GNU bug report logs - #21730
25.0.50; Random errors in redisplay--pre-redisplay-functions

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Message #38 received at 21730 <at> debbugs.gnu.org (full text, mbox):

From: Philipp Stephani <p.stephani2 <at> gmail.com>
To: Eli Zaretskii <eliz <at> gnu.org>, 21730 <at> debbugs.gnu.org, mwd <at> md5i.com
Subject: Re: bug#21730: 25.0.50;
 Random errors in redisplay--pre-redisplay-functions
Date: Wed, 14 Sep 2016 19:11:57 +0000

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Philipp Stephani <p.stephani2 <at> gmail.com> schrieb am Mi., 14. Sep. 2016 um
18:54 Uhr:

> Eli Zaretskii <eliz <at> gnu.org> schrieb am Sa., 31. Okt. 2015 um 14:34 Uhr:
>
> > From: Michael Welsh Duggan <mwd <at> md5i.com>
> > Date: Sat, 31 Oct 2015 09:07:05 -0400
> >
> > > I've changed the (bobp) to (= point 1).  I'll run it for a couple of
> > > weeks and report back.
> >
> > This change seems to have done the trick.  I have not encountered the
> > error in several days.
>
> Thanks for testing.  I pushed the change, and I'm arking this bug as
> done.
>
>
>
> This change was  reverted in 76ef52267cf887e3e1aa6d25b3b16dd0601dd459.
> It also doesn't seem correct. cursor-sensor--detect is only used in
> pre-redisplay-functions, and the documentation of that variable says:
> "Hook run just before redisplay.
> It is called in each window that is to be redisplayed.  It takes one
> argument,
> which is the window that will be redisplayed.  When run, the
> ‘current-buffer’
> is set to the buffer displayed in that window."
> That means that (bobp) is correct and (= point 1) cannot give a different
> result, unless narrowing is in effect (then only bobp is correct).
> Given that replacing (bobp) with (= point 1) does solve this bug, the
> documentation of pre-redisplay-functions must be incorrect, i.e. the
> current buffer is not the buffer of the window passed as argument. I think
> the only way how this can happen is that a previous entry in
> pre-redisplay-functions has changed the current buffer. Probably the
> implementation of redisplay--pre-redisplay-functions should be changed from
> (with-current-buffer (window-buffer win)
>           (run-hook-with-args 'pre-redisplay-functions win))
> to
> (run-hook-wrapped 'pre-redisplay-functions
>   (lambda (func) (with-current-buffer (window-buffer win)
>      (funcall func win)
>      nil))
> or so.
>

I've attached a patch for this.

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[0001-Restore-buffer-in-pre-redisplay-functions.txt (text/plain, attachment)]

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