chapter no newpage and headings

Question

I have a document (scrbook class), in which I want some chapters not to start on a new page. I therefore defined the following:

%define a chapter that does not add space at the top of the page
\usepackage{etoolbox}
\makeatletter
\let\chapterNoSpace\chapter 
\patchcmd\chapterNoSpace{\if@openright\cleardoublepage\else\clearpage\fi}{}{}{}
\patchcmd{\chapterNoSpace}{\thispagestyle{plain}}{\thispagestyle{fancy}}{}{}
\makeatother

This does nearly what I want. However, there are three problems:

1. I need to add a new paragraph before any \chapterNoSpace command, or it will put the chapter directly on the same line as the last text.

2. On the page where the chapter starts, I am missing my headers.

3. If the command coincides with a new page, the headers are missing on the page before and there is a spurious \vskip before the heading, which looks odd.

I added a minimal script below.

\documentclass[11pt, a4paper, twoside, openany]{scrbook}
%headers
\usepackage{fancyhdr}\pagestyle{fancy}
\renewcommand{\chaptermark}[1]{\markboth{\thepart.\ #1}{}}
\renewcommand{\sectionmark}[1]{\markright{\thepart.\thechapter.\ #1}}
\fancyhf{}
\fancyhead[LE,RO]{\thepage}
\fancyhead[LO]{\rightmark}
\fancyhead[RE]{\leftmark}
\fancypagestyle{plain}{\fancyhead{}\renewcommand{\headrulewidth}{0pt}}

%Define a chapter that doesn't start on new page
\usepackage{etoolbox}
\makeatletter
\let\chapterNoSpace\chapter 
\patchcmd\chapterNoSpace{\if@openright\cleardoublepage\else\clearpage\fi}{}{}{}
%\renewcommand*{\chapterheadstartvskip}{\vspace*{1cm}}
%\patchcmd\chapterNoSpace{\chapterheadstartvskip}{\vspace{1cm}}{}{}
\patchcmd{\chapterNoSpace}{\thispagestyle{plain}}{\thispagestyle{fancy}}{}{}
\makeatother
\begin{document}
\part{Part 1}
\chapter{Normal chapter 1}
text text text text text text
\chapter{Normal chapter 2}
text text text text text
\chapterNoSpace{Chapter on same page 1}
text text text

\chapterNoSpace{Chapter on same page 2 with line brake above}
text text text
\chapter{Normal chapter 3}
text text text

\end{document}

Any suggestions?

Answer 1

Update: Maybe better with KOMA-Script version 3.16

\documentclass[open=any]{scrbook}
%headers
\usepackage[automark,headsepline]{scrlayer-scrpage}
\clearpairofpagestyles
\ohead*{\pagemark}
\ihead{\headmark}
\addtokomafont{pagehead}{\normalfont}

%Define a chapter that doesn't start on new page
\usepackage{etoolbox}
\makeatletter
\let\chapterNoSpace\chapter 
\patchcmd\chapterNoSpace{\if@openright\cleardoublepage\else\clearpage\fi}{\par\vspace{\baselineskip}}{}{}
\patchcmd{\chapterNoSpace}{\thispagestyle{\chapterpagestyle}}{}{}{}
\makeatother

\RedeclareSectionCommand[beforeskip=0pt]{chapter}

\usepackage{blindtext}% dummy text
\usepackage{showframe}% to show the page layout

\begin{document}
\part{Part 1}
\chapter{Normal chapter 1}
\blindtext[20]
\chapter{Normal chapter 2}
text
\chapterNoSpace{Chapter on same page 1}
\Blindtext[3]
\chapterNoSpace{Chapter on same page 2 with line brake above}
\blindtext
\chapter{Normal chapter 3}
\blindtext
\blinddocument
\end{document}

---

Old answer: Changing your patch to

\patchcmd\chapterNoSpace{\if@openright\cleardoublepage\else\clearpage\fi}{\par}{}{}
\patchcmd{\chapterNoSpace}{\thispagestyle{\chapterpagestyle}}{\thispagestyle{fancy}}{}{}

will solve 1. und 2.

If you want that all chapters adding less space as normal at the top of the page you can use

\renewcommand*\chapterheadstartvskip{\vspace*{0pt}}

Code:

\documentclass[openany]{scrbook}
%headers
\usepackage{fancyhdr}\pagestyle{fancy}
\renewcommand{\chaptermark}[1]{\markboth{\thepart.\ #1}{}}
\renewcommand{\sectionmark}[1]{\markright{\thepart.\thechapter.\ #1}}
\fancyhf{}
\fancyhead[LE,RO]{\thepage}
\fancyhead[LO]{\rightmark}
\fancyhead[RE]{\leftmark}
\fancypagestyle{plain}{\fancyhead{}\renewcommand{\headrulewidth}{0pt}}

%Define a chapter that doesn't start on new page
\usepackage{etoolbox}
\makeatletter
\let\chapterNoSpace\chapter 
\patchcmd\chapterNoSpace{\if@openright\cleardoublepage\else\clearpage\fi}{\par}{}{}
\patchcmd{\chapterNoSpace}{\thispagestyle{\chapterpagestyle}}{\thispagestyle{fancy}}{}{}
%
\renewcommand*\chapterheadstartvskip{\vspace*{0pt}}
\makeatother
\usepackage{blindtext}% dummy text

\begin{document}
\part{Part 1}
\chapter{Normal chapter 1}
\blindtext[20]
\chapter{Normal chapter 2}
text
\chapterNoSpace{Chapter on same page 1}
\Blindtext[3]
\chapterNoSpace{Chapter on same page 2 with line brake above}
\blindtext
\chapter{Normal chapter 3}
\blindtext
\blinddocument
\end{document}

Note that it is not recommanded to use fancyhdr together with KOMA-Script classes. Try scrlayer-scrpage instead.