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1 | ;;; scroll-lock.el --- Scroll lock scrolling. |
2 | ||
acaf905b | 3 | ;; Copyright (C) 2005-2012 Free Software Foundation, Inc. |
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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 | ||
eb3fa2cf | 11 | ;; GNU Emacs is free software: you can redistribute it and/or modify |
94396ace | 12 | ;; it under the terms of the GNU General Public License as published by |
eb3fa2cf GM |
13 | ;; the Free Software Foundation, either version 3 of the License, or |
14 | ;; (at your option) any later version. | |
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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 | |
eb3fa2cf | 22 | ;; along with GNU Emacs. If not, see <http://www.gnu.org/licenses/>. |
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23 | |
24 | ;;; Commentary: | |
25 | ||
26 | ;; By activating Scroll Lock mode, keys for moving point by line or | |
27 | ;; paragraph will scroll the buffer by the respective amount of lines | |
28 | ;; instead. Point will be kept vertically fixed relative to window | |
29 | ;; boundaries. | |
30 | ||
31 | ;;; Code: | |
32 | ||
33 | (defvar scroll-lock-mode-map | |
34 | (let ((map (make-sparse-keymap))) | |
35 | (define-key map [remap next-line] 'scroll-lock-next-line) | |
36 | (define-key map [remap previous-line] 'scroll-lock-previous-line) | |
a0aeeaa7 KS |
37 | (define-key map [remap forward-paragraph] 'scroll-lock-forward-paragraph) |
38 | (define-key map [remap backward-paragraph] 'scroll-lock-backward-paragraph) | |
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39 | map) |
40 | "Keymap for Scroll Lock mode.") | |
41 | ||
42 | (defvar scroll-lock-preserve-screen-pos-save scroll-preserve-screen-position | |
43 | "Used for saving the state of `scroll-preserve-screen-position'.") | |
44 | (make-variable-buffer-local 'scroll-lock-preserve-screen-pos-save) | |
45 | ||
46 | (defvar scroll-lock-temporary-goal-column 0 | |
47 | "Like `temporary-goal-column' but for scroll-lock-* commands.") | |
48 | ||
49 | ;;;###autoload | |
50 | (define-minor-mode scroll-lock-mode | |
c44a951a | 51 | "Buffer-local minor mode for pager-like scrolling. |
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52 | Keys which normally move point by line or paragraph will scroll |
53 | the buffer by the respective amount of lines instead and point | |
54 | will be kept vertically fixed relative to window boundaries | |
55 | during scrolling." | |
56 | :lighter " ScrLck" | |
57 | :keymap scroll-lock-mode-map | |
58 | (if scroll-lock-mode | |
59 | (progn | |
60 | (setq scroll-lock-preserve-screen-pos-save | |
61 | scroll-preserve-screen-position) | |
62 | (set (make-local-variable 'scroll-preserve-screen-position) 'always)) | |
63 | (setq scroll-preserve-screen-position | |
64 | scroll-lock-preserve-screen-pos-save))) | |
65 | ||
66 | (defun scroll-lock-update-goal-column () | |
67 | "Update `scroll-lock-temporary-goal-column' if necessary." | |
68 | (unless (memq last-command '(scroll-lock-next-line | |
69 | scroll-lock-previous-line | |
70 | scroll-lock-forward-paragraph | |
71 | scroll-lock-backward-paragraph)) | |
72 | (setq scroll-lock-temporary-goal-column (current-column)))) | |
73 | ||
74 | (defun scroll-lock-move-to-column (column) | |
75 | "Like `move-to-column' but cater for wrapped lines." | |
76 | (if (or (bolp) | |
77 | ;; Start of a screen line. | |
78 | (not (zerop (mod (- (point) (line-beginning-position)) | |
79 | (window-width))))) | |
80 | (move-to-column column) | |
81 | (forward-char (min column (- (line-end-position) (point)))))) | |
82 | ||
83 | (defun scroll-lock-next-line (&optional arg) | |
84 | "Scroll up ARG lines keeping point fixed." | |
85 | (interactive "p") | |
86 | (or arg (setq arg 1)) | |
87 | (scroll-lock-update-goal-column) | |
88 | (if (pos-visible-in-window-p (point-max)) | |
97546017 | 89 | (forward-line arg) |
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90 | (scroll-up arg)) |
91 | (scroll-lock-move-to-column scroll-lock-temporary-goal-column)) | |
92 | ||
93 | (defun scroll-lock-previous-line (&optional arg) | |
94 | "Scroll up ARG lines keeping point fixed." | |
95 | (interactive "p") | |
96 | (or arg (setq arg 1)) | |
97 | (scroll-lock-update-goal-column) | |
98 | (condition-case nil | |
99 | (scroll-down arg) | |
97546017 | 100 | (beginning-of-buffer (forward-line (- arg)))) |
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101 | (scroll-lock-move-to-column scroll-lock-temporary-goal-column)) |
102 | ||
103 | (defun scroll-lock-forward-paragraph (&optional arg) | |
104 | "Scroll down ARG paragraphs keeping point fixed." | |
105 | (interactive "p") | |
106 | (or arg (setq arg 1)) | |
107 | (scroll-lock-update-goal-column) | |
108 | (scroll-up (count-screen-lines (point) (save-excursion | |
109 | (forward-paragraph arg) | |
110 | (point)))) | |
111 | (scroll-lock-move-to-column scroll-lock-temporary-goal-column)) | |
112 | ||
113 | (defun scroll-lock-backward-paragraph (&optional arg) | |
114 | "Scroll up ARG paragraphs keeping point fixed." | |
115 | (interactive "p") | |
116 | (or arg (setq arg 1)) | |
117 | (scroll-lock-update-goal-column) | |
118 | (let ((goal (save-excursion (backward-paragraph arg) (point)))) | |
119 | (condition-case nil | |
120 | (scroll-down (count-screen-lines goal (point))) | |
121 | (beginning-of-buffer (goto-char goal)))) | |
122 | (scroll-lock-move-to-column scroll-lock-temporary-goal-column)) | |
123 | ||
124 | (provide 'scroll-lock) | |
125 | ||
126 | ;;; scroll-lock.el ends here |