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From: Alan Mackenzie <acm@muc.de>
To: Eli Zaretskii <eliz@gnu.org>
Cc: gregory@heytings.org, emacs-devel@gnu.org
Subject: Re: Major modes using `widen' is a good, even essential, programming practice.
Date: Sun, 7 Aug 2022 17:01:09 +0000	[thread overview]
Message-ID: <Yu/v1bmvRhXq186v@ACM> (raw)
In-Reply-To: <83y1w0w0gk.fsf@gnu.org>

Hello, Eli.

On Sun, Aug 07, 2022 at 18:13:47 +0300, Eli Zaretskii wrote:
> > Date: Sun, 7 Aug 2022 14:59:06 +0000
> > Cc: gregory@heytings.org, emacs-devel@gnu.org
> > From: Alan Mackenzie <acm@muc.de>

> > > jit-lock calls the functions with two arguments, BEG and END, and
> > > expects them to work only on that chunk of text.

> > I don't think you really mean that.

> No, I really do.

> > Consider the second jit-lock chunk
> > at the beginning of xdisp.c.  Fontifying that chunk involves looking
> > back 1500 characters before BEG to see that it needs
> > font-lock-comment-face.  You might argue that that information will be
> > in a cache anyway, but that's not dependable.

> Either in the cache or in the buffer: the previous chunk was
> fontified, so its end has the font-lock-comment-face.  So you know.

No, you don't.  The buffer might be being opened by desktop in a large
comment in the middle of the file.

What jit-lock/font-lock actually do at the moment is to widen, then use
syntax-ppss, i.e. in effect scan from BOB.

> > Also, the (BEG END) region will typically get rounded up to whole lines,
> > again "violating" that chunk.

> That's a far cry from going to BOB.  And if you ask nicely, we could
> arrange that jit-lock calls you only on line boundaries (unless lines
> are longer than some reasonable value).

The search for line boundaries is done by font-lock.el.

> > In principle, font-lock needs to look outside of (BEG END).

> No, it doesn't.  A string cannot begin before a beginning of a
> function, for example.  And if you need to go too far, just give up
> and blame the user who writes such code.  It is much better than
> letting every use of CC Mode wait because once in a blue moon someone
> could have a very long string.

That "needing to go too far" is an instantaneous jump, not a scanning.
The string start will be in a parse-partial-sexp result somewhere.
Sometimes people write long strings.  They certainly write long comments.

-- 
Alan Mackenzie (Nuremberg, Germany).



  reply	other threads:[~2022-08-07 17:01 UTC|newest]

Thread overview: 136+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2022-08-06 20:13 Major modes using `widen' is a good, even essential, programming practice Alan Mackenzie
2022-08-06 21:05 ` Stefan Monnier
2022-08-07  6:03 ` Eli Zaretskii
2022-08-07 13:31 ` Gregory Heytings
2022-08-07 14:13   ` Alan Mackenzie
2022-08-07 14:20     ` Eli Zaretskii
2022-08-07 14:59       ` Alan Mackenzie
2022-08-07 15:13         ` Eli Zaretskii
2022-08-07 17:01           ` Alan Mackenzie [this message]
2022-08-07 17:23             ` Eli Zaretskii
2022-08-07 17:53               ` Dmitry Gutov
2022-08-07 18:00                 ` Eli Zaretskii
2022-08-07 18:05                   ` Dmitry Gutov
2022-08-07 18:37                     ` Eli Zaretskii
2022-08-07 23:02                       ` Stefan Monnier
2022-08-07 18:49                   ` Óscar Fuentes
2022-08-07 18:59                     ` Eli Zaretskii
2022-08-07 18:56                   ` Lars Ingebrigtsen
2022-08-07 19:20               ` Alan Mackenzie
2022-08-07 19:26                 ` Dmitry Gutov
2022-08-08  2:36                 ` Eli Zaretskii
2022-08-08  9:58                   ` Alan Mackenzie
2022-08-08 11:39                     ` Eli Zaretskii
2022-08-08 15:05                       ` CC Mode with font-lock-maximum-decoration 2 [Was Major modes using `widen' is a good, even essential, programming practice.] Alan Mackenzie
2022-08-08 15:51                         ` Gregory Heytings
2022-08-08 16:05                           ` CC Mode with font-lock-maximum-decoration 2 Alan Mackenzie
2022-08-08 16:50                             ` Gregory Heytings
2022-08-09 19:49                               ` Gregory Heytings
2022-08-08 17:15                         ` CC Mode with font-lock-maximum-decoration 2 [Was Major modes using `widen' is a good, even essential, programming practice.] Eli Zaretskii
2022-08-08 17:41                           ` Eli Zaretskii
2022-08-08 18:41                             ` CC Mode with font-lock-maximum-decoration 2 Alan Mackenzie
2022-08-08 18:51                               ` Eli Zaretskii
2022-08-08 19:09                                 ` Alan Mackenzie
2022-08-09  2:24                                   ` Eli Zaretskii
2022-08-09  8:00                                     ` Alan Mackenzie
2022-08-09 11:07                                       ` Eli Zaretskii
2022-08-09 11:24                                         ` Alan Mackenzie
2022-08-09 11:57                                           ` Eli Zaretskii
2022-08-09 16:36                                             ` Alan Mackenzie
2022-08-09 16:59                                               ` Eli Zaretskii
2022-08-09 17:43                                                 ` Alan Mackenzie
2022-08-09 17:55                                                   ` Eli Zaretskii
2022-08-10  0:22                                                     ` Why tree-sitter instead of Semantic? (was Re: CC Mode with font-lock-maximum-decoration 2) Lynn Winebarger
2022-08-10  2:14                                                       ` Po Lu
2022-08-10  2:42                                                         ` Eli Zaretskii
2022-08-10 10:05                                                           ` Lynn Winebarger
2022-08-10 10:49                                                             ` Po Lu
2022-08-10 11:31                                                             ` Eli Zaretskii
2022-08-12 12:37                                                               ` Lynn Winebarger
2022-08-12 12:50                                                                 ` Eli Zaretskii
2022-08-12 21:50                                                                   ` Ideal performance of ELisp (was: Why tree-sitter instead of Semantic? (was Re: CC Mode with font-lock-maximum-decoration 2)) Stefan Monnier
2022-08-12 23:26                                                                     ` Lynn Winebarger
2022-08-13  2:11                                                                       ` Ideal performance of ELisp Stefan Monnier
2022-08-13 10:51                                                                         ` Lynn Winebarger
2022-08-13 11:13                                                                           ` Lynn Winebarger
2022-08-13 14:07                                                                           ` Stefan Monnier
2022-08-13 14:56                                                                             ` Lynn Winebarger
2022-08-16 16:46                                                                               ` Lynn Winebarger
2022-08-16 17:22                                                                                 ` Stefan Monnier
2022-08-17 12:41                                                                                   ` Lynn Winebarger
2022-08-17 14:04                                                                                     ` Stefan Monnier
2022-08-17 14:19                                                                                       ` Mattias Engdegård
2022-08-17 22:18                                                                                         ` Stefan Monnier
2022-08-17 14:25                                                                                       ` Lynn Winebarger
2022-08-13  4:39                                                                     ` Ideal performance of ELisp (was: Why tree-sitter instead of Semantic? (was Re: CC Mode with font-lock-maximum-decoration 2)) Ihor Radchenko
2022-08-13  7:45                                                                       ` Ideal performance of ELisp Philip Kaludercic
2022-08-13 11:58                                                                         ` Ihor Radchenko
2022-08-13 14:15                                                                       ` Stefan Monnier
2022-08-14  9:25                                                                         ` Andrea Corallo
2022-08-14  9:34                                                                           ` Ihor Radchenko
2022-08-14 13:01                                                                             ` Eli Zaretskii
2022-08-16 19:23                                                                             ` Andrea Corallo
2022-08-14 13:01                                                                           ` Stefan Monnier
2022-08-16  8:59                                                                             ` Andrea Corallo
2022-08-16  9:50                                                                               ` Ihor Radchenko
2022-08-16 18:21                                                                                 ` Andrea Corallo
2022-08-17  9:48                                                                                   ` Ihor Radchenko
2022-08-17 12:02                                                                                     ` Eli Zaretskii
2022-08-16 15:06                                                                               ` Lynn Winebarger
2022-08-16 18:24                                                                                 ` Andrea Corallo
2022-08-17 13:04                                                                                   ` Lynn Winebarger
2022-08-17 14:18                                                                                     ` Andrea Corallo
2022-08-18 12:17                                                                                       ` Lynn Winebarger
2022-08-12 16:00                                                                 ` Why tree-sitter instead of Semantic? (was Re: CC Mode with font-lock-maximum-decoration 2) Akib Azmain Turja
2022-08-12 19:06                                                                   ` tomas
2022-08-13  4:41                                                                     ` Akib Azmain Turja
2022-08-13  5:14                                                                       ` tomas
2022-08-13 11:57                                                                   ` Lynn Winebarger
2022-08-13 14:28                                                                     ` Akib Azmain Turja
2022-08-14 19:24                                                         ` Eric Ludlam
2022-08-16 10:42                                                           ` Lynn Winebarger
2022-08-17  1:56                                                             ` Eric Ludlam
2022-08-10 17:03                                                       ` Tassilo Horn
2022-08-13 14:40                                                       ` Jostein Kjønigsen
2022-08-14  1:23                                                         ` Po Lu
2022-08-16  9:06                                                           ` Lynn Winebarger
2022-08-16 11:05                                                             ` Po Lu
2022-08-16 11:41                                                             ` Eli Zaretskii
2022-08-16 16:33                                                               ` Lynn Winebarger
2022-08-16 17:19                                                                 ` Stefan Monnier
2022-08-16 17:40                                                                   ` Lynn Winebarger
2022-08-17  1:41                                                                     ` Eric Ludlam
2022-08-18 12:34                                                                       ` Lynn Winebarger
2022-08-20 13:15                                                                         ` Eric Ludlam
2022-08-08 18:20                           ` CC Mode with font-lock-maximum-decoration 2 Alan Mackenzie
2022-08-07 20:17     ` Major modes using `widen' is a good, even essential, programming practice Gregory Heytings
2022-08-07 20:46       ` Alan Mackenzie
2022-08-07 20:53         ` Gregory Heytings
2022-08-08  2:37         ` Eli Zaretskii
2022-08-08 10:33           ` Alan Mackenzie
2022-08-08 11:41             ` Eli Zaretskii
2022-08-07 23:21     ` Stefan Monnier
2022-08-08  2:29       ` Eli Zaretskii
2022-08-08  9:25         ` Stefan Monnier
2022-08-08 11:16           ` Lynn Winebarger
2022-08-08 11:47             ` Eli Zaretskii
2022-08-08 14:24               ` Lynn Winebarger
2022-08-08 11:30           ` Eli Zaretskii
2022-08-08 12:05             ` Stefan Monnier
2022-08-08 12:40               ` Eli Zaretskii
2022-08-08 17:22                 ` Stefan Monnier
2022-08-08 17:34                   ` Eli Zaretskii
2022-08-08 21:16             ` Dmitry Gutov
2022-08-09 11:30               ` Eli Zaretskii
2022-08-09 14:38                 ` Dmitry Gutov
2022-08-09 16:12                   ` Eli Zaretskii
2022-08-09 16:52                     ` Dmitry Gutov
2022-08-09 17:05                       ` Eli Zaretskii
2022-08-09 18:52                         ` Dmitry Gutov
2022-08-09 19:46                           ` Gregory Heytings
2022-08-08 10:38       ` Alan Mackenzie
2022-08-08 11:49         ` Eli Zaretskii
2022-08-08 10:41       ` Gregory Heytings
2022-08-07 17:57 ` Dmitry Gutov
2022-08-22 11:26   ` Alan Mackenzie
2022-08-22 23:59     ` Dmitry Gutov

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