bug#28339: 25.2; Emacs shows ZWNJ character (Zero Width non-Joiner) as Space

[Nima Aryan <nimawebgard@gmail.com>]

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In previous email I just open the test file but now I try to write the
example again this behavior is shown which might be useful:

When I type A[ZWNJ]B it's OK. In Persian when I type first character and
then ZWNJ it's exactly the same as English but just after I type the next
character it replaced by '['. So some another mechanism might be involved.
I've provided a screen shot which now show these three cases:

Regards,

On Mon, Sep 4, 2017 at 4:12 PM Nima Aryan <nimawebgard@gmail.com> wrote:

> It got interesting and I've found a workaround for the issue. display of
> ZWNJ as SPACE or any other character is matter of font. Different fonts
> uses different characters. Default Emacs font shows '[' instead of space
> which is better and more readable at least.
>
> The only minor problem I've seen so far is the irrelevance of displayed
> character (shown as ZWNJ) to the 'glyphless-char-display-control' for
> Persian alphabet.
>
> I've attached a screenshot which shows different behavior of display for
> both English and Persian at the same time. I execute `emacs -q` to launch
> default Emacs. Then I open Test.text sample attached in previous emails.
> Set the `glyphless-char-display-control` to show hex-box. It's clearly
> shown that The English one is replaced by a hex-box but the Persian one
> with a '[' (or SPACE).  No matter what the 'glyphless-char-display-control'
> the Persian case shows same character.
>
> Note, To type the ZWNJ for the English text, AB, I used Persian input (A,
> switch keyboard layout, SHIFT+Space, switch back to English, B). So when I
> put ZWNJ between the AB it's shown as hex-box (and affected by
> 'glyphless-char-display-control' as expected) but when I type it between
> Persian characters it's shown as fixed '[' or 'SPACE' (font based) no
> matter what the glyphless-char dictates.
>
> Best Regards,
>
>
> On Mon, Sep 4, 2017 at 1:45 PM Eli Zaretskii <eliz@gnu.org> wrote:
>
>> > From: sadid sahami <sadidsahami@gmail.com>
>> > Date: Mon, 04 Sep 2017 05:05:03 +0000
>> >
>> > I've provided a minimal test text, written in Emacs (Test.text) and its
>> display for Gedit (Gedit_display.png) and
>> > Emacs (Emacs_display.png). The Gedit display is the correct one.
>>
>> Hmm.. on my system I see a display that is almost identical to what
>> your "Gedit" display shows.
>>
>> CC'ing Handa-san who might be able to help us with verifying the
>> composition rules for Persian.  Or maybe this is a problem with the
>> shaping engine used on GNU/Linux?
>>
>> In any case, disabling bidi reordering doesn't fix the display (it
>> makes the display much worse for me), so it is not the problem.
>>
>

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