bug#54488: 29.0.50; move-to-column/overlay-related regression in latest master, perhaps 28?

["João Távora" <joaotavora@gmail.com>]

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On Mon, Mar 21, 2022 at 12:32 PM Eli Zaretskii <eliz@gnu.org> wrote:

> Emacs 29 has a fix for an old bug, whereby current-column etc. didn't
> take display strings and overlays into account; now they do.
>
> Of course, it could be that this fix introduced a bug in some
> not-so-simple situations, so I'd appreciate if you could show a simple
> recipe to reproduce the problem without the need of firing up
> company-mode and/or Eglot.
>

The only pathological problem -- that I know of -- is the "not-so-simple"
example/situation I described.  But it's pretty real and easy trigger
if you happen to use those two extensions which are both reasonably
popular.

If you are aware of the behaviour change , then I don't see the point
with coming up with a simpler repro: I'd just be showing what you
confirmed: that move-to-column now is affected by overlays such
as company's whereas before (emacs 27.2/28) it didn't.

If this is a bugfix in Emacs, then the logical conclusion is that the
problem should be fixed in company-mode.  It should somehow (tm)
find a way to create a visual popup that works in terminals for which
move-to-column behaves as before. Alternatively, some variation of
move-to-column that retains the old behaviour could be invented to
give the old behaviour.

Both these solutions would be better than the current defensive
one in Eglot, which makes Eglot LSP-abiding column-finding
less performant than it used to be.

João

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