(rmail-cease-edit): Notice changes in buffer's encoding during editing.

Make sure to use encoding that can safely encode the message.
Rewrite MIME charset= header if the new encoding is different from the old one.

2 files changed, 49 insertions, 1 deletions

diff --git a/lisp/ChangeLog b/lisp/ChangeLog
index 0c3db1833d8..5e018f9d5f5 100644
--- a/lisp/ChangeLog
+++ b/lisp/ChangeLog
@@ -1,3 +1,10 @@
+2009-02-21  Eli Zaretskii  <eliz@gnu.org>
+
+        * mail/rmailedit.el (rmail-cease-edit): Notice changes in buffer's
+        encoding during editing.  Make sure to use encoding that can
+        safely encode the message.  Rewrite MIME charset= header if the
+        new encoding is different from the old one.
+
 2009-02-21  Glenn Morris  <rgm@gnu.org>
 
         * mail/supercite.el (sc-mail-glom-frame): Handle a "From " line
diff --git a/lisp/mail/rmailedit.el b/lisp/mail/rmailedit.el
index 826e5da06e3..46c1ab6e03c 100644
--- a/lisp/mail/rmailedit.el
+++ b/lisp/mail/rmailedit.el
@@ -136,9 +136,18 @@ This functions runs the normal hook `rmail-edit-mode-hook'.
       (insert "\n")))
   (let ((old rmail-old-text)
         (pruned rmail-old-pruned)
+        ;; People who know what they are doing might have modified the
+        ;; buffer's encoding if editing the message included inserting
+        ;; characters that were unencodable by the original message's
+        ;; encoding.  Make note of the new encoding and use it for
+        ;; encoding the edited message.
+        (edited-coding buffer-file-coding-system)
         new-headers
         character-coding is-text-message coding-system
         headers-end limit)
+    ;; Make sure `edited-coding' can safely encode the edited message.
+    (setq edited-coding
+          (select-safe-coding-system (point-min) (point-max) edited-coding))
     ;; Go back to Rmail mode, but carefully.
     (force-mode-line-update)
     (let ((rmail-buffer-swapped nil)) ; Prevent change-major-mode-hook
@@ -154,6 +163,33 @@ This functions runs the normal hook `rmail-edit-mode-hook'.
                  (string= old (buffer-substring (point-min) (point-max))))
       (setq old nil)
       (goto-char (point-min))
+      ;; If they changed the message's encoding, rewrite the charset=
+      ;; header for them, so that subsequent rmail-show-message
+      ;; decodes it correctly.
+      (let ((buffer-read-only nil)
+            (new-coding (coding-system-base edited-coding))
+            old-coding mime-charset mime-beg mime-end)
+        (when (re-search-forward rmail-mime-charset-pattern
+                                 (1- (save-excursion (search-forward "\n\n")))
+                                 'move)
+            (setq mime-beg (match-beginning 1)
+                  mime-end (match-end 1)
+                  old-coding (coding-system-from-name (match-string 1))))
+        (setq mime-charset
+              (symbol-name
+               (or (coding-system-get new-coding :mime-charset)
+                   (if (coding-system-equal new-coding 'undecided)
+                       'us-ascii
+                     new-coding))))
+        (cond
+         ((null old-coding)
+          ;; If there was no charset= spec, insert one.
+          (insert "Content-type: text/plain; charset=" mime-charset "\n"))
+         ((not (coding-system-equal (coding-system-base old-coding)
+                                    new-coding))
+          (delete-region mime-beg mime-end)
+          (insert mime-charset))))
+      (goto-char (point-min))
       (search-forward "\n\n")
       (setq headers-end (point))
       (setq new-headers (rmail-edit-headers-alist t))
@@ -171,7 +207,12 @@ This functions runs the normal hook `rmail-edit-mode-hook'.
         (setq character-coding
               (mail-fetch-field "content-transfer-encoding")
               is-text-message (rmail-is-text-p)
-              coding-system (rmail-get-coding-system)))
+              coding-system (if (and edited-coding
+                                     (not (coding-system-equal
+                                           (coding-system-base edited-coding)
+                                           'undecided)))
+                                edited-coding
+                              (rmail-get-coding-system))))
       (if character-coding
           (setq character-coding (downcase character-coding)))