bug#19993: 25.0.50; Unicode fonts defective on Windows

[Ilya Zakharevich <ilya@math.berkeley.edu>]

On Wed, Mar 04, 2015 at 07:59:56PM +0200, Eli Zaretskii wrote:
> > Date: Tue, 3 Mar 2015 14:02:28 -0800
> > From: Ilya Zakharevich <nospam-abuse@ilyaz.org>
> > 
> > (A) On Windows, most Unicode characters won’t be shown, even if the system 
> >     has (many) fonts covering the characters (and these fonts are listed in 
> >     `font-log'!).
> 
> Examples, please: they are required to debug the issue.  Please
> include with the examples the information about the font(s) which
> support the problematic characters, but are not used although
> installed.  Or, if you already debugged this and can tell which code
> misbehaves, please post that information.

I won’t be able to debug this.  However, I just take

   the MOST IMPORTANT font (plug plug!  See ilyaz.org/fonts  ;-] ),

and grep for it in the result of `font-show-log' (family = «Unifont
Smooth»; it is usable, and has all the glyphs for BMP of Unicode 7.0):

  grep -B 3 -A 3 Smooth- font-show-log-post >font-show-log-post-Smooth

I see several occurences:

     -outline-FangSong-normal-normal-normal-mono-*-c-*-gb2312.1980*-*
     -outline-SimHei-normal-normal-normal-mono-*-c-*-gb2312.1980*-*
     -outline-KaiTi-normal-normal-normal-mono-*-c-*-gb2312.1980*-*
     -outline-Unifont Smooth-normal-normal-normal-mono-*-c-*-gb2312.1980*-*
   w32font-list: -outline-*-mono-*-gb2312.1980*-*
     -outline-BatangChe-normal-normal-normal-mono-*-c-*-gb2312.1980*-*
     -outline-GungsuhChe-normal-normal-normal-mono-*-c-*-gb2312.1980*-*
   --
     -outline-FangSong-normal-normal-normal-mono-*-c-*-gb2312.1980*-*
     -outline-SimHei-normal-normal-normal-mono-*-c-*-gb2312.1980*-*
     -outline-KaiTi-normal-normal-normal-mono-*-c-*-gb2312.1980*-*
     -outline-Unifont Smooth-normal-normal-normal-mono-*-c-*-gb2312.1980*-*
   list: -outline-*-mono-*-gb2312.1980*-*
     -outline-BatangChe-normal-normal-normal-mono-*-c-*-gb2312.1980*-*
     -outline-GungsuhChe-normal-normal-normal-mono-*-c-*-gb2312.1980*-*
   --
     -outline-FangSong-normal-normal-normal-mono-*-c-*-gb2312.1980*-*
     -outline-SimHei-normal-normal-normal-mono-*-c-*-gb2312.1980*-*
     -outline-KaiTi-normal-normal-normal-mono-*-c-*-gb2312.1980*-*
     -outline-Unifont Smooth-normal-normal-normal-mono-*-c-*-gb2312.1980*-*
     -outline-BatangChe-normal-normal-normal-mono-*-c-*-gb2312.1980*-*
     -outline-GungsuhChe-normal-normal-normal-mono-*-c-*-gb2312.1980*-*
     -outline-GulimChe-normal-normal-normal-mono-*-c-*-gb2312.1980*-*
   --
   uniscribe-list: -outline-*-mono-*-jisx0208*-*
     -outline-MS Gothic-normal-normal-normal-mono-*-c-*-jisx0208*-*
     -outline-MS Mincho-normal-normal-normal-mono-*-c-*-jisx0208*-*
     -outline-Unifont Smooth-normal-normal-normal-mono-*-c-*-jisx0208*-*
   w32font-list: -outline-*-mono-*-jisx0208*-*
     -outline-MS Gothic-normal-normal-normal-mono-*-c-*-jisx0208*-*
     -outline-MS Mincho-normal-normal-normal-mono-*-c-*-jisx0208*-*
     -outline-Unifont Smooth-normal-normal-normal-mono-*-c-*-jisx0208*-*
   list: -outline-*-mono-*-jisx0208*-*
     -outline-MS Gothic-normal-normal-normal-mono-*-c-*-jisx0208*-*
     -outline-MS Mincho-normal-normal-normal-mono-*-c-*-jisx0208*-*
     -outline-Unifont Smooth-normal-normal-normal-mono-*-c-*-jisx0208*-*
     -outline-MS Gothic-normal-normal-normal-mono-*-c-*-jisx0208*-*
     -outline-MS Mincho-normal-normal-normal-mono-*-c-*-jisx0208*-*
     -outline-Unifont Smooth-normal-normal-normal-mono-*-c-*-jisx0208*-*
   sort-by: -*-normal-normal-normal-*-13-*
     uniscribe:-outline-MS Gothic-normal-normal-normal-mono-*-c-*-jisx0208*-*
   open: -outline-MS Gothic-normal-normal-normal-mono-*-c-*-jisx0208*-*

but only with some specialized encodings (instead of iso10646).  How comes?

Would not this explain why the glyph is not shown?

Thanks,
Ilya