bug#34035: 26.1; Arabic shadda-kasrah renders incorrectly

[Eli Zaretskii <eliz@gnu.org>]

> From: Stephen Berman <stephen.berman@gmx.net>
> Cc: craven@gmx.net,  34035@debbugs.gnu.org
> Date: Fri, 11 Jan 2019 10:47:11 +0100
> 
> > Please show the entire output of "C-x =" 
> 
> I assume you meant `C-u C-x ='
> 
> >                                          (I presume you invoke it on
> > the position of sin?).
> 
> Yes.  Here's the output on master:
> 
> ==============================================================================
>              position: 1 of 3 (0%), column: 0
>             character: س‎ (displayed as س‎) (codepoint 1587, #o3063, #x633)
>               charset: unicode (Unicode (ISO10646))
> code point in charset: 0x0633
>                script: arabic
>                syntax: w 	which means: word
>              category: .:Base, R:Right-to-left (strong), b:Arabic
>              to input: type "s" with arabic input method
>           buffer code: #xD8 #xB3
>             file code: #xD8 #xB3 (encoded by coding system utf-8-unix)
>               display: composed to form "سِّ" (see below)
> 
> Composed with the following character(s) "ِّ" using this font:
>   xft:-PfEd-DejaVu Sans-normal-normal-semicondensed-*-15-*-*-*-*-0-iso10646-1
> by these glyphs:
>   [0 2 1587 1377 16 0 16 6 4 nil]
>   [0 2 0 6022 0 -15 -10 13 -11 [-16 2 0]]
> 
> Character code properties: customize what to show
>   name: ARABIC LETTER SEEN
>   general-category: Lo (Letter, Other)
>   decomposition: (1587) ('س')
> ==============================================================================

This clearly says that Emacs uses DejaVu Sans for this grapheme
cluster, so I wonder what does "switch the font to Symbola" mean in
this case.  Can you tell what you did to switch to Symbola?

> On the harfbuzz branch the output is the same except for the glyphs:
> 
>   [0 2 1587 6022 0 1 6 16 -8 [0 3 0]]
>   [0 2 1587 1377 16 0 16 6 4 nil]
> 
> Note the second line here is identical to the first line of glyphs on
> master.

I would hardly call this "identical", since the offsets are also
different.  But I don't think that matters at this point.