Classicthesis - Multiline section headings do not work

Question

I am using classicthesis for my thesis project. Some section names are very long and either go into the right 'padding area' or are split into multiple line. Often this creates ugly word hyphenations. Unfortunately, trying to include linebreaks explicitely

\section{This is a very very \\ very long section heading}

does not really work. While it does create a linebreak the second line is simply not visible in the generated pdf output.

With classicthesis there are many packages involved at once and I have not been able to create a minimal example for this problem. Therefore, I'm just asking for pointers what the problem could be and suggestions that could solve the problem.

Answer 1

The following example illustrates the problem:

\documentclass{scrbook}
\usepackage{classicthesis}

\begin{document}

\chapter{Test}
\section[String for ToC and header]{This is a very very very long section heading additional technical words}

\end{document}

classicthesis hass the following settings for section titles (titlesec is loaded internally):

\titleformat{\section}
   {\relax}{\textsc{\MakeTextLowercase{\thesection}}}{1em}{\spacedlowsmallcaps}

If you want to prevent the hyphenation, you can use \raggedright:

\documentclass{scrbook}
\usepackage{classicthesis}

\titleformat{\section}
  {\raggedright}{\textsc{\MakeTextLowercase{\thesection}}}{1em}{\spacedlowsmallcaps}

\begin{document}

\chapter{Test}
\section[String for ToC and header]{This is a very very very long section heading additional technical words}

\end{document}

Similar changes will have to be applied to subsections and subsubsections (for chapters this is not needed, since \raggedright was internally used):

\documentclass{scrbook}
\usepackage{classicthesis}

\titleformat{\section}
  {\raggedright}{\textsc{\MakeTextLowercase{\thesection}}}{1em}{\spacedlowsmallcaps}
\titleformat{\subsection}
  {\raggedright}{\textsc{\MakeTextLowercase{\thesubsection}}}{1em}{\normalsize\itshape}
\titleformat{\subsubsection}
  {\raggedright}{\textsc{\MakeTextLowercase{\thesubsubsection}}}{1em}{\normalsize\itshape} 

\begin{document}

\chapter{Test}
\section[String for ToC and header]{This is a very very very long section heading additional technical words}

\end{document}