bug#54970: 28.1; Some emoji no longer display

[Robert Pluim]

>>>>> On Sun, 17 Apr 2022 08:53:37 +0300, Eli Zaretskii <eliz@gnu.org> said:

    Eli> The fundamental issue here is that some symbols have both an Emoji
    Eli> presentation and a "text" presentation, and the VARIATION SELECTOR n
    Eli> characters tell the rendering system which presentation to display.
    Eli> The U+FE0F VARIATION SELECTOR 16 character tells Emacs to show the
    Eli> Emoji presentation.  Without the variation selectors, Emacs displays
    Eli> as Emoji only characters that are explicitly given the Emoji
    Eli> presentation as the default by the Unicode Character Database files.
    Eli> And AFAICT, U+1F37D is not one of them.

    Eli> (Robert, please correct me if I'm wrong here.)

Thatʼs exactly how it works. See
<https://unicode.org/emoji/charts/emoji-style.html> for a listing of
the affected codepoints and default styles.

    >> I said, I don't understand this stuff.  Is this extra codepoint supposed
    >> to be added for me?  It doesn't seem like other apps require it.

    Eli> Emacs currently doesn't insert the variation selectors automatically,
    Eli> although perhaps the Emoji input method should (or maybe already
    Eli> does, I didn't check).

The stuff Lars added on master puts in variation selectors where
needed.

    Eli> No, that wouldn't be right.  We introduced the special 'emoji'
    Eli> pseudo-script in Emacs 28 to solve the problems of being unable to
    Eli> distinguish between Emoji codepoints and the other symbols and
    Eli> punctuation.  We definitely do NOT want to use an Emoji font for
    Eli> symbols and punctuation characters and character sequences that aren't
    Eli> Emoji.  Moreover, configuring the fontset to use some font for the
    Eli> 'symbol' pseudo-script by default doesn't do what you expect, because
    Eli> Emacs uses the default font for symbols for which the default font has
    Eli> a glyph.

Modulo `use-default-font-for-symbols'

    Eli> So I think the recipe in NEWS is correct, and your expectations were
    Eli> inconsistent with the Emacs support for Emoji, at least with its state
    Eli> in Emacs 28.1.

Iʼm not sure what we could change. I guess we could add a
configuration variable that says 'treat every code point that has a
default text presentation and an emoji one as emoji', except we
already have that: VARIATION SELECTOR 16

Robert
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