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

[Daniel Colascione]

On 8/30/21 12:25 PM, Eli Zaretskii wrote:
> > Date: Mon, 30 Aug 2021 18:50:34 +0000
> > From: Alan Mackenzie <acm@muc.de>
> > Cc: emacs-devel@gnu.org
> >
> > The following patch is an attempt to improve this situation.  It is best
> > used with jit-stealth-lock enabled.  I have tried it out with the
> > following settings:
> >
> >      jit-lock-stealth-load: 200 ; i.e. inactive.
> >      jit-lock-stealth-nice: 0.1 ; 100 ms between fontifying stealth
> >                                   chunks.
> >      jit-lock-stealth-time: 1   ; 1 second idle time before stealth kicks
> >                                   in.
> >
> > Whenever a new found type is entered into the CC Mode table, it marks
> > all occurrences of the type in the buffer for fontification (by setting
> > the 'fontified text property to nil on it), and causes an immediate
> > redisplay when there are occurrences of the new type in a window.
> 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.


> 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?

> > I think stealth lock could be enhanced by having it fontify several
> > 500-byte chunks together, say until 0.05s time has been taken up.  This
> > could speed up stealth fontification while still leaving the keyboard
> > responsive to the user.
> 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.