Overfull \hbox in the Table of Figures when using custom page numbering

Question

I use a custom page numbering for appendices:

    \renewcommand{\thepage}{A~--~\arabic{page}}

The problem is there is a overfull \hbox in the Table of Figures for the custom page numbering:

The problem does not appear in the Table of Contents, so I am really wondering why it happens and what can I do to prevent it ?

Thank you for your help.

Answer 1

You have to increase the width of the box used to typeset page numbers in the toc, lot and lof etc since A - 1 is not fitting in (it protrudes in to the right margin in your figure). The following diagram is useful.

Here \@pnumwidth is the width of the box where page numbers are typeset. Note that \@tocrmarg should be greater than \@pnumwidth for otherwise, the dots will hit the page number in toc.

You can change \@tocrmarg and \@pnumwidth by adding these in your preamble.

\makeatletter
  \renewcommand{\@pnumwidth}{3em}
  \renewcommand{\@tocrmarg}{4em}
\makeatother

As an alternative, you can use tocloft package and add these in your preamble

\cftsetpnumwidth{3em}
\cftsetrmarg{4em}  %% make sure that this is larger than above

MWE

\documentclass{book}

%% without packages
\makeatletter
  \renewcommand{\@pnumwidth}{3em}
  \renewcommand{\@tocrmarg}{4em}
\makeatother
%% with tocloft
%\usepackage{tocloft}
%\cftsetpnumwidth{3em}
%\cftsetrmarg{4em}
\begin{document}
\tableofcontents
\listoffigures
\setcounter{page}{1000}
\chapter{Some}
\section{some}
\begin{figure}
  \caption{some figure}
\end{figure}
\end{document}