I've written some Java which will allow sketches to be stacked one on top of another.

Why's it useful? You can make up simple sketches which do simple things, and then combine them in more complex ways. Layers of functionality can then be added and removed dynamically. This was really written with component/sketch re-usability in mind.

How does it work? It works by using a composite and proxy patterns. Instead of sketches calling methods on PApplet, it uses a proxy. These proxys then call the methods on the real PApplet. When a event is reported to the PApplet, e.g. mousePressed(), all the proxies get informed.

Drawbacks?
Unfortunately:
* it requires modification to the compiled code (SketchClass.java) files,
* is annoying to maintain across versions (i.e. new methods are not automatically supported).

Questions:
I'm not entirely sure where this would fit in to the current tool chain - where would you put it
Naming - has any one got a good name for it - P5Layer is the current name, but I'm betting there are better names. Naming - are there any naming conventions to follow.
Demand - is any one interested in this sort of thing? If so, I'll try and post some kind of demo for folks to try.

would love to mess around with this - post it if you can. just thinking about how to implement layering / compositing of different parts of a sketch - this would be fantastic...