I have a GUI example Knowledge Graph Navigator in my Lisp book [1] and I am separating out for a new edition the library code and the CAPI code. I also have plans to supply UIs written with McCLIM and Open Graphics. I am motivated because some readers said that having a CAPI example was useful to them. I write just for fun, and I tend to put emphasis on material where I get the most feedback.
[1] slide the price to ‘free’ https://leanpub.com/lovinglisp