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

[Eli Zaretskii]

> From: hossein valizadeh <valizadeh.ho@gmail.com>
> Date: Fri, 1 May 2020 22:32:31 +0430
> 
> 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?

I don't know.  Was your Emacs built with HarfBuzz?  You didn't attach
the data collected by "M-x report-emacs-bug", so I cannot know.

I suggest to start by attaching a sample file that exhibits the
problem, as text, not as an image, and then showing what it looked
like in previous versions of Emacs and what it looks like in Emacs
27.0.91 on your system.  Also, please tell which font was in use when
the problematic display was produced.  Then we can look into this
issue and see what could have caused it.

Thanks.