GNU bug report logs - #71384
treesit-font-lock-fontify-region unnecessarily re-unfontify's

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Message #5 received at submit <at> debbugs.gnu.org (full text, mbox):

From: JD Smith <jdtsmith <at> gmail.com>
To: bug-gnu-emacs <at> gnu.org
Subject: treesit-font-lock-fontify-region unnecessarily re-unfontify's
Date: Wed, 5 Jun 2024 18:06:54 -0400

The function treesit-font-lock-fontify-region in treesit.el calls (font-lock-unfontify-region start end) right away (see below).  But this function is called as the value of font-lock-fontify-syntactically-function from font-lock-default-fontify-region, which has just itself made the exact same call to font-lock-unfontify-region. I commented out that superfluous call in treesit-font-lock-fontify-region and noticed no ill effects.

(defun treesit-font-lock-fontify-region (start end &optional loudly)
  "Fontify the region between START and END.
If LOUDLY is non-nil, display some debugging information."
  (when (or loudly treesit--font-lock-verbose)
    (message "Fontifying region: %s-%s" start end))
  (treesit-update-ranges start end)
  (font-lock-unfontify-region start end)

Message #8 received at 71384 <at> debbugs.gnu.org (full text, mbox):

From: Eli Zaretskii <eliz <at> gnu.org>
To: JD Smith <jdtsmith <at> gmail.com>, Yuan Fu <casouri <at> gmail.com>
Cc: 71384 <at> debbugs.gnu.org
Subject: Re: bug#71384: treesit-font-lock-fontify-region unnecessarily
 re-unfontify's
Date: Thu, 06 Jun 2024 08:34:13 +0300

> From: JD Smith <jdtsmith <at> gmail.com>
> Date: Wed, 5 Jun 2024 18:06:54 -0400
> 
> The function treesit-font-lock-fontify-region in treesit.el calls (font-lock-unfontify-region start end) right away (see below).  But this function is called as the value of font-lock-fontify-syntactically-function from font-lock-default-fontify-region, which has just itself made the exact same call to font-lock-unfontify-region. I commented out that superfluous call in treesit-font-lock-fontify-region and noticed no ill effects.

Why is that duplicate call a problem?  We don't say that
treesit-font-lock-fontify-region _must_ be called _only_ from
font-lock-default-fontify-region, do we?

Adding Yuan in case he has comments.

Message #11 received at 71384 <at> debbugs.gnu.org (full text, mbox):

From: JD Smith <jdtsmith <at> gmail.com>
To: Eli Zaretskii <eliz <at> gnu.org>
Cc: Yuan Fu <casouri <at> gmail.com>, 71384 <at> debbugs.gnu.org
Subject: Re: bug#71384: treesit-font-lock-fontify-region unnecessarily
 re-unfontify's
Date: Thu, 6 Jun 2024 07:35:03 -0400

> On Jun 6, 2024, at 1:34 AM, Eli Zaretskii <eliz <at> gnu.org> wrote:
> 
>> From: JD Smith <jdtsmith <at> gmail.com>
>> Date: Wed, 5 Jun 2024 18:06:54 -0400
>> 
>> The function treesit-font-lock-fontify-region in treesit.el calls (font-lock-unfontify-region start end) right away (see below).  But this function is called as the value of font-lock-fontify-syntactically-function from font-lock-default-fontify-region, which has just itself made the exact same call to font-lock-unfontify-region. I commented out that superfluous call in treesit-font-lock-fontify-region and noticed no ill effects.
> 
> Why is that duplicate call a problem?  

I don't know if it's ever really a problem, other than the small amount of time spent removing properties that have just been removed.

> We don't say that treesit-font-lock-fontify-region _must_ be called _only_ from
> font-lock-default-fontify-region, do we?


I presume the same logic would apply to font-lock-fontify-keywords-region, but that does not re-run unfontify (and is obviously much older code).   Maybe treesit reuses treesit-font-lock-fontify-region in non-font-lock contexts?  Feel free to close if Yuan concurs.

Message #14 received at 71384 <at> debbugs.gnu.org (full text, mbox):

From: Stefan Kangas <stefankangas <at> gmail.com>
To: JD Smith <jdtsmith <at> gmail.com>
Cc: Eli Zaretskii <eliz <at> gnu.org>, 71384 <at> debbugs.gnu.org,
 Yuan Fu <casouri <at> gmail.com>
Subject: Re: bug#71384: treesit-font-lock-fontify-region unnecessarily
 re-unfontify's
Date: Fri, 28 Feb 2025 18:08:29 -0800

JD Smith <jdtsmith <at> gmail.com> writes:

>> On Jun 6, 2024, at 1:34 AM, Eli Zaretskii <eliz <at> gnu.org> wrote:
>>
>>> From: JD Smith <jdtsmith <at> gmail.com>
>>> Date: Wed, 5 Jun 2024 18:06:54 -0400
>>>
>>> The function treesit-font-lock-fontify-region in treesit.el calls
>>> (font-lock-unfontify-region start end) right away (see below).  But this
>>> function is called as the value of font-lock-fontify-syntactically-function
>>> from font-lock-default-fontify-region, which has just itself made the exact
>>> same call to font-lock-unfontify-region. I commented out that superfluous
>>> call in treesit-font-lock-fontify-region and noticed no ill effects.
>>
>> Why is that duplicate call a problem?
>
> I don't know if it's ever really a problem, other than the small amount of time spent removing properties that have just been removed.
>
>> We don't say that treesit-font-lock-fontify-region _must_ be called _only_ from
>> font-lock-default-fontify-region, do we?
>
>
> I presume the same logic would apply to font-lock-fontify-keywords-region, but
> that does not re-run unfontify (and is obviously much older code).  Maybe
> treesit reuses treesit-font-lock-fontify-region in non-font-lock contexts?  Feel
> free to close if Yuan concurs.

Yuan, WDYT?  Should we do anything here, or should we close this?

Message #19 received at 71384 <at> debbugs.gnu.org (full text, mbox):

From: Yuan Fu <casouri <at> gmail.com>
To: Stefan Kangas <stefankangas <at> gmail.com>
Cc: Eli Zaretskii <eliz <at> gnu.org>, 71384 <at> debbugs.gnu.org,
 JD Smith <jdtsmith <at> gmail.com>
Subject: Re: bug#71384: treesit-font-lock-fontify-region unnecessarily
 re-unfontify's
Date: Wed, 5 Mar 2025 07:04:09 -0800

> On Feb 28, 2025, at 6:08 PM, Stefan Kangas <stefankangas <at> gmail.com> wrote:
> 
> JD Smith <jdtsmith <at> gmail.com> writes:
> 
>>> On Jun 6, 2024, at 1:34 AM, Eli Zaretskii <eliz <at> gnu.org> wrote:
>>> 
>>>> From: JD Smith <jdtsmith <at> gmail.com>
>>>> Date: Wed, 5 Jun 2024 18:06:54 -0400
>>>> 
>>>> The function treesit-font-lock-fontify-region in treesit.el calls
>>>> (font-lock-unfontify-region start end) right away (see below).  But this
>>>> function is called as the value of font-lock-fontify-syntactically-function
>>>> from font-lock-default-fontify-region, which has just itself made the exact
>>>> same call to font-lock-unfontify-region. I commented out that superfluous
>>>> call in treesit-font-lock-fontify-region and noticed no ill effects.
>>> 
>>> Why is that duplicate call a problem?
>> 
>> I don't know if it's ever really a problem, other than the small amount of time spent removing properties that have just been removed.
>> 
>>> We don't say that treesit-font-lock-fontify-region _must_ be called _only_ from
>>> font-lock-default-fontify-region, do we?
>> 
>> 
>> I presume the same logic would apply to font-lock-fontify-keywords-region, but
>> that does not re-run unfontify (and is obviously much older code).  Maybe
>> treesit reuses treesit-font-lock-fontify-region in non-font-lock contexts?  Feel
>> free to close if Yuan concurs.
> 
> Yuan, WDYT?  Should we do anything here, or should we close this?

I suggest we keep it. Unless a duplicate call actually impacts performance. The call helps with debugging: you can evaluate treesit-font-lock-fontify-region with M-x eval-expression to manually update fontification for a region.

Yuan

Message #22 received at 71384 <at> debbugs.gnu.org (full text, mbox):

From: Stefan Kangas <stefankangas <at> gmail.com>
To: Yuan Fu <casouri <at> gmail.com>
Cc: Eli Zaretskii <eliz <at> gnu.org>, 71384 <at> debbugs.gnu.org,
 JD Smith <jdtsmith <at> gmail.com>
Subject: Re: bug#71384: treesit-font-lock-fontify-region unnecessarily
 re-unfontify's
Date: Sun, 9 Mar 2025 07:14:06 -0400

tags 71384 wontfix
close 71384
thanks

Yuan Fu <casouri <at> gmail.com> writes:

> I suggest we keep it. Unless a duplicate call actually impacts performance. The call helps with debugging: you can evaluate treesit-font-lock-fontify-region with M-x eval-expression to manually update fontification for a region.

OK, I'm therefore closing this as wontfix.

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