If you wanna be sincere about this, I think you should have a section dedicated to Gezira, and not only the more traditional imperative styles of graphics programming. The style of GUI that came out of PARC is no longer "modern", and has problems with modern development styles (e.g, single-threaded global event loops makes writing concurrent programs difficult).
If you're not familiar with it, Gezira is a full vector graphics API, including compositing, written in less than a thousand lines of Nile - a small flow-based programming language. It does its magic by treating quadratic bezier curves as the main primitive, where the author has developed an algorithm to calculate the pixel coverage of a given bezier, with anti-aliasing.. Because most operations can be treated independently, it lends itself nicely to concurrency - each operation in a data flow can run independently, and many operations can be parallelised if given sufficient inputs.
Gezira/Nile was created by Dan Amelang while working for VPRI (the research institute headed by Alan Kay). A demo of it in action can be seen here: (http://tinlizzie.org/~bert/Gezira.ogv), where it's worth noting that the entire Editor UI in this example (after first 5 seconds), including font rendering, is written with Gezira itself.