[plt-scheme] macro stepper enhancements

Jon Rafkind wrote:
>
>>
>>> 2. Going a step back takes a long time, I guess because the entire 
>>> computation from beginning to end is re-computed? Can all the steps 
>>> be cached along the way instead?
>>
>> They are. The steps are only recomputed when you change the hiding 
>> policy. The time is being taken up by pretty-printing, coloring, 
>> clickback-attaching, etc. I'll check to see if any of the latter 
>> parts are happening outside of edit-sequences, but other than that I 
>> don't know of any way to speed it up.
>>
>
> If you can't speed it up can you provide '<- step 5' ? Or something 
> like that.

Or... can you render the s-expressions in a new thread so that if I hit 
'<- step' it will cancel the current rendering and just go back a step?

Also it would be nice to see what step I'm on (if you can know such a 
thing). Like 'you are on step 5 out of 200'.