master 1866e66 6/6: * lisp/international/mule-cmds.el: Use group-function in read-char-by-name.

[Juri Linkov]

branch: master
commit 1866e66a73083fa5466b040d2cc44ca73da891e9
Author: Juri Linkov <juri@linkov.net>
Commit: Juri Linkov <juri@linkov.net>

    * lisp/international/mule-cmds.el: Use group-function in read-char-by-name.
    
    (mule--ucs-names-group): Simplify for using by group-function.
    (read-char-by-name-group): Remove defcustom
    obsoleted by completions-group.
    (read-char-by-name): Mention completions-group and
    completions-group-sort in docstring.  Use group-function when
    completions-group is non-nil.
    https://lists.gnu.org/archive/html/emacs-devel/2021-05/msg00791.html
---
 etc/NEWS                        | 15 ++++++-----
 lisp/international/mule-cmds.el | 56 ++++++++++-------------------------------
 2 files changed, 22 insertions(+), 49 deletions(-)

diff --git a/etc/NEWS b/etc/NEWS
index 32d7c4f..0bdb79e 100644
--- a/etc/NEWS
+++ b/etc/NEWS
@@ -1090,12 +1090,11 @@ so e.g. like 'C-x 8 [' inserts a left single quotation 
mark,
 'C-x \ [' does the same.
 
 ---
-*** New user options 'read-char-by-name-sort' and 'read-char-by-name-group'.
-'read-char-by-name-sort' defines the sorting order of characters for
-completion of 'C-x 8 RET TAB' and can be customized to sort them
-by codepoints instead of character names by default.  The 't' value of
-'read-char-by-name-group' groups the characters for completion of
-'C-x 8 RET TAB' by Unicode blocks.
+*** New user option 'read-char-by-name-sort'.
+It defines the sorting order of characters for completion of 'C-x 8 RET TAB'
+and can be customized to sort them by codepoints instead of character names.
+Additionally, you can group characters by Unicode blocks after customizing
+'completions-group' and 'completions-group-sort'.
 
 ---
 *** Improved language transliteration in Malayalam input methods.
@@ -2768,6 +2767,10 @@ each element is a list with three elements: a completion,
 a prefix string, and a suffix string.
 
 +++
+** New completion function 'group-function' for grouping candidates.
+It takes two arguments: a completion candidate and a 'transform' flag.
+
++++
 ** 'read-char-from-minibuffer' and 'y-or-n-p' support 'help-form'.
 If you bind 'help-form' to a non-nil value while calling these functions,
 then pressing 'C-h' ('help-char') causes the function to evaluate 'help-form'
diff --git a/lisp/international/mule-cmds.el b/lisp/international/mule-cmds.el
index 7f8d98b..432ca29 100644
--- a/lisp/international/mule-cmds.el
+++ b/lisp/international/mule-cmds.el
@@ -3104,35 +3104,11 @@ on encoding."
               (list name (concat (if char (list char) " ") "\t") "")))
           names))
 
-(defun mule--ucs-names-group (names)
-  (let* ((codes-and-names
-          (mapcar (lambda (name) (cons (gethash name ucs-names) name)) names))
-         (grouped
-          (seq-group-by
-           (lambda (code-name)
-             (let ((script (aref char-script-table (car code-name))))
-               (if script (symbol-name script) "ungrouped")))
-           codes-and-names))
-         names-with-header header)
-    (dolist (group (sort grouped (lambda (a b) (string< (car a) (car b)))))
-      (setq header t)
-      (dolist (code-name (cdr group))
-        (push (list
-               (cdr code-name)
-               (concat
-                (if header
-                    (progn
-                      (setq header nil)
-                      (concat "\n" (propertize
-                                    (format "* %s\n" (car group))
-                                    'face 'header-line)))
-                  "")
-                ;; prefix
-                (if (car code-name) (format "%c" (car code-name)) " ") "\t")
-               ;; suffix
-               "")
-              names-with-header)))
-    (nreverse names-with-header)))
+(defun mule--ucs-names-group (name transform)
+  (if transform
+      name
+    (let ((script (aref char-script-table (gethash name ucs-names))))
+      (if script (symbol-name script) "ungrouped"))))
 
 (defun char-from-name (string &optional ignore-case)
   "Return a character as a number from its Unicode name STRING.
@@ -3164,14 +3140,6 @@ Defines the sorting order either by character names or 
their codepoints."
   :group 'mule
   :version "28.1")
 
-(defcustom read-char-by-name-group nil
-  "How to group characters for `read-char-by-name' completion.
-When t, split characters to sections of Unicode blocks
-sorted alphabetically."
-  :type 'boolean
-  :group 'mule
-  :version "28.1")
-
 (defun read-char-by-name (prompt)
   "Read a character by its Unicode name or hex number string.
 Display PROMPT and read a string that represents a character by its
@@ -3185,8 +3153,9 @@ preceded by an asterisk `*' and use completion, it will 
show all
 the characters whose names include that substring, not necessarily
 at the beginning of the name.
 
-The options `read-char-by-name-sort' and `read-char-by-name-group'
-define the sorting order of completion characters and how to group them.
+The options `read-char-by-name-sort', `completions-group', and
+`completions-group-sort' define the sorting order of completion characters,
+whether to group them, and how to sort groups.
 
 Accept a name like \"CIRCULATION FUNCTION\", a hexadecimal
 number like \"2A10\", or a number in hash notation (e.g.,
@@ -3204,11 +3173,12 @@ as names, not numbers."
                 `(metadata
                   (display-sort-function
                    . ,(when (eq read-char-by-name-sort 'code)
-                         #'mule--ucs-names-sort-by-code))
+                        #'mule--ucs-names-sort-by-code))
                   (affixation-function
-                   . ,(if read-char-by-name-group
-                           #'mule--ucs-names-group
-                         #'mule--ucs-names-affixation))
+                   . ,#'mule--ucs-names-affixation)
+                  (group-function
+                   . ,(when completions-group
+                        #'mule--ucs-names-group))
                   (category . unicode-name))
               (complete-with-action action (ucs-names) string pred)))))
         (char