lisp/saveplace.el

   1 ;;; saveplace.el --- automatically save place in files
   2
   3 ;; Copyright (C) 1993-1994, 2001-2011 Free Software Foundation, Inc.
   4
   5 ;; Author: Karl Fogel <kfogel@red-bean.com>
   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 3 of the License, or
  15 ;; (at your option) 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.  If not, see <http://www.gnu.org/licenses/>.
  24
  25 ;;; Commentary:
  26
  27 ;; Automatically save place in files, so that visiting them later
  28 ;; (even during a different Emacs session) automatically moves point
  29 ;; to the saved position, when the file is first found.  Uses the
  30 ;; value of buffer-local variable save-place to determine whether to
  31 ;; save position or not.
  32 ;;
  33 ;; Thanks to Stefan Schoef, who sent a patch with the
  34 ;; `save-place-version-control' stuff in it.
  35
  36 ;;; Code:
  37
  38 ;; this is what I was using during testing:
  39 ;; (define-key ctl-x-map "p" 'toggle-save-place-globally)
  40
  41 (defgroup save-place nil
  42   "Automatically save place in files."
  43   :group 'data)
  44
  45
  46 (defvar save-place-alist nil
  47   "Alist of saved places to go back to when revisiting files.
  48 Each element looks like (FILENAME . POSITION);
  49 visiting file FILENAME goes automatically to position POSITION
  50 rather than the beginning of the buffer.
  51 This alist is saved between Emacs sessions.")
  52
  53 (defcustom save-place nil
  54   "Non-nil means automatically save place in each file.
  55 This means when you visit a file, point goes to the last place
  56 where it was when you previously visited the same file.
  57 This variable is automatically buffer-local.
  58
  59 If you wish your place in any file to always be automatically saved,
  60 simply put this in your `~/.emacs' file:
  61
  62 \(setq-default save-place t)
  63 \(require 'saveplace)
  64
  65 or else use the Custom facility to set this option."
  66   :type 'boolean
  67   :require 'saveplace
  68   :group 'save-place)
  69
  70 (make-variable-buffer-local 'save-place)
  71
  72 (defcustom save-place-file (convert-standard-filename "~/.emacs-places")
  73   "Name of the file that records `save-place-alist' value."
  74   :type 'file
  75   :group 'save-place)
  76
  77 (defcustom save-place-version-control nil
  78   "Controls whether to make numbered backups of master save-place file.
  79 It can have four values: t, nil, `never', and `nospecial'.  The first
  80 three have the same meaning that they do for the variable
  81 `version-control', and the final value `nospecial' means just use the
  82 value of `version-control'."
  83   :type '(radio (const :tag "Unconditionally" t)
  84                 (const :tag "For VC Files" nil)
  85                 (const never)
  86                 (const :tag "Use value of `version-control'" nospecial))
  87   :group 'save-place)
  88
  89 (defvar save-place-loaded nil
  90   "Non-nil means that the `save-place-file' has been loaded.")
  91
  92 (defcustom save-place-limit nil
  93   "Maximum number of entries to retain in the list; nil means no limit."
  94   :type '(choice (integer :tag "Entries" :value 1)
  95                  (const :tag "No Limit" nil))
  96   :group 'save-place)
  97
  98 (defcustom save-place-forget-unreadable-files t
  99   "Non-nil means forget place in unreadable files.
 100
 101 The filenames in `save-place-alist' that do not match
 102 `save-place-skip-check-regexp' are filtered through
 103 `file-readable-p'. if nil, their alist entries are removed.
 104
 105 You may do this anytime by calling the complementary function,
 106 `save-place-forget-unreadable-files'.  When this option is turned on,
 107 this happens automatically before saving `save-place-alist' to
 108 `save-place-file'."
 109   :type 'boolean :group 'save-place)
 110
 111 (defcustom save-place-save-skipped t
 112   "If non-nil, remember files matching `save-place-skip-check-regexp'.
 113
 114 When filtering `save-place-alist' for unreadable files, some will not
 115 be checked, based on said regexp, and instead saved or forgotten based
 116 on this flag."
 117   :type 'boolean :group 'save-place)
 118
 119 (defcustom save-place-skip-check-regexp
 120   ;; thanks to ange-ftp-name-format
 121   "\\`/\\(?:cdrom\\|floppy\\|mnt\\|\\(?:[^@/:]*@\\)?[^@/:]*[^@/:.]:\\)"
 122   "Regexp whose file names shall not be checked for readability.
 123
 124 When forgetting unreadable files, file names matching this regular
 125 expression shall not be checked for readability, but instead be
 126 subject to `save-place-save-skipped'.
 127
 128 Files for which such a check may be inconvenient include those on
 129 removable and network volumes."
 130   :type 'regexp :group 'save-place)
 131
 132 (defun toggle-save-place (&optional parg)
 133   "Toggle whether to save your place in this file between sessions.
 134 If this mode is enabled, point is recorded when you kill the buffer
 135 or exit Emacs.  Visiting this file again will go to that position,
 136 even in a later Emacs session.
 137
 138 If called with a prefix arg, the mode is enabled if and only if
 139 the argument is positive.
 140
 141 To save places automatically in all files, put this in your `.emacs' file:
 142
 143 \(setq-default save-place t\)"
 144   (interactive "P")
 145   (if (not buffer-file-name)
 146       (message "Buffer `%s' not visiting a file" (buffer-name))
 147     (if (and save-place (or (not parg) (<= parg 0)))
 148         (progn
 149           (message "No place will be saved in this file")
 150           (setq save-place nil))
 151       (message "Place will be saved")
 152       (setq save-place t))))
 153
 154 (defun save-place-to-alist ()
 155   ;; put filename and point in a cons box and then cons that onto the
 156   ;; front of the save-place-alist, if save-place is non-nil.
 157   ;; Otherwise, just delete that file from the alist.
 158   ;; first check to make sure alist has been loaded in from the master
 159   ;; file.  If not, do so, then feel free to modify the alist.  It
 160   ;; will be saved again when Emacs is killed.
 161   (or save-place-loaded (load-save-place-alist-from-file))
 162   (if buffer-file-name
 163       (progn
 164         (let ((cell (assoc buffer-file-name save-place-alist))
 165               (position (if (not (eq major-mode 'hexl-mode))
 166                             (point)
 167                           (with-no-warnings
 168                             (1+ (hexl-current-address))))))
 169           (if cell
 170               (setq save-place-alist (delq cell save-place-alist)))
 171           (if (and save-place
 172                    (not (= position 1)))  ;; Optimize out the degenerate case.
 173               (setq save-place-alist
 174                     (cons (cons buffer-file-name position)
 175                           save-place-alist)))))))
 176
 177 (defun save-place-forget-unreadable-files ()
 178   "Remove unreadable files from `save-place-alist'.
 179 For each entry in the alist, if `file-readable-p' returns nil for the
 180 filename, remove the entry.  Save the new alist \(as the first pair
 181 may have changed\) back to `save-place-alist'."
 182   (interactive)
 183   ;; the following was adapted from an in-place filtering function,
 184   ;; `filter-mod', used in the original.
 185   (unless (null save-place-alist)       ;says it better than `when'
 186     ;; first, check all except first
 187     (let ((fmprev save-place-alist) (fmcur (cdr save-place-alist)))
 188       (while fmcur                      ;not null
 189         ;; a value is only saved when it becomes FMPREV.
 190         (if (if (string-match save-place-skip-check-regexp (caar fmcur))
 191                 save-place-save-skipped
 192               (file-readable-p (caar fmcur)))
 193             (setq fmprev fmcur)
 194           (setcdr fmprev (cdr fmcur)))
 195         (setq fmcur (cdr fmcur))))
 196     ;; test first pair, keep it if OK, otherwise 2nd element, which
 197     ;; may be '()
 198     (unless (if (string-match save-place-skip-check-regexp
 199                               (caar save-place-alist))
 200                 save-place-save-skipped
 201               (file-readable-p (caar save-place-alist)))
 202       (setq save-place-alist (cdr save-place-alist)))))
 203
 204 (defun save-place-alist-to-file ()
 205   (let ((file (expand-file-name save-place-file))
 206         (coding-system-for-write 'utf-8))
 207     (with-current-buffer (get-buffer-create " *Saved Places*")
 208       (delete-region (point-min) (point-max))
 209       (when save-place-forget-unreadable-files
 210         (save-place-forget-unreadable-files))
 211       (insert (format ";;; -*- coding: %s -*-\n"
 212                       (symbol-name coding-system-for-write)))
 213       (let ((print-length nil)
 214             (print-level nil))
 215         (pp (sort save-place-alist
 216                   (lambda (a b) (string< (car a) (car b))))
 217             (current-buffer)))
 218       (let ((version-control
 219              (cond
 220               ((null save-place-version-control) nil)
 221               ((eq 'never save-place-version-control) 'never)
 222               ((eq 'nospecial save-place-version-control) version-control)
 223               (t
 224                t))))
 225         (condition-case nil
 226             ;; Don't use write-file; we don't want this buffer to visit it.
 227             (write-region (point-min) (point-max) file)
 228           (file-error (message "Saving places: can't write %s" file)))
 229         (kill-buffer (current-buffer))))))
 230
 231 (defun load-save-place-alist-from-file ()
 232   (if (not save-place-loaded)
 233       (progn
 234         (setq save-place-loaded t)
 235         (let ((file (expand-file-name save-place-file)))
 236           ;; make sure that the alist does not get overwritten, and then
 237           ;; load it if it exists:
 238           (if (file-readable-p file)
 239               ;; don't want to use find-file because we have been
 240               ;; adding hooks to it.
 241               (with-current-buffer (get-buffer-create " *Saved Places*")
 242                 (delete-region (point-min) (point-max))
 243                 (insert-file-contents file)
 244                 (goto-char (point-min))
 245                 (setq save-place-alist
 246                       (car (read-from-string
 247                             (buffer-substring (point-min) (point-max)))))
 248
 249                 ;; If there is a limit, and we're over it, then we'll
 250                 ;; have to truncate the end of the list:
 251                 (if save-place-limit
 252                     (if (<= save-place-limit 0)
 253                         ;; Zero gets special cased.  I'm not thrilled
 254                         ;; with this, but the loop for >= 1 is tight.
 255                         (setq save-place-alist nil)
 256                       ;; Else the limit is >= 1, so enforce it by
 257                       ;; counting and then `setcdr'ing.
 258                       (let ((s save-place-alist)
 259                             (count 1))
 260                         (while s
 261                           (if (>= count save-place-limit)
 262                               (setcdr s nil)
 263                             (setq count (1+ count)))
 264                           (setq s (cdr s))))))
 265
 266                 (kill-buffer (current-buffer))))
 267           nil))))
 268
 269 (defun save-places-to-alist ()
 270   ;; go through buffer-list, saving places to alist if save-place is
 271   ;; non-nil, deleting them from alist if it is nil.
 272   (let ((buf-list (buffer-list)))
 273     (while buf-list
 274       ;; put this into a save-excursion in case someone is counting on
 275       ;; another function in kill-emacs-hook to act on the last buffer
 276       ;; they were in:
 277       (with-current-buffer (car buf-list)
 278         ;; save-place checks buffer-file-name too, but we can avoid
 279         ;; overhead of function call by checking here too.
 280         (and buffer-file-name (save-place-to-alist))
 281         (setq buf-list (cdr buf-list))))))
 282
 283 (defun save-place-find-file-hook ()
 284   (or save-place-loaded (load-save-place-alist-from-file))
 285   (let ((cell (assoc buffer-file-name save-place-alist)))
 286     (if cell
 287         (progn
 288           (or revert-buffer-in-progress-p
 289               (goto-char (cdr cell)))
 290           ;; and make sure it will be saved again for later
 291           (setq save-place t)))))
 292
 293 (defun save-place-kill-emacs-hook ()
 294   ;; First update the alist.  This loads the old save-place-file if nec.
 295   (save-places-to-alist)
 296   ;; Now save the alist in the file, if we have ever loaded the file
 297   ;; (including just now).
 298   (if save-place-loaded
 299       (save-place-alist-to-file)))
 300
 301 (add-hook 'find-file-hook 'save-place-find-file-hook t)
 302
 303 (unless noninteractive
 304   (add-hook 'kill-emacs-hook 'save-place-kill-emacs-hook))
 305
 306 (add-hook 'kill-buffer-hook 'save-place-to-alist)
 307
 308 (provide 'saveplace) ; why not...
 309
 310 ;;; saveplace.el ends here