bug#63271: 29.0.90; broken mouse-face

[Eli Zaretskii]

> From: Po Lu <luangruo@yahoo.com>
> Cc: Gregory Heytings <gregory@heytings.org>,  juri@linkov.net,
>   63271@debbugs.gnu.org,  stephen.berman@gmx.net
> Date: Thu, 11 May 2023 08:51:05 +0800
> 
> Eli Zaretskii <eliz@gnu.org> writes:
> 
> > Po Lu, was that change intentional?  If not, let's remove that line or
> > move it under some conditional that doesn't include all Cairo builds.
> > If it was intentional, please explain why, and let's take it from
> > there.
> 
> It was needed to prevent drawing overhangs as part of the cursor from
> overwriting surrounding characters with the glyph string background.
> 
> Unfortunately, I don't remember why it was needed, though I think the
> underlying reason has been fixed.

So can we undo that now?  If there is still a reason for doing
something special there, it will pop up sooner or later, and we can
deal with it at that time.  At the very least, the setting of
s->background_filled_p should not be done when s->hl is one of the
last 3 values in enum draw_glyphs_face, I think, and maybe also when
s->for_overlaps is zero.

I'd like to fix this soon, because I want to make another pretest of
29.1.

Thanks.