## Wednesday, July 28, 2010

### Compiling LaTeX without a local LaTeX compiler

I recently started working on my (long long overdue) master's thesis, and naturally I came to LaTeX for typesetting. As a LaTeX newbie*, I was pleased to find out that compiling LaTeX is just like compiling any program: there's a bunch of source code files (.tex) and resources (.bib, .sty, images) which you feed to preprocessors and compilers to yield a dvi/ps/pdf document. TeX is actually a turing-complete language, and LaTeX is a macro collection and a preprocessor for TeX.

There's even an online package repository!

And since writing LaTeX has so many similarities with writing code, even if you're just writing text and using existing LaTeX macros and not developing your own, some of the development practices can be applied here as well, like a build system, refactoring to keep the document manageable, version control, and continuous integration.

Continuous integration is nice not only because it asserts that the document is valid (yes, you can screw up TeX documents), but also you automatically get the resulting PDF as a build artifact. You could even hook a diff step in the process, to make reviews easier.

But finding a public continuous integration server is hard, not to mention one with a LaTeX distribution installed. Luckily, LaTeX compilation can be delegated to a remote server, thanks to CLSI (Common LaTeX Service Interface). So all the integration server has to do is forward a compilation request to the CLSI server when it detects changes in the VCS.

The arrow directions in the graphic indicate information flow, and the numbers order the actions.

How you implement this depends on what the integration server supports. For example, if it's Windows you can send a manually assembled compilation request (it's a simple XML) with a JScript script.

You can also use a CLSI server as a replacement for a local LaTeX installation. In that case you have to send the actual .tex file contents instead of just an URL, wrapped in a CLSI XML compilation request. I wrote a simple CLSI client in F# to do this, so a compilation script looks like this:

I'm using git and github for version control and ScribTeX's CLSI server, which is the only public CLSI server I have found so far. Kudos to ScribTeX for that! It's very fast (even faster than compiling locally!) and open source.

If you just want an online editor with integrated revision control and preview, check out ScribTeX's editor.

Also worth checking out is LaTeX Lab, a very cool open source, online LaTeX editor for Google Docs, by the same guy that developed CLSI (Bobby Soares).  It's currently on a preview release but it's very usable.

* Actually, I did use LaTeX several years ago, but I did so through LyX, which combines LaTeX with WYSIWYG, so I didn't really learn LaTeX.

#### 1 comment:

Rich Traube said...

Thanks. Food for lots of hacking here. One idea... use CLSI to generate a printable gallery from a shotwell db.