avoid garbling of certain multibyte characters .

Author: jixiuf

vterm.el

@@ -430,6 +430,7 @@ Only background is used."
 (defvar-local vterm--redraw-immididately nil)
 (defvar-local vterm--linenum-remapping nil)
 (defvar-local vterm--prompt-tracking-enabled-p nil)
+(defvar-local vterm--undecoded-bytes nil)
 
 (defvar vterm-timer-delay 0.1
   "Delay for refreshing the buffer after receiving updates from libvterm.
@@ -960,10 +961,35 @@ be set to BUFFER-NAME, otherwise it will be `vterm'"
 Then triggers a redraw from the module."
   (let ((inhibit-redisplay t)
         (inhibit-read-only t)
-        (buf (process-buffer process)))
+        (buf (process-buffer process))
+        (decoded-str))
     (when (buffer-live-p buf)
       (with-current-buffer buf
-        (vterm--write-input vterm--term input)
+        ;; Borrowed from term.el
+        ;;
+        ;; Avoid garbling of certain multibyte characters by decoding the string
+        ;; before counting characters.  See,
+        ;; https://github.com/akermu/emacs-libvterm/issues/394, and the
+        ;; https://debbugs.gnu.org/cgi/bugreport.cgi?bug=1006 (for term.el).
+        (when vterm--undecoded-bytes
+          (setq input (concat vterm--undecoded-bytes input))
+          (setq vterm--undecoded-bytes nil))
+        (setq decoded-str
+              (decode-coding-string input locale-coding-system t))
+        (let ((partial 0)
+              (count (length decoded-str)))
+          (while (and (< partial count)
+                      (eq (char-charset (aref decoded-str
+                                              (- count 1 partial)))
+                          'eight-bit))
+            (cl-incf partial))
+          (when (> count partial 0)
+            (setq vterm--undecoded-bytes
+                  (substring decoded-str (- partial)))
+            (setq decoded-str
+                  (substring decoded-str 0 (- partial)))))
+
+        (vterm--write-input vterm--term decoded-str)
         (vterm--update vterm--term)))))
 
 (defun vterm--sentinel (process event)