Re: Profiling font-lock in xemacs

[Ben Wing]

what we do is something like this:

--all the signal handler does is set a flag. (this flag also gets set by a 
0.25-second asynchronous timer, on systems like MS Windows that have no 
SIGIO.)

--QUIT notices this, which causes it (on most platforms) to drain the input 
queue, storing it into an internal "dispatch queue".  we iterate through 
this to look for C-g. (under X we actually use something like XCheckIfInput 
(i forget the proper name) instead of draining the queue, but that's bogus 
and left over from a long time ago and should be fixed like the other 
platforms.) the dispatch queue is one of the sources of next-event (your 
read-event).

i don't think sigchld should do *anything* except set a flag.

ben

> From: "Stefan Monnier" <monnier+gnu/address@hidden>
> To: Richard Stallman <address@hidden>
> CC: monnier+gnu/address@hidden, address@hidden, address@hidden,   
> address@hidden, address@hidden, address@hidden
> Subject: Re: Profiling font-lock in xemacs
> Date: Sun, 23 Jun 2002 14:40:36 -0400
>
> > Emacs does not do very much in signal handlers now.  For sigchld it
> > just records the status, something that is best done right away.
> > XTread_socket is complex; if some of that can be done later on, that
> > might be good.  But it can't wait too long.  For instance, quit has to
> > be detected reasonably soon.  Perhaps the QUIT macro could run the
> > code to process the input.
> >
> > On the other hand, this code works; we have had little problem with
> > it for a long time.
>
> The problem is indeed XTread_socket.  It is complex and it has
> introduced really nasty bugs which were very difficult to trace.
> Also, it is dangerous to try to extend its functionality because
> it is run asynchronously (the recent "selected-window follows mouse"
> patch is a case in point).
>
> I think it would be worth it to try and move the bulk of it out of the
> signal handler as the XEmacs folks did.  I haven't checked when the do
> the "check for input".  Doing it from QUIT is indeed one obvious
> possibility.
>
>
>         Stefan




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