Re: Nested sit-for's

[Chong Yidong <cyd@stupidchicken.com>]

storm@cua.dk (Kim F. Storm) writes:

>> It would work to have ONE timer that does sit-for if we make a rule
>> that no others can do so.  We could define jit-lock as this one
>> exception.  (This has the advantage of not involving any change in the
>> code, just comments and the Lisp Manual.)
>
> I agree with your analysis.  
>
> But, IMO, if we make it a rule that timers should generally not use
> sit-for, then a central function like jit-lock should definitely not
> use sit-for!

If we simply document that "timers (and process filters) should avoid
using sit-for", it should be clear to the reader that rare exceptions
may exist (especially if we add a comment to jit-lock-stealth-fontify
stating this).  After the release, we can probably rework
jit-lock-stealth-fontify to avoid using sit-for, but I don't think the
current situation is bad enough to block the release.

OTOH, I don't remember any other timers or process filters in the
Emacs tree that use a long sit-for or loop waiting for input.  Anyone
know of any?