From: Stefan Monnier <monnier@iro.umontreal.ca>
To: emacs-devel@gnu.org
Subject: Re: An idea: combine-change-calls
Date: Sat, 24 Mar 2018 18:18:05 -0400 [thread overview]
Message-ID: <jwvy3ihp2ik.fsf-monnier+gmane.emacs.devel@gnu.org> (raw)
In-Reply-To: 20180324135024.GA6319@ACM
> The motivation is bug #30735,
[ Not surprised: I told you CC-mode's change-functions are too costly,
because they presumes that before&after-change-functions are called at
a "human" rate (comparable to pre/post-command-hook).
before&after-change-functions should be handled a bit like POSIX
signals: do as little work as possible there, and handle them
later elsewhere. `comment-region` is not the only command that can
make many small changes. ]
> What do people think?
I actually do like the idea of combining such things, tho it's risky:
e.g. if the code within combine-change-calls uses syntax-ppss it might
get wrong results since syntax-ppss-flush-cache is triggered via
before-change-functions. The same problem would affect
syntax-propertize, of course.
Grepping for `add-hook.*before-change-functions` indicates that similar
problem could appear elsewhere. Not sure what to do about it other than
to say "don't over-use it, it might bite you".
Also we'd need such a system to check that the bounds
are indeed obeyed.
One more thing: with the sample code you showed, undoing will still be
just as slow since it won't benefit from combine-change-calls.
Maybe combine-change-calls should also combine all those changes on the
undo-list into a big "delete+insert" (of course, it could also try and
keep the undo granularity but mark those undo entries so that they're
undone within their own combine-change-calls).
Stefan
next prev parent reply other threads:[~2018-03-24 22:18 UTC|newest]
Thread overview: 32+ messages / expand[flat|nested] mbox.gz Atom feed top
2018-03-24 13:50 An idea: combine-change-calls Alan Mackenzie
2018-03-24 22:18 ` Stefan Monnier [this message]
2018-03-25 19:14 ` Alan Mackenzie
2018-03-25 20:05 ` Stefan Monnier
2018-03-26 20:17 ` Alan Mackenzie
2018-03-26 21:07 ` Stefan Monnier
2018-03-27 16:58 ` Alan Mackenzie
2018-03-27 18:30 ` Stefan Monnier
2018-03-27 19:45 ` Alan Mackenzie
2018-03-27 20:24 ` Stefan Monnier
2018-03-28 20:42 ` Alan Mackenzie
2018-03-28 21:26 ` Stefan Monnier
2018-03-29 15:10 ` Alan Mackenzie
2018-03-29 15:40 ` Stefan Monnier
2018-03-29 17:11 ` Alan Mackenzie
2018-03-29 19:10 ` Stefan Monnier
2018-03-30 11:46 ` Alan Mackenzie
2018-03-30 15:05 ` Stefan Monnier
2018-03-31 21:00 ` Alan Mackenzie
2018-03-31 23:38 ` Stefan Monnier
2018-04-01 14:24 ` Alan Mackenzie
2018-04-01 19:22 ` Stefan Monnier
2018-03-30 9:12 ` Johan Bockgård
2018-03-30 13:04 ` Stefan Monnier
2018-04-02 16:25 ` Alan Mackenzie
2018-04-02 17:52 ` Johan Bockgård
2018-04-03 0:41 ` Stefan Monnier
2018-04-03 1:43 ` Clément Pit-Claudel
2018-04-03 3:15 ` Richard Stallman
2018-03-26 21:09 ` Stefan Monnier
2018-03-27 0:36 ` Stefan Monnier
2018-03-27 17:00 ` Alan Mackenzie
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