lisp/view.el

   1 ;;; view.el --- peruse file or buffer without editing
   2
   3 ;; Copyright (C) 1985, 1989, 1994, 1995, 1997, 2000
   4 ;;   Free Software Foundation, Inc.
   5
   6 ;; Author: K. Shane Hartman
   7 ;; Maintainer: Inge Frick <inge@nada.kth.se>
   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 GNU Emacs; see the file COPYING.  If not, write to the
  23 ;; Free Software Foundation, Inc., 59 Temple Place - Suite 330,
  24 ;; Boston, MA 02111-1307, USA.
  25
  26 ;;; Commentary:
  27
  28 ;; This package provides the `view' minor mode documented in the Emacs
  29 ;; user's manual.
  30 ;; View mode entry and exit is done through the functions view-mode-enter
  31 ;; and view-mode-exit.  Use these functions to enter or exit view-mode from
  32 ;; emacs lisp programs.
  33 ;; We use both view- and View- as prefix for symbols.  View- is used as
  34 ;; prefix for commands that have a key binding.  view- is used for commands
  35 ;; without key binding.  The purpose of this is to make it easier for a
  36 ;; user to use command name completion.
  37
  38 ;;; Suggested key bindings:
  39 ;;
  40 ;; (define-key ctl-x-4-map "v" 'view-file-other-window)  ; ^x4v
  41 ;; (define-key ctl-x-5-map "v" 'view-file-other-frame)  ; ^x5v
  42 ;;
  43 ;; You could also bind view-file, view-buffer, view-buffer-other-window and
  44 ;; view-buffer-other-frame to keys.
  45
  46 ;;; Code:
  47
  48 (defgroup view nil
  49   "Peruse file or buffer without editing."
  50   :link '(function-link view-mode)
  51   :link '(custom-manual "(emacs)Misc File Ops")
  52   :group 'wp
  53   :group 'editing)
  54
  55 (defcustom view-read-only nil
  56   "*Non-nil means buffers visiting files read-only, do it in view mode."
  57   :type 'boolean
  58   :group 'view)
  59
  60 (defcustom view-highlight-face 'highlight
  61    "*The face used for highlighting the match found by View mode search."
  62    :type 'face
  63    :group 'view)
  64
  65 ;; `view-mode-auto-exit' is replaced by the following option variable which
  66 ;; only says if scrolling past buffer end should leave view mode or not, it
  67 ;; doesn't say if leaving view mode should restore windows or not.  The latter
  68 ;; is now controlled by the presence of a value in `view-return-to-alist'.
  69 (defcustom view-scroll-auto-exit nil
  70   "*Non-nil means scrolling past the end of buffer exits View mode.
  71 nil means attempting to scroll past the end of the buffer,
  72 only rings the bell and gives a message on how to leave."
  73   :type 'boolean
  74   :group 'view)
  75
  76 (defcustom view-try-extend-at-buffer-end nil
  77  "*Non-nil means try load more of file when reaching end of buffer.
  78 This variable is mainly intended to be temporarily set to non-nil by
  79 the F command in view-mode, but you can set it to t if you want the action
  80 for all scroll commands in view mode."
  81   :type 'boolean
  82   :group 'view)
  83
  84 (defcustom view-remove-frame-by-deleting nil
  85   "*Determine how View mode removes a frame no longer needed.
  86 If nil, make an icon of the frame.  If non-nil, delete the frame."
  87   :type 'boolean
  88   :group 'view)
  89
  90 (defcustom view-exits-all-viewing-windows nil
  91   "*Non-nil means restore all windows used to view buffer.
  92 Commands that restore windows when finished viewing a buffer, apply to all
  93 windows that display the buffer and have restore information in
  94 `view-return-to-alist'.
  95 If `view-exits-all-viewing-windows' is nil, only the selected window is
  96 considered for restoring."
  97   :type 'boolean
  98   :group 'view)
  99
 100 ;;;###autoload
 101 (defvar view-mode nil
 102   "Non-nil if View mode is enabled.
 103 Don't change this variable directly, you must change it by one of the
 104 functions that enable or disable view mode.")
 105 ;;;###autoload
 106 (make-variable-buffer-local 'view-mode)
 107
 108 (defcustom view-mode-hook nil
 109   "Normal hook run when starting to view a buffer or file."
 110   :type 'hook
 111   :group 'view)
 112
 113 (defvar view-old-buffer-read-only nil)
 114 (make-variable-buffer-local 'view-old-buffer-read-only)
 115
 116 (defvar view-old-Helper-return-blurb)
 117 (make-variable-buffer-local 'view-old-Helper-return-blurb)
 118
 119 (defvar view-page-size nil
 120   "Default number of lines to scroll by View page commands.
 121 If nil then the local value of this is initially set to window size.")
 122 (make-variable-buffer-local 'view-page-size)
 123
 124 (defvar view-half-page-size nil
 125   "Default number of lines to scroll by View half page commands.
 126 If nil then the local value of this is initially set to half window size.")
 127 (make-variable-buffer-local 'view-half-page-size)
 128
 129 (defvar view-last-regexp nil)
 130 (make-variable-buffer-local 'view-last-regexp) ; Global is better???
 131
 132 (defvar view-return-to-alist nil
 133   "What to do with used windows and where to go when finished viewing buffer.
 134 This is local in each buffer being viewed.
 135 It is added to by `view-mode-enter' when starting to view a buffer and
 136 subtracted from by `view-mode-exit' when finished viewing the buffer.
 137
 138 See RETURN-TO-ALIST argument of function `view-mode-exit' for the format of
 139 `view-return-to-alist'.")
 140 (make-variable-buffer-local 'view-return-to-alist)
 141
 142 (defvar view-exit-action nil
 143   "nil or a function with one argument (a buffer) called when finished viewing.
 144 This is local in each buffer being viewed.
 145 The \\[view-file] and \\[view-file-other-window] commands may set this to
 146 `kill-buffer'.")
 147 (make-variable-buffer-local 'view-exit-action)
 148
 149 (defvar view-no-disable-on-exit nil
 150   "If non-nil, View mode \"exit\" commands don't actually disable View mode.
 151 Instead, these commands just switch buffers or windows.
 152 This is set in certain buffers by specialized features such as help commands
 153 that use View mode automatically.")
 154
 155 (defvar view-overlay nil
 156   "Overlay used to display where a search operation found its match.
 157 This is local in each buffer, once it is used.")
 158 (make-variable-buffer-local 'view-overlay)
 159
 160 (or (assq 'view-mode minor-mode-alist)
 161     (setq minor-mode-alist
 162           (cons (list 'view-mode
 163                       (propertize " View"
 164                                   'help-echo "mouse-2: exit View mode"
 165                                   'local-map (make-mode-line-mouse2-map
 166                                               #'view-mode)))
 167                 minor-mode-alist)))
 168
 169 ;; Define keymap inside defvar to make it easier to load changes.
 170 ;; Some redundant "less"-like key bindings below have been commented out.
 171 (defvar view-mode-map
 172   (let ((map (make-sparse-keymap)))
 173     (define-key map "C" 'View-kill-and-leave)
 174     (define-key map "c" 'View-leave)
 175     (define-key map "Q" 'View-quit-all)
 176     (define-key map "E" 'View-exit-and-edit)
 177 ;    (define-key map "v" 'View-exit)
 178     (define-key map "e" 'View-exit)
 179     (define-key map "q" 'View-quit)
 180 ;    (define-key map "N" 'View-search-last-regexp-backward)
 181     (define-key map "p" 'View-search-last-regexp-backward)
 182     (define-key map "n" 'View-search-last-regexp-forward)
 183 ;    (define-key map "?" 'View-search-regexp-backward) ; Less does this.
 184     (define-key map "\\" 'View-search-regexp-backward)
 185     (define-key map "/" 'View-search-regexp-forward)
 186     (define-key map "r" 'isearch-backward)
 187     (define-key map "s" 'isearch-forward)
 188     (define-key map "m" 'point-to-register)
 189     (define-key map "'" 'register-to-point)
 190     (define-key map "x" 'exchange-point-and-mark)
 191     (define-key map "@" 'View-back-to-mark)
 192     (define-key map "." 'set-mark-command)
 193     (define-key map "%" 'View-goto-percent)
 194 ;    (define-key map "G" 'View-goto-line-last)
 195     (define-key map "g" 'View-goto-line)
 196     (define-key map "=" 'what-line)
 197     (define-key map "F" 'View-revert-buffer-scroll-page-forward)
 198 ;    (define-key map "k" 'View-scroll-line-backward)
 199     (define-key map "y" 'View-scroll-line-backward)
 200 ;    (define-key map "j" 'View-scroll-line-forward)
 201     (define-key map "\n" 'View-scroll-line-forward)
 202     (define-key map "\r" 'View-scroll-line-forward)
 203     (define-key map "u" 'View-scroll-half-page-backward)
 204     (define-key map "d" 'View-scroll-half-page-forward)
 205     (define-key map "z" 'View-scroll-page-forward-set-page-size)
 206     (define-key map "w" 'View-scroll-page-backward-set-page-size)
 207 ;    (define-key map "b" 'View-scroll-page-backward)
 208     (define-key map "\C-?" 'View-scroll-page-backward)
 209 ;    (define-key map "f" 'View-scroll-page-forward)
 210     (define-key map " " 'View-scroll-page-forward)
 211     (define-key map "o" 'View-scroll-to-buffer-end)
 212     (define-key map ">" 'end-of-buffer)
 213     (define-key map "<" 'beginning-of-buffer)
 214     (define-key map "-" 'negative-argument)
 215     (define-key map "9" 'digit-argument)
 216     (define-key map "8" 'digit-argument)
 217     (define-key map "7" 'digit-argument)
 218     (define-key map "6" 'digit-argument)
 219     (define-key map "5" 'digit-argument)
 220     (define-key map "4" 'digit-argument)
 221     (define-key map "3" 'digit-argument)
 222     (define-key map "2" 'digit-argument)
 223     (define-key map "1" 'digit-argument)
 224     (define-key map "0" 'digit-argument)
 225     (define-key map "H" 'describe-mode)
 226     (define-key map "?" 'describe-mode) ; Maybe do as less instead? See above.
 227     (define-key map "h" 'describe-mode)
 228     map))
 229
 230 (or (assq 'view-mode minor-mode-map-alist)
 231     (setq minor-mode-map-alist
 232           (cons (cons 'view-mode view-mode-map) minor-mode-map-alist)))
 233
 234 ;;; Commands that enter or exit view mode.
 235
 236 ;;;###autoload
 237 (defun view-file (file)
 238   "View FILE in View mode, returning to previous buffer when done.
 239 Emacs commands editing the buffer contents are not available; instead,
 240 a special set of commands (mostly letters and punctuation)
 241 are defined for moving around in the buffer.
 242 Space scrolls forward, Delete scrolls backward.
 243 For list of all View commands, type H or h while viewing.
 244
 245 This command runs the normal hook `view-mode-hook'."
 246   (interactive "fView file: ")
 247   (let ((had-a-buf (get-file-buffer file)))
 248     (view-buffer (find-file-noselect file)
 249                  (and (not had-a-buf) 'kill-buffer))))
 250
 251 ;;;###autoload
 252 (defun view-file-other-window (file)
 253   "View FILE in View mode in another window.
 254 Return that window to its previous buffer when done.
 255 Emacs commands editing the buffer contents are not available; instead,
 256 a special set of commands (mostly letters and punctuation)
 257 are defined for moving around in the buffer.
 258 Space scrolls forward, Delete scrolls backward.
 259 For list of all View commands, type H or h while viewing.
 260
 261 This command runs the normal hook `view-mode-hook'."
 262   (interactive "fIn other window view file: ")
 263   (let ((had-a-buf (get-file-buffer file)))
 264     (view-buffer-other-window (find-file-noselect file) nil
 265                               (and (not had-a-buf) 'kill-buffer))))
 266
 267 ;;;###autoload
 268 (defun view-file-other-frame (file)
 269   "View FILE in View mode in another frame.
 270 Maybe delete other frame and/or return to previous buffer when done.
 271 Emacs commands editing the buffer contents are not available; instead,
 272 a special set of commands (mostly letters and punctuation)
 273 are defined for moving around in the buffer.
 274 Space scrolls forward, Delete scrolls backward.
 275 For list of all View commands, type H or h while viewing.
 276
 277 This command runs the normal hook `view-mode-hook'."
 278   (interactive "fIn other frame view file: ")
 279   (let ((had-a-buf (get-file-buffer file)))
 280     (view-buffer-other-frame (find-file-noselect file) nil
 281                              (and (not had-a-buf) 'kill-buffer))))
 282
 283
 284 ;;;###autoload
 285 (defun view-buffer (buffer &optional exit-action)
 286   "View BUFFER in View mode, returning to previous buffer when done.
 287 Emacs commands editing the buffer contents are not available; instead,
 288 a special set of commands (mostly letters and punctuation)
 289 are defined for moving around in the buffer.
 290 Space scrolls forward, Delete scrolls backward.
 291 For list of all View commands, type H or h while viewing.
 292
 293 This command runs the normal hook `view-mode-hook'.
 294
 295 Optional argument EXIT-ACTION is either nil or a function with buffer as
 296 argument.  This function is called when finished viewing buffer.
 297 Use this argument instead of explicitly setting `view-exit-action'."
 298
 299   (interactive "bView buffer: ")
 300   (let ((undo-window (list (window-buffer) (window-start) (window-point))))
 301     (switch-to-buffer buffer)
 302     (view-mode-enter (cons (selected-window) (cons nil undo-window))
 303                      exit-action)))
 304
 305 ;;;###autoload
 306 (defun view-buffer-other-window (buffer &optional not-return exit-action)
 307   "View BUFFER in View mode in another window.
 308 Return to previous buffer when done, unless optional NOT-RETURN is non-nil.
 309 Emacs commands editing the buffer contents are not available; instead,
 310 a special set of commands (mostly letters and punctuation)
 311 are defined for moving around in the buffer.
 312 Space scrolls forward, Delete scrolls backward.
 313 For list of all View commands, type H or h while viewing.
 314
 315 This command runs the normal hook `view-mode-hook'.
 316
 317 Optional argument EXIT-ACTION is either nil or a function with buffer as
 318 argument.  This function is called when finished viewing buffer.
 319 Use this argument instead of explicitly setting `view-exit-action'."
 320   (interactive "bIn other window view buffer:\nP")
 321   (let* ((win                           ; This window will be selected by
 322           (get-lru-window))             ; switch-to-buffer-other-window below.
 323          (return-to
 324           (and (not not-return)
 325                (cons (selected-window)
 326                      (if (eq win (selected-window))
 327                          t                      ; Has to make new window.
 328                        (list
 329                         (window-buffer win)     ; Other windows old buffer.
 330                         (window-start win)
 331                         (window-point win)))))))
 332     (switch-to-buffer-other-window buffer)
 333     (view-mode-enter (and return-to (cons (selected-window) return-to))
 334                      exit-action)))
 335
 336 ;;;###autoload
 337 (defun view-buffer-other-frame (buffer &optional not-return exit-action)
 338   "View BUFFER in View mode in another frame.
 339 Return to previous buffer when done, unless optional NOT-RETURN is non-nil.
 340 Emacs commands editing the buffer contents are not available; instead,
 341 a special set of commands (mostly letters and punctuation)
 342 are defined for moving around in the buffer.
 343 Space scrolls forward, Delete scrolls backward.
 344 For list of all View commands, type H or h while viewing.
 345
 346 This command runs the normal hook `view-mode-hook'.
 347
 348 Optional argument EXIT-ACTION is either nil or a function with buffer as
 349 argument.  This function is called when finished viewing buffer.
 350 Use this argument instead of explicitly setting `view-exit-action'."
 351   (interactive "bView buffer in other frame: \nP")
 352   (let ((return-to
 353          (and (not not-return) (cons (selected-window) t)))) ; Old window.
 354     (switch-to-buffer-other-frame buffer)
 355     (view-mode-enter (and return-to (cons (selected-window) return-to))
 356                      exit-action)))
 357
 358 ;;;###autoload
 359 (defun view-mode (&optional arg)
 360   ;; In the following documentation string we have to use some explicit key
 361   ;; bindings instead of using the \\[] construction.  The reason for this
 362   ;; is that most commands have more than one key binding.
 363   "Toggle View mode, a minor mode for viewing text but not editing it.
 364 With ARG, turn View mode on iff ARG is positive.
 365
 366 Emacs commands that do not change the buffer contents are available as usual.
 367 Kill commands insert text in kill buffers but do not delete.  Other commands
 368 \(among them most letters and punctuation) beep and tell that the buffer is
 369 read-only.
 370 \\<view-mode-map>
 371 The following additional commands are provided.  Most commands take prefix
 372 arguments.  Page commands default to \"page size\" lines which is almost a whole
 373 window full, or number of lines set by \\[View-scroll-page-forward-set-page-size] or \\[View-scroll-page-backward-set-page-size].  Half page commands default to
 374 and set \"half page size\" lines which initially is half a window full.  Search
 375 commands default to a repeat count of one.
 376
 377 H, h, ?  This message.
 378 Digits  provide prefix arguments.
 379 \\[negative-argument]   negative prefix argument.
 380 \\[beginning-of-buffer] move to the beginning of buffer.
 381 >       move to the end of buffer.
 382 \\[View-scroll-to-buffer-end]   scroll so that buffer end is at last line of window.
 383 SPC     scroll forward \"page size\" lines.
 384           With prefix scroll forward prefix lines.
 385 DEL     scroll backward \"page size\" lines.
 386           With prefix scroll backward prefix lines.
 387 \\[View-scroll-page-forward-set-page-size]      like  \\[View-scroll-page-forward]  but with prefix sets \"page size\" to prefix.
 388 \\[View-scroll-page-backward-set-page-size]     like  \\[View-scroll-page-backward]  but with prefix sets \"page size\" to prefix.
 389 \\[View-scroll-half-page-forward]       scroll forward \"half page size\" lines.  With prefix, sets
 390           \"half page size\" to prefix lines and scrolls forward that much.
 391 \\[View-scroll-half-page-backward]      scroll backward \"half page size\" lines.  With prefix, sets
 392           \"half page size\" to prefix lines and scrolls backward that much.
 393 RET, LFD  scroll forward one line.  With prefix scroll forward prefix line(s).
 394 y       scroll backward one line.  With prefix scroll backward prefix line(s).
 395 \\[View-revert-buffer-scroll-page-forward]      revert-buffer if necessary and scroll forward.
 396           Use this to view a changing file.
 397 \\[what-line]   prints the current line number.
 398 \\[View-goto-percent]   goes prefix argument (default 100) percent into buffer.
 399 \\[View-goto-line]      goes to line given by prefix argument (default first line).
 400 .       set the mark.
 401 x       exchanges point and mark.
 402 \\[View-back-to-mark]   return to mark and pops mark ring.
 403           Mark ring is pushed at start of every successful search and when
 404           jump to line occurs.  The mark is set on jump to buffer start or end.
 405 \\[point-to-register]   save current position in character register.
 406 '       go to position saved in character register.
 407 s       do forward incremental search.
 408 r       do reverse incremental search.
 409 \\[View-search-regexp-forward]  searches forward for regular expression, starting after current page.
 410           ! and @ have a special meaning at the beginning of the regexp.
 411           ! means search for a line with no match for regexp.  @ means start
 412           search at beginning (end for backward search) of buffer.
 413 \\      searches backward for regular expression, starting before current page.
 414 \\[View-search-last-regexp-forward]     searches forward for last regular expression.
 415 p       searches backward for last regular expression.
 416 \\[View-quit]   quit View mode, trying to restore window and buffer to previous state.
 417           \\[View-quit] is the normal way to leave view mode.
 418 \\[View-exit]   exit View mode but stay in current buffer.  Use this if you started
 419           viewing a buffer (file) and find out you want to edit it.
 420 \\[View-exit-and-edit]  exit View mode and make the current buffer editable.
 421 \\[View-quit-all]       quit View mode, trying to restore windows and buffer to previous state.
 422 \\[View-leave]  quit View mode and maybe switch buffers, but don't kill this buffer.
 423 \\[View-kill-and-leave] quit View mode, kill current buffer and go back to other buffer.
 424
 425 The effect of \\[View-leave] , \\[View-quit] and \\[View-kill-and-leave] depends on how view-mode was entered.  If it was
 426 entered by view-file, view-file-other-window or view-file-other-frame
 427 \(\\[view-file], \\[view-file-other-window], \\[view-file-other-frame] or the dired mode v command), then \\[View-quit] will
 428 try to kill the current buffer.  If view-mode was entered from another buffer
 429 as is done by View-buffer, View-buffer-other-window, View-buffer-other frame,
 430 View-file, View-file-other-window or View-file-other-frame then \\[View-leave] , \\[View-quit] and \\[View-kill-and-leave]
 431 will return to that buffer.
 432
 433 Entry to view-mode runs the normal hook `view-mode-hook'."
 434   (interactive "P")
 435   (unless (and arg                      ; Do nothing if already OK.
 436                (if (> (prefix-numeric-value arg) 0) view-mode (not view-mode)))
 437     (if view-mode (view-mode-disable)
 438       (view-mode-enable))))
 439
 440 (defun view-mode-enable ()
 441   "Turn on View mode."
 442   ;; Always leave view mode before changing major mode.
 443   ;; This is to guarantee that the buffer-read-only variable is restored.
 444   (make-local-hook 'change-major-mode-hook)
 445   (add-hook 'change-major-mode-hook 'view-mode-disable nil t)
 446   (setq view-mode t
 447         view-page-size (view-page-size-default view-page-size)
 448         view-half-page-size (or view-half-page-size (/ (view-window-size) 2))
 449         view-old-buffer-read-only buffer-read-only
 450         buffer-read-only t
 451         view-old-Helper-return-blurb (and (boundp 'Helper-return-blurb)
 452                                           Helper-return-blurb)
 453         Helper-return-blurb
 454         (format "continue viewing %s"
 455                 (if (buffer-file-name)
 456                     (file-name-nondirectory (buffer-file-name))
 457                   (buffer-name))))
 458   (force-mode-line-update)
 459   (run-hooks 'view-mode-hook))
 460
 461 (defun view-mode-disable ()
 462   "Turn off View mode."
 463   (remove-hook 'change-major-mode-hook 'view-mode-disable t)
 464   (and view-overlay (delete-overlay view-overlay))
 465   (force-mode-line-update)
 466   ;; Calling toggle-read-only while View mode is enabled
 467   ;; sets view-read-only to t as a buffer-local variable
 468   ;; after exiting View mode.  That arranges that the next toggle-read-only
 469   ;; will reenable View mode.
 470   ;; Cancelling View mode in any other way should cancel that, too,
 471   ;; so that View mode stays off if toggle-read-only is called.
 472   (if (local-variable-p 'view-read-only)
 473       (kill-local-variable 'view-read-only))
 474   (setq view-mode nil
 475         Helper-return-blurb view-old-Helper-return-blurb)
 476   (if buffer-read-only
 477       (setq buffer-read-only view-old-buffer-read-only)))
 478
 479 ;;;###autoload
 480 (defun view-mode-enter (&optional return-to exit-action) "\
 481 Enter View mode and set up exit from view mode depending on optional arguments.
 482 If RETURN-TO is non-nil it is added as an element to the buffer local alist
 483 `view-return-to-alist'.
 484 Save EXIT-ACTION in buffer local variable `view-exit-action'.
 485 It should be either nil or a function that takes a buffer as argument.
 486 This function will be called by `view-mode-exit'.
 487
 488 RETURN-TO is either nil, meaning do nothing when exiting view mode, or
 489 it has the format (WINDOW OLD-WINDOW . OLD-BUF-INFO).
 490 WINDOW is a window used for viewing.
 491 OLD-WINDOW is nil or the window to select after viewing.
 492 OLD-BUF-INFO tells what to do with WINDOW when exiting.  It is one of:
 493 1) nil       Do nothing.
 494 2) t         Delete WINDOW or, if it is the only window, its frame.
 495 3) (OLD-BUFF START POINT)  Display buffer OLD-BUFF with displayed text
 496                            starting at START and point at POINT in WINDOW.
 497 4) quit-window   Do `quit-window' in WINDOW.
 498
 499 For list of all View commands, type H or h while viewing.
 500
 501 This function runs the normal hook `view-mode-hook'."
 502   (if return-to
 503       (let ((entry (assq (car return-to) view-return-to-alist)))
 504         (if entry (setcdr entry (cdr return-to))
 505           (setq view-return-to-alist (cons return-to view-return-to-alist)))))
 506   (if exit-action (setq view-exit-action exit-action))
 507   (unless view-mode                     ; Do nothing if already in view mode.
 508     (view-mode-enable)
 509     (force-mode-line-update)
 510     (message "%s"
 511              (substitute-command-keys "\
 512 Type \\[help-command] for help, \\[describe-mode] for commands, \\[View-quit] to quit."))))
 513
 514 (defun view-mode-exit (&optional return-to-alist exit-action all-win)
 515   "Exit View mode in various ways, depending on optional arguments.
 516 RETURN-TO-ALIST, EXIT-ACTION and ALL-WIN determine what to do after exit.
 517 EXIT-ACTION is nil or a function that is called with current buffer as
 518 argument.
 519 RETURN-TO-ALIST is an alist that for some of the windows displaying the
 520 current buffer, associate information on what to do with those windows.
 521 If ALL-WIN or the variable `view-exits-all-viewing-windows' is non-nil,
 522 then all windows on RETURN-TO-ALIST are restored to their old state.
 523 Otherwise only the selected window is affected (if it is on RETURN-TO-ALIST).
 524
 525 Elements of RETURN-TO-ALIST have the format (WINDOW OLD-WINDOW . OLD-BUF-INFO).
 526 WINDOW is a window displaying the current buffer.
 527 OLD-WINDOW is nil or a window to select after viewing.
 528 OLD-BUF-INFO is information on what to do with WINDOW and is one of:
 529 1) nil       Do nothing.
 530 2) t         Delete WINDOW and, if it is the only window, its frame.
 531 3) (OLD-BUF START POINT)  Display buffer OLD-BUF with displayed text
 532                           starting at START and point at POINT in WINDOW.
 533 4) quit-window   Do `quit-window' in WINDOW.
 534
 535 If one of the WINDOW in RETURN-TO-ALIST is the selected window and the
 536 corresponding OLD-WINDOW is a live window, then select OLD-WINDOW."
 537   (setq all-win
 538         (and return-to-alist (or all-win view-exits-all-viewing-windows)))
 539   (if view-mode         ; Only do something if in view mode.
 540       (let* ((buffer (current-buffer))
 541              window notlost
 542              (sel-old (assq (selected-window) return-to-alist))
 543              (alist (cond
 544                      (all-win           ; Try to restore all windows.
 545                       (append return-to-alist nil)) ; Copy.
 546                      (sel-old           ; Only selected window.
 547                       (list sel-old))))
 548              (old-window (if sel-old (car (cdr sel-old)))))
 549         (if all-win                     ; Follow chains of old-windows.
 550             (let ((c (length alist)) a)
 551               (while (and (> c 0)       ; Safety if mutually refering windows.
 552                           (or (not (window-live-p old-window))
 553                               (eq buffer (window-buffer old-window)))
 554                           (setq a (assq old-window alist)))
 555                 (setq c (1- c))
 556                 (setq old-window (car (cdr a))))
 557               (if (or (zerop c) (not (window-live-p old-window)))
 558                   (setq old-window (selected-window)))))
 559         (or view-no-disable-on-exit
 560             (view-mode-disable))
 561         (while alist                    ; Restore windows with info.
 562           (setq notlost nil)
 563           (if (and (window-live-p (setq window (car (car alist))))
 564                    (eq buffer (window-buffer window)))
 565               (let ((frame (window-frame window))
 566                     (old-buf-info (cdr (cdr (car alist)))))
 567                 (if all-win (select-window window))
 568                 (cond
 569                  ((and (consp old-buf-info) ; Case 3.
 570                        (buffer-live-p (car old-buf-info)))
 571                   (set-window-buffer window (car old-buf-info)) ; old-buf
 572                   (set-window-start window (car (cdr old-buf-info)))
 573                   (set-window-point window (car (cdr (cdr old-buf-info)))))
 574                  ((eq old-buf-info 'quit-window)
 575                   (quit-window))        ; Case 4.
 576                  ((not (eq old-buf-info t)) nil) ; Not case 2, do nothing.
 577                  ((not (one-window-p t)) (delete-window))
 578                  ((not (eq frame (next-frame)))
 579                   ;; Not the only frame, so can safely be removed.
 580                   (if view-remove-frame-by-deleting
 581                       (delete-frame frame)
 582                     (setq notlost t)    ; Keep the window. See below.
 583                     (iconify-frame frame))))))
 584           ;; If a frame is removed by iconifying it, then the window is not
 585           ;; really lost.  In this case we keep the entry in
 586           ;; view-return-to-alist so that if the user deiconifies the frame
 587           ;; and then press q, then the frame is iconified again.
 588           (unless notlost
 589             (setq view-return-to-alist
 590                   (delete (car alist) view-return-to-alist)))
 591           (setq alist (cdr alist)))
 592         (if (window-live-p old-window)  ; still existing window
 593             (select-window old-window))
 594         (when exit-action
 595           (setq view-exit-action nil)
 596           (funcall exit-action buffer))
 597         (force-mode-line-update))))
 598
 599 (defun View-exit ()
 600   "Exit View mode but stay in current buffer."
 601   (interactive)
 602   (view-mode-exit))
 603
 604 ;;;###autoload
 605 (defun View-exit-and-edit ()
 606   "Exit View mode and make the current buffer editable."
 607   (interactive)
 608   (let ((view-old-buffer-read-only nil)
 609         (view-no-disable-on-exit nil))
 610     (view-mode-exit)))
 611
 612 (defun View-leave ()
 613   "Quit View mode and maybe switch buffers, but don't kill this buffer."
 614   (interactive)
 615   (view-mode-exit view-return-to-alist))
 616
 617 (defun View-quit ()
 618   "Quit View mode, trying to restore window and buffer to previous state.
 619 Maybe kill this buffer.  Try to restore selected window to previous state
 620 and go to previous buffer or window."
 621   (interactive)
 622   (view-mode-exit view-return-to-alist view-exit-action))
 623
 624 (defun View-quit-all ()
 625   "Quit View mode, trying to restore windows and buffers to previous state.
 626 Maybe kill current buffer.  Try to restore all windows viewing buffer to
 627 previous state and go to previous buffer or window."
 628   (interactive)
 629   (view-mode-exit view-return-to-alist view-exit-action t))
 630
 631 (defun View-kill-and-leave ()
 632   "Quit View mode, kill current buffer and return to previous buffer."
 633   (interactive)
 634   (view-mode-exit view-return-to-alist (or view-exit-action 'kill-buffer) t))
 635
 636
 637 ;;; Some help routines.
 638
 639 (defun view-window-size ()
 640   ;; Window height excluding mode line.
 641   (1- (window-height)))
 642
 643 ;(defun view-last-command (&optional who what)
 644 ;  (setq view-last-command-entry this-command)
 645 ;  (setq view-last-command who)
 646 ;  (setq view-last-command-argument what))
 647
 648 ;(defun View-repeat-last-command ()
 649 ;  "Repeat last command issued in View mode."
 650 ;  (interactive)
 651 ;  (if (and view-last-command
 652 ;          (eq view-last-command-entry last-command))
 653 ;      (funcall view-last-command view-last-command-argument))
 654 ;  (setq this-command view-last-command-entry))
 655
 656 (defun view-recenter ()
 657   ;; Center point in window.
 658   (recenter (/ (view-window-size) 2)))
 659
 660 (defun view-page-size-default (lines)
 661   ;; Get page size.
 662   (let ((default (- (view-window-size) next-screen-context-lines)))
 663     (if (or (null lines) (zerop (setq lines (prefix-numeric-value lines))))
 664         default
 665       (min (abs lines) default))))
 666
 667 (defun view-set-half-page-size-default (lines)
 668   ;; Get and maybe set half page size.
 669   (if (not lines) view-half-page-size
 670     (setq view-half-page-size
 671           (if (zerop (setq lines (prefix-numeric-value lines)))
 672               (/ (view-window-size) 2)
 673             (view-page-size-default lines)))))
 674
 675
 676 ;;; Commands for moving around in the buffer.
 677
 678 (defun View-goto-percent (&optional percent)
 679   "Move to end (or prefix PERCENT) of buffer in View mode.
 680 Display is centered at point.
 681 Also set the mark at the position where point was."
 682   (interactive "P")
 683   (push-mark)
 684   (goto-char
 685    (if percent
 686        (+ (point-min)
 687           (floor (* (- (point-max) (point-min)) 0.01
 688                     (max 0 (min 100 (prefix-numeric-value percent))))))
 689      (point-max)))
 690   (view-recenter))
 691
 692 ;(defun View-goto-line-last (&optional line)
 693 ;"Move to last (or prefix LINE) line in View mode.
 694 ;Display is centered at LINE.
 695 ;Sets mark at starting position and pushes mark ring."
 696 ;  (interactive "P")
 697 ;  (push-mark)
 698 ;  (if line (goto-line (prefix-numeric-value line))
 699 ;    (goto-char (point-max))
 700 ;    (beginning-of-line))
 701 ;  (view-recenter))
 702
 703 (defun View-goto-line (&optional line)
 704   "Move to first (or prefix LINE) line in View mode.
 705 Display is centered at LINE.
 706 Also set the mark at the position where point was."
 707   (interactive "p")
 708   (push-mark)
 709   (goto-line line)
 710   (view-recenter))
 711
 712 (defun View-scroll-to-buffer-end ()
 713   "Scroll backward or forward so that buffer end is at last line of window."
 714   (interactive)
 715   (let ((p (if (pos-visible-in-window-p (point-max)) (point))))
 716     (goto-char (point-max))
 717     (recenter -1)
 718     (and p (goto-char p))))
 719
 720 (defun view-scroll-lines (lines backward default maxdefault)
 721   ;; This function does the job for all the scrolling commands.
 722   ;; Scroll forward LINES lines.  If BACKWARD is true scroll backwards.
 723   ;; If LINES is negative scroll in the other direction.  If LINES is 0 or nil,
 724   ;; scroll DEFAULT lines.  If MAXDEFAULT is true then scroll no more than a
 725   ;; window full.
 726   (if (or (null lines) (zerop (setq lines (prefix-numeric-value lines))))
 727       (setq lines default))
 728   (when (< lines 0)
 729     (setq backward (not backward)) (setq lines (- lines)))
 730   (setq default (view-page-size-default nil)) ; Max scrolled at a time.
 731   (if maxdefault (setq lines (min lines default)))
 732   (cond
 733    (backward (scroll-down lines))
 734    ((view-really-at-end)
 735     (if view-scroll-auto-exit (View-quit)
 736       (ding)
 737       (view-end-message)))
 738    (t (while (> lines default)
 739         (scroll-up default)
 740         (setq lines (- lines default))
 741         (if (view-really-at-end) (setq lines 0)))
 742       (scroll-up lines)
 743       (if (view-really-at-end) (view-end-message))
 744       (move-to-window-line -1)
 745       (beginning-of-line))))
 746
 747 (defun view-really-at-end ()
 748   ;; Return true if buffer end visible.  Maybe revert buffer and test.
 749   (and (pos-visible-in-window-p (point-max))
 750        (let ((buf (current-buffer))
 751              (bufname (buffer-name))
 752              (file (buffer-file-name)))
 753          (or (not view-try-extend-at-buffer-end)
 754              (null file)
 755              (verify-visited-file-modtime buf)
 756              (not (file-exists-p file))
 757              (when (buffer-modified-p buf)
 758                (setq file (file-name-nondirectory file))
 759                (not (yes-or-no-p
 760                      (format
 761                       "File %s changed on disk.  Discard your edits%s? "
 762                       file
 763                       (if (string= bufname file) ""
 764                         (concat " in " bufname))))))
 765              (progn
 766                (revert-buffer t t t)
 767                (pos-visible-in-window-p (point-max)))))))
 768
 769 (defun view-end-message ()
 770   ;; Tell that we are at end of buffer.
 771   (goto-char (point-max))
 772   (if view-return-to-alist
 773       (message "End of buffer.  Type %s to quit viewing."
 774                (substitute-command-keys
 775                 (if view-scroll-auto-exit "\\[View-scroll-page-forward]"
 776                   "\\[View-quit]")))
 777     (message "End of buffer")))
 778
 779 (defun View-scroll-page-forward (&optional lines)
 780   "Scroll \"page size\" or prefix LINES lines forward in View mode.
 781 Exit if end of text is visible and `view-scroll-auto-exit' is non-nil.
 782 \"page size\" is whole window full, or number of lines set by
 783 \\[View-scroll-page-forward-set-page-size] or
 784 \\[View-scroll-page-backward-set-page-size].
 785 If LINES is more than a window-full, only the last window-full is shown."
 786   (interactive "P")
 787   (view-scroll-lines lines nil view-page-size nil))
 788
 789 (defun View-scroll-page-backward (&optional lines)
 790   "Scroll \"page size\" or prefix LINES lines backward in View mode.
 791 See also `View-scroll-page-forward'."
 792   (interactive "P")
 793   (view-scroll-lines lines t view-page-size nil))
 794
 795 (defun View-scroll-page-forward-set-page-size (&optional lines)
 796   "Scroll forward LINES lines in View mode, setting the \"page size\".
 797 This is the number of lines which \\[View-scroll-page-forward] and
 798 \\[View-scroll-page-backward] scroll by default.
 799 If LINES is omitted or = 0, sets \"page size\" to window height and
 800 scrolls forward that much, otherwise scrolls forward LINES lines and sets
 801 \"page size\" to the minimum of window height and the absolute value of LINES.
 802 See also `View-scroll-page-forward'."
 803   (interactive "P")
 804   (view-scroll-lines lines nil
 805                      (setq view-page-size (view-page-size-default lines))
 806                      nil))
 807
 808 (defun View-scroll-page-backward-set-page-size (&optional lines)
 809   "Scroll backward prefix LINES lines in View mode, setting the \"page size\".
 810 See also `View-scroll-page-forward-set-page-size'."
 811   (interactive "P")
 812   (view-scroll-lines lines t
 813                      (setq view-page-size (view-page-size-default lines))
 814                      nil))
 815
 816 (defun View-scroll-line-forward (&optional lines)
 817   "Scroll forward one line (or prefix LINES lines) in View mode.
 818 See also `View-scroll-page-forward,' but note that scrolling is limited
 819 to minimum of LINES and one window-full."
 820   (interactive "P")
 821   (view-scroll-lines lines nil 1 t))
 822
 823 (defun View-scroll-line-backward (&optional lines)
 824   "Scroll backward one line (or prefix LINES lines) in View mode.
 825 See also `View-scroll-line-forward'."
 826   (interactive "P")
 827   (view-scroll-lines lines t 1 t))
 828
 829 (defun View-scroll-half-page-forward (&optional lines)
 830   "Scroll forward a \"half page\" (or prefix LINES) lines in View mode.
 831 If LINES is not omitted, the \"half page size\" is set to the minimum of
 832 window height and the absolute value of LINES.
 833 LINES=0 resets \"half page size\" to half window height."
 834   (interactive "P")
 835   (view-scroll-lines lines nil (view-set-half-page-size-default lines) t))
 836
 837 (defun View-scroll-half-page-backward (&optional lines)
 838   "Scroll backward a \"half page\" (or prefix LINES) lines in View mode.
 839 See also `View-scroll-half-page-forward'."
 840   (interactive "P")
 841   (view-scroll-lines lines t (view-set-half-page-size-default lines) t))
 842
 843 (defun View-revert-buffer-scroll-page-forward (&optional lines)
 844   "Scroll forward, reverting buffer if needed, in View mode.
 845 If buffer has not been changed and the corresponding file is newer, first
 846 revert the buffer, then scroll.
 847 This command is useful if you are viewing a changing file.
 848
 849 The prefix argument LINES says how many lines to scroll.
 850 If you don't specify a prefix argument, it uses the number of lines set by
 851 \\[View-scroll-page-forward-set-page-size] or
 852 \\[View-scroll-page-backward-set-page-size].
 853 If LINES is more than a window-full, only the last window-full is shown."
 854   (interactive "P")
 855   (let ((view-scroll-auto-exit nil)
 856         (view-try-extend-at-buffer-end t))
 857     (view-scroll-lines lines nil view-page-size nil)))
 858
 859 (defun View-back-to-mark (&optional ignore)
 860   "Return to last mark set in View mode, else beginning of file.
 861 Display that line at the center of the window.
 862 This command pops the mark ring, so that successive
 863 invocations return to earlier marks."
 864   (interactive)
 865   (goto-char (or (mark t) (point-min)))
 866   (pop-mark)
 867   (view-recenter))
 868
 869 (defun View-search-regexp-forward (n regexp)
 870   "Search forward for first (or prefix Nth) occurrence of REGEXP in View mode.
 871
 872 Displays line found at center of window.  Sets mark at starting position and
 873 pushes mark ring.
 874
 875 Characters @ and ! are special at the beginning of REGEXP.  They modify
 876 the search rather than become part of the pattern searched for.
 877 @ means search all the buffer i.e. start search at the beginning of buffer.
 878 ! means search for a line that contains no match for the pattern.
 879 If REGEXP is empty or only consist of these control characters, then
 880 an earlier remembered REGEXP is used, otherwise REGEXP is remembered
 881 for use by later search commands.
 882
 883 The variable `view-highlight-face' controls the face that is used
 884 for highlighting the match that is found."
 885   (interactive "p\nsSearch forward (regexp): ")
 886   (view-search n regexp))
 887
 888 (defun View-search-regexp-backward (n regexp)
 889   "Search backward for first (or prefix Nth) occurrence of REGEXP in View mode.
 890
 891 Displays line found at center of window.  Sets mark at starting position and
 892 pushes mark ring.
 893
 894 Characters @ and ! are special at the beginning of REGEXP.  They modify
 895 the search rather than become part of the pattern searched for.
 896 @ means search all the buffer i.e. start search at the end of buffer.
 897 ! means search for a line that contains no match for the pattern.
 898 If REGEXP is empty or only consist of these control characters, then
 899 an earlier remembered REGEXP is used, otherwise REGEXP is remembered
 900 for use by later search commands.
 901
 902 The variable `view-highlight-face' controls the face that is used
 903 for highlighting the match that is found."
 904   (interactive "p\nsSearch backward (regexp): ")
 905   (view-search (- n) regexp))
 906
 907 (defun View-search-last-regexp-forward (n) "\
 908 Search forward for first (or prefix Nth) instance of last regexp in View mode.
 909 Displays line found at center of window.  Sets mark at starting position and
 910 pushes mark ring.
 911
 912 The variable `view-highlight-face' controls the face that is used
 913 for highlighting the match that is found."
 914   (interactive "p")
 915   (view-search n nil))
 916
 917 (defun View-search-last-regexp-backward (n) "\
 918 Search backward for first (or prefix Nth) instance of last regexp in View mode.
 919 Displays line found at center of window.  Sets mark at starting position and
 920 pushes mark ring.
 921
 922 The variable `view-highlight-face' controls the face that is used
 923 for highlighting the match that is found."
 924   (interactive "p")
 925   (view-search (- n) nil))
 926
 927 (defun view-search (times regexp)
 928   ;; This function does the job for all the View-search- commands.
 929   ;; Search for the TIMESt match for REGEXP. If TIMES is negative
 930   ;; search backwards. If REGEXP is nil use `view-last-regexp'.
 931   ;; Charcters "!" and "@" have a special meaning at the beginning of
 932   ;; REGEXP and are removed from REGEXP before the search "!" means
 933   ;; search for lines with no match for REGEXP.  "@" means search in
 934   ;; the whole buffer, don't start searching from the present point.
 935   (let (where no end ln)
 936     (cond
 937      ((and regexp (> (length regexp) 0)
 938            (or (not (memq (string-to-char regexp) '(?! ?@)))
 939                (progn
 940                  (if (member (substring regexp 0 2) '("!@" "@!"))
 941                      (setq end t no t ln 2)
 942                    (setq no (not (setq end (eq ?@ (string-to-char regexp))))
 943                          ln 1))
 944                  (> (length (setq regexp (substring regexp ln))) 0))))
 945       (setq view-last-regexp (if no (list regexp) regexp)))
 946      ((consp view-last-regexp)
 947       (setq regexp (car view-last-regexp))
 948       (unless (setq no (not no)) (setq view-last-regexp regexp)))
 949      (view-last-regexp (setq regexp view-last-regexp)
 950                        (if no (setq view-last-regexp (list regexp))))
 951      (t (error "No previous View-mode search")))
 952     (save-excursion
 953       (if end (goto-char (if (< times 0) (point-max) (point-min)))
 954         (move-to-window-line (if (< times 0) 0 -1)))
 955       (if (if no (view-search-no-match-lines times regexp)
 956             (re-search-forward regexp nil t times))
 957           (setq where (point))))
 958     (if where
 959         (progn
 960           (push-mark)
 961           (goto-char where)
 962           (if view-overlay
 963               (move-overlay view-overlay (match-beginning 0) (match-end 0))
 964             (setq view-overlay
 965                   (make-overlay (match-beginning 0) (match-end 0))))
 966           (overlay-put view-overlay 'face view-highlight-face)
 967           (beginning-of-line)
 968           (view-recenter))
 969       (message "Can't find occurrence %d of %s%s"
 970                times (if no "no " "") regexp)
 971       (sit-for 4))))
 972
 973 (defun view-search-no-match-lines (times regexp)
 974   ;; Search for the TIMESt occurrence of line with no match for REGEXP.
 975   (let ((back (and (< times 0) (setq times (- times)) -1))
 976         n)
 977     (while (> times 0)
 978       (save-excursion (beginning-of-line (if back (- times) (1+ times)))
 979                       (setq n (point)))
 980       (setq times
 981             (cond
 982              ((< (count-lines (point) n) times) -1) ; Not enough lines.
 983              ((or (null (re-search-forward regexp nil t back))
 984                   (if back (and (< (match-end 0) n)
 985                                 (> (count-lines (match-end 0) n) 1))
 986                     (and (< n (match-beginning 0))
 987                          (> (count-lines n (match-beginning 0)) 1))))
 988               0)                        ; No match within lines.
 989              (back (count-lines (max n (match-beginning 0)) (match-end 0)))
 990              (t (count-lines (match-beginning 0) (min n (match-end 0))))))
 991       (goto-char n))
 992     (and (zerop times) (looking-at "^.*$"))))
 993
 994
 995 (provide 'view)
 996
 997 ;;; view.el ends here