Re: [PATCH] Re: cc-mode fontification feels random

[Eli Zaretskii]

> Cc: emacs-devel@gnu.org
> From: Daniel Colascione <dancol@dancol.org>
> Date: Mon, 30 Aug 2021 12:28:01 -0700
> 
> > So you are saying that this will cause the display of the visible
> > portion of the window to flicker whenever jit-lock-stealth finds such
> > a "new type"?  That could annoy, can't it?  jit-lock-stealth is for
> > fontifying portions of the buffer(s) that are not on display, it would
> > be wrong for it to apply this enhancement, I think, certainly by
> > default.
> 
> Any literal "flicker" issues should have been fixed for a long time now. 
> What do you mean? That the fontification might change? That happens anyway.

It doesn't happen with jit-stealth-lock now, because it only handles
portions of the buffer that are not displayed.  The portions that are
displayed get fontified before they are shown in the window.

> > And jit-lock-stealth-time of 1 sec is too short.  I use 16, because
> > once jit-lock-stealth starts fontifying a chunk, Emacs can be
> > relatively slow to react to keyboard input, so I prefer to let
> > jit-lock-stealth start its thing only when there's a very good chance
> > I indeed stopped typing, not just thinking about something for a
> > second or two.
> 
> Isn't this problem what while-no-input is intended to prevent?

while-no-input doesn't cause an immediate interruption of a running
Lisp code, as you well know.

> > Users can already arrange for that by manipulating the
> > jit-stealth-lock parameters.  Why should we change code to force upon
> > everyone what seems like a good idea to you (but isn't a good idea
> > IME, see above)?  If you want that, you can easily arrange for Emacs
> > to behave like that without changing any code.
> 
> Because good defaults matter, and if we have proper input preemption of 
> stealth JIT working, there should be no downside.

I invite you to try.  I use jit-stealth-lock all the time, and that is
my experience.  With it running, Emacs sometimes is slow to respond to
keyboard input.  "Slow" relatively, of course: it takes less than a
second even in the slow cases, but that's already somewhat annoying.
Which is why I avoid letting it run when I'm still typing, albeit
slowly.