Introducing Arbitrary book cuts for Tex4Ebook

Question

Whenever I try to introduce arbitrary cut points with tex4ebook, I'm getting the pages returned in a strange, incorrectly ordered way. Here's my MWE:

\newcommand{\mycut}{}
\begin{document}
A
\mycut{}
B
\mycut{}
C
\chapter{First}
D
\mycut{}
E
\end{document}

And my config file:

\Preamble{xhtml,svg,no-cut}
\NewSection\mycut{} 
\CutAt{chapter,chapter,mycut}
\CutAt{mycut,mycut,chapter}

I expected to see my MWE cut into 5 pages, with the pages being ordered like so:

A -> B -> C -> Chapter "First" + D (same page) -> E.

Instead, I get:

A -> Chapter "First" + D (same page) -> B -> C -> E.

Does anyone know why this is happening, and how I could instead introduce arbitrary cuts that will cut the way I described above?(In reality, outside my MWE, I would like arbitrary cuts to respect not just chapters correctly, but also sections and parts)

Answer 1

TeX4ebook needs that all generated pages are recorded in the reading order using the \OpfRegisterFile command. You \mycut command doesn't do this, so the resulting pages are placed at the end of the Epub file, after the page produced by the \chapter command.

The following configuration file should fix that:

\Preamble{xhtml,svg,no-cut}
\NewSection\mycut{} 

\csgappto{c:mycut}{\OpfRegisterFile}%
\csgappto{c:chapter}{\OpfRegisterFile}%
\CutAt{chapter,chapter,mycut}
\CutAt{mycut,mycut,chapter}

\begin{document}
\EndPreamble

The important code is this:

\csgappto{c:mycut}{\OpfRegisterFile}%
\csgappto{c:chapter}{\OpfRegisterFile}%

This code adds the \OpfRegisterFile to the hook used by TeX4ht before the section title. It should ensure that the \OpfRegisterFile is called on the correct file.