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#56682
Fix the long lines font locking related slowdowns
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Message #2145 received at 56682 <at> debbugs.gnu.org (full text, mbox):
On 30/01/2023 21:02, Eli Zaretskii wrote:
>> Date: Mon, 30 Jan 2023 20:56:15 +0200
>> Cc:56682 <at> debbugs.gnu.org,monnier <at> iro.umontreal.ca
>> From: Dmitry Gutov<dgutov <at> yandex.ru>
>>
>> On 30/01/2023 19:11, Eli Zaretskii wrote:
>>>> Date: Mon, 30 Jan 2023 15:03:54 +0000
>>>> From: Gregory Heytings<gregory <at> heytings.org>
>>>> cc:56682 <at> debbugs.gnu.org,monnier <at> iro.umontreal.ca
>>>>
>>>>> What exactly will that remove? only what's on the feature branch, or
>>>>> also some stuff on the emacs-29 branch?
>>>> The "locked narrowing" feature, IOW, the portions of editfns.c in which it
>>>> is implemented, and its use around pre-command-hook, post-command-hook and
>>>> fontification-functions.
>>>>
>>>>> And what are your reasons for removing this? It is hard to tell whether
>>>>> or not I agree without knowing to what I should agree 😉
>>>>>
>>>> The reason is that I'm now convinced that it is not a good solution to the
>>>> problem of ill-behaving modes in the presence of long lines.
>>> So we are removing all the stuff that prevented font-lock from slowing
>>> down redisplay when long lines are in the buffer? IOW, something
>>> which we have for several months, and which so far brought up only one
>>> complaint?
>> More than one, FTR.
>>
>> I'm not 100% sure what Gregory's plan is, but note that a significant
>> part of the redisplay slowdowns wasn't caused by font-lock, and thus the
>> removal of locking will not regress those performance improvements.
>>
>> And for those (potential?) cases where font-lock is a real problem for
>> performance, we could stop it from widening using an existing knob.
> Yes, this is an old and known disagreement between us. But this is my
> decision to make, not anyone else's.
With the previous change that Gregory had made (different limits for
different features, i.e. font-lock uses much wider narrowing bounds
which are also customizable) I don't have that much of a horse in that
race anymore.
Just helping clear up some misconceptions, if any.
Also note that previously, I'd never have suggested that redisplay code
changes the value of font-lock-dont-widen.
This bug report was last modified 2 years and 8 days ago.
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