Prevent save-buffer in Rmail buffers from using the coding-system

of the current message, and from clobbering the encoding mnemonics
in the mode line (Bug#4623).

(rmail-swap-buffers): Swap encoding and modified flag, too.
(rmail-message-encoding): New variable.
(rmail-write-region-annotate): Record the encoding of the current message
in rmail-message-encoding.
(rmail-after-save-hook): New function, restores the encoding of the current
message after the message collection is saved.

2 files changed, 42 insertions, 7 deletions

diff --git a/lisp/ChangeLog b/lisp/ChangeLog
index 01096305437..9a13c3d51d8 100644
--- a/lisp/ChangeLog
+++ b/lisp/ChangeLog
@@ -1,3 +1,17 @@
+2009-12-07  Eli Zaretskii  <eliz@gnu.org>
+
+	Prevent save-buffer in Rmail buffers from using the coding-system
+	of the current message, and from clobbering the encoding mnemonics
+	in the mode line (Bug#4623).
+
+	* mail/rmail.el (rmail-swap-buffers): Swap encoding and modified
+	flag, too.
+	(rmail-message-encoding): New variable.
+	(rmail-write-region-annotate): Record the encoding of the current
+	message in rmail-message-encoding.
+	(rmail-after-save-hook): New function, restores the encoding of
+	the current message after the message collection is saved.
+
 2009-12-07  Juri Linkov  <juri@jurta.org>
 
 	* progmodes/grep.el (grep-read-files): Use `completing-read'
diff --git a/lisp/mail/rmail.el b/lisp/mail/rmail.el
index 18fd1f6f727..21be36fae38 100644
--- a/lisp/mail/rmail.el
+++ b/lisp/mail/rmail.el
@@ -1316,13 +1316,19 @@ Create the buffer if necessary."
 This function preserves the current buffer's modified flag, and also
 sets the current buffer's `buffer-file-coding-system' to that of
 `rmail-view-buffer'."
-  (let ((modp (buffer-modified-p))
-	(coding
+  (let ((modp-this (buffer-modified-p))
+	(modp-that
+	 (with-current-buffer rmail-view-buffer (buffer-modified-p)))
+	(coding-this buffer-file-coding-system)
+	(coding-that
 	 (with-current-buffer rmail-view-buffer
 	   buffer-file-coding-system)))
     (buffer-swap-text rmail-view-buffer)
-    (setq buffer-file-coding-system coding)
-    (restore-buffer-modified-p modp)))
+    (setq buffer-file-coding-system coding-that)
+    (with-current-buffer rmail-view-buffer
+      (setq buffer-file-coding-system coding-this)
+      (restore-buffer-modified-p modp-that))
+    (restore-buffer-modified-p modp-this)))
 
 (defun rmail-buffers-swapped-p ()
   "Return non-nil if the message collection is in `rmail-view-buffer'."
@@ -4179,16 +4185,31 @@ encoded string (and the same mask) will decode the string."
 (add-to-list 'desktop-buffer-mode-handlers
 	     '(rmail-mode . rmail-restore-desktop-buffer))
 
+;; We use this to record the encoding of the current message before
+;; saving the message collection.
+(defvar rmail-message-encoding nil)
+
 ;; Used in `write-region-annotate-functions' to write rmail files.
 (defun rmail-write-region-annotate (start end)
   (when (and (null start) (rmail-buffers-swapped-p))
+    (setq rmail-message-encoding buffer-file-coding-system)
     (set-buffer rmail-view-buffer)
-    ;; Prevent viewing different messages from messing up the coding. (Bug#4623)
-    ;; FIXME is there a better solution?
-    (set (make-local-variable 'coding-system-for-write) 'no-conversion)
     (widen)
     nil))
 
+;; Used to restore the encoding of the buffer where we show the
+;; current message, after we save the message collection.  This is
+;; needed because rmail-write-region-annotate switches buffers behind
+;; save-file's back, with the side effect that last-coding-system-used
+;; is assigned to buffer-file-coding-system of the wrong buffer.
+(defun rmail-after-save-hook ()
+  (if (or (eq rmail-view-buffer (current-buffer))
+	  (eq rmail-buffer (current-buffer)))
+      (with-current-buffer
+	  (if (rmail-buffers-swapped-p) rmail-buffer rmail-view-buffer)
+	(setq buffer-file-coding-system rmail-message-encoding))))
+(add-hook 'after-save-hook 'rmail-after-save-hook)
+
 
 ;;; Start of automatically extracted autoloads.