Writing your own CUPS printer driver in 100 lines of Python

Summary

In version 1.8 of pretix, we introduced shipping management as a new feature for the pretix Hosted and Enterprise editions. With this plug-in, you can choose not to deliver your tickets to your visitors as a downloadable file, but to send them via snail mail instead. Of course, you can just download those tickets as regular-sized PDF files, print them out and ship them, but the feature is usually most interesting if you want to send out high-quality tickets that look good e.g. in a gift wrapping under a christmas tree or pinned to a wall as a souvenier of the event. For this purpose, you will need a thermal ticket printer as well as suitable ticket paper. Last year, I took a closer look at this market and tested devices from two of the major ticket printer vendors: The BOCA Lemur as well as the Practical Automation uITL+2003CF model. In our test, the printing quality of both printers was very similar. The uITL+ is missing a network port in contrast to the BOCA Lemur, but the uITL+ features a nicer case (smaller and metal instead of plastic) and is way more affordable to obtain, at least here in Europe. For this reason, we chose the uITL+ as our reference printer and for our first customer installation. You’ve already seen a photo of the uITL+ in our last blogpost: However, there is another downside to the uITL+: It only comes with a Windows driver, while the BOCA printers come with drivers for all platforms, including packages for Debian, Ubuntu, Fedora, CentOS, Arch Linux, FreeBSD, and even an ARM build for the Raspberry Pi. Both printers speak FGL (“Friendly Ghost Language”) over the wire, a communication protocol common to the world of ticketing printers. With FGL, you can send ASCII text and style information in order to render your tickets directly on the printer (but we want to send PDFs rendered on the server instead, which is why we need a driver to convert). Documentations of FGL can be obtained via the websites of both vendors. This also means that the dri...