Add new function string-glyph-split

* doc/lispref/strings.texi (Creating Strings): Document it.
* lisp/emacs-lisp/shortdoc.el (string): Mention it.

* lisp/emacs-lisp/subr-x.el (string-glyph-split): New function.

2 files changed, 18 insertions, 0 deletions

diff --git a/lisp/emacs-lisp/shortdoc.el b/lisp/emacs-lisp/shortdoc.el
index 817dfa6b71e..daf362dd88b 100644
--- a/lisp/emacs-lisp/shortdoc.el
+++ b/lisp/emacs-lisp/shortdoc.el
@@ -159,6 +159,8 @@ There can be any number of :example/:result elements."
    :eval (split-string-and-unquote "foo \"bar zot\""))
   (split-string-shell-command
    :eval (split-string-shell-command "ls /tmp/'foo bar'"))
+  (string-glyph-split
+   :eval (string-glyph-split "Hello, 👼🏻🧑🏼‍🤝‍🧑🏻"))
   (string-lines
    :eval (string-lines "foo\n\nbar")
    :eval (string-lines "foo\n\nbar" t))
diff --git a/lisp/emacs-lisp/subr-x.el b/lisp/emacs-lisp/subr-x.el
index 9a82fe2449d..e3caf88c2f5 100644
--- a/lisp/emacs-lisp/subr-x.el
+++ b/lisp/emacs-lisp/subr-x.el
@@ -449,6 +449,22 @@ is inserted before adjusting the number of empty lines."
     (car (window-text-pixel-size
           (current-buffer) (point-min) (point)))))
 
+;;;###autoload
+(defun string-glyph-split (string)
+  "Split STRING into a list of strings representing separate glyphs.
+This takes into account combining characters and grapheme clusters."
+  (let ((result nil)
+        (start 0)
+        comp)
+    (while (< start (length string))
+      (if (setq comp (find-composition-internal start nil string nil))
+          (progn
+            (push (substring string (car comp) (cadr comp)) result)
+            (setq start (cadr comp)))
+        (push (substring string start (1+ start)) result)
+        (setq start (1+ start))))
+    (nreverse result)))
+
 (provide 'subr-x)
 
 ;;; subr-x.el ends here