Time for action – shortening the table of content entries

We will use the optional argument of the sectioning commands to produce shorter entries, different to the actual headings:

1. Take our example and modify the sectioning commands as shown in the highlighted lines:

   \documentclass[a4paper,12pt]{book}
   \usepackage[english]{babel}
   \usepackage{blindtext}
   \usepackage[a4paper, inner=1.5cm, outer=3cm, top=2cm,
   bottom=3cm, bindingoffset=1cm]{geometry}
   \begin{document}
   \tableofcontents
   \chapter[Page layout]{Exploring the page layout}
   In this chapter we will study the layout of pages.
   \section[Filler text]{Some filler text}
   \blindtext
   \section[More]{A lot more filler text}
   More blindtext will follow.
   \subsection[Plenty]{Plenty of filler text}
   \blindtext[10]
   \end{document}	

2. Typeset twice and look at the modified table of contents:

   

What just happened?

Besides the mandatory argument producing the heading, each sectioning command understands an optional argument. If this is given, it will be used instead...