"`header-line-format' used in ruler mode.
Call `ruler-mode-ruler-function' to compute the ruler value.")
+;;;###autoload
+(defvar ruler-mode nil
+ "Non-nil if Ruler mode is enabled.
+Use the command `ruler-mode' to change this variable.")
+(make-variable-buffer-local 'ruler-mode)
+
+(defun ruler--save-header-line-format ()
+ "Install the header line format for Ruler mode.
+Unless Ruler mode is already enabled, save the old header line
+format first."
+ (when (and (not ruler-mode)
+ (local-variable-p 'header-line-format)
+ (not (local-variable-p 'ruler-mode-header-line-format-old)))
+ (set (make-local-variable 'ruler-mode-header-line-format-old)
+ header-line-format))
+ (setq header-line-format ruler-mode-header-line-format))
+
;;;###autoload
(define-minor-mode ruler-mode
- "Display a ruler in the header line if ARG > 0."
+ "Toggle Ruler mode.
+In Ruler mode, Emacs displays a ruler in the header line."
nil nil
ruler-mode-map
:group 'ruler-mode
+ :variable (ruler-mode
+ . (lambda (enable)
+ (when enable
+ (ruler--save-header-line-format))
+ (setq ruler-mode enable)))
(if ruler-mode
- (progn
- ;; When `ruler-mode' is on save previous header line format
- ;; and install the ruler header line format.
- (when (and (local-variable-p 'header-line-format)
- (not (local-variable-p 'ruler-mode-header-line-format-old)))
- (set (make-local-variable 'ruler-mode-header-line-format-old)
- header-line-format))
- (setq header-line-format ruler-mode-header-line-format)
- (add-hook 'post-command-hook 'force-mode-line-update nil t))
+ (add-hook 'post-command-hook 'force-mode-line-update nil t)
;; When `ruler-mode' is off restore previous header line format if
;; the current one is the ruler header line format.
(when (eq header-line-format ruler-mode-header-line-format)