bug#81630: 32.0.50; completions-format 'vertical scrolls the completion window on TAB tapping

On Sun, 16 Aug 2026 21:07:42 +0000 lucas jimenez <[email protected]> wrote:

> I can’t say if it’s correct or not, but it’s fixed for me. Thanks

Thanks for confirming.

> On another note:  This patches will be applied to emacs 31.1 also?

This issue already exists in Emacs 30 (thus, in particular, before the
significant changes involving the vertical completions-format made in
commit 77ca60b48d01), so since Emacs 31 is close to being released, I
think it's too late to add my fix to the release branch (assuming it's
acceptable in the first place).  But that decision is up to the
maintainers; Eli, Sean?

Steve Berman

> On 16-08-2026, at 11:29, Stephen Berman
> <[email protected]<mailto:[email protected]>> wrote:
>
> On Sat, 15 Aug 2026 13:03:00 +0000 lucas jimenez
> <[email protected]<mailto:[email protected]>> wrote:
>
> Hi.
>
> When setting completions-format to 'vertical
>
> and start TAB tapping the completions window starts scrolling up and
> down even though all the candidates can be seen in the window.
>
> To reproduce do:
> emacs -Q --eval "(setq completions-format 'vertical)"
> `M-x 5x5`  and start tapping TAB key or `M-x minibuffer-`
>
> Workaround: set (completion-auto-select 'second-tab) or
> (completion-auto-select t) or just don't tap TAB.
>
> This behaviour isn't noticed with 'horizontal or 'one-column
>
> This happens because when `completions-format' is 'vertical the
> *Completions* buffer ends in a newline, and that makes
> `(pos-visible-in-window-p (point-max) window)' in the "normal tab" case
> in `completion--in-region-1' return nil, resulting in the window being
> scrolled.  The attached patch prevents this scrolling for me; can you
> confirm?  But I cannot tell if such a change might have undesirable
> consequences; maybe Stefan Monnier (added in CC:) can tell.
>
> Steve Berman
> <Mail Attachment>