GNU bug report logs - #59963
29.0.50; 'window-max-chars-per-line' doesn't always work on GUI without fringe

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From: martin rudalics <rudalics <at> gmx.at>
To: Eli Zaretskii <eliz <at> gnu.org>
Cc: 59963 <at> debbugs.gnu.org, akib <at> disroot.org
Subject: bug#59963: 29.0.50; 'window-max-chars-per-line' doesn't always work on GUI without fringe
Date: Mon, 12 Dec 2022 17:50:44 +0100

>> (let (max-chars)
>>     (setq right-fringe-width 0)
>>     (setq max-chars (window-max-chars-per-line))
>>     (set-window-buffer nil (window-buffer))
>>     max-chars)
>>
>> which currently yields 79 and would yield 80 with your proposal.
>
> Do we have such code somewhere?

No.  Fringes should be set by users only.

> The correct way of doing that is to
> swap the lines that call window-max-chars-per-line and
> set-window-buffer, because AFAIU the latter will cause window-margins

... 'window-max-chars-per-line' I presume ...

> to return the values consistent with right-fringe-width just set.

My example is a simplification.  There might be many more buffer-local
variables to set and the conclusive 'set-window-buffer' call to put them
into action might appear much later, maybe also in some other function.

The simplest approach should be to put an extra

(set-window-buffer nil (window-buffer))

right after the

  (with-selected-window (window-normalize-window window t)

in 'window-max-chars-per-line'.  But there's no right KEEP-MARGINS value
to pass here.

Maybe you should just say in the doc-string that if there are any
pending buffer-local changes, they should be applied before calling
'window-max-chars-per-line'.

martin

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