Re: Unicode 13 Emoji ranges composed with wrong font on NS port

[Robert Pluim]

    Robert> On Gnu/Linux with Noto Color Emoji they all look very colourful. For
    Robert> some reason on macOS the code thatʼs supposed to handle VS16 is not
    Robert> working correctly.

    Robert> Hmm, the bit in font_range that does the lookup based off
    Robert> Vscript_representative_chars is working correctly, which means Iʼll
    Robert> need to look into the macOS font/display code. Given that
    Robert> glyphless-char-display appears not to be honored on macOS, maybe
    Robert> thereʼs some code missing. Alan?

This turns out not to be due to macOS differences, but because of this
code in lisp/composite.el:

(let ((elt '([".." 1 compose-gstring-for-variation-glyph])))
  (set-char-table-range composition-function-table '(#xFE00 . #xFE0F) elt)
  (set-char-table-range composition-function-table '(#xE0100 . #xE01EF) elt))

If I change that to use `compose-gstring-for-graphic' instead, then
the emoji+VS-16 display works correctly on macOS and GNU/Linux.

Eli, something like the following for emacs-28?

diff --git a/lisp/composite.el b/lisp/composite.el
index 859253ec7e..983398f469 100644
--- a/lisp/composite.el
+++ b/lisp/composite.el
@@ -835,8 +835,11 @@ compose-gstring-for-variation-glyph
              (throw 'tag gstring)))))))
 
 (let ((elt '([".." 1 compose-gstring-for-variation-glyph])))
-  (set-char-table-range composition-function-table '(#xFE00 . #xFE0F) elt)
+  (set-char-table-range composition-function-table '(#xFE00 . #xFE0E) elt)
   (set-char-table-range composition-function-table '(#xE0100 . #xE01EF) elt))
+;; We don't want variation selectors to be used to look up glyphs for FE0F
+(set-char-table-range composition-function-table #xFE0F
+                      '([".." 1 compose-gstring-for-graphic]))
 
 (defun auto-compose-chars (func from to font-object string direction)
   "Compose the characters at FROM by FUNC.