How can I make long section titles wrap all the way to the margin?

Question

LaTeX by default indents section titles so that the left edge of the text is in alignment, as follows:

I would like to make it wrap all the way to the left margin, as shown:

How could I do that? I thought of the titlesec package, but it does not seem to provide a way to do it. (Yes, I know this formatting is ugly, but I would like to know how to do it.)

Minimum working example that I have so far:

\documentclass{article}

\begin{document}

\section{Lorem ipsum dolor sit amet, consectetur adipiscing elit.}

Lorem ipsum dolor sit amet.

\end{document}

Answer 1

titleformat from titlesec is usually the way to format sections (link to documentation). In your case, change the default shape from [hang] to [block]. Extra spacing can be adjusted by \titlespacing* define in the same document. There are also some example definitions of the default and more fancy formats, so you may want to have a look at those, as well.

\documentclass{article}
\usepackage{titlesec}

\titleformat{\section}[block]
  {\normalfont\Large\bfseries}{\thesection}{1em}{}


\begin{document}
\section{Lorem ipsum dolor sit amet, consectetur adipiscing elit.}

Lorem ipsum dolor sit amet.
\end{document}

Answer 2

The KOMA-Script classes provide their own interface to configure headings. To not use hanging headings, just remove the \@hangfrom from the default definition of \sectionlinesformat (shown in the user manual):

\documentclass[emulatestandardclasses]{scrartcl}

\renewcommand*{\sectionlinesformat}[4]{\hskip#2#3#4}

\begin{document}

\section{Lorem ipsum dolor sit amet, consectetur adipiscing elit.}

Lorem ipsum dolor sit amet.

\end{document}

In the example I've also used option emulatestandardclasses to make the KOMA-Script classes more lookalike to the standard classes.

If you want to distinguish the different levels, you can use the first argument: If you also want justifying (and hyphenation) of the headings, you can redefine \raggedsection:

\documentclass[emulatestandardclasses]{scrartcl}

\makeatletter
\renewcommand*{\sectionlinesformat}[4]{%
  \Ifstr{#1}{section}{\hskip#2#3#4}{\@hangfrom{\hskip#2#3}#4}%
}
\makeatother
\renewcommand\raggedsection{\noindent}

\begin{document}

\section{Lorem ipsum dolor sit amet, consectetur adipiscing elit esse est.}

\subsection{Lorem ipsum dolor sit amet, consectetur adipiscing elit.}
Lorem ipsum dolor sit amet.

\end{document}

For the levels \part and \chapter there are different commands \partlineswithprefixformat, \chapterlinesformat, and \chapterlineswithprefixformat. See the user manual for more information.

Answer 3

To do the same thing in the memoir class, use the \sethangfrom{} command, as follows:

\documentclass{memoir}

\setsecnumdepth{subsection}
\sethangfrom{\noindent #1}

\begin{document}

\chapter{Lorem ipsum dolor sit amet}
\section{Lorem ipsum dolor sit amet, consectetur adipiscing elit.}
Lorem ipsum dolor sit amet.
\subsection{Lorem ipsum dolor sit amet, consectetur adipiscing elit.}
Lorem ipsum dolor sit amet.

\end{document}

Note that this macro will affect all the lower-level sectioning commands at once.

Output:

If you want to change just one section level (say, subsections but not sections), use the \setNhook{} macro, where N refers to the short name of the sectioning command. Here is a list of commands to use:

Section type	Short name	Command
section	sec	\setsechook{\sethangfrom{\noindent ##1}}
subsection	subsec	\setsubsechook{\sethangfrom{\noindent ##1}}
subsubsection	subsubsec	\setsubsubsechook{\sethangfrom{\noindent ##1}}
para	paragraph	\setparahook{\sethangfrom{\noindent ##1}}
subpara	subparagraph	\setsubparahook{\sethangfrom{\noindent ##1}}

Note that the argument must be preceded with two pound signs (##) instead of one.

The following code formats subsections as block text, but creates the default hanging indent for sections:

\documentclass{memoir}

\setsecnumdepth{subsection}
\setsubsechook{\sethangfrom{\noindent ##1}}

\begin{document}

\chapter{Lorem ipsum dolor sit amet}
\section{Lorem ipsum dolor sit amet, consectetur adipiscing elit.}
Lorem ipsum dolor sit amet.
\subsection{Lorem ipsum dolor sit amet, consectetur adipiscing elit.}
Lorem ipsum dolor sit amet.

\end{document}

Output: