-this does no charset conversion."
- (let ((args `("show" "--format=raw"
- ,(format "--part=%d" (plist-get part :id))
- ,@(when process-crypto '("--decrypt"))
- ,(notmuch-id-to-query (plist-get msg :id)))))
- (with-temp-buffer
- (let ((coding-system-for-read 'no-conversion))
- (apply #'call-process notmuch-command nil '(t nil) nil args)
- (buffer-string)))))
-
-(defun notmuch-get-bodypart-text (msg part process-crypto)
+this does no charset conversion.
+
+If CACHE is non-nil, the content of this part will be saved in
+MSG (if it isn't already)."
+ (let ((data (plist-get part :binary-content)))
+ (when (not data)
+ (let ((args `("show" "--format=raw"
+ ,(format "--part=%d" (plist-get part :id))
+ ,@(when process-crypto '("--decrypt"))
+ ,(notmuch-id-to-query (plist-get msg :id)))))
+ (with-temp-buffer
+ ;; Emacs internally uses a UTF-8-like multibyte string
+ ;; representation by default (regardless of the coding
+ ;; system, which only affects how it goes from outside data
+ ;; to this internal representation). This *almost* never
+ ;; matters. Annoyingly, it does matter if we use this data
+ ;; in an image descriptor, since Emacs will use its internal
+ ;; data buffer directly and this multibyte representation
+ ;; corrupts binary image formats. Since the caller is
+ ;; asking for binary data, a unibyte string is a more
+ ;; appropriate representation anyway.
+ (set-buffer-multibyte nil)
+ (let ((coding-system-for-read 'no-conversion))
+ (apply #'call-process notmuch-command nil '(t nil) nil args)
+ (setq data (buffer-string)))))
+ (when cache
+ ;; Cheat. part is non-nil, and `plist-put' always modifies
+ ;; the list in place if it's non-nil.
+ (plist-put part :binary-content data)))
+ data))
+
+(defun notmuch-get-bodypart-text (msg part process-crypto &optional cache)