Right-align numbers in ToC

Question

How do I right-align the section/subsection/.. number in the ToC? The distance between the number and the heading should be fixed.

Instead of

|  1     Section
|        1.1      Subsection

I'd like to have something like

|      1 Section
|             1.1 Subsection

(|= left margin)

There must be a package for that...

(And I'd like to play with the indentation as well)

Answer 1

\numberline could be redefined:

\documentclass{article}

\makeatletter
\renewcommand*{\numberline}[1]{%
  \hb@xt@\@tempdima{\hfil#1 }%
}
\makeatother

\begin{document}
\tableofcontents

\section{First}
\subsection{Sub}
\addtocounter{subsection}{9}
\subsection{Foo}
\addtocounter{section}{9}
\section{Next}
\subsection{bar}
\end{document}

Specific settings

Since \numberline is used for all levels. When \numberline is executed, the information about the level is no longer available. Therefore, it is much more cumbersome to configure the alignment of \numberline specific to a level.

The following code hooks into \contentsline for catching the level name in macro \nl@current@levelname. Then \numberline reads the level name and calls its implementation for the specified alignment, see the comments in the example.

\documentclass{article}
% \usepackage[bookmarksnumbered, bookmarksopen]{hyperref}

\makeatletter
% Patch, that hooks into \contentsline to store the
% level name in \nl@current@levelname.
%   If package 'hyperref' is loaded, then this
% needs to be called *after* package `hyperref`.
\AtBeginDocument{%
  \let\nl@org@contentsline\contentsline
  \def\contentsline#1{%
    \def\nl@current@levelname{#1}%
    \nl@org@contentsline{#1}%
  }%
}

% \numberline evaluates \nl@current@levelname to find
% the horizontal alignment
\protected\def\numberline#1{%
  \begingroup
    \edef\nl@align{%
      nl@align@%
      \@ifundefined{nl@current@levelname}{}{\nl@current@levelname}%
    }%
    \edef\nl@align{%
      \@ifundefined{\nl@align}\nl@align@{\csname\nl@align\endcsname}%
    }%
    \@ifundefined{nl@numberline@\nl@align}{%
      \errmessage{Unknown alignment '\nl@align' for \noexpand\numberline}%
      \nl@numberline@l{#1}%
    }{%
      \csname nl@numberline@\nl@align\endcsname{#1}%
    }%
  \endgroup
}

% Implementations of `\numberline` for the different horizontal alignments
\newcommand*{\nl@numberline@l}[1]{% left-aligned
  \hb@xt@\@tempdima{#1 \hfil}%
}
\newcommand*{\nl@numberline@c}[1]{% centered
  \hb@xt@\@tempdima{\hfil#1 \hfil}%
}
\newcommand*{\nl@numberline@r}[1]{% right-aligned
  \hb@xt@\@tempdima{\hfil#1 }%
}

% Configuration
% -------------
% Horizonal alignment in \numberline:
%   l: left-aligned
%   c: centered
%   r: right-aligned
% \nl@align@: Default setting
% \nl@align@<levelname>: Setting for specific level

\def\nl@align@{l}% default
\def\nl@align@section{r}

\makeatother

\begin{document}
\tableofcontents

\section{First}
\subsection{Sub}
\addtocounter{subsection}{9}
\subsection{Foo}
\addtocounter{section}{9}
\section{Next}
\subsection{bar}
\end{document}