Most likely by way of Quil (https://github.com/quil/quil). Using quil in your ide of choice is a dream and a remarkable improvement over the native processing env in terms of interactivity with the sketch.
It does indeed use Quil and was really happy to see there recent (May of this year) addition of ClojureScript support. It is a great library and made building up this tutorial great fun using the repl.
> This truly was an amazing place. Here, dreams and reality had been drawn together - all in one Process. "_Why would I ever leave?" he barked with joy! _Why indeed!
Is this implying that this framework was the work of _why the lucky stiff, or is it just some kind of reference to him? The description does very much seem like his style.
I think this will be a hoot to play with my cousin starting out. Clojure is a bit more elegant than processing's language, but with the awesome ease of drawing of the processing frame work.
And the documentation's purple prose is just fantastic!
If you like processing, checkout p5.js[0] (released on HN yesterday) which is a pure javascript port with some other differences[1].
The main goal of Processing.js is to execute Processing files in HTML5, but not necessarily to write native HTML5. It supports a mixed syntax of Processing and JavaScript, where the JavaScript is not really meant to be consumed by the end-user. Processing.js is a port of Processing to JS, using regex to convert Java into JS. It is a good tool for those that want to run simple sketches on the web, however, it is quite opaque. It can be difficult for someone to understand how it works, how to fix things when it doesn't work, or how to modify or extend the library. As Processing.js says on their website, "it's not magic, but almost."
I'm going to be knocking around if anyone has any questions, as I think you all deserve a finished post.
If anyone wants to contribute or have a look at the code it is all hosted at https://github.com/tombooth/painting-in-clojure
Tom