Allow multiple whiskers

I wanted to experiment with multiple whiskers but creating the second whisker failed with the error:

Error[program:0:0]: "Cannot read property 'getContext' of null"

The problem seems to be that paper.get('supporterCanvas') only returns a reference to the canvas on the first call. I assume the reason for this is that you can call transferControlToOffscreen only once. Instead of just returning null I think it would be nicer if paper.get(‘supporterCanvas’) would cache the reference to the canvas on the worker side and return the cached reference instead. I think this would be generally useful independent of the whisker issue. To improve handling multiple whiskers I would like to change the current implementation so only a single setInterval is created by paper.whenPointsAt().

[paulsonnentag]

No this is a separate issue. The problem is the following line, where the whisker canvas is requested:

https://github.com/janpaul123/paperprograms/blob/a35abb97008d711c29e5092c9b99117529c02037/client/paper/entry.js#L125

If this is called twice the second time null is returned instead of a reference to the canvas. I quick fix would be to generate a unique id for each whisker canvas.

[janpaul123]

Ah that’s a good idea! Maybe we should drop the two different colours in the default case too and just use the moving dot animation? In any case, sounds good to me. 💯