# Have the chapter title stick out of the type area

I'm trying to place my chapter titles to the edge of the page, with a colored background box surrounding them. The surrounding boxes would need to be set outside of the body of the document. So far I have read the documentation of typearea, geometry, layouts, titlesec, TikZ and others but haven't been able to find a solution.

See http://latex-project.org/guides/lb2-ch4.pdf for an example of the effect I want to achieve. There the chapter title reaches farther right than the text body. What I want is to have my chapter titles in a a colored box similar to the headings on the 2nd page of the attached document on the left edge on the page.

Here is the code for the box. I just need a way to place it on the left page edge.

\documentclass[a4paper,12pt]{report}

\usepackage{tikz}
\usepackage[uppercase, sf, explicit, raggedright]{titlesec} %
\usepackage{xcolor}

\makeatletter
\titleformat{\chapter}
{\sffamily\huge\bfseries}
{}
{0pt}
{
\usetikzlibrary{backgrounds}
\tikzstyle{background rectangle}=[fill=cyan]
\begin{tikzpicture}[framed]
\color{white}
\draw (0,0) +(3ex,0) node[anchor=west]{Chapter \thechapter{} \filright#1};
\end{tikzpicture}
}
\makeatother
\begin{document}
\chapter{Chaptertitle}
\end{document}

-
Welcome to TeX.SX! You can have a look at our starter guide to familiarize yourself further with our format. –  karlkoeller Feb 28 at 12:44
With your current settings, long title will protrude into the right margin. A solution would be to declare an appropriate value for text width for the node. Also, unnumbered chapters produced with \chapter* will have an spurious chapter number. –  Gonzalo Medina Feb 28 at 13:15

You can simply set the 4th argument of \titleformat to a negative value.

In the following MWE I've set it at the left margin of the page:

\documentclass[a4paper,12pt]{report}

\usepackage{tikz}
\usetikzlibrary{backgrounds}

\usepackage[uppercase, sf, explicit, raggedright]{titlesec} %
\usepackage{xcolor}
\usepackage{lipsum} % only for the example

\titleformat{\chapter}
{\sffamily\huge\bfseries}
{}
{\dimexpr-\oddsidemargin-\hoffset-1in}
{%
\tikzstyle{background rectangle}=[fill=cyan]%
\begin{tikzpicture}[framed]
\color{white}
\draw (0,0) +(3ex,0) node[anchor=west]{Chapter \thechapter{} \filright#1};
\end{tikzpicture}%
}
\begin{document}
\chapter{Chaptertitle}
\lipsum[1-5]
\end{document}


Output:

Some remarks:

1. \makeatletter...\makeatother is not needed since no @ character is involved.
2. I've put \usetikzlibrary{backgrounds} outside the definition.
3. I've removed some spurious spaces in the definition adding % at the end of some lines

## EDIT

To achieve the same result for unnumbered chapters as \tableofcontents you have to declare a separate \titleformat:

\titleformat{name=\chapter,numberless}
{\sffamily\huge\bfseries}
{}
{\dimexpr-\oddsidemargin-\hoffset-1in}
{%
\tikzstyle{background rectangle}=[fill=cyan]%
\begin{tikzpicture}[framed]
\color{white}
\draw (0,0) +(3ex,0) node[anchor=west]{#1};
\end{tikzpicture}%
}


Complete MWE

\documentclass[a4paper,12pt]{report}

\usepackage{tikz}
\usetikzlibrary{backgrounds}

\usepackage[uppercase, sf, explicit, raggedright]{titlesec} %
\usepackage{xcolor}
\usepackage{lipsum} % only for the example

\titleformat{\chapter}
{\sffamily\huge\bfseries}
{}
{\dimexpr-\oddsidemargin-\hoffset-1in}
{%
\tikzstyle{background rectangle}=[fill=cyan]%
\begin{tikzpicture}[framed]
\color{white}
\draw (0,0) +(3ex,0) node[anchor=west]{Chapter \thechapter{} \filright#1};
\end{tikzpicture}%
}

\titleformat{name=\chapter,numberless}
{\sffamily\huge\bfseries}
{}
{\dimexpr-\oddsidemargin-\hoffset-1in}
{%
\tikzstyle{background rectangle}=[fill=cyan]%
\begin{tikzpicture}[framed]
\color{white}
\draw (0,0) +(3ex,0) node[anchor=west]{#1};
\end{tikzpicture}%
}

\begin{document}
\tableofcontents

\chapter{Chaptertitle}
\lipsum[1-5]
\end{document}


Output (ToC)

-
Huh. I missed the forest for the trees there. How would I put it right at the edge of the page then? {-\oddsidemargin-\hoffset-1in} does not seem to work... –  P-B Feb 28 at 13:02
That does the job just perfect. –  P-B Feb 28 at 13:14
@Peter-BenediktvonNiebelschtz Happy to help :-) –  karlkoeller Feb 28 at 13:17
Addition to the problem: I added \tableofcontents and now the Box of every Chapter moves a bit to the right again. The Title of the TOC itself comes out as if I hadn't tried to move it at all... –  P-B Feb 28 at 14:28
@P-B See the edit. –  karlkoeller Feb 28 at 16:41