Section title gradient

Question

Background

Writing a manual using KOMA Script. The default fonts are perfect and should not be changed.

Problem

KOMA Script produces the following section outline:

The desired outline looks similar to the following (gradient extended to left and right margins):

The troubles I have encountered:

• The fount for numerals and text changes.
• Retaining the text spacing.
• Expanding or extending the gradient box to:
  • the left and right margins (\textwidth?); and
  • a bit larger than the section (or subsection) text's top and bottom margins.

Source Code

My first attempt resembles:

\let\oldsection\section
\renewcommand{\section}[1]{%
  \oldsection[#1]{
    \setlength\fboxrule{0pt}%
    \setlength\fboxsep{0pt}%
    \tikz[background rectangle/.style={left color=blue!20,right color=white},
    show background rectangle] 
    \node [inner sep=0pt] (0,0) {#1};%
  }
}

This produces:

Update

Changing the text width for the node helps:

\node [text width=\textwidth, inner sep=0pt] (0,0) {#1};%

This produces:

Related

• How to set the font for a \section title (and chapter etc)
• Framing section headings

Question

How would you implement a margin-to-margin gradient (preferably using TikZ) that is slightly larger than the text?

Answer 1

This is relatively easy to achieve using the titlesec package:

\documentclass{scrbook}
\usepackage{tikz,titlesec}

\usepackage[english]{babel}
\usepackage{blindtext}      % for a test document

\titleformat{\section}[block]%              
    {\usekomafont{sectioning}\usekomafont{section}%
     \tikz[overlay] \shade[left color=blue!20,right color=white] (0,-1ex) rectangle (\textwidth,1em);}%    
    {\thesection}%                   
    {1em}%
    {}

\begin{document}
\blinddocument 
\end{document}

Note the following:

• \usekomafont{sectioning}\usekomafont{section} sets the font to whatever is chosen using the KOMA Script styling mechanism.

• The [overlay] option of \tikz means that TikZ won't take any space.

• This breaks if the title is longer than a line.

---

Edit: Here is second version, that works with long lines and does not ignore ascenders and descenders. The code is more complicated, though. It draws the whole section heading with TikZ.

\documentclass{scrbook}
\usepackage{tikz,titlesec}
\usetikzlibrary{calc}

\pgfdeclarelayer{background}
\pgfsetlayers{background,main}

\newcommand\boxedsection[1]{{%
    \usekomafont{sectioning}\usekomafont{section}%
    \begin{tikzpicture}[inner sep=0pt, inner ysep=0.3ex]
        \node[anchor=base west] at (0,0) (counter) {\thesection};
        \path let \p1 = (counter.base east) in node[anchor=base west, text width={\textwidth-\x1-0.33em}] (content) at ($(counter.base east)+(0.33em,0)$) {#1};
        \begin{pgfonlayer}{background}
            \shade[left color=blue!20,right color=white] let \p1=(counter.north), \p2=(content.north) in
            (0,{max(\y1,\y2)}) rectangle (content.south east);
        \end{pgfonlayer}
    \end{tikzpicture}%
}}

\titleformat{\section}%              
    {}%
    {}%
    {0pt}%
    {\boxedsection}%

\begin{document}
\chapter{test}
\section{Overview}
\section{Implementation}
\section{a very long section entry a very long section entry a very long section entry a very long section entry a very long section entry}
\end{document}

Answer 2

It is not recommended to use titlesec together with a KOMA-Script class. But with KOMA-Script Version 3.19 or newer you can redefine \sectionlinesformat to get the desired section title layout.

\usepackage{tikz}
\makeatletter
  \renewcommand\sectionlinesformat[4]{%
    \ifstr{#1}{section}
      {\tikz\node[inner xsep=0pt,inner ysep=0.3ex,left color=blue!20,right color=white]
        {\parbox{\textwidth}{\raggedsection\@hangfrom{\hspace*{#2}#3}{#4}}};}
      {\@hangfrom{\hspace*{#2}#3}{#4}}%
}
\makeatother

Note that this works also for \addsec and \section*.

Code:

\documentclass{scrbook}
%\providecommand*\Ifstr{\ifstr}% needed up to and including KOMA-Script version 3.27, see https://komascript.de/faq_deprecatedif

\usepackage{tikz}
\makeatletter
  \renewcommand\sectionlinesformat[4]{%
    \Ifstr{#1}{section}
      {\tikz\node[inner xsep=0pt,inner ysep=0.3ex,left color=blue!20,right color=white]
        {\parbox{\textwidth}{\raggedsection\@hangfrom{\hspace*{#2}#3}{#4}}};}
      {\@hangfrom{\hspace*{#2}#3}{#4}}%
}
\makeatother

\usepackage{blindtext} %dummy text
\begin{document}
\tableofcontents
\chapter{test}
\section{Overview}
\addsec{Section without number}
\section*{Second section without number}
\section{Implementation}
\section{a very long section entry a very long section entry a very long section entry a very long section entry a very long section entry}
\Blindtext
\end{document}