* mu4e: improve display of the flags-field in the message view

mu4e/mu4e-vars.el

@@ -268,6 +268,11 @@ flag set)."
   view."
   :group 'mu4e-faces)
 
+(defface mu4e-view-special-header-value-face
+  '((t :inherit font-lock-variable-name-face))
+  "Face for special header values in the message view."
+  :group 'mu4e-faces)
+
 (defface mu4e-view-link-face
   '((t :inherit font-lock-type-face :underline t))
   "Face for showing URLs and attachments in the message view."

mu4e/mu4e-view.el

@@ -165,8 +165,7 @@ plist."
 	    (:subject  (mu4e~view-construct-header field fieldval))
 	    (:path     (mu4e~view-construct-header field fieldval))
 	    (:maildir  (mu4e~view-construct-header field fieldval))
-	    (:flags    (mu4e~view-construct-header field
-			 (if fieldval (format "%S" fieldval) "")))
+	    (:flags    (mu4e~view-construct-flags-header fieldval))
 	    ;; contact fields
 	    (:to       (mu4e~view-construct-contacts-header msg field))
 	    (:from     (mu4e~view-construct-contacts-header msg field))
@@ -322,6 +321,16 @@ at POINT, or if nil, at (point)."
       (plist-get msg field) ", ") t))
 
 
+(defun mu4e~view-construct-flags-header (flags)
+  "Construct a Flags: header."
+  (mu4e~view-construct-header
+    :flags
+    (mapconcat
+      (lambda (flag)
+	(propertize (symbol-name flag) 'face 'mu4e-view-special-header-value-face))
+      flags
+      (propertize ", " 'face 'mu4e-view-header-value-face)) t))
+
 (defun mu4e~view-open-save-attach-func (msg attachnum is-open)
   "Return a function that offers to save attachment NUM. If IS-OPEN
 is nil, and otherwise open it."