I'm reading a document created with TeX, and it has rather nice chapter headings. Does anyone know how this was done?

Update

Ok, I've got quite far using TikZ, the only thing I haven't got is the number extending into the margin:

\usepackage{titlesec}
\usepackage{tikz}
\usetikzlibrary{calc}

\titleformat{\chapter}[display]
{}
{\hfill \tikz[remember picture] \node[] (nr) {\fontsize{20}{70}\selectfont\color{black}\textsc{Chapter~~} \fontsize{60}{70}\selectfont\color{black}\thechapter};
\begin{tikzpicture}[overlay,remember picture]
\coordinate (rightborder) at ($(nr)+(100,0)$);
\coordinate (right) at ($(nr.east) + (0.5,0)$);
\draw[line width=4.5em] (right) -- (rightborder);
\end{tikzpicture}}
{-1ex}
{\filleft\fontsize{30}{50}\selectfont}
[\vspace{-1ex}]

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Probably using the TikZ package. This is not an answer to your question, but you can find some useful examples here: web.slzm.de/blog/latex/schone-kapiteltitelseiten-in-latex – Harold Cavendish Mar 26 '11 at 16:26
I'm experimenting with TikZ now, seems to screw up all my sub/section headings, stretching them across the whole line width... – fredley Mar 26 '11 at 16:48

It's the Veelo chapterstyle from the memoir class.

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Well spotted! Thanks Martin, but this is still technically the correct answer. – fredley Mar 26 '11 at 17:44
+1 Beat me by 1 minute! Well done – Brent.Longborough Mar 26 '11 at 17:48

You can create this effect using a \rlap{} box in a ragged-left chapter line. The huge number could be zoomed using graphics and the black box can be simply created using \rule.

You can use the titlesec package to adjust the \chapter style to use this code (I adapted Stefan Kottwitz's solution of Center aligning chapters).

\documentclass{book}
\usepackage{graphics}

\usepackage{titlesec}
\titleformat{\chapter}[display]
{\normalfont\Large\raggedleft}
{\MakeUppercase{\chaptertitlename}%
\rlap{ \resizebox{!}{1.5cm}{\thechapter} \rule{5cm}{1.5cm}}}
{10pt}{\Huge}
\titlespacing*{\chapter}{0pt}{30pt}{20pt}

\usepackage{lipsum}
\setcounter{chapter}{2}
\begin{document}

\chapter{Implementation}
\lipsum
\end{document}


The rule width of 5cm is just a guess. You could calculate the exact value but simply using a large enough value works as well. Any overhang over the page is not shown anyway.

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I've used this, with a ~ after Chapter and another after the numeral for a slightly nicer layout. Otherwise great, thank you very much! – fredley Mar 26 '11 at 16:59