Subject: Re: bug#66970: 29.1; Overwrite-mode is not working with Korean characters

From: João Távora <[email-masked]>
Date: Thu, 9 Nov 2023 16:37:17 +0000

Eli brought up this bug in emacs-devel and I thought
I would give it a shot.

I had never touched this code or anything like it, but I do
use input methods a bit for portuguese.  Let me know what
you think.

diff --git a/lisp/leim/quail/hangul.el b/lisp/leim/quail/hangul.el
index 46a2e5a6ba2..7e6c7310179 100644
--- a/lisp/leim/quail/hangul.el
+++ b/lisp/leim/quail/hangul.el
@@ -146,21 +146,34 @@ hangul-insert-character
       (progn
         (delete-region (region-beginning) (region-end))
         (deactivate-mark)))
-  (quail-delete-region)
-  (let ((first (car queues)))
-    (insert
-     (hangul-character
-      (+ (aref first 0) (hangul-djamo 'cho (aref first 0) (aref first 1)))
-      (+ (aref first 2) (hangul-djamo 'jung (aref first 2) (aref first 3)))
-      (+ (aref first 4) (hangul-djamo 'jong (aref first 4) (aref first 5))))))
-  (move-overlay quail-overlay (overlay-start quail-overlay) (point))
-  (dolist (queue (cdr queues))
-    (insert
-     (hangul-character
-      (+ (aref queue 0) (hangul-djamo 'cho (aref queue 0) (aref queue 1)))
-      (+ (aref queue 2) (hangul-djamo 'jung (aref queue 2) (aref queue 3)))
-      (+ (aref queue 4) (hangul-djamo 'jong (aref queue 4) (aref queue 5)))))
-    (move-overlay quail-overlay (1+ (overlay-start quail-overlay)) (point))))
+  (let* ((chars-to-insert
+          (with-temp-buffer
+            (dolist (queue queues (mapcar #'identity (buffer-string)))
+              (insert
+               (hangul-character
+                (+ (aref queue 0) (hangul-djamo 'cho (aref queue 0)
(aref queue 1)))
+                (+ (aref queue 2) (hangul-djamo 'jung (aref queue 2)
(aref queue 3)))
+                (+ (aref queue 4) (hangul-djamo 'jong (aref queue 4)
(aref queue 5))))))))
+         (may-have-to-overwrite-p
+          (or
+           ;; If the overlay isn't showing (i.e. it has 0 length) then
+           ;; we may want to insert char overwriting (iff overwrite-mode is
+           ;; non-nil, of course)
+           (= (overlay-start quail-overlay) (overlay-end quail-overlay))
+           ;; Likewise we want to do it if there is more then one
+           ;; character that were combined.
+           (cdr chars-to-insert))))
+    (quail-delete-region) ; this kills the overlay
+    (dolist (c chars-to-insert)
+      (let ((last-command-event c)
+            (overwrite-mode (and overwrite-mode
+                                 may-have-to-overwrite-p
+                                 overwrite-mode)))
+        (self-insert-command 1)
+        ;; TODO: maybe use cl-loop for an easier-to-read loop?
+        (setq may-have-to-overwrite-p nil)))
+    ; this revives it (TODO: do we really always revive?)
+    (move-overlay quail-overlay (1- (point)) (point))))

 (defun hangul-djamo (jamo char1 char2)
   "Return the double Jamo index calculated from the arguments.

-- 
João Távora