bug#39799: 28.0.50; Most emoji sequences don’t render correctly

[Mike FABIAN]

Eli Zaretskii <eliz@gnu.org> さんはかきました:

>> From: Robert Pluim <rpluim@gmail.com>
>> Cc: mfabian@redhat.com,  39799@debbugs.gnu.org
>> Date: Fri, 28 Feb 2020 22:47:36 +0100
>> 
>> -fn "Noto Color Emoji" doesnʼt change the default font for me for some
>>  reason, but if I change the font after startup then those sequences
>>  display correctly.
>> 
>>   (char-table-range composition-function-table #xFE0F)
>> => ([".." 1 compose-gstring-for-variation-glyph])
>
> OK, so this feature already works for suitable fonts.
>
>> and #xFE0F is always composable according to composite.c, so I donʼt
>> understand why composing only works with Noto Color Emoji. Or does the
>> font need specific support for it?
>
> Yes, the font needs to have glyph variations, see
> font-variation-glyphs and its underlying font-backend method
> get_variation_glyphs.

http://unicode.org/reports/tr51/#Presentation_Style

doesn’t seem to say that the fonts should have the variations.

-- 
Mike FABIAN <mfabian@redhat.com>
睡眠不足はいい仕事の敵だ。