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[bpt/emacs.git] / lisp / ruler-mode.el

;;; ruler-mode.el --- Display a ruler in the header line

;; Copyright (C) 2001 Free Software Foundation, Inc.

;; Author: David Ponce <david@dponce.com>
;; Maintainer: David Ponce <david@dponce.com>
;; Created: 24 Mar 2001
;; Version: 1.3.1
;; Keywords: environment

;; This file is part of GNU Emacs.

;; This program is free software; you can redistribute it and/or
;; modify it under the terms of the GNU General Public License as
;; published by the Free Software Foundation; either version 2, or (at
;; your option) any later version.

;; This program is distributed in the hope that it will be useful, but
;; WITHOUT ANY WARRANTY; without even the implied warranty of
;; MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
;; General Public License for more details.

;; You should have received a copy of the GNU General Public License
;; along with this program; see the file COPYING.  If not, write to
;; the Free Software Foundation, Inc., 59 Temple Place - Suite 330,
;; Boston, MA 02111-1307, USA.

;;; Commentary:

;; This library provides a minor mode to display a ruler in the header
;; line.  It works only on Emacs 21.
;;
;; You can use the mouse to change the `fill-column', `window-margins'
;; and `tab-stop-list' settings:
;;
;; [header-line (shift down-mouse-1)] set left margin to the ruler
;; graduation where the mouse pointer is on.
;;
;; [header-line (shift down-mouse-3)] set right margin to the ruler
;; graduation where the mouse pointer is on.
;;
;; [header-line down-mouse-2] set `fill-column' to the ruler
;; graduation where the mouse pointer is on.
;;
;; [header-line (control down-mouse-1)] add a tab stop to the ruler
;; graduation where the mouse pointer is on.
;;
;; [header-line (control down-mouse-3)] remove the tab stop at the
;; ruler graduation where the mouse pointer is on.
;;
;; [header-line (control down-mouse-2)] or M-x
;; `ruler-mode-toggle-show-tab-stops' toggle showing and visually
;; editing `tab-stop-list' setting.  The `ruler-mode-show-tab-stops'
;; option controls if the ruler shows tab stops by default.
;;
;; In the ruler the character `ruler-mode-current-column-char' shows
;; the `current-column' location, `ruler-mode-fill-column-char' shows
;; the `fill-column' location and `ruler-mode-tab-stop-char' shows tab
;; stop locations.  `window-margins' areas are shown with a different
;; background color.
;;
;; It is also possible to customize the following characters:
;;
;; - `ruler-mode-margins-char' character used to pad margin areas
;;   (space by default).
;; - `ruler-mode-basic-graduation-char' character used for basic
;;   graduations ('.' by default).
;; - `ruler-mode-inter-graduation-char' character used for
;;   intermediate graduations ('!' by default).
;;
;; The following faces are customizable:
;;
;; - `ruler-mode-default-face' the ruler default face.
;; - `ruler-mode-fill-column-face' the face used to highlight the
;;   `fill-column' character.
;; - `ruler-mode-current-column-face' the face used to highlight the
;;   `current-column' character.
;; - `ruler-mode-tab-stop-face' the face used to highlight tab stop
;;   characters.
;; - `ruler-mode-margins-face' the face used to highlight the
;;   `window-margins' areas.
;; - `ruler-mode-column-number-face' the face used to highlight the
;;   number graduations.
;;
;; `ruler-mode-default-face' inherits from the built-in `default' face.
;; All `ruler-mode' faces inerit from `ruler-mode-default-face'.
;;
;; WARNING: To keep ruler graduations aligned on text columns it is
;; important to use the same font family and size for ruler and text
;; areas.

;; Installation
;;
;; To automatically display the ruler in specific major modes use:
;;
;;    (add-hook '<major-mode>-hook 'ruler-mode)
;;

;;; History:
;;

;;; Code:
(eval-when-compile
  (require 'wid-edit))

(defgroup ruler-mode nil
  "Display a ruler in the header line."
  :version "21.2"
  :group 'environment)

(defcustom ruler-mode-show-tab-stops nil
  "*If non-nil the ruler shows tab stop positions.
Also allowing to visually change `tab-stop-list' setting using
<C-down-mouse-1> and <C-down-mouse-3> on the ruler to respectively add
or remove a tab stop.  \\[ruler-mode-toggle-show-tab-stops] or
<C-down-mouse-2> on the ruler toggles showing/editing of tab stops."
  :group 'ruler-mode
  :type 'boolean)

;; IMPORTANT: This function must be defined before the following
;; defcustoms because it is used in their :validate clause.
(defun ruler-mode-character-validate (widget)
  "Ensure WIDGET value is a valid character value."
  (save-excursion
    (let ((value (widget-value widget)))
      (if (char-valid-p value)
          nil
        (widget-put widget :error
                    (format "Invalid character value: %S" value))
        widget))))
      
(defcustom ruler-mode-fill-column-char (if window-system