\fill-with-pattern does not center when line-width is overridden?

[Federico Bruni]

Hello LilyPonders

I want to reduce the distance between the tocItem text and its page 
number while keeping the list *centered on the page*.
I tried the following but the list is left-aligned:


\version "2.19.29"
\paper {
 tocItemMarkup = \markup \large \column {
   \override #'(line-width . 80)
   \fill-with-pattern #1 #CENTER . \fromproperty #'toc:text 
\fromproperty #'toc:page
   }
}

\markuplist \table-of-contents

{
 \tocItem \markup "Piece 1"
 \tocItem \markup "Piece 2"
 \tocItem \markup "Piece 3"
 \repeat unfold 20 g'1
}


I guess that this is related to what is explained here for line-width:
http://www.lilypond.org/doc/v2.19/Documentation/notation/horizontal-spacing-paper-variables#paper-variables-for-widths-and-margins

but I'm not sure how it should work within a \markup block.

Thanks in advance
Federico