+(defvar wl-message-mode-line-format-spec-alist
+ '((?f (if (memq 'modeline wl-use-folder-petname)
+ (wl-folder-get-petname wl-message-buffer-cur-folder)
+ wl-message-buffer-cur-folder))
+ (?n wl-message-buffer-cur-number))
+ "An alist of format specifications for message buffer's mode-lines.
+Each element is a list of following:
+\(SPEC STRING-EXP)
+SPEC is a character for format specification.
+STRING-EXP is an expression to get string to insert.")
+
+(defcustom wl-message-mode-line-format "Wanderlust: << %f / %n >>"
+ "*A format string for message buffer's mode-line of Wanderlust.
+It may include any of the following format specifications
+which are replaced by the given information:
+
+%f The folder name.
+%n The number of the message."
+ :group 'wl-pref
+ :type 'string)
+