bug#69385: 30.0.50; Long lines with bidi text slow down Emacs

[Stephen Berman]

On Mon, 26 Feb 2024 17:52:50 +0200 Eli Zaretskii <eliz@gnu.org> wrote:

>> From: Stephen Berman <stephen.berman@gmx.net>
>> Cc: 69385@debbugs.gnu.org
>> Date: Mon, 26 Feb 2024 16:17:53 +0100
>>
>> On Mon, 26 Feb 2024 16:22:59 +0200 Eli Zaretskii <eliz@gnu.org> wrote:
>>
>> >> Cc: 69385@debbugs.gnu.org
>> >> Date: Mon, 26 Feb 2024 16:19:15 +0200
>> >> From: Eli Zaretskii <eliz@gnu.org>
>> >>
>> >> > From: Stephen Berman <stephen.berman@gmx.net>
>> >> > Cc: 69385@debbugs.gnu.org
>> >> > Date: Mon, 26 Feb 2024 15:13:38 +0100
>> >> >
>> >> > On Mon, 26 Feb 2024 14:33:18 +0200 Eli Zaretskii <eliz@gnu.org> wrote:
>> >> >
>> >> > > The CPU is fast.  My HarfBuzz version is much older, but I doubt that
>> >> > > HarfBuzz became so much slower for Arabic.  So it's very strange.  But
>> >> > > maybe it's worth to try downgrading to an earlier version, just to be
>> >> > > sure this is not the culprit?
>> >> >
>> >> > That's not so straightforward on this system, where I build system
>> >> > packages from source, so downgrading HarfBuzz may require also
>> >> > rebuilding packages that depend on it.  I have a somewhat older system
>> >> > on this machine with HarfBuzz 7.1.0, so I can easily try that.  What
>> >> > version of HarfBuzz are you using?
>> >>
>> >> I have 2.4.0 here.
>> >
>> > Btw, another possibility could be that this is specific to the Cairo
>> > build.  So maybe try a build without Cairo.
>>
>> I did, and the slowdown seems just as bad as in the build with Cairo.
>
> Can you try the emacs-29 branch?

I already did and see the same slowdown with it as with master.  (Or did
you mean try emacs-29 without Cairo?  That I haven't done, but given I
saw no noticeable difference on master, I wouldn't expect to see one on
emacs-29 either.)

Steve Berman