;;; scroll-LR-by-20.el
;;;
;;; Copyright (C) 1993, 1994, 1995, 1996, 1997, 1998, 1999,
;;;   2004, 2007, 2008 Thien-Thi Nguyen
;;;
;;; This file is part of ttn's personal elisp library, released under
;;; the terms of the GNU General Public License as published by the
;;; Free Software Foundation; either version 3, or (at your option) any
;;; later version.  There is NO WARRANTY.  See file COPYING for details.

;;; Description: Horizontal scrolling support used by many modes hooks.

(require 'cl)
(require 'map-table)

(defvar scroll-LR-by-20-minor-mode nil
  "See function `scroll-LR-by-20-minor-mode'.")

(defvar scroll-LR-by-20-minor-mode-map nil
  "See function `scroll-LR-by-20-minor-mode'.")

;;;###autoload
(defun scroll-left-20 () (interactive)
  (scroll-left 20))

;;;###autoload
(defun scroll-right-20 () (interactive)
  (scroll-right 20))

;;;###autoload
(defun scroll-LR-by-20-minor-mode (&optional arg)
  "Toggle scroll-LR-by-20 minor mode.
With ARG, turn minor mode on if ARG is positive, off otherwise.
When minor mode is on, `[' and `]' scroll the window horizontally
left and right, respectively."
  (interactive "P")
  (setq scroll-LR-by-20-minor-mode
        (if (null arg)
            (not scroll-LR-by-20-minor-mode)
          (> (prefix-numeric-value arg) 0)))
  (set (make-local-variable 'automatic-hscrolling)
       (not scroll-LR-by-20-minor-mode)))

(make-variable-buffer-local 'scroll-LR-by-20-minor-mode)
(put scroll-LR-by-20-minor-mode 'permanent-local t)

(unless scroll-LR-by-20-minor-mode-map
  (setq scroll-LR-by-20-minor-mode-map (make-sparse-keymap))
  (map-table-2col
   (lambda (key binding)
     (define-key scroll-LR-by-20-minor-mode-map key binding))
   '("[" scroll-left-20
     "]" scroll-right-20))
  (pushnew (cons 'scroll-LR-by-20-minor-mode scroll-LR-by-20-minor-mode-map)
           minor-mode-map-alist
           :test 'equal))

(provide 'scroll-LR-by-20)

;;; scroll-LR-by-20.el ends here