Subject: bug#76186: 31.0.50; (recenter 0) sometimes does not recenter as expected

From: Stephen Berman <[email-masked]>
Date: Sun, 16 Mar 2025 14:20:33 +0100

On Sat, 15 Mar 2025 14:36:29 +0200 Eli Zaretskii <[email-masked]> wrote:

>> From: Markus Triska <[email-masked]>
>> Cc: [email-masked],  [email-masked]
>> Date: Sat, 15 Mar 2025 12:28:17 +0100
>>
>> Eli Zaretskii <[email-masked]> writes:
>>
>> > Ping!  Do we still need to discuss this issue?  Or can it be closed,
>> > given my explanations below?
>>
>> I can still reproduce the problem on 3 different Emacs installations
>> (Debian, Ubuntu and OSX), and I would prefer this issue only to be
>> closed when Emacs handles the example reliably because I consider it
>> unsaticsfactory that recentering sometimes work, and sometimes not.
>
> I thought I explained why this cannot be done as reliably as you
> expect it to be.
>
>> The other remaining question is why you cannot reproduce the issue with
>> your configuration whereas Steve and I can do so on ours.
>
> I don't know.

Although you already said upthread you could not reproduce the issue
with the test code I posted, I'd ask you to try again with the attached
file, i.e. from the shell:

emacs -Q -l bug#76186.el

This file differs from the one I posted upthread only in that the first
occurrence of `(redisplay)' is commented out, so possibly you overlooked
that when you tested previously (my explanation of my testing was a bit
terse).  With that difference I consistently get the unexpected
recentering after a single iteration.  What's more, I've now also
reproduced this with emacs-30 running under MS-Windows 10 in a virtual
machine (I used emacs-30.1-installer.exe downloaded from a GNU mirror).
Perhaps I missed something when debugging this, so if you can also
reproduce it, you might be able to debug it better than I did.

Steve Berman