1;;; scroll-lock.el --- Scroll lock scrolling. 2 3;; Copyright (C) 2005, 2006, 2007 Free Software Foundation, Inc. 4 5;; Author: Ralf Angeli <angeli@iwi.uni-sb.de> 6;; Maintainer: FSF 7;; Created: 2005-06-18 8 9;; This file is part of GNU Emacs. 10 11;; GNU Emacs is free software; you can redistribute it and/or modify 12;; it under the terms of the GNU General Public License as published by 13;; the Free Software Foundation; either version 2, or (at your option) 14;; any later version. 15 16;; GNU Emacs is distributed in the hope that it will be useful, 17;; but WITHOUT ANY WARRANTY; without even the implied warranty of 18;; MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the 19;; GNU General Public License for more details. 20 21;; You should have received a copy of the GNU General Public License 22;; along with this program; see the file COPYING. If not, write to 23;; the Free Software Foundation, Inc., 51 Franklin Street, Fifth Floor, 24;; Boston, MA 02110-1301, USA. 25 26;;; Commentary: 27 28;; By activating Scroll Lock mode, keys for moving point by line or 29;; paragraph will scroll the buffer by the respective amount of lines 30;; instead. Point will be kept vertically fixed relative to window 31;; boundaries. 32 33;;; Code: 34 35(defvar scroll-lock-mode-map 36 (let ((map (make-sparse-keymap))) 37 (define-key map [remap next-line] 'scroll-lock-next-line) 38 (define-key map [remap previous-line] 'scroll-lock-previous-line) 39 (define-key map [remap forward-paragraph] 'scroll-lock-forward-paragraph) 40 (define-key map [remap backward-paragraph] 'scroll-lock-backward-paragraph) 41 map) 42 "Keymap for Scroll Lock mode.") 43 44(defvar scroll-lock-preserve-screen-pos-save scroll-preserve-screen-position 45 "Used for saving the state of `scroll-preserve-screen-position'.") 46(make-variable-buffer-local 'scroll-lock-preserve-screen-pos-save) 47 48(defvar scroll-lock-temporary-goal-column 0 49 "Like `temporary-goal-column' but for scroll-lock-* commands.") 50 51;;;###autoload 52(define-minor-mode scroll-lock-mode 53 "Minor mode for pager-like scrolling. 54Keys which normally move point by line or paragraph will scroll 55the buffer by the respective amount of lines instead and point 56will be kept vertically fixed relative to window boundaries 57during scrolling." 58 :lighter " ScrLck" 59 :keymap scroll-lock-mode-map 60 (if scroll-lock-mode 61 (progn 62 (setq scroll-lock-preserve-screen-pos-save 63 scroll-preserve-screen-position) 64 (set (make-local-variable 'scroll-preserve-screen-position) 'always)) 65 (setq scroll-preserve-screen-position 66 scroll-lock-preserve-screen-pos-save))) 67 68(defun scroll-lock-update-goal-column () 69 "Update `scroll-lock-temporary-goal-column' if necessary." 70 (unless (memq last-command '(scroll-lock-next-line 71 scroll-lock-previous-line 72 scroll-lock-forward-paragraph 73 scroll-lock-backward-paragraph)) 74 (setq scroll-lock-temporary-goal-column (current-column)))) 75 76(defun scroll-lock-move-to-column (column) 77 "Like `move-to-column' but cater for wrapped lines." 78 (if (or (bolp) 79 ;; Start of a screen line. 80 (not (zerop (mod (- (point) (line-beginning-position)) 81 (window-width))))) 82 (move-to-column column) 83 (forward-char (min column (- (line-end-position) (point)))))) 84 85(defun scroll-lock-next-line (&optional arg) 86 "Scroll up ARG lines keeping point fixed." 87 (interactive "p") 88 (or arg (setq arg 1)) 89 (scroll-lock-update-goal-column) 90 (if (pos-visible-in-window-p (point-max)) 91 (next-line arg) 92 (scroll-up arg)) 93 (scroll-lock-move-to-column scroll-lock-temporary-goal-column)) 94 95(defun scroll-lock-previous-line (&optional arg) 96 "Scroll up ARG lines keeping point fixed." 97 (interactive "p") 98 (or arg (setq arg 1)) 99 (scroll-lock-update-goal-column) 100 (condition-case nil 101 (scroll-down arg) 102 (beginning-of-buffer (previous-line arg))) 103 (scroll-lock-move-to-column scroll-lock-temporary-goal-column)) 104 105(defun scroll-lock-forward-paragraph (&optional arg) 106 "Scroll down ARG paragraphs keeping point fixed." 107 (interactive "p") 108 (or arg (setq arg 1)) 109 (scroll-lock-update-goal-column) 110 (scroll-up (count-screen-lines (point) (save-excursion 111 (forward-paragraph arg) 112 (point)))) 113 (scroll-lock-move-to-column scroll-lock-temporary-goal-column)) 114 115(defun scroll-lock-backward-paragraph (&optional arg) 116 "Scroll up ARG paragraphs keeping point fixed." 117 (interactive "p") 118 (or arg (setq arg 1)) 119 (scroll-lock-update-goal-column) 120 (let ((goal (save-excursion (backward-paragraph arg) (point)))) 121 (condition-case nil 122 (scroll-down (count-screen-lines goal (point))) 123 (beginning-of-buffer (goto-char goal)))) 124 (scroll-lock-move-to-column scroll-lock-temporary-goal-column)) 125 126(provide 'scroll-lock) 127 128;; arch-tag: 148fc8e8-67e0-4638-bb34-3291595ab7e1 129;;; scroll-lock.el ends here 130