[PATCH v4 5/7] emacs/show: Make the insertion of part headers overridable.

[Mark Walters]

From: David Edmondson <dme at dme.org>

This allows callers of notmuch-show-insert-bodypart to use a `let'
binding to override the default function for specifying when part
headers should be inserted.
---
 emacs/notmuch-show.el | 16 ++++++++++++----
 1 file changed, 12 insertions(+), 4 deletions(-)

diff --git a/emacs/notmuch-show.el b/emacs/notmuch-show.el
index f8184e2..f4a65cc 100644
--- a/emacs/notmuch-show.el
+++ b/emacs/notmuch-show.el
@@ -945,8 +945,16 @@ (defun notmuch-show-mime-type (part)
 	     "text/x-diff")
 	content-type)))
 
+;; The following variable can be overridden by let bindings.
+(defvar notmuch-show-insert-header-p-function 'notmuch-show-insert-header-p
+  "Specify which function decides which part headers get inserted.
+
+The function should take two parameters, PART and HIDE, and
+should return non-NIL if a header button should be inserted for
+this part.")
+
 (defun notmuch-show-insert-header-p (part hide)
-  "Return non-NIL if a header button should be inserted for this part."
+  ;; Show all part buttons except for the first part if it is text/plain.
   (let ((mime-type (notmuch-show-mime-type part)))
     (not (and (string= mime-type "text/plain")
 	      (<= (plist-get part :id) 1)))))
@@ -965,9 +973,9 @@ (defun notmuch-show-insert-bodypart (msg part depth &optional hide)
 		    (> notmuch-show-max-text-part-size 0)
 		    (> (length (plist-get part :content)) notmuch-show-max-text-part-size)))
 	 (beg (point))
-	 ;; We omit the part button for the first (or only) part if
-	 ;; this is text/plain, or HIDE is 'no-buttons.
-	 (button (when (notmuch-show-insert-header-p part hide)
+	 ;; This default header-p function omits the part button for
+	 ;; the first (or only) part if this is text/plain.
+	 (button (when (funcall notmuch-show-insert-header-p-function part hide)
 		   (notmuch-show-insert-part-header nth mime-type content-type (plist-get part :filename))))
 	 ;; Hide the part initially if HIDE is t, or if it is too long
 	 ;; and we have a button to allow toggling (thus reply which
-- 
2.1.4