bug#23934: 25.1.50; Incorrect rendering of cyrillic text on OS X

[Eli Zaretskii <eliz@gnu.org>]

> Date: Sun, 10 Jul 2016 17:28:02 +0100
> From: Alan Third <alan@idiocy.org>
> Cc: 23934@debbugs.gnu.org
> 
> > How do we know it isn't a problem with that font?
> > 
> > I think the problem is triggered by displaying the u+0301 acute accent
> > above the а (to show the vowel with the accent).  Does Menlo has a
> > glyph for that codepoint?
> 
> Yes, Emacs seems to think that the composed character takes up no
> space. This may be no help whatsoever, but I've attached another image
> showing a cyrillic a with acute alongside the latin version. The latin
> one is not, afaik, composed, because I don't know how to do that.

The Latin character is composed, because Emacs knows how to do that.
You can verify with "C-u C-x =".

Can you tell what does window-text-pixel-size return for the а́ part of
the text, both with Menlo and with Monaco?

> I don't know how to check whether the font supports it.
> Here's what describe-char says:
> 
>              position: 148 of 234 (63%), column: 2
>             character: а (displayed as а) (codepoint 1072, #o2060, #x430)
>     preferred charset: cyrillic-iso8859-5 (Right-Hand Part of ISO/IEC 8859/5 (Latin/Cyrillic): ISO-IR-144)
> code point in charset: 0x50
>                script: cyrillic
>                syntax: w 	which means: word
>              category: .:Base, L:Left-to-right (strong), Y:2-byte Cyrillic, c:Chinese, h:Korean, j:Japanese, y:Cyrillic
>              to input: type "C-x 8 RET 430" or "C-x 8 RET CYRILLIC SMALL LETTER A"
>           buffer code: #xD0 #xB0
>             file code: #xD0 #xB0 (encoded by coding system utf-8-unix)
>               display: composed to form "а́" (see below)
> 
> Composed with the following character(s) "́" using this font:
>   mac-ct:-*-Menlo-normal-normal-normal-*-12-*-*-*-m-0-iso10646-1
    ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
The above line says that Menlo does have the glyph for the accent.
Emacs will not compose characters from different fonts.

> by these glyphs:
>   [0 1 1072 870 7 0 7 7 1 nil]
>   [0 1 769 646 7 2 6 10 -7 [-8 -1 -8]]

Can you show the corresponding data when you use the Monaco font?

Thanks.