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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 16:52:55 +0000	[thread overview]
Message-ID: <YTJS5/+RYKG9H6FV@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"?

OK, so the problem is how do we cope with two (or even several) "first"
functions?

How about something like this:
o - We still have a first function, font-lock-fontify-region.
o - We call the next function with the jit-lock-bounds returned by the
  previous one.  Repeat this step with steadily expanding bounds for
  each function in jit-lock-functions.
o - if (< BEG-final BEG-1) we go through jit-lock-functions again on the
  region (BEG-final BEG-1).  Do the same for END-final.  During this
  stage, we ignore the returned jit-lock-bounds.
o - We set the `fontified' text properties on the region (BEG-final
  END-final).

This needn't actually be too complicated.  The current
jit-lock--run-functions already calculates BEG-final and END-final (it
calls them loose-beg and loose-end).

For this mechanism, it would still be best to have all the functions
using jit-lock-bounds together at the start of jit-lock-functions,
though this would be an optimsation rather than essential to the
functionality.

-- 
Alan Mackenzie (Nuremberg, Germany).



  parent reply	other threads:[~2021-09-03 16:52 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
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 [this message]
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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