[PATCH v2] Make buttons for attachments allow viewing as well as saving

[Mark Walters]

Define a keymap for attachment buttons to allow multiple actions.
Define 3 possible actions:
    save attachment: exactly as currently,
    view attachment: uses mailcap entry,
    view attachment with user chosen program

Keymap on a button is: s for save, v for view and o for view with
other program. Default (i.e. enter or mouse button) is save but this
is configurable in notmuch customize.

One implementation detail: the view attachment function forces all
attachments to be "displayed" using mailcap even if emacs could
display them itself. Thus, for example, text/html appears in a browser
and text/plain asks whether to save (on a standard debian setup)
---
 emacs/notmuch-show.el |   89 +++++++++++++++++++++++++++++++++++++++---------
 1 files changed, 72 insertions(+), 17 deletions(-)

diff --git a/emacs/notmuch-show.el b/emacs/notmuch-show.el
index 03c1f6b..6935525 100644
--- a/emacs/notmuch-show.el
+++ b/emacs/notmuch-show.el
@@ -281,10 +281,21 @@ message at DEPTH in the current thread."
 	(run-hooks 'notmuch-show-markup-headers-hook)))))
 
 (define-button-type 'notmuch-show-part-button-type
-  'action 'notmuch-show-part-button-action
+  'action 'notmuch-show-part-button-default
+  'keymap 'notmuch-show-part-button-map
   'follow-link t
   'face 'message-mml)
 
+(defvar notmuch-show-part-button-map
+  (let ((map (make-sparse-keymap)))
+       (set-keymap-parent map button-map)
+       (define-key map "s" 'notmuch-show-part-button-save)
+       (define-key map "v" 'notmuch-show-part-button-view)
+       (define-key map "o" 'notmuch-show-part-button-interactively-view)
+    map)
+  "Submap for button commands")
+(fset 'notmuch-show-part-button-map notmuch-show-part-button-map)
+
 (defun notmuch-show-insert-part-header (nth content-type declared-type &optional name comment)
   (let ((button))
     (setq button
@@ -299,29 +310,43 @@ message at DEPTH in the current thread."
 		   " ]")
 	   :type 'notmuch-show-part-button-type
 	   :notmuch-part nth
-	   :notmuch-filename name))
+	   :notmuch-filename name
+	   :notmuch-content-type content-type))
     (insert "\n")
     ;; return button
     button))
 
 ;; Functions handling particular MIME parts.
 
+;; this function is kept for the tests and any external users
 (defun notmuch-show-save-part (message-id nth &optional filename)
+  (notmuch-show-part-action 'notmuch-show-part-save-action message-id nth nil filename))
+
+(defun notmuch-show-part-action (action message-id nth content-type &optional filename)
   (let ((process-crypto notmuch-show-process-crypto))
     (with-temp-buffer
       (setq notmuch-show-process-crypto process-crypto)
       ;; Always acquires the part via `notmuch part', even if it is
       ;; available in the JSON output.
       (insert (notmuch-show-get-bodypart-internal message-id nth))
-      (let ((file (read-file-name
-		   "Filename to save as: "
-		   (or mailcap-download-directory "~/")
-		   nil nil
-		   filename)))
-	;; Don't re-compress .gz & al.  Arguably we should make
-	;; `file-name-handler-alist' nil, but that would chop
-	;; ange-ftp, which is reasonable to use here.
-	(mm-write-region (point-min) (point-max) file nil nil nil 'no-conversion t)))))
+      (cond ((eq action 'notmuch-show-part-save-action)
+	     (let ((file (read-file-name
+			  "Filename to save as: "
+			  (or mailcap-download-directory "~/")
+			  nil nil
+			  filename)))
+	       ;; Don't re-compress .gz & al.  Arguably we should make
+	       ;; `file-name-handler-alist' nil, but that would chop
+	       ;; ange-ftp, which is reasonable to use here.
+	       (mm-write-region (point-min) (point-max) file nil nil nil 'no-conversion t)))
+	    ((eq action 'notmuch-show-part-view-action)
+	     ;; set mm-inlined-types to nil to force an external viewer
+	     (let ((handle (mm-make-handle (current-buffer) (list content-type)))
+		   (mm-inlined-types nil))
+	       (mm-display-part handle)))
+	    ((eq action 'notmuch-show-part-interactively-view-action)
+	     (let ((handle (mm-make-handle (current-buffer) (list content-type))))
+	       (mm-interactively-view-part handle)))))))
 
 (defun notmuch-show-mm-display-part-inline (msg part nth content-type)
   "Use the mm-decode/mm-view functions to display a part in the
@@ -1502,12 +1527,42 @@ buffer."
 
 ;; Commands typically bound to buttons.
 
-(defun notmuch-show-part-button-action (button)
-  (let ((nth (button-get button :notmuch-part)))
-    (if nth
-	(notmuch-show-save-part (notmuch-show-get-message-id) nth
-				(button-get button :notmuch-filename))
-      (message "Not a valid part (is it a fake part?)."))))
+(defcustom notmuch-show-part-button-default-action 'notmuch-show-part-save-action
+  "Default part header button action (on ENTER or mouse click)."
+  :group 'notmuch
+  :type '(choice (const :tag "Save part"
+			notmuch-show-part-save-action)
+		 (const :tag "View part"
+			notmuch-show-part-view-action)
+		 (const :tag "View interactively"
+			notmuch-show-part-interactively-view-action)))
+
+(defun notmuch-show-part-button-default (&optional button)
+  (interactive)
+  (notmuch-show-part-button notmuch-show-part-button-default-action button))
+
+(defun notmuch-show-part-button-save (&optional button)
+  (interactive)
+  (notmuch-show-part-button 'notmuch-show-part-save-action button))
+
+(defun notmuch-show-part-button-view (&optional button)
+  (interactive)
+  (notmuch-show-part-button 'notmuch-show-part-view-action button))
+
+(defun notmuch-show-part-button-interactively-view (&optional button)
+  (interactive)
+  (notmuch-show-part-button 'notmuch-show-part-interactively-view-action button))
+
+(defun notmuch-show-part-button (action &optional button)
+  (interactive)
+  (let ((button (or button (button-at (point)))))
+    (if button
+      (let ((nth (button-get button :notmuch-part)))
+	(if nth
+	    (notmuch-show-part-action action (notmuch-show-get-message-id) nth
+				    (button-get button :notmuch-content-type)
+				    (button-get button :notmuch-filename))
+	  (message "Not a valid part (is it a fake part?)."))))))
 
 ;;
 
-- 
1.7.2.3