Centrar una parte de varias líneas en el toc

Question

Estoy perplejo. ¿Cómo puedo centrar el título de una parte de varias líneas en el índice?

\documentclass[a4paper,12pt,openright]{book}  

\usepackage{tocloft}% toc spacing and ragged right (below)  
\cftpagenumbersoff{part}  
\renewcommand{\cfttoctitlefont}{\hfill\Large}  
\renewcommand{\cftaftertoctitle}{\hfill}  

\begin{document}

\tableofcontents  
\chapter{Chapter 1}  
\chapter{Chapter 2}  
\part{A moderately long part title}  
\chapter{Chapter 3}  
\chapter{Chapter 4}  
\chapter{Chapter 5}  
\part{A Very very very long part title which runs over multiple lines in the table of contents}  
\chapter{Chapter 6}  
\chapter{Chapter 7}  
\chapter{Chapter 8}  

\end{document}

Idealmente, me gustaría que el toc se presentara como:

                       Contents             

1. Introducción . . . . . . . . . . . . . . . . . . . . . . . . . 1

                       Part I
            A moderately long part title
   

2. Capitulo 2 . . . . . . . . . . . . . . . . . . . . . . . . . . . 10

3. Capítulo 3 . . . . . . . . . . . . . . . . . . . . . . . . . . . 20

4. Capítulo 4 . . . . . . . . . . . . . . . . . . . . . . . . . . . 30

                      Part II
    A Very very very long part title which runs 
    over multiple lines in the table of contents
   

5. Capítulo 5 . . . . . . . . . . . . . . . . . . . . . . . . . . . 40

6. Capítulo 6 . . . . . . . . . . . . . . . . . . . . . . . . . . . 50

Lo siento si me han preguntado esto antes, pero he pasado horas intentando encontrar una solución en vano.

Answer 1

Desde mi punto de vista, usar un parche \@partes más fácil que usar tocloftcomandos aquí.

\documentclass[a4paper,12pt,openright]{book}  

\usepackage{xpatch}
\usepackage{tocloft}% toc spacing and ragged right (below)  



%\cftpagenumbersoff{part}  
\makeatletter
\xpatchcmd{\@part}{%
  \addcontentsline{toc}{part}{\thepart\hspace{1em}#1}%
}{%
  % Rather use an `\addcontentsline` to get rid off the restrictions of `\contentsline` etc. 
  \addtocontents{toc}{\begingroup\Large \mdseries\protect\centering\partname\ \thepart\par\large\protect\centering#1\par\endgroup}
}{}{}


\makeatother

\renewcommand{\cfttoctitlefont}{\hfill\Large}  
\renewcommand{\cftaftertoctitle}{\hfill}  


\begin{document}

\tableofcontents  
\chapter{Chapter 1}  
\chapter{Chapter 2}  
\part{A moderately long part title}  
\chapter{Chapter 3}  
\chapter{Chapter 4}  
\chapter{Chapter 5}  
\part{A Very very very long part title which runs over multiple lines in the table of contents}  
\chapter{Chapter 6}  
\chapter{Chapter 7}  
\chapter{Chapter 8}  

\end{document}

Una configuración diferente con un\parbox

\documentclass[a4paper,12pt,openright]{book}  




\usepackage{xpatch}
\usepackage{tocloft}% toc spacing and ragged right (below)  


\DeclareRobustCommand{\wrapmytitles}[1]{%
  \leavevmode

  \centering
  \parbox{0.7\linewidth}{\centering #1}%

}

\makeatletter
\xpatchcmd{\@part}{%
  \addcontentsline{toc}{part}{\thepart\hspace{1em}#1}%
}{%
  \addtocontents{toc}{\begingroup\Large \mdseries\protect\centering\partname\ \thepart\par\large\wrapmytitles{#1}\endgroup}
}{}{}


\makeatother

\renewcommand{\cfttoctitlefont}{\hfill\Large}  
\renewcommand{\cftaftertoctitle}{\hfill}  


\begin{document}

\tableofcontents  
\chapter{Chapter 1}  
\chapter{Chapter 2}  
\part{A moderately long part title}  
\chapter{Chapter 3}  
\chapter{Chapter 4}  
\chapter{Chapter 5}  
\part{A Very very very long part title which runs over multiple lines in the table of contents}  
\chapter{Chapter 6}  
\chapter{Chapter 7}  
\chapter{Chapter 8}  

\end{document}