How would you implement a margin-to-margin gradient using TikZ
that is slightly larger than the text and that cover the whole lines of section text?
The following code produced the results shown below
\documentclass[a4paper,svgnames,10pt]{book}
\usepackage[utf8x]{inputenc}
\usepackage{tikz}
\usepackage[explicit]{titlesec}
\usepackage{xcolor}
\usepackage{colortbl}
\usepackage[margin=1.5cm]{geometry}
\usepackage{lipsum}
\usepackage{calc}
%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
\usepackage[cm-default]{fontspec}
\setromanfont{FreeSerif}
\setsansfont{FreeSans}
\setmonofont{FreeMono}
\usepackage{xgreek}
\setmainfont{Arial}
%%%%%%%%%%%%%%%%%%%% fancy heading \section %%%%%%%%%%%%%%%%%%%%%%
\titleformat{\section}[block]%
{\huge\bfseries%
\tikz[overlay] \shade[left color=LightSkyBlue,right color=white,] (0,-1ex) rectangle (\textwidth,1em);}%
{\thesection}%
{1em}%
{#1}
%%%%%%%%%%%%%%%%%% fancy heading \chapter %%%%%%%%%%%%%%%%%%%%%%%%
\newcommand*\chapterlabel{}
\titleformat{\chapter}
{\gdef\chapterlabel{}
\normalfont\sffamily\Huge\bfseries\scshape}
{\gdef\chapterlabel{\thechapter\ }}{0pt}
{\begin{tikzpicture}[remember picture,overlay]
\node[yshift=-3cm] at (current page.north west)
{\begin{tikzpicture}[remember picture, overlay]
\draw[fill=LightSkyBlue] (0,0) rectangle
(\paperwidth,3cm);
\node[anchor=east,xshift=.9\paperwidth,rectangle,
rounded corners=20pt,inner sep=11pt,
fill=MidnightBlue]
{\color{white}\chapterlabel#1};
\end{tikzpicture}
};
\end{tikzpicture}
}
\titlespacing*{\chapter}{0pt}{50pt}{0pt}
%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
\begin{document}
\part{Developmental Disturbance of Oral and Paraoral tissues}
\chapter{Soso and Mimi}
\section{Toto}
\lipsum[1]
\section{Developmental Disturbance of Oral and Paraoral tissues and Related Structures}
\lipsum[1]
\section{Lolo}
\lipsum[1]
\end{document}
The desired output should be like this
{}
button in the question editor.