Tectonic: A modernized, complete, self-contained TeX/LaTeX engine
tectonic-typesetting.github.io
tectonic-typesetting.github.io
Tectonic is a cool project, but hasn't seen any significant changes in a few years---and likely won't anytime soon. It seems we maintainers don't have the time and motivation to put serious work into Tectonic.
I haven't looked at the code in years (and thus may be wrong), but here's a quick overview:
Tectonic's code consists of thin bindings to /harfbuzz/graphite/etc and a vendored XeTeX (in C, with some tweaks to make the build easier), driven by Rust that tries to keep the TeX environment predictable and sane. A few components have been fully ported to Rust (bibtex, spx2html), but the project is very unfinished.
I've looked into the dark corners of TeX when I worked on Tectonic, and it is not pretty. TeX relies on a stack of evil hacks and esoteric behavior that is very hard to replicate, and very difficult to expose in an ergonomic way. This is true of the core system, and of many packages on CTAN.
A quick example: code highlighting does not work in Tectonic. The canonical solution is https://ctan.org/pkg/minted, which spawns a python process to style your code. Reproducibility is one of Tectonic's selling points, so we cannot replicate this behavior.
With https://typst.app/ as good as it is, there's little motivation to modernize TeX---especially considering the effort required. Typst _is_ modern TeX, and I'd rather spend my time there.
It is so snappy and with great error messages. I encourage people to try it out. The typst tutorial is very approachable.
"corpus-scale conversion work aimed at 90% error-free HTML (currently 75%)"
although there may be issues that I do not understand or did not see (I looked at the paper very quickly) that make it more difficult for the authors than for the simplest possible translation.
Having tried both TeXmacs and Typst¹, it’s easy for me to understand why Typst is rapidly gaining adoption and why, after — how long, over a decade? — essentially nobody uses TeXmacs.
Typora & Obsidian apply the same ideas to Markdown.
I do think WYSIWYG is an absolutely broken paradigm for anything outside of literally just desktop publishing --- but WYSIWYM has a lot of merit.
Enough that I've been working on a stand-alone Markdown editor component that takes ideas from Typora et al.
Ooo I thought of another example of good WYSIWYG - Qt Creator's form editor. The only good GUI form editor I've used. Again the editing experience doesn't exactly match the output (e.g. some layout features are visible), but it's clearly WYSIWYG. It just doesn't suck like MS Word.
J. van der Hoeven. GNU TeXmacs: a free, structured, wysiwyg and technical text editor. In Daniel Filipo, editor, Le document au XXI-ième siècle, volume 39–40, pages 39–50. Metz, 14–17 mai 2001. Actes du congrès GUTenberg.
Reproduced at https://www.texmacs.org/Data/TeXmacs.pdf
For why so few people use TeXmacs, it may be that it is because few people believe that it is worth trying, as one would not expect that it works so well :-)
It's because they gave it a terrible name that strongly implies it's some kind of Emacs TeX editor.
I also found the very useful comparison website https://polytype.dev/ on the subject!
Tectonic is forked from the XeTeX TeX engine. However, the build process for XeTeX (and all other mainstream TeX engines) is extremely baroque:
1. The original Knuth sources are written in a language called WEB (which is basically used by nobody else)
2. Those sources are then patched with a series of “change files” due to restrictions on distributing modified sources
3. These patched files are then converted to the Pascal language using some custom processing scripts
4. That Pascal code is then converted to C code using additional custom tools
5. Those C files are then compiled against a set of extension files and libraries written natively in C and C++
One of the big motivators for the launch of the Tectonic project was to break out of this ridiculously unwelcoming development process. Tectonic is based on the C/C++ files that emerge from the XeTeX build process, and is gradually translating that code to modern Rust.
While the core TeX architecture and XeTeX are largely stable, they do, however, evolve with time. This repository recreates the final XeTeX C/C++ files from their source, so that modifications can be ported into the main Tectonic codebase.
https://github.com/tectonic-typesetting/tectonic-staging/blo...
(Disclaimer: I'm on the TeX Live team)
Yes, the build process is rather unusual internally, but this is pretty well insulated from the user. The "standard" build commands used by lots of other open source projects
git clone […] && ./configure && make
And only some of the engines require this complex build process; LuaTeX is the recommended engine these days [2], and it's written entirely in C (with a few C++ libraries), and it uses a standard autotools build process [3].
> One of the big motivators for the launch of the Tectonic project was to break out of this ridiculously unwelcoming development process.
TeX development is pretty welcoming in my personal experience: the first time that I built TL (~5 years ago), I was able to follow the official instructions without any problems, and I got a working TeX engine by the end of it. And it was only 2 or 3 years after that that I became an "official" member of the TL team, so I like to think that the development process is fairly welcoming.
But if you have any suggestions on what we can do better, please let me know, either by replying to this comment or to the email address linked in my profile.
> Tectonic is based on the C/C++ files that emerge from the XeTeX build process
I haven't looked at the Tectonic source, but the problem is that the C code generated by Web2C is fairly unreadable, so it's not really very usable as source code.
> While the core TeX architecture and XeTeX are largely stable, they do, however, evolve with time.
XeTeX is essentially frozen for the time being [4], unless someone steps up to maintain it. We are cautiously optimistic regarding LLMs though: they seem to be fairly decent at writing WEB code, and since even the TL development team only has 2 developers who are proficient in WEB, we'll take any help that we can get. (We don't have any non-trivial AI-written code yet, but it's definitely something that we're looking into)
[0]: https://tug.org/texlive/build.html
[1]: https://ftp.math.utah.edu/pub/texlive-utah/
[2]: https://www.latex-project.org/news/2024/11/01/issue40-of-lat...
Nowadays, with Typst existing, it's vital for TeX ecosystem to solve these issues, since none of them are present in Typst. Projects like Tectonic would solve this for TeX, but they lack enough hands and (maybe) financial support.
Otherwise, using TeX only makes sense nowadays only if 1) you already have some templates 2) some features are still missing in Typst 3) you are just forced to use TeX/LaTeX for whatever reason.
I'm writing two books, both in LaTeX.
I really don't get what the problem is.
I'm maintaining an internally used LaTeX document class and the development experience is even worse. TeX has no concept of such avant-garde ideas like lists, dictionaries, or namespaces. Things break all the time, and sometimes only when you load three specific packages in a specific order because they all patch each other's routines. I still haven't completely groked the idea of fragile commands and expanding macros. Characters can change meaning depending on context, even the `comment` character (%) or the `escape` character (\), (and I believe even the curly braces) for example when used inside `\path{}` or `\url{}` [1]. It makes a difference whether you comment out line endings or not. The LaTeX3 syntax looks like a bad joke. I mean, look at it:
\ExplSyntaxOn \tl_set:Nn \l_tmpa_tl {A} \group_begin: \tl_set:Nn \l_tmpa_tl {B} \par value~inside~group:~\tl_use:N \l_tmpa_tl \group_end: \par value~outside~group:~\tl_use:N \l_tmpa_tl
\tl_set:Nn \l_tmpb_tl {A} \group_begin: \tl_gset:Nn \l_tmpb_tl {B} \par value~inside~group:~\tl_use:N \l_tmpb_tl \group_end: \par value~outside~group:~\tl_use:N \l_tmpb_tl \ExplSyntaxOff
????
Let's just let it retire and focus our efforts on Typst and pushing publishers to accept Typst.
[1] Just look at all these poor souls trying to achieve something as exotic as putting a URL with a percent sign inside a footnote: https://tex.stackexchange.com/questions/12230/getting-percen...
Some of these have been fixed; see my sibling comment [0] for more details.
> TeX has no concept of such avant-garde ideas like lists, dictionaries, or namespaces. […]. The LaTeX3 syntax looks like a bad joke.
But that is in fact the entire purpose of LaTeX3. I agree that the syntax looks intimidating, but it's actually quite nice once you learn it, and it's written that way to provide namespacing in TeX. Similarly, LaTeX3 defines lists, dictionaries, and most other conventional datastructures.
> Things break all the time, and sometimes only when you load three specific packages in a specific order because they all patch each other's routines.
Hmm, well it depends. The LaTeX kernel and the TeX engines are more stable than nearly all other software, but the third-party packages do indeed break occasionally. But you see similar dynamics play out in most other ecosystems: JavaScript the language is incredibly stable and has excellent backwards compatibility, but if you use 50+ third-party packages, then things do indeed break occasionally.
> Characters can change meaning depending on context
Much like operator overloading in other languages, catcode changes in TeX can indeed be misused and are sometimes confusing, but they're also a pretty useful solution to problems that would otherwise be tricky to solve.
All this isn't to say that TeX doesn't have issues—I criticize LaTeX myself fairly frequently—but most of these are due to the fact that LaTeX is 40-year-old software built on a 50-year-old engine, and has remained backwards-compatible with documents throughout that entire time. And La(TeX) is slowly modernizing, so I'm fairly hopeful that things will continue to improve.
However, regarding this:
> Much like operator overloading in other languages, catcode changes in TeX can indeed be misused and are sometimes confusing, but they're also a pretty useful solution to problems that would otherwise be tricky to solve.
I'm sorry, but I've never seen overloading of such fundamental characters like the comment character or escape character anywhere. Or at least if you use these characters inside a string, it's pretty clear that the string context is special. In LaTeX I have no way of knowing which catcodes a macro has modified without essentially parsing the entire thing, which breaks syntax highlighters and language servers (something that increases quality of life in other languages substantially), because the compile times are prohibitive. The decision to let users redefine %, \ and literally every character seems like a really, really bad idea to me.
Other languages and syntaxes seem to do just fine, so I'm not sure what you mean by tricky to solve.
> most of these are due to the fact that LaTeX is 40-year-old software built on a 50-year-old engine, and has remained backwards-compatible with documents throughout that entire time
I realize that, and I appreciate what LaTeX (and by extension TeX) has done. It's a giant in sciences and the software world, of absolutely critical importance, but still. We learned a lot of lessons about writing software in the last 50 years, and Typst is applying these from the ground up. Unfortunately I don't have a lot of confidence that LaTeX can be modernized.
I believe that Racket [0], Mathematica [1], Raku [2], and Rust [3] let you assign arbitrary meanings to most symbols, but these are indeed much more restricted than TeX is (and for good reason). But the issue is really more that TeX barely supports lexical scoping, and that it lets you change the global catcodes at any point in the document, since changing the meanings of characters before any code runs or only in the middle of a scope is pretty useful.
> Or at least if you use these characters inside a string, it's pretty clear that the string context is special.
Verbatim is essentially equivalent to strings in other languages, and it mostly works pretty well, aside from the huge problem that it's impossible to nest it or pass it as an argument to most macros.
> In LaTeX I have no way of knowing which catcodes a macro has modified without essentially parsing the entire thing
Agreed, this is pretty annoying, but the only consolation is that most documents don't change their catcodes very often (since it's usually a pretty terrible idea).
> Other languages and syntaxes seem to do just fine, so I'm not sure what you mean by tricky to solve.
Texinfo [4] is what I was mainly thinking of, since that is able to completely redefine TeX's syntax without needing to manually implement parsing itself (which would be the best strategy today, but was less feasible back when computers were much slower). Similarly, active characters are pretty useful (this is how ~ is defined to insert a non-breaking space, and is also useful for faux-Markdown [5]).
> We learned a lot of lessons about writing software in the last 50 years, and Typst is applying these from the ground up.
Yup, I first learned about Typst on the first day that it was released, and even then I thought that it had a good chance of suceeding, since it solved the problems that most users had (bad error messages and slow compile times), whereas the other TeX competitors focused on things like better typesetting quality, better extensibility, or easier programability, which most users don't care about at all.
I would be personally a little disappointed if Typst replaced LaTeX, but until that happens, I definitely hope that it continues to do well.
> Unfortunately I don't have a lot of confidence that LaTeX can be modernized.
There are lots of other non-LaTeX TeX formats that are quite modern (ConTeXt [6] is my personal favourite, but OpTeX [7] is nice too), and even LaTeX itself has improved quite a bit over the last 5 years or so [8]. But yeah, it's modernization process is still much slower than nearly any other piece of software, so I am also worried that this may end up being too little too late.
[0]: https://docs.racket-lang.org/guide/language-get-info.html
[1]: https://reference.wolfram.com/language/Notation/tutorial/Not...
[2]: https://docs.raku.org/language/slangs
[3]: https://doc.rust-lang.org/book/ch20-05-macros.html#function-...
[4]: https://en.wikipedia.org/wiki/Texinfo#Texinfo_source_file
[5]: https://tex.stackexchange.com/a/236457/270600
[6]: https://www.ctan.org/pkg/context
[7]: https://petr.olsak.net/optex/
[8]: https://www.latex-project.org/news/latex2e-news/ltnews.pdf#s...
I'm curious about why you'd be disappointed. Is it because you think typst is an irremediably inferior technology to you or is it because you are invested in LaTex?
I do not mean to ask this in accusatory way. I'm not very well informed about typst or tex (I've only used typst once and I thought it was easy and nice).
I'm just curious about what is worse about typst that would make someone disappointed if that was the reason why you would be.
I do have a few minor concerns about Typst, mainly that its parsing/compiling strategy allows less introspection and extensibility than TeX does (but this is necessary for its fast compile times), and the fact that it's backed by a for-profit company seems less robust than TeX's 50-year history of volunteer maintainership. And of course Typst is still missing quite a few features, but if it's successful I can't imagine that this will be an issue.
Also, I personally mostly use ConTeXt [1], which compiles much faster than LaTeX and has a very uniform syntax, so switching to Typst wouldn't have as many benefits compared to if I were switching from LaTeX.
So if Typst were to take over, I'd mainly be disappointed that my very deep knowledge of TeX would be no longer relevant. But I also wouldn't be surprised if Typst ultimately revitalized TeX, since it might motivate us to improve TeX even more, and Typst might be a good entrypoint for users interested in plain text typesetting (who might then switch to TeX if they find Typst too limiting).
[1]: ConTeXt uses the same underlying TeX engine as LaTeX, but different macros. See https://tug.org/TUGboat/tb46-3/tb144berry-engines-formats.pd... for a brief overview.
> cryptic error messages
These have somewhat improved recently, but I agree that they're still not great.
> complex pipeline
You can typically just run "latexmk --lualatex <filename.tex>" and your document should compile in a single step.
> lack of the proper Unicode symbols support out of the box
UTF-8 has been the default input encoding since 2018 [0], so character input should mostly just work. Using complex scripts (Arabic, Devanagari, etc.) requires XeLaTeX or LuaLaTeX, but LuaLaTeX is recommended for most documents anyways [1].
Now, you still won't be able to typeset arbitrary characters without any additional setup, but this is because there is no single font that contains all characters, and since mismatched fallback fonts usually looks bad, the (La)TeX developers do not want this to be the default. But
\usepackage{fontspec}
\setmainfont{Some Font with your Characters}
> Projects like Tectonic would solve this for TeX
All of these have already been fixed in TeX, except for the error messages, which would be impossible for Tectonic to fix.
(Background: the TeX engines give excellent error messages, and LaTeX gives good error messages for "expected" errors, but unexpected errors usually give a TeX engine error message unrelated to your LaTeX input, since LaTeX is internally implemented on top of TeX engine macros. So much like C++ template errors, it isn't really possible to fix this.)
> Otherwise, using TeX only makes sense nowadays only if
4) If you actually like TeX for some reason like I do :)
[0]: https://www.latex-project.org/news/latex2e-news/ltnews28.pdf...
[1]: https://www.latex-project.org/news/2024/11/01/issue40-of-lat...
The core/official LaTeX code is really quite stable, but it's also very limited, so it's pretty reasonable to conflate it with the LaTeX ecosystem as a whole. But yes, the LaTeX Team is definitely aware of the problems caused by Babel shorthands (which is what " is in German), and they're trying to figure out some way to fix it without breaking other documents.
That is an option that you can enable. If you're only using a few different languages (which is by far the most typical case), it's mostly automatic with Babel (by using "\babelfont"), but if you really want to support everything, you can use something like [0] (which is admittedly rather convoluted).
> just always having broken output as I use more unicode (maths symbols, emojis) in my documents.
Adding "\tracinglostchars=3" anywhere in your document (before the offending character) will turn any missing characters into an error message, and using the "--halt-on-error" command-line flag will make that error fatal. I've talked to the LaTeX Team and they'd really like it if they could make those the default, but they have 40 years of backwards compatibility to deal with. I've also talked to the Overleaf support team, and it's depressingly common for documents to compile with 50+ errors and for users to think that that's completely okay.
LaTeX is fairly similar to C here, because in both cases, the errors are nearly always important, a good document/program should compile with zero errors, yet thousands of old documents/programs do compile with errors and their users complain if you make them fatal by default.
The thing that often hits me nowadays is using pandoc (or pandoc via quarto) to go markdown -> latex -> pdf, which tends to bury these issues (and in markdown it's more tempting to just write emojis / unicode maths symbols.
Why use markdown, because I want good HTML output (which I realise is getting better in latex, but still not as good as markdown -> HTML.
The pdftex engine is pretty much a dead end these days and I would only recommend its use for compiling legacy documents.
That said, the biggest problem is nothing to do with the source code of TeX. The change file mechanism is pretty straightforward and there have been tools for decades to allow application of more than one change file against the source, although with the standardization on web2c in the build process as well as better cross-platform C compilation in 2026 vs 1982, there isn’t the proliferation of platform-dependent change files that there were in the 80s when people were compiling on Pascal compilers that supported different subsets of the language.
But as I was saying before I got into that digression, the source language isn’t the issue with TeX so much as the basic architecture which is highly coupled to the limitations of computers in the late 70s/early 80s when even 7-bit ASCII couldn’t be assumed to be consistent between systems¹. As much as I enjoy writing TeX macros and can do wonderful things with them that most people would consider dark magic, it’s a cursed way to do programming and has no parallel in any other programming paradigm.
⸻
1. The SAIL platform at Stanford where Knuth did the initial work, for example, had ↑ in the code space ASCII designates as ^, and IBM mainframes all used EBCDIC which has the complication of having | and ¦ as two separate characters both of which were typically mapped to | in EBCDIC to ASCII conversions with the reverse conversions arbitrarily choosing one of the two characters so that there was no guarantee that you’d get the expected character in your text file conversion² or your ASCII terminal controller.
2. Which is yet another reason why non-Unix operating systems would have distinct text and binary modes for opening files.
Well LuaTeX solves both of these problems, but I'm pretty sure that you're already aware of that :)
> it’s a cursed way to do programming and has no parallel in any other programming paradigm
It's fairly similar to C preprocessor macros, and writing Mathematica code occasionally reminds me of TeX, but these aren't exactly the most flattering comparisons.
Thank you for fully fixing LaTeX for me.
It reminds me of that very embarrassing dance we used to do around 2008 :)