[Patch v2 2/3] emacs: Add `notmuch-show-line-faces' and apply it.

[Mark Walters <markwalters1009@gmail.com>]

Similar to `notmuch-search-line-faces', `notmuch-show-line-faces'
allows the header line in `notmuch-show-mode' buffers to be coloured
according to the tags of the message. This is just a rebased version of
the  emacs/notmuch-show.el of David Edmondson's patch
id:"1325006003-27152-1-git-send-email-dme@dme.org"
---
 emacs/notmuch-show.el |   33 +++++++++++++++++++++++++++++----
 1 files changed, 29 insertions(+), 4 deletions(-)

diff --git a/emacs/notmuch-show.el b/emacs/notmuch-show.el
index 37f0ebb..bb7db6e 100644
--- a/emacs/notmuch-show.el
+++ b/emacs/notmuch-show.el
@@ -93,6 +93,24 @@ any given message."
   :group 'notmuch-show
   :group 'notmuch-hooks)
 
+(defcustom notmuch-show-line-faces nil
+  "Tag to face mapping for header line highlighting in `notmuch-show-mode'.
+
+Here is an example of how to color search results based on tags.
+ (the following text would be placed in your ~/.emacs file):
+
+ (setq notmuch-search-line-faces '((\"delete\" . (:foreground \"red\"
+						  :background \"blue\"))
+                                   (\"unread\" . (:foreground \"green\"))))
+
+The attributes defined for matching tags are merged, with later
+attributes overriding earlier. A message having both \"delete\"
+and \"unread\" tags with the above settings would have a green
+foreground and blue background."
+  :type '(alist :key-type (string) :value-type (custom-face-edit))
+  :group 'notmuch-show
+  :group 'notmuch-faces)
+
 ;; Mostly useful for debugging.
 (defcustom notmuch-show-all-multipart/alternative-parts t
   "Should all parts of multipart/alternative parts be shown?"
@@ -411,7 +429,8 @@ unchanged ADDRESS if parsing fails."
 (defun notmuch-show-insert-headerline (headers date tags depth)
   "Insert a notmuch style headerline based on HEADERS for a
 message at DEPTH in the current thread."
-  (let ((start (point)))
+  (let ((start (point))
+	overlay)
     (insert (notmuch-show-spaces-n (* notmuch-show-indent-messages-width depth))
 	    (notmuch-show-clean-address (plist-get headers :From))
 	    " ("
@@ -420,7 +439,9 @@ message at DEPTH in the current thread."
 	    (propertize (mapconcat 'identity tags " ")
 			'face 'notmuch-tag-face)
 	    ")\n")
-    (overlay-put (make-overlay start (point)) 'face 'notmuch-message-summary-face)))
+    (setq overlay (make-overlay start (point)))
+    (overlay-put overlay 'face 'notmuch-message-summary-face)
+    (overlay-put overlay 'priority 2)))
 
 (defun notmuch-show-insert-header (header header-value)
   "Insert a single header."
@@ -852,7 +873,8 @@ current buffer, if possible."
 	 body-start body-end
 	 (headers-invis-spec (notmuch-show-make-symbol "header"))
 	 (message-invis-spec (notmuch-show-make-symbol "message"))
-	 (bare-subject (notmuch-show-strip-re (plist-get headers :Subject))))
+	 (bare-subject (notmuch-show-strip-re (plist-get headers :Subject)))
+	 (tags (plist-get msg :tags)))
 
     ;; Set `buffer-invisibility-spec' to `nil' (a list), otherwise
     ;; removing items from `buffer-invisibility-spec' (which is what
@@ -877,10 +899,13 @@ current buffer, if possible."
 					    (plist-get msg :date_relative)
 					  nil)
 					(plist-get headers :Date))
-				    (plist-get msg :tags) depth)
+				    tags depth)
 
     (setq content-start (point-marker))
 
+    ;; Colour the header line according to the tags of the message.
+    (notmuch-color-line message-start content-start tags notmuch-show-line-faces)
+
     (plist-put msg :headers-invis-spec headers-invis-spec)
     (plist-put msg :message-invis-spec message-invis-spec)
 
-- 
1.7.9.1