info.el

;;; info.el --- info package for Emacs.

;; Copyright (C) 1985, 86, 92, 93, 94, 95, 96, 97 Free Software
;; Foundation, Inc.

;; Maintainer: FSF
;; Keywords: help

;; 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 2, 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, Inc., 59 Temple Place - Suite 330,
;; Boston, MA 02111-1307, USA.

;;; Commentary:

;; Note that nowadays we expect info files to be made using makeinfo.

;;; Code:

(defgroup info nil
  "Info subsystem"
  :group 'help
  :group 'docs)


(defvar Info-history nil
  "List of info nodes user has visited.
Each element of list is a list (FILENAME NODENAME BUFFERPOS).")

(defcustom Info-enable-edit nil
  "*Non-nil means the \\<Info-mode-map>\\[Info-edit] command in Info can edit the current node.
This is convenient if you want to write info files by hand.
However, we recommend that you not do this.
It is better to write a Texinfo file and generate the Info file from that,
because that gives you a printed manual as well."
  :type 'boolean
  :group 'info)

(defvar Info-enable-active-nodes nil
  "Non-nil allows Info to execute Lisp code associated with nodes.
The Lisp code is executed when the node is selected.")
(put 'Info-enable-active-nodes 'risky-local-variable t)

(defcustom Info-fontify t
  "*Non-nil enables highlighting and fonts in Info nodes."
  :type 'boolean
  :group 'info)

(defface info-node
  '((t (:bold t :italic t)))
  "Face for Info node names."
  :group 'info)

(defface info-menu-5
  '((t (:underline t)))
  "Face for the fifth and tenth `*' in an Info menu."
  :group 'info)

(defface info-xref
  '((t (:bold t)))
  "Face for Info cross-references."
  :group 'info)

(defcustom Info-fontify-maximum-menu-size 30000
  "*Maximum size of menu to fontify if `Info-fontify' is non-nil."
  :type 'integer
  :group 'info)

(defvar Info-directory-list
  (let ((path (getenv "INFOPATH"))
	;; This is for older Emacs versions
	;; which might get this info.el from the Texinfo distribution.
	(path-separator (if (boundp 'path-separator) path-separator
			  (if (eq system-type 'ms-dos) ";" ":")))
	(source (expand-file-name "info/" source-directory))
	(sibling (if installation-directory
		     (expand-file-name "info/" installation-directory)))
	alternative)
    (if path
	(let ((list nil)
	      idx)
	  (while (> (length path) 0)
	    (setq idx (or (string-match path-separator path) (length path))
		  list (cons (substring path 0 idx) list)
		  path (substring path (min (1+ idx)
					    (length path)))))
	  (nreverse list))
      (if (and sibling (file-exists-p sibling))
	  (setq alternative sibling)
	(setq alternative source))
      (if (or (member alternative Info-default-directory-list)
	      (not (file-exists-p alternative))
	      ;; On DOS/NT, we use movable executables always,
	      ;; and we must always find the Info dir at run time.
	      (if (or (eq system-type 'ms-dos) (eq system-type 'windows-nt))
		  nil
		;; Use invocation-directory for Info only if we used it for
		;; exec-directory also.
		(not (string= exec-directory
			      (expand-file-name "lib-src/"
						installation-directory)))))
	  Info-default-directory-list
	(reverse (cons alternative
		       (cdr (reverse Info-default-directory-list)))))))
  "List of directories to search for Info documentation files.
nil means not yet initialized.  In this case, Info uses the environment
variable INFOPATH to initialize it, or `Info-default-directory-list'
if there is no INFOPATH variable in the environment.
The last element of `Info-default-directory-list' is the directory
where Emacs installs the Info files that come with it.

If you run the Emacs executable from the `src' directory in the Emacs
source tree, the `info' directory in the source tree is used as the last
element, in place of the installation Info directory.  This is useful
when you run a version of Emacs without installing it.")

(defcustom Info-additional-directory-list nil
  "List of additional directories to search for Info documentation files.
These directories are not searched for merging the `dir' file."
  :type '(repeat directory)
  :group 'info)

(defvar Info-current-file nil
  "Info file that Info is now looking at, or nil.
This is the name that was specified in Info, not the actual file name.
It doesn't contain directory names or file name extensions added by Info.")

(defvar Info-current-subfile nil
  "Info subfile that is actually in the *info* buffer now,
or nil if current info file is not split into subfiles.")

(defvar Info-current-node nil
  "Name of node that Info is now looking at, or nil.")

(defvar Info-tag-table-marker nil
  "Marker pointing at beginning of current Info file's tag table.
Marker points nowhere if file has no tag table.")

(defvar Info-tag-table-buffer nil
  "Buffer used for indirect tag tables.")

(defvar Info-current-file-completions nil
  "Cached completion list for current Info file.")

(defvar Info-index-alternatives nil
  "List of possible matches for last Info-index command.")

(defvar Info-standalone nil
  "Non-nil if Emacs was started solely as an Info browser.")

(defvar Info-suffix-list
  ;; The MS-DOS list should work both when long file names are
  ;; supported (Windows 9X), and when only 8+3 file names are available.
  (if (eq system-type 'ms-dos)
      '( (".gz"      . "gunzip")
	 (".z"       . "gunzip")
	 (".inz"     . "gunzip")
	 (".igz"     . "gunzip")
	 (".info.Z"  . "gunzip")
	 (".info.gz" . "gunzip")
	 ("-info.Z"  . "gunzip")
	 ("-info.gz" . "gunzip")
	 ("/index.gz". "gunzip")
	 ("/index.z" . "gunzip")
	 (".inf"     . nil)
	 (".info"    . nil)
	 ("-info"    . nil)
	 ("/index"   . nil)
	 (""         . nil))
    '( (".info.Z".    "uncompress")
       (".info.Y".    "unyabba")
       (".info.gz".   "gunzip")
       (".info.z".    "gunzip")
       (".info".      nil)
       ("-info.Z".   "uncompress")
       ("-info.Y".   "unyabba")
       ("-info.gz".  "gunzip")
       ("-info.z".   "gunzip")
       ("-info".     nil)
       ("/index.Z".   "uncompress")
       ("/index.Y".   "unyabba")
       ("/index.gz".  "gunzip")
       ("/index.z".   "gunzip")
       ("/index".     nil)
       (".Z".         "uncompress")
       (".Y".         "unyabba")
       (".gz".        "gunzip")
       (".z".         "gunzip")
       ("".           nil)))
  "List of file name suffixes and associated decoding commands.
Each entry should be (SUFFIX . STRING); the file is given to
the command as standard input.  If STRING is nil, no decoding is done.
Because the SUFFIXes are tried in order, the empty string should
be last in the list.")

;; Concatenate SUFFIX onto FILENAME.  SUFFIX should start with a dot.
;; First, on ms-dos, delete some of the extension in FILENAME
;; to make room.
(defun info-insert-file-contents-1 (filename suffix)
  (if (not (eq system-type 'ms-dos))
      (concat filename suffix)
    (let* ((sans-exts (file-name-sans-extension filename))
	   ;; How long is the extension in FILENAME (not counting the dot).
	   (ext-len (max 0 (- (length filename) (length sans-exts) 1)))
	   ext-left)
      ;; SUFFIX starts with a dot.  If FILENAME already has one,
      ;; get rid of the one in SUFFIX (unless suffix is empty).
      (or (and (<= ext-len 0)
	       (not (eq (aref filename (1- (length filename))) ?.)))
	  (= (length suffix) 0)
	  (setq suffix (substring suffix 1)))
      ;; How many chars of that extension should we keep?
      (setq ext-left (min ext-len (max 0 (- 3 (length suffix)))))
      ;; Get rid of the rest of the extension, and add SUFFIX.
      (concat (substring filename 0 (- (length filename)
				       (- ext-len ext-left)))
	      suffix))))

(defun info-insert-file-contents (filename &optional visit)
  "Insert the contents of an info file in the current buffer.
Do the right thing if the file has been compressed or zipped."
  (let ((tail Info-suffix-list)
	fullname decoder)
    (if (file-exists-p filename)
	;; FILENAME exists--see if that name contains a suffix.
	;; If so, set DECODE accordingly.
	(progn
	  (while (and tail
		      (not (string-match
			    (concat (regexp-quote (car (car tail))) "$")
			    filename)))
	    (setq tail (cdr tail)))
	  (setq fullname filename
		decoder (cdr (car tail))))
      ;; Try adding suffixes to FILENAME and see if we can find something.
      (while (and tail
		  (not (file-exists-p (info-insert-file-contents-1
				       filename (car (car tail))))))
	(setq tail (cdr tail)))
      ;; If we found a file with a suffix, set DECODER according to the suffix
      ;; and set FULLNAME to the file's actual name.
      (setq fullname (info-insert-file-contents-1 filename (car (car tail)))
	    decoder (cdr (car tail)))
      (or tail
	  (error "Can't find %s or any compressed version of it" filename)))
    ;; check for conflict with jka-compr
    (if (and (featurep 'jka-compr)
	     (jka-compr-installed-p)
	     (jka-compr-get-compression-info fullname))
	(setq decoder nil))
    (if decoder
	(progn
	  (insert-file-contents-literally fullname visit)
	  (let ((buffer-read-only nil)
		(coding-system-for-write 'no-conversion)
		(default-directory (or (file-name-directory fullname)
				       default-directory)))
	    (call-process-region (point-min) (point-max) decoder t t)))
      (insert-file-contents fullname visit))))

;;;###autoload (add-hook 'same-window-buffer-names "*info*")

;;;###autoload
(defun info (&optional file)
  "Enter Info, the documentation browser.
Optional argument FILE specifies the file to examine;
the default is the top-level directory of Info.

In interactive use, a prefix argument directs this command
to read a file name from the minibuffer.

The search path for Info files is in the variable `Info-directory-list'.
The top-level Info directory is made by combining all the files named `dir' 
in all the directories in that path."
  (interactive (if current-prefix-arg
		   (list (read-file-name "Info file name: " nil nil t))))
  (pop-to-buffer "*info*")
  (if file
      (Info-goto-node (concat "(" file ")"))
    (Info-directory)))

;;;###autoload
(defun info-standalone ()
  "Run Emacs as a standalone Info reader.
Usage:  emacs -f info-standalone [filename]
In standalone mode, \\<Info-mode-map>\\[Info-exit] exits Emacs itself."
  (setq Info-standalone t)
  (if (and command-line-args-left
	   (not (string-match "^-" (car command-line-args-left))))
      (condition-case err
	  (progn
	    (info (car command-line-args-left))
	    (setq command-line-args-left (cdr command-line-args-left)))
	(error (send-string-to-terminal
		(format "%s\n" (if (eq (car-safe err) 'error)
				   (nth 1 err) err)))
	       (save-buffers-kill-emacs)))
    (info)))

;; Go to an info node specified as separate filename and nodename.
;; no-going-back is non-nil if recovering from an error in this function;
;; it says do not attempt further (recursive) error recovery.
(defun Info-find-node (filename nodename &optional no-going-back)
  ;; Convert filename to lower case if not found as specified.
  ;; Expand it.
  (if filename
      (let (temp temp-downcase found)
	(setq filename (substitute-in-file-name filename))
	(if (string= (downcase filename) "dir")
	    (setq found t)
	  (let ((dirs (if (string-match "^\\./" filename)
			  ;; If specified name starts with `./'
			  ;; then just try current directory.
			  '("./")
			(if (file-name-absolute-p filename)
			    ;; No point in searching for an
			    ;; absolute file name
			    '(nil)
			  (if Info-additional-directory-list
			      (append Info-directory-list
				      Info-additional-directory-list)
			    Info-directory-list)))))
	    ;; Search the directory list for file FILENAME.
	    (while (and dirs (not found))
	      (setq temp (expand-file-name filename (car dirs)))
	      (setq temp-downcase
		    (expand-file-name (downcase filename) (car dirs)))
	      ;; Try several variants of specified name.
	      (let ((suffix-list Info-suffix-list))
		(while (and suffix-list (not found))
		  (cond ((file-exists-p
			  (info-insert-file-contents-1
			   temp (car (car suffix-list))))
			 (setq found temp))
			((file-exists-p
			  (info-insert-file-contents-1
			   temp-downcase (car (car suffix-list))))
			 (setq found temp-downcase)))
		  (setq suffix-list (cdr suffix-list))))
	      (setq dirs (cdr dirs)))))
	(if found
	    (setq filename found)
	  (error "Info file %s does not exist" filename))))
  ;; Record the node we are leaving.
  (if (and Info-current-file (not no-going-back))
      (setq Info-history
	    (cons (list Info-current-file Info-current-node (point))
		  Info-history)))
  ;; Go into info buffer.
  (or (eq major-mode 'Info-mode) (pop-to-buffer "*info*"))
  (buffer-disable-undo (current-buffer))
  (or (eq major-mode 'Info-mode)
      (Info-mode))
  (widen)
  (setq Info-current-node nil)
  (unwind-protect
      (progn
	;; Switch files if necessary
	(or (null filename)
	    (equal Info-current-file filename)
	    (let ((buffer-read-only nil))
	      (setq Info-current-file nil
		    Info-current-subfile nil
		    Info-current-file-completions nil
		    buffer-file-name nil)
	      (erase-buffer)
	      (if (eq filename t)
		  (Info-insert-dir)
		(info-insert-file-contents filename t)
		(setq default-directory (file-name-directory filename)))
	      (set-buffer-modified-p nil)
	      ;; See whether file has a tag table.  Record the location if yes.
	      (goto-char (point-max))
	      (forward-line -8)
	      ;; Use string-equal, not equal, to ignore text props.
	      (if (not (or (string-equal nodename "*")
			   (not
			    (search-forward "\^_\nEnd tag table\n" nil t))))
		  (let (pos)
		    ;; We have a tag table.  Find its beginning.
		    ;; Is this an indirect file?
		    (search-backward "\nTag table:\n")
		    (setq pos (point))
		    (if (save-excursion
			  (forward-line 2)
			  (looking-at "(Indirect)\n"))
			;; It is indirect.  Copy it to another buffer
			;; and record that the tag table is in that buffer.
			(let ((buf (current-buffer))
			      (tagbuf
			       (or Info-tag-table-buffer
				   (generate-new-buffer " *info tag table*"))))
			  (setq Info-tag-table-buffer tagbuf)
			  (save-excursion
			    (set-buffer tagbuf)
                            (buffer-disable-undo (current-buffer))
			    (setq case-fold-search t)
			    (erase-buffer)
			    (insert-buffer-substring buf))
			  (set-marker Info-tag-table-marker
				      (match-end 0) tagbuf))
		      (set-marker Info-tag-table-marker pos)))
		(set-marker Info-tag-table-marker nil))
	      (setq Info-current-file
		    (if (eq filename t) "dir" filename))))
	;; Use string-equal, not equal, to ignore text props.
	(if (string-equal nodename "*")
	    (progn (setq Info-current-node nodename)
		   (Info-set-mode-line))
	  ;; Search file for a suitable node.
	  (let ((guesspos (point-min))
		(regexp (concat "Node: *" (regexp-quote nodename) " *[,\t\n\177]")))
	    ;; First get advice from tag table if file has one.
	    ;; Also, if this is an indirect info file,
	    ;; read the proper subfile into this buffer.
	    (if (marker-position Info-tag-table-marker)
		(save-excursion
		  (let ((m Info-tag-table-marker)
			found found-mode)
		    (save-excursion
		      (set-buffer (marker-buffer m))
		      (goto-char m)
		      (beginning-of-line) ;so re-search will work.
		      (setq found (re-search-forward regexp nil t))
		      (if found
			  (setq guesspos (read (current-buffer))))
		      (setq found-mode major-mode))
		    (if found
			(progn
			  ;; If this is an indirect file, determine
			  ;; which file really holds this node and
			  ;; read it in.
			  (if (not (eq found-mode 'Info-mode))
			      ;; Note that the current buffer must be
			      ;; the *info* buffer on entry to
			      ;; Info-read-subfile.  Thus the hackery
			      ;; above.
			      (setq guesspos (Info-read-subfile guesspos))))
		      (error "No such node: %s" nodename)))))
	    (goto-char (max (point-min) (- guesspos 1000)))
	    ;; Now search from our advised position (or from beg of buffer)
	    ;; to find the actual node.
	    (catch 'foo
	      (while (search-forward "\n\^_" nil t)
		(forward-line 1)
		(let ((beg (point)))
		  (forward-line 1)
		  (if (re-search-backward regexp beg t)
		      (throw 'foo t))))
	      (error "No such node: %s" nodename)))
	  (Info-select-node)))
    ;; If we did not finish finding the specified node,
    ;; go back to the previous one.
    (or Info-current-node no-going-back (null Info-history)
	(let ((hist (car Info-history)))
	  (setq Info-history (cdr Info-history))
	  (Info-find-node (nth 0 hist) (nth 1 hist) t)
	  (goto-char (nth 2 hist)))))
  (goto-char (point-min)))

;; Cache the contents of the (virtual) dir file, once we have merged
;; it for the first time, so we can save time subsequently.
(defvar Info-dir-contents nil)

;; Cache for the directory we decided to use for the default-directory
;; of the merged dir text.
(defvar Info-dir-contents-directory nil)

;; Record the file attributes of all the files from which we
;; constructed Info-dir-contents.
(defvar Info-dir-file-attributes nil)

;; Construct the Info directory node by merging the files named `dir'
;; from various directories.  Set the *info* buffer's
;; default-directory to the first directory we actually get any text
;; from.
(defun Info-insert-dir ()
  (if (and Info-dir-contents Info-dir-file-attributes
	   ;; Verify that none of the files we used has changed
	   ;; since we used it.
	   (eval (cons 'and
		       (mapcar '(lambda (elt)
				  (let ((curr (file-attributes (car elt))))
				    ;; Don't compare the access time.
				    (if curr (setcar (nthcdr 4 curr) 0))
				    (setcar (nthcdr 4 (cdr elt)) 0)
				    (equal (cdr elt) curr)))
			       Info-dir-file-attributes))))
      (insert Info-dir-contents)
    (let ((dirs Info-directory-list)
	  buffers buffer others nodes dirs-done)

      (setq Info-dir-file-attributes nil)

      ;; Search the directory list for the directory file.
      (while dirs
	(let ((truename (file-truename (expand-file-name (car dirs)))))
	  (or (member truename dirs-done)
	      (member (directory-file-name truename) dirs-done)
	      ;; Try several variants of specified name.
	      ;; Try upcasing, appending `.info', or both.
	      (let* (file
		     (attrs
		      (or
		       (progn (setq file (expand-file-name "dir" truename))
			      (file-attributes file))
		       (progn (setq file (expand-file-name "DIR" truename))
			      (file-attributes file))
		       (progn (setq file (expand-file-name "dir.info" truename))
			      (file-attributes file))
		       (progn (setq file (expand-file-name "DIR.INFO" truename))
			      (file-attributes file)))))
		(setq dirs-done
		      (cons truename
			    (cons (directory-file-name truename)
				  dirs-done)))
		(if attrs
		    (save-excursion
		      (or buffers
			  (message "Composing main Info directory..."))
		      (set-buffer (generate-new-buffer " info dir"))
		      (insert-file-contents file)
		      (setq buffers (cons (current-buffer) buffers)
			    Info-dir-file-attributes
			    (cons (cons file attrs)
				  Info-dir-file-attributes))))))
	  (or (cdr dirs) (setq Info-dir-contents-directory
			       (file-name-as-directory (car dirs))))
	  (setq dirs (cdr dirs))))
      
      (or buffers
	  (error "Can't find the Info directory node"))
      ;; Distinguish the dir file that comes with Emacs from all the
      ;; others.  Yes, that is really what this is supposed to do.
      ;; If it doesn't work, fix it.
      (setq buffer (car buffers)
	    others (cdr buffers))

      ;; Insert the entire original dir file as a start; note that we've
      ;; already saved its default directory to use as the default
      ;; directory for the whole concatenation.
      (insert-buffer buffer)

      ;; Look at each of the other buffers one by one.
      (while others
	(let ((other (car others)))
	  ;; In each, find all the menus.
	  (save-excursion
	    (set-buffer other)
	    (goto-char (point-min))
	    ;; Find each menu, and add an elt to NODES for it.
	    (while (re-search-forward "^\\* Menu:" nil t)
	      (let (beg nodename end)
		(forward-line 1)
		(setq beg (point))
		(search-backward "\n\^_")
		(search-forward "Node: ")
		(setq nodename (Info-following-node-name))
		(search-forward "\n\^_" nil 'move)
		(beginning-of-line)
		(setq end (point))
		(setq nodes (cons (list nodename other beg end) nodes))))))
	(setq others (cdr others)))
      ;; Add to the main menu a menu item for each other node.
      (re-search-forward "^\\* Menu:")
      (forward-line 1)
      (let ((menu-items '("top"))
	    (nodes nodes)
	    (case-fold-search t)
	    (end (save-excursion (search-forward "\^_" nil t) (point))))
	(while nodes
	  (let ((nodename (car (car nodes))))
	    (save-excursion
	      (or (member (downcase nodename) menu-items)
		  (re-search-forward (concat "^\\* "
					     (regexp-quote nodename)
					     "::")
				     end t)
		  (progn
		    (insert "* " nodename "::" "\n")
		    (setq menu-items (cons nodename menu-items))))))
	  (setq nodes (cdr nodes))))
      ;; Now take each node of each of the other buffers
      ;; and merge it into the main buffer.
      (while nodes
	(let ((nodename (car (car nodes))))
	  (goto-char (point-min))
	  ;; Find the like-named node in the main buffer.
	  (if (re-search-forward (concat "\n\^_.*\n.*Node: "
					 (regexp-quote nodename)
					 "[,\n\t]")
				 nil t)
	      (progn
		(search-forward "\n\^_" nil 'move)
		(beginning-of-line)
		(insert "\n"))
	    ;; If none exists, add one.
	    (goto-char (point-max))
	    (insert "\^_\nFile: dir\tNode: " nodename "\n\n* Menu:\n\n"))
	  ;; Merge the text from the other buffer's menu
	  ;; into the menu in the like-named node in the main buffer.
	  (apply 'insert-buffer-substring (cdr (car nodes))))
	(setq nodes (cdr nodes)))
      ;; Kill all the buffers we just made.
      (while buffers
	(kill-buffer (car buffers))
	(setq buffers (cdr buffers)))
      (message "Composing main Info directory...done"))
    (setq Info-dir-contents (buffer-string)))
  (setq default-directory Info-dir-contents-directory))

;; Note that on entry to this function the current-buffer must be the
;; *info* buffer; not the info tags buffer.
(defun Info-read-subfile (nodepos)
  ;; NODEPOS is either a position (in the Info file as a whole,
  ;; not relative to a subfile) or the name of a subfile.
  (let (lastfilepos
	lastfilename)
    (if (numberp nodepos)
	(save-excursion
	  (set-buffer (marker-buffer Info-tag-table-marker))
	  (goto-char (point-min))
	  (search-forward "\n\^_")
	  (forward-line 2)
	  (catch 'foo
	    (while (not (looking-at "\^_"))
	      (if (not (eolp))
		  (let ((beg (point))
			thisfilepos thisfilename)
		    (search-forward ": ")
		    (setq thisfilename  (buffer-substring beg (- (point) 2)))
		    (setq thisfilepos (read (current-buffer)))
		    ;; read in version 19 stops at the end of number.
		    ;; Advance to the next line.
		    (forward-line 1)
		    (if (> thisfilepos nodepos)
			(throw 'foo t))
		    (setq lastfilename thisfilename)
		    (setq lastfilepos thisfilepos))
		(forward-line 1)))))
      (setq lastfilename nodepos)
      (setq lastfilepos 0))
    ;; Assume previous buffer is in Info-mode.
    ;; (set-buffer (get-buffer "*info*"))
    (or (equal Info-current-subfile lastfilename)
	(let ((buffer-read-only nil))
	  (setq buffer-file-name nil)
	  (widen)
	  (erase-buffer)
	  (info-insert-file-contents lastfilename)
	  (set-buffer-modified-p nil)
	  (setq Info-current-subfile lastfilename)))
    (goto-char (point-min))
    (search-forward "\n\^_")
    (if (numberp nodepos)
	(+ (- nodepos lastfilepos) (point)))))

;; Select the info node that point is in.
(defun Info-select-node ()
  (save-excursion
   ;; Find beginning of node.
   (search-backward "\n\^_")
   (forward-line 2)
   ;; Get nodename spelled as it is in the node.
   (re-search-forward "Node:[ \t]*")
   (setq Info-current-node
	 (buffer-substring-no-properties (point)
					 (progn
					  (skip-chars-forward "^,\t\n")
					  (point))))
   (Info-set-mode-line)
   ;; Find the end of it, and narrow.
   (beginning-of-line)
   (let (active-expression)
     (narrow-to-region (point)
		       (if (re-search-forward "\n[\^_\f]" nil t)
			   (prog1
			    (1- (point))
			    (if (looking-at "[\n\^_\f]*execute: ")
				(progn
				  (goto-char (match-end 0))
				  (setq active-expression
					(read (current-buffer))))))
			 (point-max)))
     (if Info-enable-active-nodes (eval active-expression))
     (if Info-fontify (Info-fontify-node))
     (run-hooks 'Info-selection-hook))))

(defun Info-set-mode-line ()
  (setq mode-line-buffer-identification
	(concat
	 "  Info:  ("
	 (if Info-current-file
	     (file-name-nondirectory Info-current-file)
	   "")
	 ")"
	 (or Info-current-node ""))))

;; Go to an info node specified with a filename-and-nodename string
;; of the sort that is found in pointers in nodes.

(defun Info-goto-node (nodename)
  "Go to info node named NAME.  Give just NODENAME or (FILENAME)NODENAME."
  (interactive (list (Info-read-node-name "Goto node: ")))
  (let (filename)
    (string-match "\\s *\\((\\s *\\([^\t)]*\\)\\s *)\\s *\\|\\)\\(.*\\)"
		  nodename)
    (setq filename (if (= (match-beginning 1) (match-end 1))
		       ""
		     (substring nodename (match-beginning 2) (match-end 2)))
	  nodename (substring nodename (match-beginning 3) (match-end 3)))
    (let ((trim (string-match "\\s *\\'" filename)))
      (if trim (setq filename (substring filename 0 trim))))
    (let ((trim (string-match "\\s *\\'" nodename)))
      (if trim (setq nodename (substring nodename 0 trim))))
    (if transient-mark-mode (deactivate-mark))
    (Info-find-node (if (equal filename "") nil filename)
		    (if (equal nodename "") "Top" nodename))))

;; This function is used as the "completion table" while reading a node name.
;; It does completion using the alist in completion-table
;; unless STRING starts with an open-paren.
(defun Info-read-node-name-1 (string predicate code)
  (let ((no-completion (and (> (length string) 0) (eq (aref string 0) ?\())))
    (cond ((eq code nil)
	   (if no-completion
	       string
	     (try-completion string completion-table predicate)))
	  ((eq code t)
	   (if no-completion
	       nil
	     (all-completions string completion-table predicate)))
	  ((eq code 'lambda)
	   (if no-completion
	       t
	     (assoc string completion-table))))))

(defun Info-read-node-name (prompt &optional default)
  (let* ((completion-ignore-case t)
	 (completion-table (Info-build-node-completions))
	 (nodename (completing-read prompt 'Info-read-node-name-1 nil t)))
    (if (equal nodename "")
	(or default
	    (Info-read-node-name prompt))
      nodename)))

(defun Info-build-node-completions ()
  (or Info-current-file-completions
      (let ((compl nil))
	(save-excursion
	  (save-restriction
	    (if (marker-buffer Info-tag-table-marker)
		(let ((marker Info-tag-table-marker))
		  (set-buffer (marker-buffer marker))
		  (widen)
		  (goto-char marker)
		  (while (re-search-forward "\nNode: \\(.*\\)\177" nil t)
		    (setq compl
			  (cons (list (buffer-substring (match-beginning 1)
							(match-end 1)))
				compl))))
	      (widen)
	      (goto-char (point-min))
	      (while (search-forward "\n\^_" nil t)
		(forward-line 1)
		(let ((beg (point)))
		  (forward-line 1)
		  (if (re-search-backward "Node: *\\([^,\n]*\\) *[,\n\t]"
					  beg t)
		      (setq compl 
			    (cons (list (buffer-substring (match-beginning 1)
							  (match-end 1)))
				  compl))))))))
	(setq Info-current-file-completions compl))))

(defun Info-restore-point (hl)
  "If this node has been visited, restore the point value when we left."
  (while hl
    (if (and (equal (nth 0 (car hl)) Info-current-file)
	     ;; Use string-equal, not equal, to ignore text props.
	     (string-equal (nth 1 (car hl)) Info-current-node))
	(progn
	  (goto-char (nth 2 (car hl)))
	  (setq hl nil))		;terminate the while at next iter
      (setq hl (cdr hl)))))

(defvar Info-last-search nil
  "Default regexp for \\<Info-mode-map>\\[Info-search] command to search for.")

(defun Info-search (regexp)
  "Search for REGEXP, starting from point, and select node it's found in."
  (interactive "sSearch (regexp): ")
  (if transient-mark-mode (deactivate-mark))
  (if (equal regexp "")
      (setq regexp Info-last-search)
    (setq Info-last-search regexp))
  (let ((found ()) current
	(onode Info-current-node)
	(ofile Info-current-file)
	(opoint (point))
	(ostart (window-start))
	(osubfile Info-current-subfile))
    (save-excursion
      (save-restriction
	(widen)
	(if (null Info-current-subfile)
	    (progn (re-search-forward regexp) (setq found (point)))
	  (condition-case err
	      (progn (re-search-forward regexp) (setq found (point)))
	    (search-failed nil)))))
    (if (not found) ;can only happen in subfile case -- else would have erred
	(unwind-protect
	    (let ((list ()))
	      (save-excursion
		(set-buffer (marker-buffer Info-tag-table-marker))
		(goto-char (point-min))
		(search-forward "\n\^_\nIndirect:")
		(save-restriction
		  (narrow-to-region (point)
				    (progn (search-forward "\n\^_")
					   (1- (point))))
		  (goto-char (point-min))
		  (search-forward (concat "\n" osubfile ": "))
		  (beginning-of-line)
		  (while (not (eobp))
		    (re-search-forward "\\(^.*\\): [0-9]+$")
		    (goto-char (+ (match-end 1) 2))
		    (setq list (cons (cons (read (current-buffer))
					   (buffer-substring
					    (match-beginning 1) (match-end 1)))
				     list))
		    (goto-char (1+ (match-end 0))))
		  (setq list (nreverse list)
			current (car (car list))
			list (cdr list))))
	      (while list
		(message "Searching subfile %s..." (cdr (car list)))
		(Info-read-subfile (car (car list)))
		(setq list (cdr list))
;;		(goto-char (point-min))
		(if (re-search-forward regexp nil t)
		    (setq found (point) list ())))
	      (if found
		  (message "")
		(signal 'search-failed (list regexp))))
	  (if (not found)
	      (progn (Info-read-subfile osubfile)
		     (goto-char opoint)
		     (Info-select-node)
		     (set-window-start (selected-window) ostart)))))
    (widen)
    (goto-char found)
    (Info-select-node)
    ;; Use string-equal, not equal, to ignore text props.
    (or (and (string-equal onode Info-current-node)
	     (equal ofile Info-current-file))
	(setq Info-history (cons (list ofile onode opoint)
				 Info-history)))))

;; Extract the value of the node-pointer named NAME.
;; If there is none, use ERRORNAME in the error message; 
;; if ERRORNAME is nil, just return nil.
(defun Info-extract-pointer (name &optional errorname)
  (save-excursion
   (goto-char (point-min))
   (forward-line 1)
   (if (re-search-backward (concat name ":") nil t)
       (progn
	 (goto-char (match-end 0))
	 (Info-following-node-name))
     (if (eq errorname t)
	 nil
       (error "Node has no %s" (capitalize (or errorname name)))))))

;; Return the node name in the buffer following point.
;; ALLOWEDCHARS, if non-nil, goes within [...] to make a regexp
;; saying which chars may appear in the node name.
(defun Info-following-node-name (&optional allowedchars)
  (skip-chars-forward " \t")
  (buffer-substring-no-properties
   (point)
   (progn
     (while (looking-at (concat "[" (or allowedchars "^,\t\n") "]"))
       (skip-chars-forward (concat (or allowedchars "^,\t\n") "("))
       (if (looking-at "(")
	   (skip-chars-forward "^)")))
     (skip-chars-backward " ")
     (point))))

(defun Info-next ()
  "Go to the next node of this node."
  (interactive)
  (Info-goto-node (Info-extract-pointer "next")))

(defun Info-prev ()
  "Go to the previous node of this node."
  (interactive)
  (Info-goto-node (Info-extract-pointer "prev[ious]*" "previous")))

(defun Info-up ()
  "Go to the superior node of this node."
  (interactive)
  (Info-goto-node (Info-extract-pointer "up"))
  (Info-restore-point Info-history))

(defun Info-last ()
  "Go back to the last node visited."
  (interactive)
  (or Info-history
      (error "This is the first Info node you looked at"))
  (let (filename nodename opoint)
    (setq filename (car (car Info-history)))
    (setq nodename (car (cdr (car Info-history))))
    (setq opoint (car (cdr (cdr (car Info-history)))))
    (setq Info-history (cdr Info-history))
    (Info-find-node filename nodename)
    (setq Info-history (cdr Info-history))
    (goto-char opoint)))

(defun Info-directory ()
  "Go to the Info directory node."
  (interactive)
  (Info-find-node "dir" "top"))

(defun Info-follow-reference (footnotename)
  "Follow cross reference named NAME to the node it refers to.
NAME may be an abbreviation of the reference name."
  (interactive
   (let ((completion-ignore-case t)
	 completions default alt-default (start-point (point)) str i bol eol)
     (save-excursion
       ;; Store end and beginning of line.
       (end-of-line)
       (setq eol (point))
       (beginning-of-line)
       (setq bol (point))

       (goto-char (point-min))
       (while (re-search-forward "\\*note[ \n\t]*\\([^:]*\\):" nil t)
	 (setq str (buffer-substring
		    (match-beginning 1)
		    (1- (point))))
	 ;; See if this one should be the default.
	 (and (null default)
	      (<= (match-beginning 0) start-point)
	      (<= start-point (point))
	      (setq default t))
	 ;; See if this one should be the alternate default.
	 (and (null alt-default)
	      (and (<= bol (match-beginning 0))
		   (<= (point) eol))
	      (setq alt-default t))
	 (setq i 0)
	 (while (setq i (string-match "[ \n\t]+" str i))
	   (setq str (concat (substring str 0 i) " "
			     (substring str (match-end 0))))
	   (setq i (1+ i)))
	 ;; Record as a completion and perhaps as default.
	 (if (eq default t) (setq default str))
	 (if (eq alt-default t) (setq alt-default str))
	 ;; Don't add this string if it's a duplicate.
	 ;; We use a loop instead of "(assoc str completions)" because
	 ;; we want to do a case-insensitive compare.
	 (let ((tail completions)
	       (tem (downcase str)))
	   (while (and tail
		       (not (string-equal tem (downcase (car (car tail))))))
	     (setq tail (cdr tail)))
	   (or tail
	       (setq completions
		     (cons (cons str nil)
			   completions))))))
     ;; If no good default was found, try an alternate.
     (or default
	 (setq default alt-default))
     ;; If only one cross-reference found, then make it default.
     (if (eq (length completions) 1)
         (setq default (car (car completions))))
     (if completions
	 (let ((input (completing-read (if default
					   (concat "Follow reference named: ("
						   default ") ")
					 "Follow reference named: ")
				       completions nil t)))
	   (list (if (equal input "")
		     default input)))
       (error "No cross-references in this node"))))
  (let (target beg i (str (concat "\\*note " (regexp-quote footnotename))))
    (while (setq i (string-match " " str i))
      (setq str (concat (substring str 0 i) "[ \t\n]+" (substring str (1+ i))))
      (setq i (+ i 6)))
    (save-excursion
      (goto-char (point-min))
      (or (re-search-forward str nil t)
	  (error "No cross-reference named %s" footnotename))
      (goto-char (+ (match-beginning 0) 5))
      (setq target
	    (Info-extract-menu-node-name "Bad format cross reference" t)))
    (while (setq i (string-match "[ \t\n]+" target i))
      (setq target (concat (substring target 0 i) " "
			   (substring target (match-end 0))))
      (setq i (+ i 1)))
    (Info-goto-node target)))

(defun Info-extract-menu-node-name (&optional errmessage multi-line)
  (skip-chars-forward " \t\n")
  (let ((beg (point))
	str i)
    (skip-chars-forward "^:")
    (forward-char 1)
    (setq str
	  (if (looking-at ":")
	      (buffer-substring-no-properties beg (1- (point)))
	    (skip-chars-forward " \t\n")
	    (Info-following-node-name (if multi-line "^.,\t" "^.,\t\n"))))
    (while (setq i (string-match "\n" str i))
      (aset str i ?\ ))
    ;; Collapse multiple spaces.
    (while (string-match "  +" str)
      (setq str (replace-match " " t t str)))
    str))

;; No one calls this.
;;(defun Info-menu-item-sequence (list)
;;  (while list
;;    (Info-menu (car list))
;;    (setq list (cdr list))))

(defun Info-complete-menu-item (string predicate action)
  (let ((case-fold-search t))
    (cond ((eq action nil)
	   (let (completions
		 (pattern (concat "\n\\* \\("
				  (regexp-quote string)
				  "[^:\t\n]*\\):")))
	     (save-excursion
	       (set-buffer Info-complete-menu-buffer)
	       (goto-char (point-min))
	       (search-forward "\n* Menu:")
	       (while (re-search-forward pattern nil t)
		 (setq completions (cons (cons (format "%s"
						       (buffer-substring
							(match-beginning 1)
							(match-end 1)))
					       (match-beginning 1))
					 completions))))
	     (try-completion string completions predicate)))
	  ((eq action t)
	   (let (completions
		 (pattern (concat "\n\\* \\("
				  (regexp-quote string)
				  "[^:\t\n]*\\):")))
	     (save-excursion
	       (set-buffer Info-complete-menu-buffer)
	       (goto-char (point-min))
	       (search-forward "\n* Menu:")
	       (while (re-search-forward pattern nil t)
		 (setq completions (cons (cons (format "%s"
						       (buffer-substring
							(match-beginning 1)
							(match-end 1)))
					       (match-beginning 1))
					 completions))))
	     (all-completions string completions predicate)))
	  (t
	   (save-excursion
	     (set-buffer Info-complete-menu-buffer)
	     (goto-char (point-min))
	     (search-forward "\n* Menu:")
	     (re-search-forward (concat "\n\\* "
					(regexp-quote string)
					":")
				nil t))))))


(defun Info-menu (menu-item)
  "Go to node for menu item named (or abbreviated) NAME.
Completion is allowed, and the menu item point is on is the default."
  (interactive
   (let ((completions '())
	 ;; If point is within a menu item, use that item as the default
	 (default nil)
	 (p (point))
	 beg
	 (last nil))
     (save-excursion
       (goto-char (point-min))
       (if (not (search-forward "\n* menu:" nil t))
	   (error "No menu in this node"))