Re: pytex: a tex engine written in python

Hi Joseph,

Thanks for the prompt feedback. Yes accessible PDF is currently not =
supported, as neither xetex nor pdftex supports them. We may implement =
the support by implementing necessary latex primitives, as we use =
reportLab under the hood for generating PDF files, and that package =
supports accessible PDFs. But that might take a long time to be =
implemented, as I am a one-person team currently.

For \XeTeXinterchartoks, It is not actually difficult to implement it. =
Yet, it seems to me that the purpose is to expose complex opentype =
kern/ligature programs beyond TFM capabilities. I would prefer implement =
what latex does, feed chunks of glyphs to the font=E2=80=99s =
kern/ligature programs until the program ends. Then we consider the =
resulting nodes as a single glyph and append it to the list. Unless you =
need specific controls, e.g., for fonts that do not support these =
Ker/ligature programs, maybe? The latter can be done in this engine =
fairly easily. Maybe I misunderstood the purpose of the interchar class =
mechanisms in XeTeX?

Best,
Junling


> On Jul 13, 2026, at 3:30=E2=80=AFAM, Joseph Wright <[email protected]> =
wrote:
>=20
> On 13/07/2026 08:15, Junling Ma wrote:
>> Hi all,
>> I've been working (with plenty of help from Codex) on a very =
preliminary TeX engine in Python called pytex, currently available on =
GitHub at roverrobot/pytex. It is built around a modular architecture to =
make it easier to extend in areas such as safe \write18 support, =
\special handling, font handling, and additional output backends such as =
HTML and DOCX. It supports Unicode out of the box. The parser itself =
supports incremental parsing and introspection, so it can be =
incorporated into other tools. In addition, the architecture is intended =
to support concurrent parser instances (more work is needed though).
>> The current focus is compatibility with existing TeX/LaTeX documents =
rather than performance. At the moment, it implements enough of pdfTeX =
and XeTeX to run the LaTeX2=CE=B5 engine, and it can produce DVI, XDV, =
PDF, SVG, HTML, and DOCX output. Since this is still at a very early =
stage, it is quite slow, does not yet support the TeX format dump files =
(it uses a compressed JSON format instead), does not support =
bidirectional text, and currently requires an existing TeX Live =
installation. I'm also sure there are many bugs and missing features. My =
hope, however, is that the overall architecture is flexible enough to =
make future extensions straightforward.
>> If you're interested, I'd be very grateful for feedback. You are also =
very welcome to contribute.
>> Best,
>> Junling Ma
>=20
> Hello Junling,
>=20
> Looks interesting. With XeTeX essentially unmaintained, this could be =
a path for users to migrate to something with updates possible (though =
accessible PDFs likely remain more realistic with LuaTeX). Have you =
considered adding \XeTeXinterchartoks support?
>=20
> Regards,
>=20
> Joseph