HowTo_ChapterWithLines

How to put a horizontal line above and below chapter headings

A requirement that can be found quite often is to add horizontal lines to chapter headings. For this the KOMA-Script classes scrbook and scrreprt offer several possible solutions. One possibility, which has been available for over twenty years, is to redefine the \chapterheadstartvskip and \chapterheadendvskip commands:

\documentclass{scrbook}
\usepackage{blindtext}
\usepackage{xpatch}
\xapptocmd{\chapterheadstartvskip}{%
  {%
    \setlength{\parskip}{0pt}%
    \setlength{\parfillskip}{0pt plus 1fil}%
    \noindent\rule[.3\baselineskip]{\linewidth}{1pt}\par
  }\nobreak
}{%
  \typeout{Horizontal line before chapter heading added.}%
}{%
  \errmessage{Failed to patch \string\chapterheadstartvskip}%
}%
\xpretocmd{\chapterheadendvskip}{%
  {%
    \setlength{\parskip}{0pt}%
    \setlength{\parfillskip}{0pt plus 1fil}%
    \noindent\rule[-.3\baselineskip]{\linewidth}{1pt}\par
  }\nobreak
}{%
  \typeout{Horizontal line after chapter heading added.}%
}{%
  \errmessage{Failed to patch \string\chapterheadendvskip}%
}%
\begin{document}
\tableofcontents
\blinddocument
\end{document}

Normally the two instructions are used to output the vertical distance before and after the chapter heading. Here, after outputting the top space in \chapterheadstartvskip and before outputting the bottom space in \chapterheadendvskip, the output of a line is patched into the two statements using the xpatch package. Since at this point the document settings for \parindent, \parskip and \parfillskip still apply, but the line is to be set across the entire width, at least \parskip and \parfillskip must be temporarily adjusted within a local group and any indentation must be prevented with \noindent.

The method works for both numbered and unnumbered headers. It would also work when using option chapterprefix and then inserting the top line as well above the prefix line.

The disadvantage of this method is that any call to \DeclareSectionCommand or \RedeclareSectionCommand to configure \chapter will undo the change, because it will reset \chapterheadstartvskip and \chapterheadendvskip to the default definition.

Since KOMA-Script classes 3.19, however, there is another, better possibility with the \chapterlinesformat and \chapterlineswithprefixformat commands:

\documentclass{scrbook}
\usepackage{blindtext}
\makeatletter% because of using \@hangfrom
\renewcommand*{\chapterlinesformat}[3]{%
  \Ifstr{#1}{chapter}{%
    \rule[.3\baselineskip]{\linewidth}{1pt}\par\nobreak
  }{}%
  \@hangfrom{#2}{#3}%
  \Ifstr{#1}{chapter}{%
    \rule[.3\baselineskip]{\linewidth}{1pt}\par\nobreak
  }{}%
}
\renewcommand*{\chapterlineswithprefixformat}[3]{%
  \Ifstr{#1}{chapter}{%
    \rule[.3\baselineskip]{\linewidth}{1pt}\par\nobreak
  }{}%
  #2#3%
  \Ifstr{#1}{chapter}{%
    \rule[.3\baselineskip]{\linewidth}{1pt}\par\nobreak
  }{}%
}
\makeatother% because of \makeatletter
\begin{document}
\tableofcontents
\blinddocument
\end{document}

Here the lines are inserted directly in the output of the heading. Via \Ifstr the change is restricted to chapter headings. In the concrete example this restriction would not be necessary, because only the chapter headings are set in the style chapter. The restriction was made only in case the user defines other headings in this style.

It is not necessary to change \parskip and \parfillskip or to prevent paragraph indentation because the heading context is already active here. In this context there is neither paragraph spacing nor paragraph indentation and the last line of a paragraph may also be completely filled.

This solution also works with both numbered and unnumbered chapter headings. The redefinition of \chapterlineswithprefixformat has also been made for the case where option chapterprefix is used. In this case the top line still appears above the prefix line. However, it is often desired that the line first appears below the prefix line. Not infrequently, this is combined with the prefix line being right-justified instead of left-justified and the complete heading being set in upper case. All of this is easily possible by suitably redefining \chapterlineswithprefixformat:

\documentclass[chapterprefix]{scrbook}
\usepackage{microtype}
\usepackage{blindtext}
\makeatletter% because of using \@hangfrom
\renewcommand*{\chapterlinesformat}[3]{%
  \Ifstr{#1}{chapter}{%
    \rule[.3\baselineskip]{\linewidth}{1pt}\par\nobreak
  }{}%
  \@hangfrom{\textsl{\MakeUppercase{#2}}}{\textsl{\MakeUppercase{#3}}}%
  \Ifstr{#1}{chapter}{%
    \rule[.3\baselineskip]{\linewidth}{1pt}\par\nobreak
  }{}%
}
\renewcommand*{\chapterlineswithprefixformat}[3]{%
  \Ifstr{#1}{chapter}{%
    \raggedleft
    \textls{\MakeUppercase{#2}}%
    \rule[.3\baselineskip]{\linewidth}{1pt}\par\nobreak
    \raggedchapter
    \textls{\MakeUppercase{#3}}%
    \rule[.3\baselineskip]{\linewidth}{1pt}\par\nobreak
  }{#2#3}%
}
\makeatother% because of \makeatletter
\begin{document}
\tableofcontents
\blinddocument
\end{document}

The package microtype is used in the example to achieve automatic letterspacing of capital letter. This is the only way I know of to achieve the necessary letterspacing with compensation at least reasonably well automatically. How well the possibility works, however, depends very much on the font used. For this reason, I take a fundamentally critical view of automatic capitalization.

The advantage of redefining \chapterlinesformat and \chapterlineswithprefixformat is that the change persists when chapter headings are reconfigured with \RedeclareSectionCommand. For example, it is possible to change the distance between the prefix line and the horizonta line using the innerskip option.

When adapting this solution for section, note that \sectionlinesformat has four arguments instead of three. For more details, see Part II of the KOMA-Script manual or the German KOMA-Script book.