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;; info.el --- info package for Emacs
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;; Copyright (C) 1985-1986, 1992-2014 Free Software Foundation, Inc.
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;; Maintainer: FSF
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;; Keywords: help
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;; This file is part of GNU Emacs.

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;; GNU Emacs is free software: you can redistribute it and/or modify
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;; it under the terms of the GNU General Public License as published by
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;; the Free Software Foundation, either version 3 of the License, or
;; (at your option) any later version.
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;; 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
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;; along with GNU Emacs.  If not, see <http://www.gnu.org/licenses/>.
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;;; Commentary:

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;; Note that nowadays we expect Info files to be made using makeinfo.
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;; In particular we make these assumptions:
;;  - a menu item MAY contain colons but not colon-space ": "
;;  - a menu item ending with ": " (but not ":: ") is an index entry
;;  - a node name MAY NOT contain a colon
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;; This distinction is to support indexing of computer programming
;; language terms that may contain ":" but not ": ".
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;;; Code:

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


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(defvar Info-history nil
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  "Stack of Info nodes user has visited.
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Each element of the stack is a list (FILENAME NODENAME BUFFERPOS).")
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(defvar Info-history-forward nil
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  "Stack of Info nodes user has visited with `Info-history-back' command.
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Each element of the stack is a list (FILENAME NODENAME BUFFERPOS).")
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(defvar Info-history-list nil
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  "List of all Info nodes user has visited.
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Each element of the list is a list (FILENAME NODENAME).")
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(defcustom Info-history-skip-intermediate-nodes t
  "Non-nil means don't record intermediate Info nodes to the history.
Intermediate Info nodes are nodes visited by Info internally in the process of
searching the node to display.  Intermediate nodes are not presented
to the user."
  :type 'boolean
  :group 'info
  :version "24.1")

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(defvar Info-enable-active-nodes nil
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  "Non-nil allows Info to execute Lisp code associated with nodes.
The Lisp code is executed when the node is selected.")
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(put 'Info-enable-active-nodes 'risky-local-variable t)
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(defface info-node
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  '((((class color) (background light)) :foreground "brown" :weight bold :slant italic)
    (((class color) (background dark)) :foreground "white" :weight bold :slant italic)
    (t :weight bold :slant italic))
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  "Face for Info node names."
  :group 'info)

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(defface info-title-1
  '((((type tty pc) (class color) (background light))
     :foreground "green" :weight bold)
    (((type tty pc) (class color) (background dark))
     :foreground "yellow" :weight bold)
    (t :height 1.2 :inherit info-title-2))
  "Face for info titles at level 1."
  :group 'info)
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(define-obsolete-face-alias 'Info-title-1-face 'info-title-1 "22.1")
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(defface info-title-2
  '((((type tty pc) (class color)) :foreground "lightblue" :weight bold)
    (t :height 1.2 :inherit info-title-3))
  "Face for info titles at level 2."
  :group 'info)
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(define-obsolete-face-alias 'Info-title-2-face 'info-title-2 "22.1")
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(defface info-title-3
  '((((type tty pc) (class color)) :weight bold)
    (t :height 1.2 :inherit info-title-4))
  "Face for info titles at level 3."
  :group 'info)
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(define-obsolete-face-alias 'Info-title-3-face 'info-title-3 "22.1")
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(defface info-title-4
  '((((type tty pc) (class color)) :weight bold)
    (t :weight bold :inherit variable-pitch))
  "Face for info titles at level 4."
  :group 'info)
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(define-obsolete-face-alias 'Info-title-4-face 'info-title-4 "22.1")
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(defface info-menu-header
  '((((type tty pc))
     :underline t
     :weight bold)
    (t
     :inherit variable-pitch
     :weight bold))
  "Face for headers in Info menus."
  :group 'info)

(defface info-menu-star
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  '((((class color)) :foreground "red1")
    (t :underline t))
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  "Face for every third `*' in an Info menu."
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  :group 'info)
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(define-obsolete-face-alias 'info-menu-5 'info-menu-star "22.1")
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(defface info-xref
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  '((t :inherit link))
  "Face for unvisited Info cross-references."
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  :group 'info)

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(defface info-xref-visited
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  '((t :inherit (link-visited info-xref)))
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  "Face for visited Info cross-references."
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  :version "22.1"
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  :group 'info)

(defcustom Info-fontify-visited-nodes t
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  "Non-nil to fontify references to visited nodes in `info-xref-visited' face."
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  :version "22.1"
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  :type 'boolean
  :group 'info)

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(defcustom Info-fontify-maximum-menu-size 100000
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  "Maximum size of menu to fontify if `font-lock-mode' is non-nil.
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Set to nil to disable node fontification."
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  :type 'integer
  :group 'info)
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(defcustom Info-use-header-line t
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  "Non-nil means to put the beginning-of-node links in an Emacs header-line.
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A header-line does not scroll with the rest of the buffer."
  :type 'boolean
  :group 'info)

(defface info-header-xref
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  '((t :inherit info-xref))
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  "Face for Info cross-references in a node header."
  :group 'info)

(defface info-header-node
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  '((t :inherit info-node))
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  "Face for Info nodes in a node header."
  :group 'info)

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(defface info-index-match
  '((t :inherit match))
  "Face used to highlight matches in an index entry."
  :group 'info
  :version "24.4")

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;; This is a defcustom largely so that we can get the benefit
;; of custom-initialize-delay.  Perhaps it would work to make it a
;; defvar and explicitly give it a standard-value property, and
;; call custom-initialize-delay on it.
;; The progn forces the autoloader to include the whole thing, not
;; just an abbreviated version.
;;;###autoload
(progn
(defcustom Info-default-directory-list
  (let* ((config-dir
	  (file-name-as-directory
	   ;; Self-contained NS build with info/ in the app-bundle.
	   (or (and (featurep 'ns)
		    (let ((dir (expand-file-name "../info" data-directory)))
		      (if (file-directory-p dir) dir)))
	       configure-info-directory)))
	 (prefixes
	  ;; Directory trees in which to look for info subdirectories
	  (prune-directory-list '("/usr/local/" "/usr/" "/opt/" "/")))
	 (suffixes
	  ;; Subdirectories in each directory tree that may contain info
	  ;; directories.  Most of these are rather outdated.
	  ;; It ought to be fine to stop checking the "emacs" ones now,
	  ;; since this is Emacs and we have not installed info files
	  ;; into such directories for a looong time...
	  '("share/" "" "gnu/" "gnu/lib/" "gnu/lib/emacs/"
	    "emacs/" "lib/" "lib/emacs/"))
	 (standard-info-dirs
	  (apply #'nconc
		 (mapcar (lambda (pfx)
			   (let ((dirs
				  (mapcar (lambda (sfx)
					    (concat pfx sfx "info/"))
					  suffixes)))
			     (prune-directory-list dirs)))
			 prefixes)))
	 ;; If $(prefix)/share/info is not one of the standard info
	 ;; directories, they are probably installing an experimental
	 ;; version of Emacs, so make sure that experimental version's Info
	 ;; files override the ones in standard directories.
	 (dirs
	  (if (member config-dir standard-info-dirs)
	      ;; FIXME?  What is the point of adding it again at the end
	      ;; when it is already present earlier in the list?
	      (nconc standard-info-dirs (list config-dir))
	    (cons config-dir standard-info-dirs))))
    (if (not (eq system-type 'windows-nt))
	dirs
      ;; Include the info directory near where Emacs executable was installed.
      (let* ((instdir (file-name-directory invocation-directory))
	     (dir1 (expand-file-name "../info/" instdir))
	     (dir2 (expand-file-name "../../../info/" instdir)))
	(cond ((file-exists-p dir1) (append dirs (list dir1)))
	      ((file-exists-p dir2) (append dirs (list dir2)))
	      (t dirs)))))

  "Default list of directories to search for Info documentation files.
They are searched in the order they are given in the list.
Therefore, the directory of Info files that come with Emacs
normally should come last (so that local files override standard ones),
unless Emacs is installed into a non-standard directory.  In the latter
case, the directory of Info files that come with Emacs should be
first in this list.

Once Info is started, the list of directories to search
comes from the variable `Info-directory-list'.
This variable `Info-default-directory-list' is used as the default
for initializing `Info-directory-list' when Info is started, unless
the environment variable INFOPATH is set.

Although this is a customizable variable, that is mainly for technical
reasons.  Normally, you should either set INFOPATH or customize
`Info-additional-directory-list', rather than changing this variable."
  :initialize 'custom-initialize-delay
  :type '(repeat directory)
  :group 'info))

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(defvar Info-directory-list nil
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  "List of directories to search for Info documentation files.
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If nil, meaning not yet initialized, Info uses the environment
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variable INFOPATH to initialize it, or `Info-default-directory-list'
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if there is no INFOPATH variable in the environment, or the
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concatenation of the two if INFOPATH ends with a `path-separator'.
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When `Info-directory-list' is initialized from the value of
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`Info-default-directory-list', and Emacs is installed in one of the
standard directories, the directory of Info files that come with Emacs
is put last (so that local Info files override standard ones).

When `Info-directory-list' is initialized from the value of
`Info-default-directory-list', and Emacs is not installed in one
of the standard directories, the first element of the resulting
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list is the directory where Emacs installs the Info files that
come with it.  This is so that Emacs's own manual, which suits the
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version of Emacs you are using, will always be found first.  This
is useful when you install an experimental version of Emacs without
removing the standard installation.

If you want to override the order of directories in
`Info-default-directory-list', set INFOPATH in the environment.
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If you run the Emacs executable from the `src' directory in the Emacs
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source tree, and INFOPATH is not defined, the `info' directory in the
source tree is used as the first element of `Info-directory-list', in
place of the installation Info directory.  This is useful when you run
a version of Emacs without installing it.")
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(defcustom Info-additional-directory-list nil
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  "List of additional directories to search for Info documentation files.
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These directories are searched after those in `Info-directory-list'."
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  :type '(repeat directory)
  :group 'info)
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(defcustom Info-scroll-prefer-subnodes nil
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  "If non-nil, \\<Info-mode-map>\\[Info-scroll-up] in a menu visits subnodes.
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If this is non-nil, and you scroll far enough in a node that its menu
appears on the screen, the next \\<Info-mode-map>\\[Info-scroll-up]
moves to a subnode indicated by the following menu item.  This means
that you visit a subnode before getting to the end of the menu.

Setting this option to nil results in behavior similar to the stand-alone
Info reader program, which visits the first subnode from the menu only
when you hit the end of the current node."
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  :version "22.1"
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  :type 'boolean
  :group 'info)

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(defcustom Info-hide-note-references t
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  "If non-nil, hide the tag and section reference in *note and * menu items.
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If value is non-nil but not `hide', also replaces the \"*note\" with \"see\".
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If value is non-nil but not t or `hide', the reference section is still shown.
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`nil' completely disables this feature.  If this is non-nil, you might
want to set `Info-refill-paragraphs'."
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  :version "22.1"
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  :type '(choice (const :tag "No hiding" nil)
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		 (const :tag "Replace tag and hide reference" t)
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		 (const :tag "Hide tag and reference" hide)
		 (other :tag "Only replace tag" tag))
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  :set (lambda (sym val)
	 (set sym val)
	 (dolist (buffer (buffer-list))
	   (with-current-buffer buffer
	     (when (eq major-mode 'Info-mode)
	       (revert-buffer t t)))))
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  :group 'info)

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(defcustom Info-refill-paragraphs nil
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  "If non-nil, attempt to refill paragraphs with hidden references.
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This refilling may accidentally remove explicit line breaks in the Info
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file, so be prepared for a few surprises if you enable this feature.
This only has an effect if `Info-hide-note-references' is non-nil."
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  :version "22.1"
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  :type 'boolean
  :group 'info)

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(defcustom Info-breadcrumbs-depth 4
  "Depth of breadcrumbs to display.
0 means do not display breadcrumbs."
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  :version "23.1"
  :type 'integer
  :group 'info)
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(defcustom Info-search-whitespace-regexp "\\s-+"
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  "If non-nil, regular expression to match a sequence of whitespace chars.
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This applies to Info search for regular expressions.
You might want to use something like \"[ \\t\\r\\n]+\" instead.
In the Customization buffer, that is `[' followed by a space,
a tab, a carriage return (control-M), a newline, and `]+'."
  :type 'regexp
  :group 'info)

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(defcustom Info-isearch-search t
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  "If non-nil, isearch in Info searches through multiple nodes.
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Before leaving the initial Info node, where isearch was started,
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it fails once with the error message [end of node], and with
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subsequent C-s/C-r continues through other nodes without failing
with this error message in other nodes.  When isearch fails for
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the rest of the manual, it displays the error message [end of manual],
wraps around the whole manual and restarts the search from the top/final
node depending on search direction.
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Setting this option to nil restores the default isearch behavior
with wrapping around the current Info node."
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  :version "22.1"
  :type 'boolean
  :group 'info)

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(defvar Info-isearch-initial-node nil)
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(defvar Info-isearch-initial-history nil)
(defvar Info-isearch-initial-history-list nil)
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(defcustom Info-mode-hook
  ;; Try to obey obsolete Info-fontify settings.
  (unless (and (boundp 'Info-fontify) (null Info-fontify))
    '(turn-on-font-lock))
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  "Hooks run when `Info-mode' is called."
  :type 'hook
  :group 'info)

(defcustom Info-selection-hook nil
  "Hooks run when `Info-select-node' is called."
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  :type 'hook
  :group 'info)

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(defvar Info-edit-mode-hook nil
  "Hooks run when `Info-edit-mode' is called.")

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(make-obsolete-variable 'Info-edit-mode-hook
			"editing Info nodes by hand is not recommended." "24.4")

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(defvar Info-current-file nil
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  "Info file that Info is now looking at, or nil.
This is the name that was specified in Info, not the actual file name.
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It doesn't contain directory names or file name extensions added by Info.")
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(defvar Info-current-subfile nil
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  "Info subfile that is actually in the *info* buffer now.
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It is nil if current Info file is not split into subfiles.")
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(defvar Info-current-node nil
  "Name of node that Info is now looking at, or nil.")

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

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

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

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(defvar Info-file-completions nil
  "Cached completion alist of visited Info files.
Each element of the alist is (FILE . COMPLETIONS)")

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(defvar Info-file-supports-index-cookies nil
  "Non-nil if current Info file supports index cookies.")

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(defvar Info-file-supports-index-cookies-list nil
  "List of Info files with information about index cookies support.
Each element of the list is a list (FILENAME SUPPORTS-INDEX-COOKIES)
where SUPPORTS-INDEX-COOKIES can be either t or nil.")

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(defvar Info-index-alternatives nil
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  "List of possible matches for last `Info-index' command.")
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(defvar Info-point-loc nil
  "Point location within a selected node.
If string, the point is moved to the proper occurrence of the
name of the followed cross reference within a selected node.
If number, the point is moved to the corresponding line.")
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(defvar Info-standalone nil
  "Non-nil if Emacs was started solely as an Info browser.")
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(defvar Info-file-attributes nil
  "Alist of file attributes of visited Info files.
Each element is a list (FILE-NAME FILE-ATTRIBUTES...).")

(defvar Info-toc-nodes nil
  "Alist of cached parent-children node information in visited Info files.
Each element is (FILE (NODE-NAME PARENT SECTION CHILDREN) ...)
where PARENT is the parent node extracted from the Up pointer,
SECTION is the section name in the Top node where this node is placed,
CHILDREN is a list of child nodes extracted from the node menu.")

(defvar Info-index-nodes nil
  "Alist of cached index node names of visited Info files.
Each element has the form (INFO-FILE INDEX-NODE-NAMES-LIST).")

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(defvar Info-virtual-files nil
  "List of definitions of virtual Info files.
Each element of the list has the format (FILENAME (OPERATION . HANDLER) ...)
where FILENAME is a regexp that matches a class of virtual Info file names.
It should be carefully chosen to not cause file name clashes with
existing file names.  OPERATION is one of the following operation
symbols `find-file', `find-node', `toc-nodes' that define what HANDLER
function to call instead of calling the default corresponding function
to override it.")

(defvar Info-virtual-nodes nil
  "List of definitions of virtual Info nodes.
Each element of the list has the format (NODENAME (OPERATION . HANDLER) ...)
where NODENAME is a regexp that matches a class of virtual Info node names.
It should be carefully chosen to not cause node name clashes with
existing node names.  OPERATION is one of the following operation
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symbols `find-node' that define what HANDLER function to call instead
of calling the default corresponding function to override it.")
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(defvar Info-current-node-virtual nil
  "Non-nil if the current Info node is virtual.")

(defun Info-virtual-file-p (filename)
  "Check if Info file FILENAME is virtual."
  (Info-virtual-fun 'find-file filename nil))

(defun Info-virtual-fun (op filename nodename)
  "Find a function that handles operations on virtual manuals.
OP is an operation symbol (`find-file', `find-node' or `toc-nodes'),
FILENAME is a virtual Info file name, NODENAME is a virtual Info
node name.  Return a function found either in `Info-virtual-files'
or `Info-virtual-nodes'."
  (or (and (stringp filename) ; some legacy code can still use a symbol
	   (cdr-safe (assoc op (assoc-default filename
					      Info-virtual-files
					      'string-match))))
      (and (stringp nodename) ; some legacy code can still use a symbol
	   (cdr-safe (assoc op (assoc-default nodename
					      Info-virtual-nodes
					      'string-match))))))

(defun Info-virtual-call (virtual-fun &rest args)
  "Call a function that handles operations on virtual manuals."
  (when (functionp virtual-fun)
    (or (apply virtual-fun args) t)))

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(defvar Info-suffix-list
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  ;; The MS-DOS list should work both when long file names are
  ;; supported (Windows 9X), and when only 8+3 file names are available.
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  (if (eq system-type 'ms-dos)
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      '( (".gz"       . "gunzip")
	 (".z"        . "gunzip")
	 (".bz2"      . ("bzip2" "-dc"))
	 (".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.bz2"  . ("bzip2" "-dc"))
       (".info.xz"   . "unxz")
       (".info"      . nil)
       ("-info.Z"    . "uncompress")
       ("-info.Y"    . "unyabba")
       ("-info.gz"   . "gunzip")
       ("-info.bz2"  . ("bzip2" "-dc"))
       ("-info.z"    . "gunzip")
       ("-info.xz"   . "unxz")
       ("-info"      . nil)
       ("/index.Z"   . "uncompress")
       ("/index.Y"   . "unyabba")
       ("/index.gz"  . "gunzip")
       ("/index.z"   . "gunzip")
       ("/index.bz2" . ("bzip2" "-dc"))
       ("/index.xz"  . "unxz")
       ("/index"     . nil)
       (".Z"         . "uncompress")
       (".Y"         . "unyabba")
       (".gz"        . "gunzip")
       (".z"         . "gunzip")
       (".bz2"       . ("bzip2" "-dc"))
       (".xz"        . "unxz")
       (""           . nil)))
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  "List of file name suffixes and associated decoding commands.
Each entry should be (SUFFIX . STRING); the file is given to
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the command as standard input.

STRING may be a list of strings.  In that case, the first element is
the command name, and the rest are arguments to that command.

If STRING is nil, no decoding is done.
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Because the SUFFIXes are tried in order, the empty string should
be last in the list.")
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;; Concatenate SUFFIX onto FILENAME.  SUFFIX should start with a dot.
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;; First, on MS-DOS with no long file names support, delete some of
;; the extension in FILENAME to make room.
(defun info-insert-file-contents-1 (filename suffix lfn)
  (if lfn	; long file names are supported
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      (concat filename suffix)
    (let* ((sans-exts (file-name-sans-extension filename))
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	   ;; How long is the extension in FILENAME (not counting the dot).
	   (ext-len (max 0 (- (length filename) (length sans-exts) 1)))
	   ext-left)
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      ;; SUFFIX starts with a dot.  If FILENAME already has one,
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      ;; get rid of the one in SUFFIX (unless suffix is empty).
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      (or (and (<= ext-len 0)
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	       (not (eq (aref filename (1- (length filename))) ?.)))
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	  (= (length suffix) 0)
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	  (setq suffix (substring suffix 1)))
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      ;; How many chars of that extension should we keep?
      (setq ext-left (min ext-len (max 0 (- 3 (length suffix)))))
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      ;; Get rid of the rest of the extension, and add SUFFIX.
      (concat (substring filename 0 (- (length filename)
				       (- ext-len ext-left)))
	      suffix))))

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(defun info-file-exists-p (filename)
  (and (file-exists-p filename)
       (not (file-directory-p filename))))

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(defun info-insert-file-contents (filename &optional visit)
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  "Insert the contents of an Info file in the current buffer.
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Do the right thing if the file has been compressed or zipped."
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  (let* ((tail Info-suffix-list)
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	 (jka-compr-verbose nil)
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	 (lfn (if (fboundp 'msdos-long-file-names)
		  (msdos-long-file-names)
		t))
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	 (check-short (and (fboundp 'msdos-long-file-names)
			   lfn))
	 fullname decoder done)
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    (if (info-file-exists-p filename)
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	;; FILENAME exists--see if that name contains a suffix.
	;; If so, set DECODE accordingly.
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	(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))))
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      ;; Try adding suffixes to FILENAME and see if we can find something.
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      (while (and tail (not done))
	(setq fullname (info-insert-file-contents-1 filename
						    (car (car tail)) lfn))
	(if (info-file-exists-p fullname)
	    (setq done t
		  ;; If we found a file with a suffix, set DECODER
		  ;; according to the suffix.
		  decoder (cdr (car tail)))
	  ;; When the MS-DOS port runs on Windows, we need to check
	  ;; the short variant of a long file name as well.
	  (when check-short
	    (setq fullname (info-insert-file-contents-1 filename
							(car (car tail)) nil))
	    (if (info-file-exists-p fullname)
		(setq done t
		      decoder (cdr (car tail))))))
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	(setq tail (cdr tail)))
      (or tail
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	  (error "Can't find %s or any compressed version of it" filename)))
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    ;; check for conflict with jka-compr
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    (if (and (jka-compr-installed-p)
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	     (jka-compr-get-compression-info fullname))
	(setq decoder nil))
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    (if decoder
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	(progn
	  (insert-file-contents-literally fullname visit)
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	  (let ((inhibit-read-only t)
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		(coding-system-for-write 'no-conversion)
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		(inhibit-null-byte-detection t) ; Index nodes include null bytes
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		(default-directory (or (file-name-directory fullname)
				       default-directory)))
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	    (or (consp decoder)
		(setq decoder (list decoder)))
	    (apply 'call-process-region (point-min) (point-max)
		   (car decoder) t t nil (cdr decoder))))
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      (let ((inhibit-null-byte-detection t)) ; Index nodes include null bytes
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	(insert-file-contents fullname visit)))

    ;; Clear the caches of modified Info files.
    (let* ((attribs-old (cdr (assoc fullname Info-file-attributes)))
	   (modtime-old (and attribs-old (nth 5 attribs-old)))
	   (attribs-new (and (stringp fullname) (file-attributes fullname)))
	   (modtime-new (and attribs-new (nth 5 attribs-new))))
      (when (and modtime-old modtime-new
		 (> (float-time modtime-new) (float-time modtime-old)))
	(setq Info-index-nodes (remove (assoc (or Info-current-file filename)
					      Info-index-nodes)
				       Info-index-nodes))
	(setq Info-toc-nodes (remove (assoc (or Info-current-file filename)
					    Info-toc-nodes)
				     Info-toc-nodes)))
      ;; Add new modtime to `Info-file-attributes'.
      (setq Info-file-attributes
	    (cons (cons fullname attribs-new)
		  (remove (assoc fullname Info-file-attributes)
			  Info-file-attributes))))))
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(defun Info-file-supports-index-cookies (&optional file)
  "Return non-nil value if FILE supports Info index cookies.
Info index cookies were first introduced in 4.7, and all later
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makeinfo versions output them in index nodes, so we can rely
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solely on the makeinfo version.  This function caches the information
in `Info-file-supports-index-cookies-list'."
  (or file (setq file Info-current-file))
  (or (assoc file Info-file-supports-index-cookies-list)
      ;; Skip virtual Info files
      (and (or (not (stringp file))
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	       (Info-virtual-file-p file))
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           (setq Info-file-supports-index-cookies-list
		 (cons (cons file nil) Info-file-supports-index-cookies-list)))
      (save-excursion
	(let ((found nil))
	  (goto-char (point-min))
	  (condition-case ()
	      (if (and (re-search-forward
			"makeinfo[ \n]version[ \n]\\([0-9]+.[0-9]+\\)"
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			(line-beginning-position 4) t)
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		       (not (version< (match-string 1) "4.7")))
		  (setq found t))
	    (error nil))
	  (setq Info-file-supports-index-cookies-list
		(cons (cons file found) Info-file-supports-index-cookies-list)))))
  (cdr (assoc file Info-file-supports-index-cookies-list)))

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(defun Info-default-dirs ()
  (let ((source (expand-file-name "info/" source-directory))
	(sibling (if installation-directory
		     (expand-file-name "info/" installation-directory)
		   (if invocation-directory
		       (let ((infodir (expand-file-name
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				       "../share/info/"
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				       invocation-directory)))
			 (if (file-exists-p infodir)
			     infodir
			   (setq infodir (expand-file-name
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					  "../../../share/info/"
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					  invocation-directory))
			   (and (file-exists-p infodir)
				infodir))))))
	alternative)
    (setq alternative
	  (if (and sibling (file-exists-p sibling))
	      ;; Uninstalled, Emacs builddir != srcdir.
	      sibling
	    ;; Uninstalled, builddir == srcdir
	    source))
    (if (or (member alternative Info-default-directory-list)
	    ;; On DOS/NT, we use movable executables always,
	    ;; and we must always find the Info dir at run time.
	    (if (memq system-type '(ms-dos 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))))
	    (not (file-exists-p alternative)))
	Info-default-directory-list
      ;; `alternative' contains the Info files that came with this
      ;; version, so we should look there first.  `Info-insert-dir'
      ;; currently expects to find `alternative' first on the list.
      (cons alternative
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	    ;; Don't drop the last part, it might contain non-Emacs stuff.
	    ;; (reverse (cdr (reverse
	    Info-default-directory-list)))) ;; )))
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(defun info-initialize ()
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  "Initialize `Info-directory-list', if that hasn't been done yet."
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  (unless Info-directory-list
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    (let ((path (getenv "INFOPATH"))
	  (sep (regexp-quote path-separator)))
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      (setq Info-directory-list
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	    (prune-directory-list
	     (if path
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		 (if (string-match-p (concat sep "\\'") path)
		     (append (split-string (substring path 0 -1) sep)
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			     (Info-default-dirs))
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		   (split-string path sep))
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	       (Info-default-dirs))))
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      ;; If we are running uninstalled, our own Info files should
      ;; always come first.  If INFOPATH was set, they might not.
      (and path
	   installation-directory
	   (let ((dir (expand-file-name "info/" installation-directory)))
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	     (when (file-directory-p dir)
	       (setq Info-directory-list (delete dir Info-directory-list))
	       (push dir Info-directory-list))))
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      ;; For a self-contained (ie relocatable) NS build, AFAICS we
      ;; always want the included info directory to be at the head of
      ;; the search path, unless it's already in INFOPATH somewhere.
      ;; It's at the head of Info-default-directory-list,
      ;; but there's no way to get it at the head of Info-directory-list
      ;; except by doing it here.
      (and path
	   (featurep 'ns)
	   (let ((dir (expand-file-name "../info" data-directory)))
	     (and (file-directory-p dir)
		  (not (member dir (split-string path ":" t)))
		  (push dir Info-directory-list)))))))
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;;;###autoload
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(defun info-other-window (&optional file-or-node buffer)
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  "Like `info' but show the Info buffer in another window."
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  (interactive (list
		(if (and current-prefix-arg (not (numberp current-prefix-arg)))
		    (read-file-name "Info file name: " nil nil t))
		(if (numberp current-prefix-arg)
		    (format "*info*<%s>" current-prefix-arg))))
  (info-setup file-or-node
	      (switch-to-buffer-other-window (or buffer "*info*"))))
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;;;###autoload (put 'info 'info-file (purecopy "emacs"))
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;;;###autoload
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(defun info (&optional file-or-node buffer)
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  "Enter Info, the documentation browser.
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Optional argument FILE-OR-NODE specifies the file to examine;
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the default is the top-level directory of Info.
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Called from a program, FILE-OR-NODE may specify an Info node of the form
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\"(FILENAME)NODENAME\".
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Optional argument BUFFER specifies the Info buffer name;
the default buffer name is *info*.  If BUFFER exists,
just switch to BUFFER.  Otherwise, create a new buffer
with the top-level Info directory.
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In interactive use, a non-numeric prefix argument directs
this command to read a file name from the minibuffer.
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A numeric prefix argument N selects an Info buffer named
\"*info*<%s>\".
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The search path for Info files is in the variable `Info-directory-list'.
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The top-level Info directory is made by combining all the files named `dir'
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in all the directories in that path.

See a list of available Info commands in `Info-mode'."
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  (interactive (list
                (if (and current-prefix-arg (not (numberp current-prefix-arg)))
                    (read-file-name "Info file name: " nil nil t))
                (if (numberp current-prefix-arg)
                    (format "*info*<%s>" current-prefix-arg))))
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  (info-setup file-or-node
	      (pop-to-buffer-same-window (or buffer "*info*"))))
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(defun info-setup (file-or-node buffer)
  "Display Info node FILE-OR-NODE in BUFFER."
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  (if (and buffer (not (derived-mode-p 'Info-mode)))
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      (Info-mode))
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  (if file-or-node
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      ;; If argument already contains parentheses, don't add another set
      ;; since the argument will then be parsed improperly.  This also
      ;; has the added benefit of allowing node names to be included
      ;; following the parenthesized filename.
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      (Info-goto-node
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       (if (and (stringp file-or-node) (string-match "(.*)" file-or-node))
           file-or-node
         (concat "(" file-or-node ")")))
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    (if (and (zerop (buffer-size))
	     (null Info-history))
	;; If we just created the Info buffer, go to the directory.
	(Info-directory))))
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;;;###autoload
(defun info-emacs-manual ()
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  "Display the Emacs manual in Info mode."
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  (interactive)
  (info "emacs"))

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;;;###autoload
(defun info-emacs-bug ()
  "Display the \"Reporting Bugs\" section of the Emacs manual in Info mode."
  (interactive)
  (info "(emacs)Bugs"))

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;;;###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)))
846

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;; See if the accessible portion of the buffer begins with a node
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;; delimiter, and the node header line which follows matches REGEXP.
;; Typically, this test will be followed by a loop that examines the
;; rest of the buffer with (search-forward "\n\^_"), and it's a pity
;; to have the overhead of this special test inside the loop.

;; This function changes match-data, but supposedly the caller might
;; want to use the results of re-search-backward.

;; The return value is the value of point at the beginning of matching
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;; REGEXP, if the function succeeds, nil otherwise.
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(defun Info-node-at-bob-matching (regexp)
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  (and (bobp)				; are we at beginning of buffer?
       (looking-at "\^_")		; does it begin with node delimiter?
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       (let (beg)
	 (forward-line 1)
	 (setq beg (point))
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	 (forward-line 1)		; does the line after delimiter match REGEXP?
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	 (re-search-backward regexp beg t))))

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(defun Info-find-file (filename &optional noerror)
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  "Return expanded FILENAME, or t if FILENAME is \"dir\".
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Optional second argument NOERROR, if t, means if file is not found
just return nil (no error)."
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  ;; Convert filename to lower case if not found as specified.
  ;; Expand it.
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  (cond
   ((Info-virtual-call
     (Info-virtual-fun 'find-file filename nil)
     filename noerror))
   ((stringp filename)
    (let (temp temp-downcase found)
      (setq filename (substitute-in-file-name filename))
      (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)))))
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	;; Fall back on the installation directory if we can't find
	;; the info node anywhere else.
	(when installation-directory
	  (setq dirs (append dirs (list (expand-file-name
					 "info" installation-directory)))))
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	;; 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)
		(lfn (if (fboundp 'msdos-long-file-names)
			 (msdos-long-file-names)
		       t)))
	    (while (and suffix-list (not found))
	      (cond ((info-file-exists-p
		      (info-insert-file-contents-1
		       temp (car (car suffix-list)) lfn))
		     (setq found temp))
		    ((info-file-exists-p
		      (info-insert-file-contents-1
		       temp-downcase (car (car suffix-list)) lfn))
		     (setq found temp-downcase))
		    ((and (fboundp 'msdos-long-file-names)
			  lfn
			  (info-file-exists-p
			   (info-insert-file-contents-1
			    temp (car (car suffix-list)) nil)))
		     (setq found temp)))
	      (setq suffix-list (cdr suffix-list))))
	  (setq dirs (cdr dirs))))
      (if found
	  (setq filename found)
	(if noerror
	    (setq filename nil)
	  (error "Info file %s does not exist" filename)))
      filename))))
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(defun Info-find-node (filename nodename &optional no-going-back strict-case)
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  "Go to an Info node specified as separate FILENAME and NODENAME.
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NO-GOING-BACK is non-nil if recovering from an error in this function;
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it says do not attempt further (recursive) error recovery.

This function first looks for a case-sensitive match for NODENAME;
if none is found it then tries a case-insensitive match (unless
STRICT-CASE is non-nil)."
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  (info-initialize)
  (setq filename (Info-find-file filename))
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  ;; Go into Info buffer.
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  (or (derived-mode-p 'Info-mode) (switch-to-buffer "*info*"))
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  ;; Record the node we are leaving, if we were in one.
  (and (not no-going-back)
       Info-current-file
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       (push (list Info-current-file Info-current-node (point))
             Info-history))
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  (Info-find-node-2 filename nodename no-going-back strict-case))
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;;;###autoload
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(defun Info-on-current-buffer (&optional nodename)
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  "Use Info mode to browse the current Info buffer.
With a prefix arg, this queries for the node name to visit first;
otherwise, that defaults to `Top'."
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  (interactive
   (list (if current-prefix-arg
	     (completing-read "Node name: " (Info-build-node-completions)
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			      nil t "Top"))))
  (unless nodename (setq nodename "Top"))
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  (info-initialize)
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  (Info-mode)
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  (set (make-local-variable 'Info-current-file)
       (or buffer-file-name
	   ;; If called on a non-file buffer, make a fake file name.
	   (concat default-directory (buffer-name))))
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  (Info-find-node-2 nil nodename))

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(defun Info-revert-find-node (filename nodename)
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  "Go to an Info node FILENAME and NODENAME, re-reading disk contents.
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When *info* is already displaying FILENAME and NODENAME, the window position
is preserved, if possible."
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  (or (derived-mode-p 'Info-mode) (switch-to-buffer "*info*"))
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  (let ((old-filename Info-current-file)
	(old-nodename Info-current-node)
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	(window-selected (eq (selected-window) (get-buffer-window)))
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	(pcolumn      (current-column))
	(pline        (count-lines (point-min) (line-beginning-position)))
	(wline        (count-lines (point-min) (window-start)))
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	(new-history  (and Info-current-file
			   (list Info-current-file Info-current-node (point)))))
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    ;; When `Info-current-file' is nil, `Info-find-node-2' rereads the file.
    (setq Info-current-file nil)
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    (Info-find-node filename nodename)
    (if (and (equal old-filename Info-current-file)
	     (equal old-nodename Info-current-node))
	(progn
	  ;; note goto-line is no good, we want to measure from point-min
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	  (when window-selected
	    (goto-char (point-min))
	    (forward-line wline)
	    (set-window-start (selected-window) (point)))
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	  (goto-char (point-min))
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	  (forward-line pline)
	  (move-to-column pcolumn))
      ;; only add to the history when coming from a different file+node
      (if new-history
	  (setq Info-history (cons new-history Info-history))))))

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(defun Info-revert-buffer-function (_ignore-auto noconfirm)
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  (when (or noconfirm (y-or-n-p "Revert info buffer? "))
    (Info-revert-find-node Info-current-file Info-current-node)
    (message "Reverted %s" Info-current-file)))

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(defun Info-find-in-tag-table-1 (marker regexp case-fold)
  "Find a node in a tag table.
MARKER specifies the buffer and position to start searching at.
REGEXP is a regular expression matching nodes or references.  Its first
group should match `Node:' or `Ref:'.
CASE-FOLD t means search for a case-insensitive match.
If a match was found, value is a list (FOUND-ANCHOR POS MODE), where
FOUND-ANCHOR is non-nil if a `Ref:' was matched, POS is the position
where the match was found, and MODE is `major-mode' of the buffer in
which the match was found."
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  (let ((case-fold-search case-fold))
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    (with-current-buffer (marker-buffer marker)
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      (goto-char marker)
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      ;; Search tag table
      (beginning-of-line)
      (when (re-search-forward regexp nil t)
	(list (string-equal "Ref:" (match-string 1))
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	      (+ (point-min) (read (current-buffer)))
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	      major-mode)))))

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(defun Info-find-in-tag-table (marker regexp &optional strict-case)
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  "Find a node in a tag table.
MARKER specifies the buffer and position to start searching at.
REGEXP is a regular expression matching nodes or references.  Its first
group should match `Node:' or `Ref:'.
If a match was found, value is a list (FOUND-ANCHOR POS MODE), where
FOUND-ANCHOR is non-nil if a `Ref:' was matched, POS is the position
where the match was found, and MODE is `major-mode' of the buffer in
which the match was found.
This function tries to find a case-sensitive match first, then a
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case-insensitive match is tried (unless optional argument STRICT-CASE
is non-nil)."
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  (let ((result (Info-find-in-tag-table-1 marker regexp nil)))
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    (or strict-case (car result)
	(setq result (Info-find-in-tag-table-1 marker regexp t)))
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    result))

(defun Info-find-node-in-buffer-1 (regexp case-fold)
  "Find a node or anchor in the current buffer.
REGEXP is a regular expression matching nodes or references.  Its first
group should match `Node:' or `Ref:'.
CASE-FOLD t means search for a case-insensitive match.
Value is the position at which a match was found, or nil if not found."
  (let ((case-fold-search case-fold)
	found)
    (save-excursion
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      (if (Info-node-at-bob-matching regexp)
          (setq found (point))
        (while (and (not found)
                    (search-forward "\n\^_" nil t))
          (forward-line 1)
          (let ((beg (point)))
            (forward-line 1)
            (if (re-search-backward regexp beg t)
                (setq found (line-beginning-position)))))))
    found))
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(defun Info-find-node-in-buffer (regexp &optional strict-case)
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  "Find a node or anchor in the current buffer.
REGEXP is a regular expression matching nodes or references.  Its first
group should match `Node:' or `Ref:'.
Value is the position at which a match was found, or nil if not found.
This function looks for a case-sensitive match first.  If none is found,
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a case-insensitive match is tried (unless optional argument STRICT-CASE
is non-nil)."
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  (or (Info-find-node-in-buffer-1 regexp nil)
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      (and (not strict-case)
	   (Info-find-node-in-buffer-1 regexp t))))
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(defun Info-find-node-2 (filename nodename &optional no-going-back strict-case)
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  (buffer-disable-undo (current-buffer))
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  (or (derived-mode-p 'Info-mode)
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      (Info-mode))
  (widen)
  (setq Info-current-node nil)
  (unwind-protect
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      (let ((case-fold-search t)
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	    (virtual-fun (Info-virtual-fun 'find-node
					   (or filename Info-current-file)
					   nodename))