[racket] Behaviour with read-only files

On Nov 17, 2011, at 1:13 PM, John Clements wrote:

> Minor problem: the "end" button.

Disable it until you have found the end or replace it with '1000 steps' button 


> More major problem (?): world/universe code with callbacks. In this case, the only way to get the picture moving again would be to manually move the stepper to the end step. 

I don't understand this. 


> For these reasons (and a general gut feeling), I think it's better to treat the stepper as a parallel process that's sending messages over to the UI side.

That's another good solution.