gnus-art.el: Improve MIME part functions.

gnus-art.el (gnus-article-jump-to-part): Error on no part; fix prompt.
 (gnus-mime-copy-part): Check coding system, not charset.
 (gnus-mime-view-part-externally): Never remove part.
 (gnus-mime-view-part-internally): Don't remove part here.
 (gnus-article-part-wrapper): Make sure MIME tag is visible.
 (gnus-article-goto-part): Go to displayed or preferred subpart if it is multipart/alternative.

mm-decode.el (mm-display-part): Take optional arg `force'.

3 files changed, 64 insertions, 18 deletions

diff --git a/lisp/gnus/ChangeLog b/lisp/gnus/ChangeLog
index f4dde8b660b..15664e87aa6 100644
--- a/lisp/gnus/ChangeLog
+++ b/lisp/gnus/ChangeLog
@@ -1,3 +1,15 @@
+2010-10-28  Katsumi Yamaoka  <yamaoka@jpl.org>
+
+        * gnus-art.el (gnus-article-jump-to-part): Error on no part; fix prompt.
+        (gnus-mime-copy-part): Check coding system, not charset.
+        (gnus-mime-view-part-externally): Never remove part.
+        (gnus-mime-view-part-internally): Don't remove part here.
+        (gnus-article-part-wrapper): Make sure MIME tag is visible.
+        (gnus-article-goto-part): Go to displayed or preferred subpart if it is
+        multipart/alternative.
+
+        * mm-decode.el (mm-display-part): Take optional arg `force'.
+
 2010-10-26  Julien Danjou  <julien@danjou.info>
 
         * gnus-group.el (gnus-group-default-list-level): Add this function to
diff --git a/lisp/gnus/gnus-art.el b/lisp/gnus/gnus-art.el
index 530e72ff5ea..b4b16797ad7 100644
--- a/lisp/gnus/gnus-art.el
+++ b/lisp/gnus/gnus-art.el
@@ -4811,11 +4811,17 @@ General format specifiers can also be used.  See Info node
 (defun gnus-article-jump-to-part (n)
   "Jump to MIME part N."
   (interactive "P")
-  (pop-to-buffer gnus-article-buffer)
-  ;; FIXME: why is it necessary?
-  (sit-for 0)
-  (let ((parts (length gnus-article-mime-handle-alist)))
-    (or n (setq n (read-number (format "Jump to part (2..%s): " parts))))
+  (let ((parts (with-current-buffer gnus-article-buffer
+                 (length gnus-article-mime-handle-alist))))
+    (when (zerop parts)
+      (error "No such part"))
+    (pop-to-buffer gnus-article-buffer)
+    ;; FIXME: why is it necessary?
+    (sit-for 0)
+    (or n
+        (setq n (if (= parts 1)
+                    1
+                  (read-number (format "Jump to part (1..%s): " parts)))))
     (unless (and (integerp n) (<= n parts) (>= n 1))
       (setq n
             (progn
@@ -5115,7 +5121,7 @@ are decompressed."
       (if (or coding-system
               (and charset
                    (setq coding-system (mm-charset-to-coding-system charset))
-                   (not (eq charset 'ascii))))
+                   (not (eq coding-system 'ascii))))
           (progn
             (mm-enable-multibyte)
             (insert (mm-decode-coding-string contents coding-system))
@@ -5290,9 +5296,7 @@ specified charset."
         (gnus-mime-view-part-as-type
          nil (lambda (type) (stringp (mailcap-mime-info type))))
       (when handle
-        (if (mm-handle-undisplayer handle)
-            (mm-remove-part handle)
-          (mm-display-part handle))))))
+        (mm-display-part handle nil t)))))
 
 (defun gnus-mime-view-part-internally (&optional handle)
   "View the MIME part under point with an internal viewer.
@@ -5311,9 +5315,7 @@ If no internal viewer is available, use an external viewer."
         (gnus-mime-view-part-as-type
          nil (lambda (type) (mm-inlinable-p handle type)))
       (when handle
-        (if (mm-handle-undisplayer handle)
-            (mm-remove-part handle)
-          (gnus-bind-safe-url-regexp (mm-display-part handle)))))))
+        (gnus-bind-safe-url-regexp (mm-display-part handle))))))
 
 (defun gnus-mime-action-on-part (&optional action)
   "Do something with the MIME attachment at \(point\)."
@@ -5376,6 +5378,10 @@ If INTERACTIVE, call FUNCTION interactivly."
           (when (gnus-article-goto-part n)
             ;; We point the cursor and the arrow at the MIME button
             ;; when the `function' prompt the user for something.
+            (unless (and (pos-visible-in-window-p)
+                         (> (count-lines (point) (window-end))
+                            (/ (1- (window-height)) 3)))
+              (recenter (/ (1- (window-height)) 3)))
             (let ((cursor-in-non-selected-windows t)
                   (overlay-arrow-string "=>")
                   (overlay-arrow-position (point-marker)))
@@ -5387,11 +5393,10 @@ If INTERACTIVE, call FUNCTION interactivly."
                     (funcall function))
                    (interactive
                     (call-interactively
-                     function
-                     (cdr (assq n gnus-article-mime-handle-alist))))
+                     function (get-text-property (point) 'gnus-data)))
                    (t
                     (funcall function
-                             (cdr (assq n gnus-article-mime-handle-alist)))))
+                             (get-text-property (point) 'gnus-data))))
                 (set-marker overlay-arrow-position nil)
                 (unless gnus-auto-select-part
                   (gnus-select-frame-set-input-focus frame)
@@ -5556,7 +5561,35 @@ all parts."
 
 (defun gnus-article-goto-part (n)
   "Go to MIME part N."
-  (gnus-goto-char (text-property-any (point-min) (point-max) 'gnus-part n)))
+  (let ((start (text-property-any (point-min) (point-max) 'gnus-part n))
+        part handle end next handles)
+    (when start
+      (goto-char start)
+      (if (setq handle (get-text-property start 'gnus-data))
+          start
+        ;; Go to the displayed subpart, assuming this is multipart/alternative.
+        (setq part start
+              end (point-at-eol))
+        (while (and (not handle)
+                    part
+                    (< part end)
+                    (setq next (text-property-not-all part end
+                                                      'gnus-data nil)))
+          (setq part next
+                handle (get-text-property part 'gnus-data))
+          (push (cons handle part) handles)
+          (unless (mm-handle-displayed-p handle)
+            (setq handle nil
+                  part (text-property-any part end 'gnus-data nil))))
+        (unless handle
+          ;; No subpart is displayed, so we find preferred one.
+          (setq part
+                (cdr (assq (mm-preferred-alternative
+                            (nreverse (mapcar 'car handles)))
+                           handles))))
+        (if part
+            (goto-char (1+ part))
+          start)))))
 
 (defun gnus-insert-mime-button (handle gnus-tmp-id &optional displayed)
   (let ((gnus-tmp-name
diff --git a/lisp/gnus/mm-decode.el b/lisp/gnus/mm-decode.el
index d1fd493a37d..531206c538e 100644
--- a/lisp/gnus/mm-decode.el
+++ b/lisp/gnus/mm-decode.el
@@ -696,13 +696,14 @@ Postpone undisplaying of viewers for types in
 (autoload 'mailcap-parse-mailcaps "mailcap")
 (autoload 'mailcap-mime-info "mailcap")
 
-(defun mm-display-part (handle &optional no-default)
+(defun mm-display-part (handle &optional no-default force)
   "Display the MIME part represented by HANDLE.
 Returns nil if the part is removed; inline if displayed inline;
 external if displayed external."
   (save-excursion
     (mailcap-parse-mailcaps)
-    (if (mm-handle-displayed-p handle)
+    (if (and (not force)
+             (mm-handle-displayed-p handle))
         (mm-remove-part handle)
       (let* ((ehandle (if (equal (mm-handle-media-type handle)
                                  "message/external-body")