bug#63731: [PATCH] Support Emoji Variation Sequence 16 (FE0F) where appropriate

[Robert Pluim <rpluim@gmail.com>]

>>>>> On Mon, 29 May 2023 20:18:41 +0300, Eli Zaretskii <eliz@gnu.org> said:

    >> From: Robert Pluim <rpluim@gmail.com>
    >> Cc: 63731@debbugs.gnu.org,  steven@stebalien.com
    >> Date: Mon, 29 May 2023 18:13:14 +0200
    >> 
    >> >>>>> On Mon, 29 May 2023 17:55:49 +0300, Eli Zaretskii <eliz@gnu.org> said:
    >> 
    Eli> That's because the first one shows two glyphs that are
    Eli> "pseudo-composed": not by the font, but by our hand-made "composition"
    Eli> in compose-gstring-for-graphic.  Try this instead:
    >> 
    Eli> (set-char-table-range
    Eli> composition-function-table
    Eli> #xFE0F
    Eli> '(["\\c.\ufe0f" 1 font-shape-gstring]))
    >> 
    Eli> so that we only see a composition if the font indeed agrees to
    Eli> compose.  What do you see?
    >> 
    >> It still displays a single glyph with a thin-space. If I customize
    >> `glyphless-char-display-control' to display hex codes for VS, then it
    >> display a hex box.
    >> 
    >> So I guess that means weʼre not composing?

    Eli> What does "C-u C-x =" say in this case?

It claims itʼs composed:

             position: 146 of 251 (58%), column: 0
            character: 👍 (displayed as 👍) (codepoint 128077, #o372115, #x1f44d)
              charset: unicode (Unicode (ISO10646))
code point in charset: 0x1F44D
               script: emoji
               syntax: w 	which means: word
             category: .:Base
             to input: type "C-x 8 RET 1f44d" or "C-x 8 RET THUMBS UP SIGN"
          buffer code: #xF0 #x9F #x91 #x8D
            file code: #xF0 #x9F #x91 #x8D (encoded by coding system utf-8-unix)
              display: composed to form "👍️" (see below)

Composed with the following character(s) "️" using this font:
  ftcrhb:-GOOG-Noto Color Emoji-regular-normal-normal-*-13-*-*-*-m-0-iso10646-1
by these glyphs:
  [0 1 128077 569 16 0 17 13 4 nil]
with these character(s):
  ️ (#xfe0f) VARIATION SELECTOR-16

Robert
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