Support for Unicode emoji sequences

This covers both sequences using Zero-Width-Joiner codepoints and
those without. Bug#39799, I hope.

* .gitignore: Add emoji-zwj.el
* admin/notes/unicode: Add emoji-zwj-sequences.txt and
emoji-sequences.txt references.  Describe how to test after updating
to a newer Unicode version.
* admin/unidata/Makefile.in (all): add emoji-zwj.el as a dependency.
(emoji-zwj.el): Add target plus rules for building.
(gen-clean): Add emoji-zwj.el.
* admin/unidata/README: Add emoji-zwj-sequences.txt and
emoji-sequences.txt references.
* admin/unidata/blocks.awk: Force emoji script to be used for certain
codepoints that are used by the Unicode sequences.
* admin/unidata/emoji-sequences.txt: New file.
* admin/unidata/emoji-zwj-sequences.txt: New file.
* admin/unidata/emoji-zwj.awk: New file.  Derives
composition-function-table rules from emoji-zwj-sequences.txt, plus
hardcodes some derived manually from emoji-sequences.txt.
* etc/NEWS: Announce change.
* lisp/international/characters.el: Load the generated emoji-zwj.el
* src/Makefile.in (emoji-zwj): New target.
(temacs): Add emoji-zwj as a dependency.

1 files changed, 11 insertions, 4 deletions

diff --git a/admin/notes/unicode b/admin/notes/unicode
index 0b2ce527948..21233ac2819 100644
--- a/admin/notes/unicode
+++ b/admin/notes/unicode
@@ -17,13 +17,15 @@ Emacs uses the following files from the Unicode Character Database
   . NormalizationTest.txt
   . SpecialCasing.txt
   . emoji-data.txt
+  . emoji-zwj-sequences.txt
+  . emoji-sequences.txt
   . BidiCharacterTest.txt
 
-First, the first 8 files need to be copied into admin/unidata/, and
+First, the first 10 files need to be copied into admin/unidata/, and
 the file https://www.unicode.org/copyright.html should be copied over
-copyright.html in admin/unidata (that file and emoji-data.txt might
-need trailing whitespace removed before they can be committed to the
-Emacs repository).
+copyright.html in admin/unidata (some of them might need trailing
+whitespace removed before they can be committed to the Emacs
+repository).
 
 Then Emacs should be rebuilt for them to take effect.  Rebuilding
 Emacs updates several derived files elsewhere in the Emacs source
@@ -112,6 +114,11 @@ FONT-NAME-REGEXP is checked using `string-match'."
       (princ (format "Font not matching '%s' was used for the following characters:\n%s"
                      font-name-regexp (reverse res))))))))
 
+Visit "emoji-zwj-sequences.txt" and "emoji-sequences.txt" with the
+rebuilt Emacs, and check that the sample sequences are composed
+properly.  Note that your emoji font might not have glyphs for the
+newest codepoints yet.
+
 Finally, etc/NEWS should be updated to announce the support for the
 new Unicode version.