lisp/saveplace.el

   1 ;;; saveplace.el --- automatically save place in files.
   2
   3 ;; Copyright (C) 1993, 1994 Free Software Foundation, Inc.
   4
   5 ;; Author: Karl Fogel <kfogel@cs.oberlin.edu>
   6 ;; Maintainer: FSF
   7 ;; Created: July, 1993
   8 ;; Keywords: bookmarks, placeholders
   9
  10 ;; This file is part of GNU Emacs.
  11
  12 ;; GNU Emacs is free software; you can redistribute it and/or modify
  13 ;; it under the terms of the GNU General Public License as published by
  14 ;; the Free Software Foundation; either version 2, or (at your option)
  15 ;; any later version.
  16
  17 ;; GNU Emacs is distributed in the hope that it will be useful,
  18 ;; but WITHOUT ANY WARRANTY; without even the implied warranty of
  19 ;; MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  20 ;; GNU General Public License for more details.
  21
  22 ;; You should have received a copy of the GNU General Public License
  23 ;; along with GNU Emacs; see the file COPYING.  If not, write to the
  24 ;; Free Software Foundation, Inc., 59 Temple Place - Suite 330,
  25 ;; Boston, MA 02111-1307, USA.
  26
  27 ;;; Commentary:
  28
  29 ;; Automatically save place in files, so that visiting them later
  30 ;; (even during a different Emacs session) automatically moves point
  31 ;; to the saved position, when the file is first found.  Uses the
  32 ;; value of buffer-local variable save-place to determine whether to
  33 ;; save position or not.
  34 ;;
  35 ;; Thanks to Stefan Schoef, who sent a patch with the
  36 ;; `save-place-version-control' stuff in it.
  37
  38 ;;; Code:
  39
  40 ;; this is what I was using during testing:
  41 ;; (define-key ctl-x-map "p" 'toggle-save-place)
  42
  43 (defvar save-place-alist nil
  44   "Alist of saved places to go back to when revisiting files.
  45 Each element looks like (FILENAME . POSITION);
  46 visiting file FILENAME goes automatically to position POSITION
  47 rather than the beginning of the buffer.
  48 This alist is saved between Emacs sessions.")
  49
  50 (defvar save-place nil
  51   "*Non-nil means automatically save place in each file.
  52 This means when you visit a file, point goes to the last place
  53 where it was when you previously visited the same file.
  54 This variable is automatically buffer-local.
  55
  56 If you wish your place in any file to always be automatically saved,
  57 simply put this in your `~/.emacs' file:
  58
  59 \(setq-default save-place t\)")
  60
  61 (make-variable-buffer-local 'save-place)
  62
  63 (defvar save-place-file (convert-standard-filename "~/.emacs-places")
  64   "*Name of the file that records `save-place-alist' value.")
  65
  66 (defvar save-place-version-control 'nospecial
  67   "*Controls whether to make numbered backups of master save-place file.
  68 It can have four values: t, nil, `never', and `nospecial'.  The first
  69 three have the same meaning that they do for the variable
  70 `version-control', and the final value `nospecial' means just use the
  71 value of `version-control'.")
  72
  73 (defvar save-place-loaded nil
  74   "Non-nil means that the `save-place-file' has been loaded.")
  75
  76 (defvar save-place-limit nil
  77   "Maximum number of entries to retain in the list; nil means no limit.")
  78
  79 (defun toggle-save-place (&optional parg)
  80   "Toggle whether to save your place in this file between sessions.
  81 If this mode is enabled, point is recorded when you kill the buffer
  82 or exit Emacs.  Visiting this file again will go to that position,
  83 even in a later Emacs session.
  84
  85 If called with a prefix arg, the mode is enabled if and only if
  86 the argument is positive.
  87
  88 To save places automatically in all files, put this in your `.emacs' file:
  89
  90 \(setq-default save-place t\)"
  91   (interactive "P")
  92   (if (not buffer-file-name)
  93       (message "Buffer `%s' not visiting a file" (buffer-name))
  94     (if (and save-place (or (not parg) (<= parg 0)))
  95         (progn
  96           (message "No place will be saved in this file")
  97           (setq save-place nil))
  98       (message "Place will be saved")
  99       (setq save-place t))))
 100
 101 (defun save-place-to-alist ()
 102   ;; put filename and point in a cons box and then cons that onto the
 103   ;; front of the save-place-alist, if save-place is non-nil.
 104   ;; Otherwise, just delete that file from the alist.
 105   ;; first check to make sure alist has been loaded in from the master
 106   ;; file.  If not, do so, then feel free to modify the alist.  It
 107   ;; will be saved again when Emacs is killed.
 108   (or save-place-loaded (load-save-place-alist-from-file))
 109   (if buffer-file-name
 110       (progn
 111         (let ((cell (assoc buffer-file-name save-place-alist)))
 112           (if cell
 113               (setq save-place-alist (delq cell save-place-alist))))
 114         (if save-place
 115             (setq save-place-alist
 116                   (cons (cons buffer-file-name
 117                               (if (not (eq major-mode 'hexl-mode))
 118                                   (point)
 119                                 (1+ (hexl-current-address))))
 120                         save-place-alist))))))
 121
 122 (defun save-place-alist-to-file ()
 123   (let ((file (expand-file-name save-place-file)))
 124     (save-excursion
 125       (message "Saving places to %s..." file)
 126       (set-buffer (get-buffer-create " *Saved Places*"))
 127       (delete-region (point-min) (point-max))
 128       (if (file-readable-p file)
 129           (insert-file-contents file))
 130       (delete-region (point-min) (point-max))
 131       (goto-char (point-min))
 132       (print save-place-alist (current-buffer))
 133       (let ((version-control
 134              (cond
 135               ((null save-place-version-control) nil)
 136               ((eq 'never save-place-version-control) 'never)
 137               ((eq 'nospecial save-place-version-control) version-control)
 138               (t
 139                t))))
 140         (write-file file)
 141         (kill-buffer (current-buffer))
 142         (message "Saving places to %s...done" file)))))
 143
 144 (defun load-save-place-alist-from-file ()
 145   (if (not save-place-loaded)
 146       (progn
 147         (setq save-place-loaded t)
 148         (let ((file (expand-file-name save-place-file)))
 149           ;; make sure that the alist does not get overwritten, and then
 150           ;; load it if it exists:
 151           (if (file-readable-p file)
 152               (save-excursion
 153                 (message "Loading places from %s..." save-place-file)
 154                 ;; don't want to use find-file because we have been
 155                 ;; adding hooks to it.
 156                 (set-buffer (get-buffer-create " *Saved Places*"))
 157                 (delete-region (point-min) (point-max))
 158                 (insert-file-contents file)
 159                 (goto-char (point-min))
 160                 (setq save-place-alist
 161                       (car (read-from-string
 162                             (buffer-substring (point-min) (point-max)))))
 163
 164                 ;; If there is a limit, and we're over it, then we'll
 165                 ;; have to truncate the end of the list:
 166                 (if save-place-limit
 167                     (if (<= save-place-limit 0)
 168                         ;; Zero gets special cased.  I'm not thrilled
 169                         ;; with this, but the loop for >= 1 is tight.
 170                         (setq save-place-alist nil)
 171                       ;; Else the limit is >= 1, so enforce it by
 172                       ;; counting and then `setcdr'ing.
 173                       (let ((s save-place-alist)
 174                             (count 1))
 175                         (while s
 176                           (if (>= count save-place-limit)
 177                               (setcdr s nil)
 178                             (setq count (1+ count)))
 179                           (setq s (cdr s))))))
 180
 181                 (kill-buffer (current-buffer))
 182                 (message "Loading places from %s...done" file)))
 183           nil))))
 184
 185 (defun save-places-to-alist ()
 186   ;; go through buffer-list, saving places to alist if save-place is
 187   ;; non-nil, deleting them from alist if it is nil.
 188   (let ((buf-list (buffer-list)))
 189     (while buf-list
 190       ;; put this into a save-excursion in case someone is counting on
 191       ;; another function in kill-emacs-hook to act on the last buffer
 192       ;; they were in:
 193       (save-excursion
 194         (set-buffer (car buf-list))
 195         ;; save-place checks buffer-file-name too, but we can avoid
 196         ;; overhead of function call by checking here too.
 197         (and buffer-file-name (save-place-to-alist))
 198         (setq buf-list (cdr buf-list))))))
 199
 200 (defun save-place-find-file-hook ()
 201   (or save-place-loaded (load-save-place-alist-from-file))
 202   (let ((cell (assoc buffer-file-name save-place-alist)))
 203     (if cell
 204         (progn
 205           (or after-find-file-from-revert-buffer
 206               (goto-char (cdr cell)))
 207           ;; and make sure it will be saved again for later
 208           (setq save-place t)))))
 209
 210 (defun save-place-kill-emacs-hook ()
 211   ;; First update the alist.  This loads the old save-place-file if nec.
 212   (save-places-to-alist)
 213   ;; Now save the alist in the file, if we have ever loaded the file
 214   ;; (including just now).
 215   (if save-place-loaded
 216       (save-place-alist-to-file)))
 217
 218 (add-hook 'find-file-hooks 'save-place-find-file-hook t)
 219
 220 (add-hook 'kill-emacs-hook 'save-place-kill-emacs-hook)
 221
 222 (add-hook 'kill-buffer-hook 'save-place-to-alist)
 223
 224 (provide 'saveplace) ; why not...
 225
 226 ;;; saveplace.el ends here
 227