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+;; View: Peruse file or buffer without editing.
+;; Copyright (C) 1985, 1989 Free Software Foundation, Inc.
+;; Principal author K. Shane Hartman
+
+;; This file is part of GNU Emacs.
+
+;; GNU Emacs is free software; you can redistribute it and/or modify
+;; it under the terms of the GNU General Public License as published by
+;; the Free Software Foundation; either version 1, or (at your option)
+;; any later version.
+
+;; GNU Emacs is distributed in the hope that it will be useful,
+;; but WITHOUT ANY WARRANTY; without even the implied warranty of
+;; MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+;; GNU General Public License for more details.
+
+;; You should have received a copy of the GNU General Public License
+;; along with GNU Emacs; see the file COPYING.  If not, write to
+;; the Free Software Foundation, 675 Mass Ave, Cambridge, MA 02139, USA.
+
+
+(provide 'view)
+
+(defvar view-mode-map nil)
+(if view-mode-map
+    nil
+  (setq view-mode-map (make-keymap))
+  (fillarray view-mode-map 'View-undefined)
+  (define-key view-mode-map "\C-c" 'view-exit)
+  (define-key view-mode-map "\C-z" 'suspend-emacs)
+  (define-key view-mode-map "q" 'view-exit)
+  (define-key view-mode-map "-" 'negative-argument)
+  (define-key view-mode-map "0" 'digit-argument)
+  (define-key view-mode-map "1" 'digit-argument)
+  (define-key view-mode-map "2" 'digit-argument)
+  (define-key view-mode-map "3" 'digit-argument)
+  (define-key view-mode-map "4" 'digit-argument)
+  (define-key view-mode-map "5" 'digit-argument)
+  (define-key view-mode-map "6" 'digit-argument)
+  (define-key view-mode-map "7" 'digit-argument)
+  (define-key view-mode-map "8" 'digit-argument)
+  (define-key view-mode-map "9" 'digit-argument)
+  (define-key view-mode-map "\C-u" 'universal-argument)
+  (define-key view-mode-map "\e" nil)
+  (define-key view-mode-map "\C-x" 'Control-X-prefix)
+  (define-key view-mode-map "\e-" 'negative-argument)
+  (define-key view-mode-map "\e0" 'digit-argument)
+  (define-key view-mode-map "\e1" 'digit-argument)
+  (define-key view-mode-map "\e2" 'digit-argument)
+  (define-key view-mode-map "\e3" 'digit-argument)
+  (define-key view-mode-map "\e4" 'digit-argument)
+  (define-key view-mode-map "\e5" 'digit-argument)
+  (define-key view-mode-map "\e6" 'digit-argument)
+  (define-key view-mode-map "\e7" 'digit-argument)
+  (define-key view-mode-map "\e8" 'digit-argument)
+  (define-key view-mode-map "\e9" 'digit-argument)
+  (define-key view-mode-map "<" 'beginning-of-buffer)
+  (define-key view-mode-map ">" 'end-of-buffer)
+  (define-key view-mode-map "\ev" 'View-scroll-lines-backward)
+  (define-key view-mode-map "\C-v" 'View-scroll-lines-forward)
+  (define-key view-mode-map " " 'View-scroll-lines-forward)
+  (define-key view-mode-map "\177" 'View-scroll-lines-backward)
+  (define-key view-mode-map "\n" 'View-scroll-one-more-line)
+  (define-key view-mode-map "\r" 'View-scroll-one-more-line)
+  (define-key view-mode-map "\C-l" 'recenter)
+  (define-key view-mode-map "z" 'View-scroll-lines-forward-set-scroll-size)
+  (define-key view-mode-map "g" 'View-goto-line)
+  (define-key view-mode-map "=" 'what-line)
+  (define-key view-mode-map "." 'set-mark-command)
+  (define-key view-mode-map "\C-@" 'set-mark-command)
+  (define-key view-mode-map "'" 'View-back-to-mark)
+  (define-key view-mode-map "@" 'View-back-to-mark)  
+  (define-key view-mode-map "x" 'exchange-point-and-mark)
+  (define-key view-mode-map "h" 'Helper-describe-bindings)
+  (define-key view-mode-map "?" 'Helper-describe-bindings)
+  (define-key view-mode-map "\C-h" 'Helper-help)
+  (define-key view-mode-map "\C-n" 'next-line)
+  (define-key view-mode-map "\C-p" 'previous-line)
+  (define-key view-mode-map "\C-s" 'isearch-forward)
+  (define-key view-mode-map "\C-r" 'isearch-backward)
+  (define-key view-mode-map "s" 'isearch-forward)
+  (define-key view-mode-map "r" 'isearch-backward)
+  (define-key view-mode-map "/" 'View-search-regexp-forward)
+  (define-key view-mode-map "\\" 'View-search-regexp-backward)
+  ;; This conflicts with the standard binding of isearch-regexp-forward
+  (define-key view-mode-map "\e\C-s" 'View-search-regexp-forward)
+  (define-key view-mode-map "\e\C-r" 'View-search-regexp-backward)  
+  (define-key view-mode-map "n" 'View-search-last-regexp-forward)
+  (define-key view-mode-map "p" 'View-search-last-regexp-backward)
+  )
+
+
+(defun view-file (file-name)
+  "View FILE in View mode, returning to previous buffer when done.
+The usual Emacs commands are not available; instead,
+a special set of commands (mostly letters and punctuation)
+are defined for moving around in the buffer.
+Space scrolls forward, Delete scrolls backward.
+For list of all View commands, type ? or h while viewing.
+
+Calls the value of  view-hook  if that is non-nil."
+  (interactive "fView file: ")
+  (let ((old-buf (current-buffer))
+	(had-a-buf (get-file-buffer file-name))
+	(buf-to-view (find-file-noselect file-name)))
+    (switch-to-buffer buf-to-view t)
+    (view-mode old-buf
+	       (and (not had-a-buf) (not (buffer-modified-p buf-to-view))
+		    'kill-buffer))))
+
+(defun view-buffer (buffer-name)
+  "View BUFFER in View mode, returning to previous buffer when done.
+The usual Emacs commands are not available; instead,
+a special set of commands (mostly letters and punctuation)
+are defined for moving around in the buffer.
+Space scrolls forward, Delete scrolls backward.
+For list of all View commands, type ? or h while viewing.
+
+Calls the value of  view-hook  if that is non-nil."
+  (interactive "bView buffer: ")
+  (let ((old-buf (current-buffer)))
+    (switch-to-buffer buffer-name t)
+    (view-mode old-buf nil)))
+
+(defun view-mode (&optional prev-buffer action)
+  "Major mode for viewing text but not editing it.
+Letters do not insert themselves.  Instead these commands are provided.
+Most commands take prefix arguments.  Commands dealing with lines
+default to \"scroll size\" lines (initially size of window).
+Search commands default to a repeat count of one.
+M-< or <	move to beginning of buffer.
+M-> or >	move to end of buffer.
+C-v or Space	scroll forward lines.
+M-v or DEL	scroll backward lines.
+CR or LF	scroll forward one line (backward with prefix argument).
+z		like Space except set number of lines for further
+		   scrolling commands to scroll by.
+C-u and Digits	provide prefix arguments.  `-' denotes negative argument.
+=		prints the current line number.
+g		goes to line given by prefix argument.
+/ or M-C-s	searches forward for regular expression
+\\ or M-C-r	searches backward for regular expression.
+n		searches forward for last regular expression.
+p		searches backward for last regular expression.
+C-@ or .	set the mark.
+x		exchanges point and mark.
+C-s or s	do forward incremental search.
+C-r or r	do reverse incremental search.
+@ or '		return to mark and pops mark ring.
+		  Mark ring is pushed at start of every
+		  successful search and when jump to line to occurs.
+		  The mark is set on jump to buffer start or end.
+? or h		provide help message (list of commands).
+C-h		provides help (list of commands or description of a command).
+C-n		moves down lines vertically.
+C-p		moves upward lines vertically.
+C-l		recenters the screen.
+q or C-c	exit view-mode and return to previous buffer.
+
+Entry to this mode calls the value of  view-hook  if non-nil.
+\\{view-mode-map}"
+;  Not interactive because dangerous things happen
+;  if you call it without passing a buffer as argument
+;  and they are not easy to fix.
+;  (interactive)
+  (make-local-variable 'view-old-mode-line-buffer-identification)
+  (setq view-old-mode-line-buffer-identification
+	mode-line-buffer-identification)
+  (make-local-variable 'view-old-buffer-read-only)
+  (setq view-old-buffer-read-only buffer-read-only)
+  (make-local-variable 'view-old-mode-name)
+  (setq view-old-mode-name mode-name)
+  (make-local-variable 'view-old-major-mode)
+  (setq view-old-major-mode major-mode)
+  (make-local-variable 'view-old-local-map)
+  (setq view-old-local-map (current-local-map))
+  (make-local-variable 'view-old-Helper-return-blurb)
+  (setq view-old-Helper-return-blurb
+	(and (boundp 'Helper-return-blurb) Helper-return-blurb))
+
+  (setq buffer-read-only t)
+  (setq mode-line-buffer-identification
+	(list
+	 (if (buffer-file-name)
+	     "Viewing %f"
+	   "Viewing %b")))
+  (setq mode-name "View")
+  (setq major-mode 'view-mode)
+  (setq Helper-return-blurb
+	(format "continue viewing %s"
+		(if (buffer-file-name)
+		    (file-name-nondirectory (buffer-file-name))
+		    (buffer-name))))
+
+  (make-local-variable 'view-exit-action)
+  (setq view-exit-action action)
+  (make-local-variable 'view-prev-buffer)
+  (setq view-prev-buffer prev-buffer)
+  (make-local-variable 'view-exit-position)
+  (setq view-exit-position (point-marker))
+
+  (make-local-variable 'view-scroll-size)
+  (setq view-scroll-size nil)
+  (make-local-variable 'view-last-regexp)
+  (setq view-last-regexp nil)
+
+  (beginning-of-line)
+  (setq goal-column nil)
+
+  (use-local-map view-mode-map)
+  (run-hooks 'view-hook)
+  (view-helpful-message))
+
+(defun view-exit ()
+  "Exit from view-mode.
+If you viewed an existing buffer, that buffer returns to its previous mode.
+If you viewed a file that was not present in Emacs, its buffer is killed."
+  (interactive)
+  (setq mode-line-buffer-identification
+	view-old-mode-line-buffer-identification)
+  (setq major-mode view-old-major-mode)
+  (setq mode-name view-old-mode-name)
+  (use-local-map (current-local-map))
+  (setq buffer-read-only view-old-buffer-read-only)
+
+  (goto-char view-exit-position)
+  (set-marker view-exit-position nil)
+
+  ;; Now do something to the buffer that we were viewing
+  ;; (such as kill it).
+  (let ((viewed-buffer (current-buffer))
+	(action view-exit-action))
+    (switch-to-buffer view-prev-buffer)
+    (if action (funcall action viewed-buffer))))
+
+(defun view-helpful-message ()
+  (message
+   (if (and (eq (key-binding "\C-h") 'Helper-help)
+	    (eq (key-binding "?") 'Helper-describe-bindings)
+	    (eq (key-binding "\C-c") 'view-exit))
+       "Type C-h for help, ? for commands, C-c to quit"
+     (substitute-command-keys
+      "Type \\[Helper-help] for help, \\[Helper-describe-bindings] for commands, \\[exit-recursive-edit] to quit."))))
+
+(defun View-undefined ()
+  (interactive)
+  (ding)
+  (view-helpful-message))
+
+(defun view-window-size () (1- (window-height)))
+
+(defun view-scroll-size ()
+  (min (view-window-size) (or view-scroll-size (view-window-size))))
+
+(defvar view-hook nil
+  "If non-nil, its value is called when viewing buffer or file.")
+
+;(defun view-last-command (&optional who what)
+;  (setq view-last-command-entry this-command)
+;  (setq view-last-command who)
+;  (setq view-last-command-argument what))
+
+;(defun View-repeat-last-command ()
+;  "Repeat last command issued in View mode."
+;  (interactive)
+;  (if (and view-last-command
+;	   (eq view-last-command-entry last-command))
+;      (funcall view-last-command view-last-command-argument))
+;  (setq this-command view-last-command-entry))
+
+(defun View-goto-line (&optional line)
+  "Move to LINE in View mode.
+Display is centered at LINE.  Sets mark at starting position and pushes
+mark ring."
+  (interactive "p")
+  (push-mark)
+  (goto-line (or line 1))
+  (recenter (/ (view-window-size) 2)))
+
+(defun View-scroll-lines-forward (&optional lines)
+  "Scroll forward in View mode, or exit if end of text is visible.
+No arg means whole window full, or number of lines set by \\[View-scroll-lines-forward-set-scroll-size].
+Arg is number of lines to scroll."
+  (interactive "P")
+  (if (pos-visible-in-window-p (point-max))
+      (exit-recursive-edit))
+  (setq lines
+	(if lines (prefix-numeric-value lines)
+	  (view-scroll-size)))
+; (view-last-command 'View-scroll-lines-forward lines)
+  (if (>= lines (view-window-size))
+      (scroll-up nil)
+    (if (>= (- lines) (view-window-size))
+	(scroll-down nil)
+      (scroll-up lines)))
+  (cond ((pos-visible-in-window-p (point-max))
+	 (goto-char (point-max))
+	 (recenter -1)
+	 (message (substitute-command-keys
+		"End.  Type \\[exit-recursive-edit] to quit viewing."))))
+  (move-to-window-line -1)
+  (beginning-of-line))
+
+(defun View-scroll-lines-forward-set-scroll-size (&optional lines)
+  "Scroll forward LINES lines in View mode, setting the \"scroll size\".
+This is the number of lines which \\[View-scroll-lines-forward] and \\[View-scroll-lines-backward] scroll by default.
+The absolute value of LINES is used, so this command can be used to scroll
+backwards (but \"scroll size\" is always positive).  If LINES is greater than
+window height or omitted, then window height is assumed.  If LINES is less
+than window height then scrolling context is provided from previous screen."
+  (interactive "P")
+  (if (not lines)
+      (setq view-scroll-size (view-window-size))
+    (setq lines (prefix-numeric-value lines))
+    (setq view-scroll-size
+	  (min (if (> lines 0) lines (- lines)) (view-window-size))))
+  (View-scroll-lines-forward lines))
+
+(defun View-scroll-one-more-line (&optional arg)
+  "Scroll one more line up in View mode.
+With ARG scroll one line down."
+  (interactive "P")
+  (View-scroll-lines-forward (if (not arg) 1 -1)))
+
+(defun View-scroll-lines-backward (&optional lines)
+  "Scroll backward in View mode.
+No arg means whole window full, or number of lines set by \\[View-scroll-lines-forward-set-scroll-size].
+Arg is number of lines to scroll."
+  (interactive "P")
+  (View-scroll-lines-forward (if lines
+				 (- (prefix-numeric-value lines))
+			       (- (view-scroll-size)))))
+  
+(defun View-search-regexp-forward (times regexp)
+  "Search forward for NTH occurrence of REGEXP in View mode.
+Displays line found at center of window.  REGEXP is remembered for
+searching with \\[View-search-last-regexp-forward] and \\[View-search-last-regexp-backward].  Sets mark at starting position and pushes mark ring."
+  (interactive "p\nsSearch forward (regexp): ")
+  (if (> (length regexp) 0)
+      (progn
+       ;(view-last-command 'View-search-last-regexp-forward times)
+	(view-search times regexp))))
+
+(defun View-search-regexp-backward (times regexp)
+  "Search backward from window start for NTH instance of REGEXP in View mode.
+Displays line found at center of window.  REGEXP is remembered for
+searching with \\[View-search-last-regexp-forward] and \\[View-search-last-regexp-backward].  Sets mark at starting position and pushes mark ring."
+  (interactive "p\nsSearch backward (regexp): ")
+  (View-search-regexp-forward (- times) regexp))
+
+(defun View-search-last-regexp-forward (times)
+  "Search forward from window end for NTH instance of last regexp in View mode.
+Displays line found at center of window.  Sets mark at starting position
+and pushes mark ring."
+  (interactive "p")
+  (View-search-regexp-forward times view-last-regexp))
+
+(defun View-search-last-regexp-backward (times)
+  "Search backward from window start for NTH instance of last regexp in View mode.
+Displays line found at center of window.  Sets mark at starting position and
+pushes mark ring."
+  (interactive "p")
+  (View-search-regexp-backward times view-last-regexp))
+
+(defun View-back-to-mark (&optional ignore)
+  "Return to last mark set in View mode, else beginning of file.
+Displays line at center of window.  Pops mark ring so successive
+invocations return to earlier marks."
+  (interactive)
+  (goto-char (or (mark) (point-min)))
+  (pop-mark)
+  (recenter (/ (view-window-size) 2)))
+	     
+(defun view-search (times regexp)
+  (setq view-last-regexp regexp)
+  (let (where)
+    (save-excursion
+      (move-to-window-line (if (< times 0) 0 -1))
+      (if (re-search-forward regexp nil t times)
+	  (setq where (point))))
+    (if where
+	(progn
+	  (push-mark)
+	  (goto-char where)
+	  (beginning-of-line)
+	  (recenter (/ (view-window-size) 2)))
+      (message "Can't find occurrence %d of %s" times regexp)
+      (sit-for 4))))
+