master 950831c: Add glyphless-char-display-control for Variation Selectors

[Robert Pluim]

branch: master
commit 950831c369636d8a681edc736a6c6151c1b1edee
Author: Robert Pluim <rpluim@gmail.com>
Commit: Robert Pluim <rpluim@gmail.com>

    Add glyphless-char-display-control for Variation Selectors
    
    * lisp/international/characters.el (update-glyphless-char-display):
    (glyphless-char-display-control): Add control knob for U+FE00 through
    U+FE0F, defaulting to 'thin-space'.
    * doc/lispref/display.texi (Glyphless Chars): Document it.
---
 doc/lispref/display.texi         |  5 +++++
 lisp/international/characters.el | 15 ++++++++++++++-
 2 files changed, 19 insertions(+), 1 deletion(-)

diff --git a/doc/lispref/display.texi b/doc/lispref/display.texi
index 510efaf..2ae04a8 100644
--- a/doc/lispref/display.texi
+++ b/doc/lispref/display.texi
@@ -7952,6 +7952,11 @@ Characters of Unicode General Category [Cf], such as 
U+200E
 @sc{left-to-right mark}, but excluding characters that have graphic
 images, such as U+00AD @sc{soft hyphen}.
 
+@item variation-selectors
+Unicode VS-1 through VS-16 (U+FE00 through U+FE0F), which are used to
+select between different glyphs for the same codepoints (typically
+emojis).
+
 @item no-font
 Characters for which there is no suitable font, or which cannot be
 encoded by the terminal's coding system.
diff --git a/lisp/international/characters.el b/lisp/international/characters.el
index e08dc27..475a669 100644
--- a/lisp/international/characters.el
+++ b/lisp/international/characters.el
@@ -1540,6 +1540,9 @@ option `glyphless-char-display'."
            ((eq target 'c1-control)
             (glyphless-set-char-table-range glyphless-char-display
                                             #x80 #x9F method))
+           ((eq target 'variation-selectors)
+            (glyphless-set-char-table-range glyphless-char-display
+                                            #xFE00 #xFE0F method))
            ((eq target 'format-control)
             (when unicode-category-table
               (map-char-table
@@ -1575,6 +1578,7 @@ option `glyphless-char-display'."
 ;;; Control of displaying glyphless characters.
 (defcustom glyphless-char-display-control
   '((format-control . thin-space)
+    (variation-selectors . thin-space)
     (no-font . hex-code))
   "List of directives to control display of glyphless characters.
 
@@ -1590,6 +1594,9 @@ GROUP must be one of these symbols:
                     such as U+200C (ZWNJ), U+200E (LRM), but
                     excluding characters that have graphic images,
                     such as U+00AD (SHY).
+  `variation-selectors': U+FE00..U+FE0F, used for choosing between
+                         glyph variations (e.g. Emoji vs Text
+                         presentation).
   `no-font':        characters for which no suitable font is found.
                     For character terminals, characters that cannot
                     be encoded by `terminal-coding-system'.
@@ -1607,7 +1614,7 @@ Do not set its value directly from Lisp; the value takes 
effect
 only via a custom `:set'
 function (`update-glyphless-char-display'), which updates
 `glyphless-char-display'."
-  :version "24.1"
+  :version "28.1"
   :type '(alist :key-type (symbol :tag "Character Group")
                :value-type (symbol :tag "Display Method"))
   :options '((c0-control
@@ -1628,6 +1635,12 @@ function (`update-glyphless-char-display'), which updates
                      (const :tag "Display as empty box" empty-box)
                      (const :tag "Display acronym" acronym)
                      (const :tag "Display hex code in a box" hex-code)))
+            (variation-selectors
+             (choice (const :tag "Don't display" zero-width)
+                     (const :tag "Display as thin space" thin-space)
+                     (const :tag "Display as empty box" empty-box)
+                     (const :tag "Display acronym" acronym)
+                     (const :tag "Display hex code in a box" hex-code)))
             (no-font
              (choice (const :tag "Don't display" zero-width)
                      (const :tag "Display as thin space" thin-space)