\AtBeginChapter?

Question

Are there any hooks that work like \AtBeginDocument for chapters, sections, etc.? Something like \AtBeginChapter? I would like to have the following code:

\AtBeginChapter{%
   \setcounter{mycounter}{2}%
   . . . 
}

Yes—I know that I can create my counter so as reset itself whenever a new chapter starts, with

\newcounter{mycounter}[chapter]

but I would like to have more control as to what happens when a new chapter, section, etc. starts.

Answer 1

You can redefine \chapter to perform the specified tasks before calling the original \chapter macro:

\documentclass{memoir}% http://ctan.org/pkg/memoir
\let\oldchapter\chapter% Store \chapter in \oldchapter
\newcounter{mycounter}
\renewcommand{\chapter}{%
  \setcounter{mycounter}{2}% Insert "your content" here
  \oldchapter%
}
\begin{document}
\chapter{A chapter}
\themycounter
\end{document}

This works because the \chapter macro doesn't gobble its arguments right away (avoiding the choice of using \LetLtxMacro from letltxmacro, although it wouldn't hurt). It conditions on a * first, allowing one to interject your requirements first. Note that the original \chapter issues a page break before setting the title (if "your content" should be influenced by this).

The above should hold for the regular \chapter-defining document classes as well (report and book).

Sections are a little easier, since they are provided with a "hook" in memoir: \setsechook{<stuff>} would execute <stuff> before \section. It also provides \setsubsechook for \subsections and \setsubsubsechook for \subsubsections.