section text positioned in the margin

Question

I work on a tufte like template and want to make section text positioned in the margin, like this:

I fiddled with \@startsection like this:

\renewcommand{\section}{\@startsection{section}{1}{\z@}
{ several values }
{ several values }
{\normalfont\large\bfseries}}

but the section text, even though positioned right or left, is always in the bounds of textwidth.

I could use marginnote instead of section, but I wonder if this can be solved within the section commands. Mind that I want to use a twoside format, thus positioning left or right should be odd or even depended.

Any thoughts will be appreciated.

EDIT

I tried this:

\usepackage{titlesec}
\titleformat{\section}[rightmargin]{\bfseries}{\thesection}%
  {0.6em}{}
.. or ..
\titleformat{\section}[leftmargin]{\bfseries}{\thesection}%
  {0.6em}{}

How can I use an if statement in order to choose rightmargin or leftmargin?

Answer 1

Here is a simple solution with titlesec, ifoddpage and marginnote:

\documentclass{article}
\usepackage[utf8]{inputenc}
\usepackage[x11names]{xcolor}
\usepackage{geometry}
\geometry{top=2.5cm, outer=0.33\paperwidth, inner=2.5cm, bottom=3.5cm, marginparwidth =0.28\paperwidth, marginparsep=10pt}
\usepackage{lipsum, marginnote,ifoddpage}
\usepackage[explicit]{titlesec}

\titleformat{\section}[runin]{\bfseries\color{Tomato4! 80! }}{}{0pt}%
{\checkoddpage\marginnote{\thesection. #1}[-\baselineskip]}[\leavevmode\hspace*{-\marginparsep}]

\begin{document}

\section{First section, long title}

\lipsum[1-2]

\section{A second section with a longer title}

\lipsum[3-7]

\section{A third section, with a really much longer title. An incredibly longer title}

\lipsum[8-10]

\end{document}