GNU bug report logs - #25672
Font-locking issues when font-lock-fontified is nil (Was: What to do when font-lock-flush + font-lock-ensure do less than font-lock-fontify-buffer? on emacs-devel)

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

From: Clément Pit--Claudel <clement.pitclaudel <at> live.com>
To: bug-gnu-emacs <at> gnu.org
Subject: Font-locking issues when font-lock-fontified is nil (Was: What to do
 when font-lock-flush + font-lock-ensure do less than
 font-lock-fontify-buffer? on emacs-devel)
Date: Thu, 9 Feb 2017 16:22:21 -0500

[Message part 1 (text/plain, inline)]

X-Debbugs-CC: monnier <at> iro.umontreal.ca

Hi bug-gnu-emacs,

Sorry for the long delay in opening this.  This is a follow-up to the Emacs-devel thread "What to do when font-lock-flush + font-lock-ensure do less than font-lock-fontify-buffer?", where Stefan asked me to open a bug report.

My original question was this:

> IIUC the proper way in Emacs 25 to signal changes that require a
> refontification to font-lock is to call font-lock-flush. This doesn't always
> do as much as font-lock-fontify-buffer does, though.  In particular, when the
> font-lock-fontified variable is nil (which does happen, though I don't know
> why; I don't know what this variable is for), then calling font-lock-fontify
> buffer does refontify the whole buffer, but font-lock-flush and
> font-lock-ensure don't seem to do anything.  What's the proper way to mark a
> buffer for refontification (and refontify the visible portion) immediately in
> 25?

And here's is my original test case:

    (with-current-buffer (get-buffer-create "temp")
      (erase-buffer)
      (setq-default prettify-symbols-unprettify-at-point 'right-edge)
      (emacs-lisp-mode)
      (prettify-symbols-mode)
      (insert "lambda\n\nlambda")
      (pop-to-buffer (current-buffer)))

    Moving around in this buffer unprettifies and reprettifies ‘lambda’s into ‘λ’s as the point moves in and out of them. Setting ‘font-lock-fontified’ to nil breaks that mechanism (the ‘λ’s are unprettified but no reprettified), and no series of ‘font-lock-flush’ and ‘font-lock-ensure’ will reprettify them.

Eli remarked the following:

> However, please explain why font-lock-ensure-function calls
> font-lock-DEFAULT-fontify-buffer.  If it's supposed to be good for any mode, why
> does it call the default fontification?
>
> As a matter of fact, if I replace the font-lock-default-fontify-buffer
> call with a call to font-lock-fontify-buffer, the problem described by
> the OP goes away.  That is why I said what I said.

And Stefan answered:

> I haven't seen the beginning of the thread, but if that fixes the
> problem, then I think it's a good change.
>
> To go back to the previous question.  I guess I used
> font-lock-default-fontify-buffer because the whole point is to get rid
> of all the misuses of font-lock-fontify-buffer, but I think in this case
> it's indeed the right thing to do.

Then Stefan said:

> > Should I open a bug report about this?
> Yes.  And put me in X-Debbugs-Cc.

Done :)

Thanks,
Clément.

[signature.asc (application/pgp-signature, attachment)]

Message #8 received at 25672 <at> debbugs.gnu.org (full text, mbox):

From: Lars Ingebrigtsen <larsi <at> gnus.org>
To: Clément Pit--Claudel <clement.pitclaudel <at> live.com>
Cc: 25672 <at> debbugs.gnu.org
Subject: Re: Font-locking issues when font-lock-fontified is nil
Date: Wed, 30 Oct 2019 17:07:10 +0100

Clément Pit--Claudel <clement.pitclaudel <at> live.com> writes:

> Eli remarked the following:
>
>> However, please explain why font-lock-ensure-function calls
>> font-lock-DEFAULT-fontify-buffer.  If it's supposed to be good for
>> any mode, why
>> does it call the default fontification?
>>
>> As a matter of fact, if I replace the font-lock-default-fontify-buffer
>> call with a call to font-lock-fontify-buffer, the problem described by
>> the OP goes away.  That is why I said what I said.
>
> And Stefan answered:
>
>> I haven't seen the beginning of the thread, but if that fixes the
>> problem, then I think it's a good change.
>>
>> To go back to the previous question.  I guess I used
>> font-lock-default-fontify-buffer because the whole point is to get rid
>> of all the misuses of font-lock-fontify-buffer, but I think in this case
>> it's indeed the right thing to do.

I think this was fixed last year-ish if I'm reading the change log
correctly.

Currently, font-lock-ensure calls the value of
font-lock-ensure-function, which has a default value of

  (lambda (beg end)
    (unless font-lock-fontified
      (save-excursion
        (font-lock-fontify-region beg end))))

If global-font-lock-mode is on, it's jit-lock-fontify-now.

So I think this now works better, and I'm closing this bug report.  If
this is still an issue, please reopen.

-- 
(domestic pets only, the antidote for overdose, milk.)
   bloggy blog: http://lars.ingebrigtsen.no

Message #11 received at 25672 <at> debbugs.gnu.org (full text, mbox):

From: Lars Ingebrigtsen <larsi <at> gnus.org>
To: Clément Pit--Claudel <clement.pitclaudel <at> live.com>
Cc: 25672 <at> debbugs.gnu.org
Subject: Re: Font-locking issues when font-lock-fontified is nil
Date: Wed, 30 Oct 2019 17:09:59 +0100

Lars Ingebrigtsen <larsi <at> gnus.org> writes:

> I think this was fixed last year-ish if I'm reading the change log
> correctly.

Oh, I didn't.  This is the definition of that function:

(defun font-lock-fontify-region (beg end &optional loudly)
  "Fontify the text between BEG and END.
If LOUDLY is non-nil, print status messages while fontifying.
This works by calling `font-lock-fontify-region-function'."
  (font-lock-set-defaults)
  (funcall font-lock-fontify-region-function beg end loudly))

which is indeed font-lock-default-fontify-region, which is what was
requested to have changed.

I think?  

-- 
(domestic pets only, the antidote for overdose, milk.)
   bloggy blog: http://lars.ingebrigtsen.no

Message #14 received at 25672 <at> debbugs.gnu.org (full text, mbox):

From: Lars Ingebrigtsen <larsi <at> gnus.org>
To: Clément Pit--Claudel <clement.pitclaudel <at> live.com>
Cc: 25672 <at> debbugs.gnu.org
Subject: Re: bug#25672: Font-locking issues when font-lock-fontified is nil
 (Was: What to do when font-lock-flush + font-lock-ensure do less than
 font-lock-fontify-buffer? on emacs-devel)
Date: Sat, 14 Aug 2021 16:17:20 +0200

Lars Ingebrigtsen <larsi <at> gnus.org> writes:

>> I think this was fixed last year-ish if I'm reading the change log
>> correctly.
>
> Oh, I didn't.  This is the definition of that function:

And now I re-read it again, and as far as I can tell, I read it right
the first time.  I.e., 21beb19d80b6a fixed the reported problem, so I'm
closing this bug report.

But I guess there may be subtleties here, so if this is still a problem,
please respond to the debbugs address and we'll reopen.

-- 
(domestic pets only, the antidote for overdose, milk.)
   bloggy blog: http://lars.ingebrigtsen.no

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