Variable memoir TOC page number box size

Question

My book long front matter page numbers which were sticking out into the margin. Following the memoir documentation, it was easy to remedy this, as in the MWE which follows.

The documentation (§9.2.2) says that:

"the length used in \setrmarg should be greater than the length set in \setpnumwidth. These values should remain constant in any given document".

It makes sense not to have all kinds of variation, but this means that in my case at least, many pages of TOC have a huge pnumwidth (and thus sacrifice width for the entries) due to a few lines of long Roman numerals.

I tried a smaller setrmarg, and this does allow for longer entries, but it doesn't seem to affect the dots, which still stop before the page number box.

So what I would like to do is to restrict the increased pnumwidth to the front matter (which, coincidentally, does not have dots).

MWE:

 \documentclass[%
    a4paper,
    11pt,
    twoside,
    one column,
    openright
    ]{memoir}

\setpnumwidth{3.55em}
\setrmarg{5.55em}

\begin{document}
\frontmatter
\setcounter{page}{33}
\tableofcontents
\cleardoublepage

\listoffigures
\cleardoublepage

\listoftables
\cleardoublepage

\mainmatter
\renewcommand{\thefigure}{\arabic{chapter}--\arabic{figure}}
\renewcommand{\thetable}{\arabic{chapter}--\arabic{table}}
\section{Section}
The section.
\begin{table}
\caption{Table}
Table contents
\end{table}

\end{document}

EDIT: I tried the first approach, putting the \resetpnum right after \mainmatter, and the result was peculiar: the box did get reset, but not until a chapter later (in my main file, with multiple chapters and appendices.

Second EDIT: using the longer solution involving \etoolbox, with the same result. Lines from the .toc follow:

\contentsline {subsection}{\numberline {1.10.4}Remarks regarding presentation}{20}{subsection.1.10.4}
\defcounter {refsection}{0}\relax
\def \@pnumwidth {0.55em}\def \@tocrmarg {1.55em}
\defcounter {refsection}{0}\relax
\contentsline {chapter}{\chapternumberline {2}Larsa/Senkereh}{21}{chapter.2}

EDIT3 (apparent solution): Having noted some remarks in the memoir documentation, section 9.2, page 156 (version v3.7f, 2016/05/16), I tried the code below, which seemed work:

...
\frontmatter
\setcounter{page}{5}% as per Olms format requirements 
\cftlocalchange{toc}{3.55em}{5.55em}
\tableofcontents
\cleardoublepage

\listoffigures
\cleardoublepage

\listoftables
\cftlocalchange{toc}{1.55em}{2.55em}
\cleardoublepage
...

Answer 1

Here is probably how I would do it. Using \cftlocalchange, is one way, but this leaves the values used in the body of the text, I like to keep layout stuff in the preamble (or in a separate package).

Instead I use memoirs build in toc hook system to insert hooks (macros) to be executed from within the toc. Note that this means that we cannot use \cftlocalchange as it writes to the toc, and the hook runs from within the toc. Thus we simply do by hand, what \cftlocalchange would add to the toc.

Note that these changes are global in this case. I you do not want this, place \tableofcontens inside a group.

\documentclass[%
    a4paper,
    11pt,
    twoside,
    one column,
    openright
    ]{memoir}


% define what the hooks do
% we cannot use \cftlocalchange as this hook is added inside the toc
% and \cftlocalchange writes to the toc
\cftinsertcode{FRONTMATTER}{%
  \protect\setpnumwidth{3.55em}
  \protect\setrmarg{5.55em}
}

\cftinsertcode{MAINMATTER}{%
  \protect\setpnumwidth{2.55em}
  \protect\setrmarg{3.55em}
}


\begin{document}

\cftinserthook{toc}{FRONTMATTER}
\frontmatter
\setcounter{page}{33}
\tableofcontents

\chapter{Test in frontmatter}

\section{Test}



\cleardoublepage

\listoffigures
\cleardoublepage

\listoftables
\cleardoublepage

\cftinserthook{toc}{MAINMATTER}
\mainmatter
\renewcommand{\thefigure}{\arabic{chapter}--\arabic{figure}}
\renewcommand{\thetable}{\arabic{chapter}--\arabic{table}}
\section{Section}
The section.
\begin{table}
\caption{Table}
Table contents
\end{table}

 \end{document}

Answer 2

The key is to write to the .toc at the point you want to change \@pnumwidth and \@tocrmarg. You could do it like this:

Create the command \resetpnum:

\newcommand\resetpnum{%
\addtocontents{toc}{%
 % I think these are the default values
 \string\def\string\@pnumwidth{1.55em}%
 \string\def\string\@tocrmarg{2.55em}%
}}

Then you either issue \resetpnum where you want to, or use etoolbox to append the command to something like \mainmatter:

\usepackage{etoolbox}
\appto\mainmatter{\resetpnum}

Full example:

\documentclass[%
    a4paper,
    11pt,
    twoside,
    one column,
    openright
    ]{memoir}

\setpnumwidth{3.55em}
\setrmarg{5.55em}

\newcommand\resetpnum{%
\makeatletter
\addtocontents{toc}{%
 \string\def\string\@pnumwidth{0.55em}%
 \string\def\string\@tocrmarg{1.55em}%
}
\makeatother
}

\usepackage{etoolbox}
\appto\mainmatter{\resetpnum}


\begin{document}
\frontmatter
\setcounter{page}{33}
\tableofcontents
\cleardoublepage

\listoffigures
\cleardoublepage

\listoftables
\cleardoublepage

\mainmatter

\renewcommand{\thefigure}{\arabic{chapter}--\arabic{figure}}
\renewcommand{\thetable}{\arabic{chapter}--\arabic{table}}
\section{Section}
The section.
\begin{table}
\caption{Table}
Table contents
\end{table}

\end{document}

Produces a .toc file that looks like this:

\contentsline {chapter}{Contents}{xxxiii}
\contentsline {chapter}{List of Figures}{xxxv}
\contentsline {chapter}{List of Tables}{xxxvii}
\def \@pnumwidth {0.55em}\def \@tocrmarg {1.55em}
\contentsline {section}{\numberline {0.1}Section}{1}