+ * elmo.el (elmo-folder): Added handlers slot.
+ (elmo-event-handler): New class.
+ (elmo-event-handler-flag-changed): New API.
+ (elmo-folder-add-handler): New function.
+ (elmo-folder-remove-handler): Ditto.
+ (elmo-folder-notify-event): Ditto.
+ (elmo-folder-set-flag): Call `elmo-folder-notify-event' with event
+ `flag-changed'.
+ (elmo-folder-unset-flag): Ditto.
+
+ * elmo-pipe.el (elmo-folder-set-flag): Ditto.
+ (elmo-folder-unset-flag): Ditto.
+
+ * elmo-multi.el (elmo-folder-set-flag): Ditto.
+ (elmo-folder-unset-flag): Ditto.
+
+ * elmo-filter.el (elmo-folder-set-flag): Ditto.
+ (elmo-folder-unset-flag): Ditto.
+