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

[Eli Zaretskii <eliz@gnu.org>]

> From: Amin Bandali <bandali@gnu.org>
> Cc: rpluim@gmail.com,  valizadeh.ho@gmail.com,  41005@debbugs.gnu.org,
>   pipcet@gmail.com
> Date: Sat, 25 Jul 2020 00:19:35 -0400
> 
> > If the result still points into some valid Emacs use pattern, please
> > describe in more detail a small part of the Wikipedia page that needs
> > to be copy/pasted, and the precise place where the result of pasting
> > is rendered incorrectly.  Please keep in mind that for people who
> > don't read Persian it is hard to find those issues in vast amounts of
> > text, so any measure that makes this significantly easier will allow
> > debugging and finding solutions to be much more efficient.
> >
> > Thanks.
> >
> 
> Having done some digging, I've found at least one reliable way to
> reproduce the issue with -Q:
> 
> 1. launch Emacs using `emacs -Q';
> 2. switch to *scratch* if not there already;
> 3. do M-x column-number-mode RET;
> 4. paste the following Persian text into *scratch*:
 
>    ویکی‌پدیا دانشنامه‌ای اینترنتی با بیش از ۲۸۰ زبان با محتوای آزاد است که با همکاری افراد داوطلب نوشته می‌شود و هر کس که به اینترنت دسترسی داشته باشد می‌تواند مقاله‌های آن را ویرایش کند.
 
>    It is from the first sentence of the "دربارهٔ ویکی‌پدیا" (About
>    Wikipedia) section on <https://fa.wikipedia.org>.
> 
>    The text should appear garbled.  However, if you omit step 3, the
>    pasted text should appear just fine.  It appears that if Persian text
>    is pasted before column-number-mode is enabled, even if the paste is
>    subsequently undone before enabling column-number-mode, the issue
>    does *not* surface.

Please help me understand what exactly do you mean by "garbled".  The
text you show is still quite long, and I cannot easily locate it in
that page (I don't see any "About Wikipedia" in the English version of
that page), nor do I understand what you mean by "garbled".

Would it be possible instead to paste only a very small portion of the
text, and tell exactly which part(s) of that short text are garbled,
and how they are garbled?  Can you, for example, post a screenshot
showing exactly which part of the Wikipedia page should be copied, and
another screenshot of the garbled text in Emacs showing which part(s)
are displayed incorrectly?  And please keep the pasted text as short
as possible, because locating the garbled part(s) in text I cannot
read which is displayed in a different font from what's in the
screenshot can be a very frustrating and error-prone experience.

Also, do you copy this from EWW or from some other Web browser?

(I tried to explain all of this in my previous message, but
unfortunately this reproduction recipe again presents the same
difficulties as I tried to avoid by explaining how to provide
information that would be easy to follow up.)

Please help me understand the problem, without that I see no way of
making any progress here.

Thanks.