The problem becomes trivial if I put

1. window.mySketch = this;

In my setup() method, but it would be nice to have enough of a clue about the namespace layout not to have to do this.

OK got it.  Sorry, the page originally said I was using had the sketch embedded inside an iframe, which certainly didn't help.

Sometimes you get the sketch with Processing.instances[0]; (in which case Processing.getInstanceById(sketchName); doesn't work).



But run from the IDE, you get the sketch with Processing.getInstanceById(sketchName); because Processing.instances[0]; doesn't work in this case.



Well that was pretty annoying, but now I've figured it out, I'm sure there's some fun to be had with live-editing any sketch I happen to be browsing ;-)