Subject: bug#41005: problem with rendering Persian text in Emacs 27

From: hossein valizadeh <[email-masked]>
Date: Fri, 1 May 2020 22:32:31 +0430

Hello,

I have been using GNU Emacs for a few years now, and I recently decided
to build Emacs 27.0.91 from the emacs-27 branch.  I use Arch GNU/Linux,
along with the i3 window manager.

I have noticed a new problem with rendering Persian text in Emacs 27,
which to my knowledge was not present in earlier Emacs versions.  If you
see the screenshots I have attached, some text seems to get garbled at
random.  The same words sometimes appear correctly and sometimes do not.
I recall John Wiegley mentioning in his EmacsConf 2019 talk that Emacs
has recently started using the HarfBuzz text shaping engine.  I wonder
if that's relevant and possibly the cause of this issue?

Thanks in advance for looking into this.  I really hope the issue can be
resolved, as I use Emacs and Org extensively for writing my documents,
and this bug effectively renders Emacs unusable for me.  I'll be happy
to try and provide any further information needed to debug this.

Regards,
Hossein Valizadeh