bug#73752: 29.4; Ligatures are randomly rendered with extra spaces

[Eli Zaretskii <eliz@gnu.org>]

> From: Tim Ruffing <dev@real-or-random.org>
> Cc: 73752@debbugs.gnu.org, Visuwesh <visuweshm@gmail.com>, xuan@xlk.me
> Date: Wed, 30 Oct 2024 19:00:17 +0100
> 
> 
> 
> On Wed, 2024-10-30 at 19:46 +0200, Eli Zaretskii wrote:
> > 
> > Did the "bad" display start from "good" at the beginning of a
> > session? Or did it start from "bad" to begin with?
> 
> I'm rather sure that it started bad from the beginning of the session
> yesterday.
> 
> In general, I'm not so sure, unfortunately. (I had disabled ligatures
> in the past months because this bug was too annoying.) Don't rely on
> any of this: I can't recall that it ever flipped suddenly from good to
> bad *when the affected ligatures was in the visible array of the
> buffer*. But I'm not so sure if this has really never flipped from good
> to bad during a session, when the ligature was not visible.

Then what exactly is the difference between the session with "good"
display and the one with the "bad" display?  How come they show the
same ligature differently?  What did you do to make them have
different looks?