage[utf8]{inputenc}
\usepackage{tikz}
\usepackage{kpfonts}
\usepackage{titletoc}
\contentsmargin{0cm}
\titlecontents{chapter}[0pc]
{\addvspace{30pt}%
\begin{tikzpicture}%
\draw[help lines,step=.4cm,color=red] (0,0) grid (3.2,1.2);%
\pgftext[left,x=.1cm,y=.6cm]{\Large\sc chapter};%
\fill[fill=white,draw=red] (2.7,.6) circle (0.35cm);%
\pgftext[x=2.7cm,y=.6cm]{\thecontentslabel};%
\end{tikzpicture}\\\color{red}\large\sc\bfseries}%
{}
{}
{\;\titlerule\;\large\bfseries \thecontentspage}%
\titlecontents{section}[2.4pc]
{\addvspace{1pt}}
{\contentslabel[\thecontentslabel]{2.4pc}}
{}
{\hfill\small \thecontentspage}
[]
\titlecontents*{subsection}[4pc]
{\addvspace{-1pt}\small}
{}
{}
{\ --- \small\thecontentspage}
[ \textbullet\ ][]
\begin{document}
\tableofcontents
\chapter{(title chapter 1)}
\section{(title section 1)}
\subsection{(title sub-section 1)}
\subsection{(title sub-section 2)}
\section{(title section 2)}
\subsection{(title sub-section 1)}
\subsection{(title sub-section 2)}
\chapter{(title chapter 2)}
\section{(title section 1)}
\subsection{(title sub-section 1)}
\subsection{(title sub-section 2)}
\section{(title section 2)}
\subsection{(title sub-section 1)}
\subsection{(title sub-section 2)}
\end{document} 

EDIT 2: second try but I do not know how to access the title of a chapter with titletoc?

\documentclass{book}
\usepackage[utf8]{inputenc}
\usepackage{kpfonts}
\usepackage[tmargin=2cm,rmargin=3.8cm,lmargin=3.8cm,bmargin=2cm]{geometry}
\usepackage{tikz}
\definecolor{doc}{RGB}{0,60,110}
\usepackage{titletoc}
\contentsmargin{0cm}
\titlecontents{chapter}[0pc]
{\addvspace{30pt}%
\begin{tikzpicture}[remember picture, overlay]%
\draw[fill=doc!30,draw=doc!30] (-4,-.1) rectangle (-1,.5);%
\pgftext[left,x=-3.7cm,y=0.2cm]{\color{white}\Large\sc\bfseries chapter\ \thecontentslabel};%
\end{tikzpicture}\color{doc!40}\large\sc\bfseries}%
{}
{}
{\;\titlerule\;\large\sc\bfseries Page \thecontentspage
\begin{tikzpicture}[remember picture, overlay]
\draw[fill=doc!25,draw=doc!20] (2pt,0) rectangle (6,0.1pt);
\end{tikzpicture}}%
\titlecontents{section}[2.4pc]
{\addvspace{1pt}}
{\contentslabel[\thecontentslabel]{2.4pc}}
{}
{\hfill\small \thecontentspage}
[]
\titlecontents*{subsection}[4pc]
{\addvspace{-1pt}\small}
{}
{}
{\ --- \small\thecontentspage}
[ \textbullet\ ][]

\makeatletter
\renewcommand{\tableofcontents}{%
\chapter*{%
\vspace*{-20\p@}%
\begin{tikzpicture}[remember picture, overlay]%
\pgftext[right,x=15cm,y=0.2cm]{\color{doc!30}\Huge\sc\bfseries \contentsname};%
\draw[fill=doc!30,draw=doc!30] (13,-.75) rectangle (20,1);%
\clip (13,-.75) rectangle (20,1);
\pgftext[right,x=15cm,y=0.2cm]{\color{white}\Huge\sc\bfseries \contentsname};%
\end{tikzpicture}}%
\@starttoc{toc}}
\makeatother
\begin{document}
\tableofcontents
\chapter{Questions of Design}
\section{(title section 1)}
\subsection{(title sub-section 1)}
\subsection{(title sub-section 2)}
\section{(title section 2)}
\subsection{(title sub-section 1)}
\subsection{(title sub-section 2)}
\chapter{Questions of Drawing}
\section{(title section 1)}
\subsection{(title sub-section 1)}
\subsection{(title sub-section 2)}
\section{(title section 2)}
\subsection{(title sub-section 1)}
\subsection{(title sub-section 2)}
\chapter{Questions of Technique}
\section{(title section 1)}
\subsection{(title sub-section 1)}
\subsection{(title sub-section 2)}
\section{(title section 2)}
\subsection{(title sub-section 1)}
\subsection{(title sub-section 2)}
\end{document} 

Answer 1

Define a macro with an argument (the title) and then apply what I've explained in How to access toc entries with titletoc