DocBook to ePub

[Thibaut Cuvelier]

On Sat, 30 Jan 2021 at 20:51, Pavel Sanda <sanda at lyx.org> wrote:

> On Fri, Jan 29, 2021 at 06:38:30PM +0100, Thibaut Cuvelier wrote:
> > As promised, I started working on ePub output, building upon the new
> > DocBook output.
>
> Generally looks fine, thanks for the effort!
>
> > Here is a script that performs the complete process of taking a DocBook
> > file and generating the ePub. It has several dependencies:
> >
> > - an XSLT processor:
> >
> >    - not xsltproc (http://xmlsoft.org/xslt/xsltproc2.html): available
> for
> >    most Linux distributions, I guess it is available by default on
> macOS, must
> >    be bundled for Windows. I tried several versions for Windows, but an
> old
> >    bug that should have been fixed in 1.1.24 (roughly 2010) is still
> there:
> >    - I/O error : No such file or directory
> >       - xsltDocumentElem: unable to save to
> >       C:/Users/Thibaut/AppData/Local/Temp/tmp6c2i6a7h/OEBPS/package.opf
> >    - Saxon 6 (available for most Linux distributions, must be bundled for
> >    Windows and macOS, requires Java). It's outdated software (circa
> 2005), but
> >    newer versions are not 100% backward compatible, so it is still very
> widely
> >    used. Other DocBook stylesheets would work on newer Saxon, but they
> are not
> >    as reliable as the old ones (like https://github.com/docbook/xslTNG).
> >    - not MSXML6 (Windows-only, mostly built-it, but not compatible with
> the
> >    DocBook stylesheets ??? it wrongly errors with chunking) or .Net XSLT
> engine
> >    (nxslt/nxslt2).
> >
> > - the official DocBook XSLT stylesheets. Three parts are required: XHTML,
> > XHTML5, and ePub. For now, I copied the needed parts in a patch. On some
> > Linux distributions, this could be replaced by a version installed by the
> > package manager (Ubuntu 20.04 has a near-up-to-date version, although the
> > latest one has been released in 2016:
> >
> https://github.com/docbook/xslt10-stylesheets/releases/tag/release%2F1.79.2
> ;
> > Fedora is up-to-date).
>
> Java dependency is sad news. Is there some bug within xsltproc which we
> can bump or ask devs to fix it so we don't need to stick with saxon in
> long term? I looked at https://gitlab.gnome.org/GNOME/libxslt/
> and the project seems to be reasonably alive (If I look on the correct
> repo).
>

That's the right repo, as far as I know. I submitted a bug report:
https://gitlab.gnome.org/GNOME/libxslt/-/issues/49. I guess I would have to
dig deeper into xsltproc to properly debug this…


> > (By the way, these patches have been written on top of the 14 others I
> just
> > submitted to the list: they should apply cleanly, but that's not 100%
> > guaranteed.)
>
> As far as I could see the only point of potential conflict are few
> configure.py
> lines of configure.py, we can easily deal with that. I still maintain that
> it
> would be better to postpone nonessential python changes post 2.4.
>

I'm attaching a rebased version on top of current master, if that helps.


> > It's open for comments :)!
>
> Small technical glitches
> - we will need to bundle those files into our tarball so Makefile.am
> entries
>   are missing. (I can help with this once in master.)
>

Indeed, I would like some help on this :).


> - I think Saxon & stylesheets belong to 3rdparty directory
>

I only see compile-time dependencies in that folder, while both Saxon and
the stylesheets are run-time dependencies. It's really like /lib/tex,
actually.


> - we need to give instructions to packagers why we bundle the stylesheets
> and
>   libraries (lib/RELEASE-NOTES looks as a good candidate) and make clear
> which
>   versions are needed to work correctly.
>

Saxon: either 6.5.4 or 6.5.5 (other versions are known not to work). For
the stylesheets, at least 1.76.
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