From: Alan Mackenzie <acm@muc.de>
To: Eli Zaretskii <eliz@gnu.org>
Cc: monnier@iro.umontreal.ca, emacs-devel@gnu.org
Subject: Re: bug-reference-prog-mode slows down CC Mode's scrolling by ~7%
Date: Fri, 3 Sep 2021 10:47:41 +0000 [thread overview]
Message-ID: <YTH9TTrouH6040hD@ACM> (raw)
In-Reply-To: <83a6kuyysv.fsf@gnu.org>
Hello, Eli.
On Fri, Sep 03, 2021 at 09:10:24 +0300, Eli Zaretskii wrote:
> > Date: Thu, 2 Sep 2021 19:24:51 +0000
> > From: Alan Mackenzie <acm@muc.de>
> > Cc: emacs-devel@gnu.org
> > In words (;-), only the first function on jit-lock-functions should be
> > able to expand the region which gets `fontified' text properties. This
> > expanded region will then be supplied to the subsequent functions.
> > Given how little used the `jit-lock-bounds' mechanism is (there is one
> > function in Emacs, font-lock-default-fontify-region, which uses it, and
> > a web search revealed only a single other instance, in lsp-mode on
> > git-hub), this shouldn't cause problems. In fact, I'm not sure the
> > lsp-mode use of it is even correct.
> Bother: this is not future-proof, and certainly isn't scalable. If we
> are changing the protocol, can we instead come up with a more scalable
> change, so that functions won't "fight" in the future who gets to be
> "the first"?
I think we need to be clear about the current situation versus my
proposal. If there is only one element (typically
font-lock-fontify-region) on jit-lock-functions, nothing changes. With
several elements:
Current situation: The region marked with 'fontified text properties is
the _smallest_ returned by the jit-lock-functions functions. If such a
function returns nil (which is usual), that region becomes precisely
(BEG END), and we lose all the benefit of jit-lock-bounds.
Proposed mechanism: The region marked with 'fontified is that supplied
by the first j-l-f function, typically font-lock-fontify-region. This
is an enhancement.
Note that it is difficult to use the jit-lock-bounds returned by a
subsequent function, if they exceed the bounds returned by the first
function. To do this safely, we would have to re-run all the previous
jit-lock-functions on the newly enlarged region. This would be clumsy,
and wouldn't fit in well with our current scheme.
As for "fighting" to be the first function in j-l-f, I don't think that
should be a problem. We can document the new &optional parameter to
jit-lock-register (not yet implemented) to say "don't use this unless
you really know what you're doing".
What we have isn't scalable in the sense you mean, and I don't think it
can be made scalable without massive changes in the jit-lock mechanism,
which might well reverse the benefits of using jit-lock-bounds (the 7%
saving in font locking time in CC Mode (and surely other modes, too)).
--
Alan Mackenzie (Nuremberg, Germany).
next prev parent reply other threads:[~2021-09-03 10:47 UTC|newest]
Thread overview: 74+ messages / expand[flat|nested] mbox.gz Atom feed top
2021-09-01 17:33 bug-reference-prog-mode slows down CC Mode's scrolling by ~7% Alan Mackenzie
2021-09-01 17:44 ` Eli Zaretskii
2021-09-01 17:55 ` Alan Mackenzie
2021-09-01 18:01 ` Eli Zaretskii
2021-09-01 18:20 ` Alan Mackenzie
2021-09-01 18:28 ` Eli Zaretskii
2021-09-01 19:19 ` Alan Mackenzie
2021-09-01 20:59 ` Stefan Monnier
2021-09-02 6:26 ` Eli Zaretskii
2021-09-02 16:57 ` Alan Mackenzie
2021-09-02 18:46 ` Stefan Monnier
2021-09-02 19:24 ` Alan Mackenzie
2021-09-02 21:08 ` Alan Mackenzie
2021-09-03 6:16 ` Eli Zaretskii
2021-09-03 12:30 ` Stefan Monnier
2021-09-03 12:38 ` Eli Zaretskii
2021-09-03 22:25 ` Stefan Monnier
2021-09-04 6:13 ` Eli Zaretskii
2021-09-04 13:36 ` Stefan Monnier
2021-09-04 13:55 ` Eli Zaretskii
2021-09-04 14:44 ` Stefan Monnier
2021-09-04 14:56 ` Eli Zaretskii
2021-09-04 15:55 ` Stefan Monnier
2021-09-04 16:12 ` Eli Zaretskii
2021-09-04 16:24 ` Stefan Monnier
2021-09-04 16:28 ` Eli Zaretskii
2021-09-04 16:40 ` Stefan Monnier
2021-09-03 6:10 ` Eli Zaretskii
2021-09-03 10:47 ` Alan Mackenzie [this message]
2021-09-03 11:24 ` Eli Zaretskii
2021-09-03 16:15 ` Alan Mackenzie
2021-09-03 12:27 ` Stefan Monnier
2021-09-03 12:19 ` Stefan Monnier
2021-09-03 12:35 ` Eli Zaretskii
2021-09-03 16:52 ` Alan Mackenzie
2021-09-03 20:51 ` Alan Mackenzie
2021-09-04 6:09 ` Eli Zaretskii
2021-09-04 14:50 ` Alan Mackenzie
2021-09-04 15:00 ` Stefan Monnier
2021-09-04 15:32 ` Alan Mackenzie
2021-09-04 15:36 ` Eli Zaretskii
2021-09-04 15:43 ` Alan Mackenzie
2021-09-04 15:48 ` Eli Zaretskii
2021-09-04 16:05 ` Alan Mackenzie
2021-09-04 16:15 ` Eli Zaretskii
2021-09-06 10:46 ` Alan Mackenzie
2021-09-06 11:10 ` Eli Zaretskii
2021-09-06 19:08 ` Alan Mackenzie
2021-09-06 19:23 ` Eli Zaretskii
2021-09-18 11:37 ` Alan Mackenzie
2021-09-18 11:59 ` Eli Zaretskii
2021-09-06 21:59 ` andrés ramírez
2021-09-07 19:47 ` Alan Mackenzie
2021-09-07 17:57 ` andrés ramírez
2021-09-06 13:24 ` Stefan Monnier
2021-09-04 16:06 ` Stefan Monnier
2021-09-04 16:23 ` Eli Zaretskii
2021-09-04 16:39 ` Stefan Monnier
2021-09-04 17:19 ` Eli Zaretskii
2021-09-04 17:47 ` Stefan Monnier
2021-09-04 18:10 ` Eli Zaretskii
2021-09-04 18:40 ` Stefan Monnier
2021-09-11 12:49 ` Eli Zaretskii
2021-09-11 17:04 ` Stefan Monnier
2021-09-11 17:17 ` Eli Zaretskii
2021-09-11 18:00 ` Stefan Monnier
2021-09-11 18:16 ` Eli Zaretskii
2021-09-11 19:55 ` Stefan Monnier
2021-09-12 3:51 ` Eli Zaretskii
2021-09-12 16:41 ` Stefan Monnier
2021-09-12 16:53 ` Eli Zaretskii
2021-09-12 17:41 ` Stefan Monnier
2021-09-12 17:55 ` Eli Zaretskii
2021-09-12 21:11 ` Stefan Monnier
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