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;;; mule-cmds.el --- commands for mulitilingual environment
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;; Copyright (C) 1995 Electrotechnical Laboratory, JAPAN.
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;; Licensed to the Free Software Foundation.
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;; Copyright (C) 2000, 2001, 2002 Free Software Foundation, Inc.
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;; Keywords: mule, multilingual

;; 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
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;; 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.
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;;; Commentary:

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;;; Code:

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(eval-when-compile (defvar dos-codepage))

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;;; MULE related key bindings and menus.

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(defvar mule-keymap (make-sparse-keymap)
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  "Keymap for Mule (Multilingual environment) specific commands.")
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;; Keep "C-x C-m ..." for mule specific commands.
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(define-key ctl-x-map "\C-m" mule-keymap)
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(define-key mule-keymap "f" 'set-buffer-file-coding-system)
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(define-key mule-keymap "r" 'revert-buffer-with-coding-system)
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(define-key mule-keymap "t" 'set-terminal-coding-system)
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(define-key mule-keymap "k" 'set-keyboard-coding-system)
(define-key mule-keymap "p" 'set-buffer-process-coding-system)
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(define-key mule-keymap "x" 'set-selection-coding-system)
(define-key mule-keymap "X" 'set-next-selection-coding-system)
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(define-key mule-keymap "\C-\\" 'set-input-method)
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(define-key mule-keymap "c" 'universal-coding-system-argument)
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(define-key mule-keymap "l" 'set-language-environment)
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(defvar mule-menu-keymap
  (make-sparse-keymap "Mule (Multilingual Environment)")
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  "Keymap for Mule (Multilingual environment) menu specific commands.")
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(defvar describe-language-environment-map
  (make-sparse-keymap "Describe Language Environment"))
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(defvar setup-language-environment-map
  (make-sparse-keymap "Set Language Environment"))
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(defvar set-coding-system-map
  (make-sparse-keymap "Set Coding System"))
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(define-key-after mule-menu-keymap [set-language-environment]
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  (list 'menu-item  "Set Language Environment" setup-language-environment-map
	:help "Multilingual environment suitable for a specific language"))
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(define-key-after mule-menu-keymap [mouse-set-font]
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  '(menu-item "Set Font/Fontset" mouse-set-font
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	       :visible (fboundp 'generate-fontset-menu)
	       :help "Select a font from list of known fonts/fontsets"))
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(define-key-after mule-menu-keymap [separator-mule]
  '("--")
  t)
(define-key-after mule-menu-keymap [toggle-input-method]
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  '(menu-item "Toggle Input Method" toggle-input-method)
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  t)
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(define-key-after mule-menu-keymap [set-input-method]
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  '(menu-item "Select Input Method..." set-input-method)
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  t)
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(define-key-after mule-menu-keymap [describe-input-method]
  '(menu-item "Describe Input Method"  describe-input-method))
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(define-key-after mule-menu-keymap [separator-input-method]
  '("--")
  t)
(define-key-after mule-menu-keymap [set-various-coding-system]
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  (list 'menu-item "Set Coding Systems" set-coding-system-map
	:enable 'enable-multibyte-characters))
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(define-key-after mule-menu-keymap [view-hello-file]
  '(menu-item "Show Multi-lingual Text" view-hello-file
	      :enable (file-readable-p
		       (expand-file-name "HELLO" data-directory))
	      :help "Display file which says HELLO in many languages")
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  t)
(define-key-after mule-menu-keymap [separator-coding-system]
  '("--")
  t)
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(define-key-after mule-menu-keymap [describe-language-environment]
  (list 'menu-item "Describe Language Environment"
	describe-language-environment-map
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	:help "Show multilingual settings for a specific language")
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  t)
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(define-key-after mule-menu-keymap [describe-input-method]
  '(menu-item "Describe Input Method..." describe-input-method
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	      :help "Keyboard layout for a specific input method")
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  t)
(define-key-after mule-menu-keymap [describe-coding-system]
  '(menu-item "Describe Coding System..." describe-coding-system)
  t)
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(define-key-after mule-menu-keymap [list-character-sets]
  '(menu-item "List Character Sets" list-character-sets
	      :help "Show table of available character sets"))
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(define-key-after mule-menu-keymap [mule-diag]
  '(menu-item "Show All of Mule Status" mule-diag
	      :help "Display multilingual environment settings")
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  t)

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(define-key-after set-coding-system-map [universal-coding-system-argument]
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  '(menu-item "For Next Command" universal-coding-system-argument
	      :help "Coding system to be used by next command")
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  t)
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(define-key-after set-coding-system-map [separator-1]
  '("--")
  t)
(define-key-after set-coding-system-map [set-buffer-file-coding-system]
  '(menu-item "For Saving This Buffer" set-buffer-file-coding-system
	      :help "How to encode this buffer when saved")
  t)
(define-key-after set-coding-system-map [revert-buffer-with-coding-system]
  '(menu-item "For Reverting This File Now" revert-buffer-with-coding-system
	      :enable buffer-file-name
	      :help "Revisit this file immediately using specified coding system")
  t)
(define-key-after set-coding-system-map [separator-2]
  '("--")
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  t)
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(define-key-after set-coding-system-map [set-keyboard-coding-system]
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  '(menu-item "For Keyboard" set-keyboard-coding-system
	      :help "How to decode keyboard input")
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  t)
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(define-key-after set-coding-system-map [set-terminal-coding-system]
  '(menu-item "For Terminal" set-terminal-coding-system
	      :enable (null (memq window-system '(x w32 mac)))
	      :help "How to encode terminal output")
  t)
(define-key-after set-coding-system-map [separator-3]
  '("--")
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  t)
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(define-key-after set-coding-system-map [set-selection-coding-system]
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  '(menu-item "For X Selections/Clipboard" set-selection-coding-system
	      :visible (display-selections-p)
	      :help "How to en/decode data to/from selection/clipboard")
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  t)
(define-key-after set-coding-system-map [set-next-selection-coding-system]
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  '(menu-item "For Next X Selection" set-next-selection-coding-system
	      :visible (display-selections-p)
	      :help "How to en/decode next selection/clipboard operation")
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  t)
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(define-key-after set-coding-system-map [set-buffer-process-coding-system]
  '(menu-item "For I/O with Subprocess" set-buffer-process-coding-system
	      :visible (fboundp 'start-process)
	      :enable (get-buffer-process (current-buffer))
	      :help "How to en/decode I/O from/to subprocess connected to this buffer")
  t)


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(define-key setup-language-environment-map
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  [Default] '(menu-item "Default" setup-specified-language-environment))
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(define-key describe-language-environment-map
  [Default] '(menu-item "Default" describe-specified-language-support))

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;; This should be a single character key binding because users use it
;; very frequently while editing multilingual text.  Now we can use
;; only two such keys: "\C-\\" and "\C-^", but the latter is not
;; convenient because it requires shifting on most keyboards.  An
;; alternative is "\C-\]" which is now bound to `abort-recursive-edit'
;; but it won't be used that frequently.
(define-key global-map "\C-\\" 'toggle-input-method)

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;; This is no good because people often type Shift-SPC
;; meaning to type SPC.  -- rms.
;; ;; Here's an alternative key binding for X users (Shift-SPACE).
;; (define-key global-map [?\S- ] 'toggle-input-method)
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;;; Mule related hyperlinks.
(defconst help-xref-mule-regexp-template
  (purecopy (concat "\\(\\<\\("
		    "\\(coding system\\)\\|"
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		    "\\(input method\\)\\|"
		    "\\(character set\\)\\|"
		    "\\(charset\\)"
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		    "\\)\\s-+\\)?"
		    ;; Note starting with word-syntax character:
		    "`\\(\\sw\\(\\sw\\|\\s_\\)+\\)'")))

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(defun coding-system-change-eol-conversion (coding-system eol-type)
  "Return a coding system which differs from CODING-SYSTEM in eol conversion.
The returned coding system converts end-of-line by EOL-TYPE
but text as the same way as CODING-SYSTEM.
EOL-TYPE should be `unix', `dos', `mac', or nil.
If EOL-TYPE is nil, the returned coding system detects
how end-of-line is formatted automatically while decoding.

EOL-TYPE can be specified by an integer 0, 1, or 2.
They means `unix', `dos', and `mac' respectively."
  (if (symbolp eol-type)
      (setq eol-type (cond ((eq eol-type 'unix) 0)
			   ((eq eol-type 'dos) 1)
			   ((eq eol-type 'mac) 2)
			   (t eol-type))))
  (let ((orig-eol-type (coding-system-eol-type coding-system)))
    (if (vectorp orig-eol-type)
	(if (not eol-type)
	    coding-system
	  (aref orig-eol-type eol-type))
      (let ((base (coding-system-base coding-system)))
	(if (not eol-type)
	    base
	  (if (= eol-type orig-eol-type)
	      coding-system
	    (setq orig-eol-type (coding-system-eol-type base))
	    (if (vectorp orig-eol-type)
		(aref orig-eol-type eol-type))))))))

(defun coding-system-change-text-conversion (coding-system coding)
  "Return a coding system which differs from CODING-SYSTEM in text conversion.
The returned coding system converts text by CODING
but end-of-line as the same way as CODING-SYSTEM.
If CODING is nil, the returned coding system detects
how text is formatted automatically while decoding."
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  (let ((eol-type (coding-system-eol-type coding-system)))
    (coding-system-change-eol-conversion
     (if coding coding 'undecided)
     (if (numberp eol-type) (aref [unix dos mac] eol-type)))))
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(defun toggle-enable-multibyte-characters (&optional arg)
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  "Change whether this buffer uses multibyte characters.
With arg, use multibyte characters if the arg is positive.

Note that this command does not convert the byte contents of
the buffer; it only changes the way those bytes are interpreted.
In general, therefore, this command *changes* the sequence of
characters that the current buffer contains.

We suggest you avoid using use this command unless you know what you
are doing.  If you use it by mistake, and the buffer is now displayed
wrong, use this command again to toggle back to the right mode."
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  (interactive "P")
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  (let ((new-flag
	 (if (null arg) (null enable-multibyte-characters)
	   (> (prefix-numeric-value arg) 0))))
    (set-buffer-multibyte new-flag))
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  (force-mode-line-update))

(defun view-hello-file ()
  "Display the HELLO file which list up many languages and characters."
  (interactive)
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  ;; We have to decode the file in any environment.
  (let ((default-enable-multibyte-characters t)
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	(coding-system-for-read 'iso-2022-7bit))
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    (find-file-read-only (expand-file-name "HELLO" data-directory))))
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(defun universal-coding-system-argument (coding-system)
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  "Execute an I/O command using the specified coding system."
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  (interactive
   (let ((default (and buffer-file-coding-system
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		       (not (eq (coding-system-type buffer-file-coding-system)
				t))
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		       buffer-file-coding-system)))
     (list (read-coding-system
	    (if default
		(format "Coding system for following command (default, %s): " default)
	      "Coding system for following command: ")
	    default))))
  (let* ((keyseq (read-key-sequence
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		  (format "Command to execute with %s:" coding-system)))
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	 (cmd (key-binding keyseq))
	 prefix)

    (when (eq cmd 'universal-argument)
      (call-interactively cmd)
      
      ;; Process keys bound in `universal-argument-map'.
      (while (progn
	       (setq keyseq (read-key-sequence nil t)
		     cmd (key-binding keyseq t))
	       (not (eq cmd 'universal-argument-other-key)))
	(let ((current-prefix-arg prefix-arg)
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	      ;; Have to bind `last-command-char' here so that
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	      ;; `digit-argument', for isntance, can compute the
	      ;; prefix arg.
	      (last-command-char (aref keyseq 0)))
	  (call-interactively cmd)))

      ;; This is the final call to `univeral-argument-other-key', which
      ;; set's the final `prefix-arg.
      (let ((current-prefix-arg prefix-arg))
	(call-interactively cmd))
	
      ;; Read the command to execute with the given prefix arg.
      (setq prefix prefix-arg
	    keyseq (read-key-sequence nil t)
	    cmd (key-binding keyseq)))

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    (let ((coding-system-for-read coding-system)
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	  (coding-system-for-write coding-system)
	  (current-prefix-arg prefix))
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      (message "")
      (call-interactively cmd))))

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(defun set-default-coding-systems (coding-system)
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  "Set default value of various coding systems to CODING-SYSTEM.
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This sets the following coding systems:
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  o coding system of a newly created buffer
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  o default coding system for subprocess I/O
This also sets the following values:
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  o default value used as `file-name-coding-system' for converting file names.
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  o default value for the command `set-terminal-coding-system' (not on MSDOS)
  o default value for the command `set-keyboard-coding-system'."
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  (check-coding-system coding-system)
  (setq-default buffer-file-coding-system coding-system)
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  (if default-enable-multibyte-characters
      (setq default-file-name-coding-system coding-system))
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  ;; If coding-system is nil, honor that on MS-DOS as well, so
  ;; that they could reset the terminal coding system.
  (unless (and (eq window-system 'pc) coding-system)
    (setq default-terminal-coding-system coding-system))
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  (setq default-keyboard-coding-system coding-system)
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  ;; Preserve eol-type from existing default-process-coding-systems.
  ;; On non-unix-like systems in particular, these may have been set
  ;; carefully by the user, or by the startup code, to deal with the
  ;; users shell appropriately, so should not be altered by changing
  ;; language environment.
  (let ((output-coding
	 (coding-system-change-text-conversion
	  (car default-process-coding-system) coding-system))
	(input-coding
	 (coding-system-change-text-conversion
	  (cdr default-process-coding-system) coding-system)))
    (setq default-process-coding-system
	  (cons output-coding input-coding))))
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(defalias 'update-iso-coding-systems 'update-coding-systems-internal)
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(make-obsolete 'update-iso-coding-systems 'update-coding-systems-internal "20.3")
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(defun prefer-coding-system (coding-system)
  "Add CODING-SYSTEM at the front of the priority list for automatic detection.
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This also sets the following coding systems:
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  o coding system of a newly created buffer
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  o default coding system for subprocess I/O
This also sets the following values:
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  o default value used as `file-name-coding-system' for converting file names.
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  o default value for the command `set-terminal-coding-system' (not on MSDOS)
  o default value for the command `set-keyboard-coding-system'

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If CODING-SYSTEM specifies a certain type of EOL conversion, the coding
systems set by this function will use that type of EOL conversion.

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This command does not change the default value of terminal coding system
for MS-DOS terminal, because DOS terminals only support a single coding
system, and Emacs automatically sets the default to that coding system at
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startup.

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A coding system that requires automatic detection of text
encoding (e.g. undecided, unix) can't be preferred.

See also `coding-category-list' and `coding-system-category'."
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  (interactive "zPrefer coding system: ")
  (if (not (and coding-system (coding-system-p coding-system)))
      (error "Invalid coding system `%s'" coding-system))
  (let ((coding-category (coding-system-category coding-system))
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	(base (coding-system-base coding-system))
	(eol-type (coding-system-eol-type coding-system)))
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    (if (not coding-category)
	;; CODING-SYSTEM is no-conversion or undecided.
	(error "Can't prefer the coding system `%s'" coding-system))
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    (set coding-category (or base coding-system))
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    (update-coding-systems-internal)
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    (or (eq coding-category (car coding-category-list))
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	;; We must change the order.
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	(set-coding-priority (list coding-category)))
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    (if (and base (interactive-p))
	(message "Highest priority is set to %s (base of %s)"
		 base coding-system))
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    ;; If they asked for specific EOL conversion, honor that.
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    (if (memq eol-type '(0 1 2))
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	(setq coding-system
	      (coding-system-change-eol-conversion base eol-type))
      (setq coding-system base))
    (set-default-coding-systems coding-system)))
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(defvar sort-coding-systems-predicate nil
  "If non-nil, a predicate function to sort coding systems.

It is called with two coding systems, and should return t if the first
one is \"less\" than the second.

The function `sort-coding-systems' use it.")

(defun sort-coding-systems (codings)
  "Sort coding system list CODINGS by a priority of each coding system.

If a coding system is most preferred, it has the highest priority.
Otherwise, a coding system corresponds to some MIME charset has higher
priorities.  Among them, a coding system included in `coding-system'
key of the current language environment has higher priorities.  See
also the documentation of `language-info-alist'.

If the variable `sort-coding-systems-predicate' (which see) is
non-nil, it is used to sort CODINGS in the different way than above."
  (if sort-coding-systems-predicate
      (sort codings sort-coding-systems-predicate)
    (let* ((most-preferred (symbol-value (car coding-category-list)))
	   (lang-preferred (get-language-info current-language-environment
					      'coding-system))
	   (func (function
		  (lambda (x)
		    (let ((base (coding-system-base x)))
		      (+ (if (eq base most-preferred) 64 0)
			 (let ((mime (coding-system-get base 'mime-charset)))
			   (if mime
			       (if (string-match "^x-" (symbol-name mime))
				   16 32)
			     0))
			 (if (memq base lang-preferred) 8 0)
			 (if (string-match "-with-esc$" (symbol-name base))
			     0 4)
			 (if (eq (coding-system-type base) 2)
			     ;; For ISO based coding systems, prefer
			     ;; one that doesn't use escape sequences.
			     (let ((flags (coding-system-flags base)))
			       (if (or (consp (aref flags 0))
				       (consp (aref flags 1))
				       (consp (aref flags 2))
				       (consp (aref flags 3)))
				   (if (or (aref flags 8) (aref flags 9))
				       0
				     1)
				 2))
			   1)))))))
      (sort codings (function (lambda (x y)
				(> (funcall func x) (funcall func y))))))))
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(defun find-coding-systems-region (from to)
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  "Return a list of proper coding systems to encode a text between FROM and TO.
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If FROM is a string, find coding systems in that instead of the buffer.
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All coding systems in the list can safely encode any multibyte characters
in the text.

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If the text contains no multibyte characters, return a list of a single
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element `undecided'."
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  (let ((codings (find-coding-systems-region-internal from to)))
    (if (eq codings t)
	;; The text contains only ASCII characters.  Any coding
	;; systems are safe.
	'(undecided)
      ;; We need copy-sequence because sorting will alter the argument.
      (sort-coding-systems (copy-sequence codings)))))
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(defun find-coding-systems-string (string)
  "Return a list of proper coding systems to encode STRING.
All coding systems in the list can safely encode any multibyte characters
in STRING.

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If STRING contains no multibyte characters, return a list of a single
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element `undecided'."
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  (find-coding-systems-region string nil))
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(defun find-coding-systems-for-charsets (charsets)
  "Return a list of proper coding systems to encode characters of CHARSETS.
CHARSETS is a list of character sets."
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  (cond ((or (null charsets)
	     (and (= (length charsets) 1)
		  (eq 'ascii (car charsets))))
	 '(undecided))
	((or (memq 'eight-bit-control charsets)
	     (memq 'eight-bit-graphic charsets))
	 '(raw-text emacs-mule))
	(t
	 (let ((codings t)
	       charset l ll)
	   (while (and codings charsets)
	     (setq charset (car charsets) charsets (cdr charsets))
	     (unless (eq charset 'ascii)
	       (setq l (aref char-coding-system-table (make-char charset)))
	       (if (eq codings t)
		   (setq codings l)
		 (let ((ll nil))
		   (while codings
		     (if (memq (car codings) l)
			 (setq ll (cons (car codings) ll)))
		     (setq codings (cdr codings)))
		   (setq codings ll)))))
	   (append codings
		   (char-table-extra-slot char-coding-system-table 0))))))
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(defun find-multibyte-characters (from to &optional maxcount excludes)
  "Find multibyte characters in the region specified by FROM and TO.
If FROM is a string, find multibyte characters in the string.
The return value is an alist of the following format:
  ((CHARSET COUNT CHAR ...) ...)
where
  CHARSET is a character set,
  COUNT is a number of characters,
  CHARs are found characters of the character set.
Optional 3rd arg MAXCOUNT limits how many CHARs are put in the above list.
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Optional 4th arg EXCLUDE is a list of character sets to be ignored.

For invalid characters, CHARs are actually strings."
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  (let ((chars nil)
	charset char)
    (if (stringp from)
	(let ((idx 0))
	  (while (setq idx (string-match "[^\000-\177]" from idx))
	    (setq char (aref from idx)
		  charset (char-charset char))
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	    (if (eq charset 'unknown)
		(setq char (match-string 0)))
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	    (if (or (memq charset '(unknown
				    eight-bit-control eight-bit-graphic))
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		    (not (or (eq excludes t) (memq charset excludes))))
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		(let ((slot (assq charset chars)))
		  (if slot
		      (if (not (memq char (nthcdr 2 slot)))
			  (let ((count (nth 1 slot)))
			    (setcar (cdr slot) (1+ count))
			    (if (or (not maxcount) (< count maxcount))
				(nconc slot (list char)))))
		    (setq chars (cons (list charset 1 char) chars)))))
	    (setq idx (1+ idx))))
      (save-excursion
	(goto-char from)
	(while (re-search-forward "[^\000-\177]" to t)
	  (setq char (preceding-char)
		charset (char-charset char))
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	  (if (eq charset 'unknown)
	      (setq char (match-string 0)))
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	  (if (or (memq charset '(unknown eight-bit-control eight-bit-graphic))
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		  (not (or (eq excludes t) (memq charset excludes))))
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	      (let ((slot (assq charset chars)))
		(if slot
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		    (if (not (member char (nthcdr 2 slot)))
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			(let ((count (nth 1 slot)))
			  (setcar (cdr slot) (1+ count))
			  (if (or (not maxcount) (< count maxcount))
			      (nconc slot (list char)))))
		  (setq chars (cons (list charset 1 char) chars))))))))
    (nreverse chars)))

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(defun search-unencodable-char (coding-system)
  "Search forward from point for a character that is not encodable.
It asks which coding system to check.
If such a character is found, set point after that character.
Otherwise, don't move point.

When called from a program, the value is a position of the found character,
or nil if all characters are encodable."
  (interactive
   (list (let ((default (or buffer-file-coding-system 'us-ascii)))
	   (read-coding-system
	    (format "Coding-system (default, %s): " default)
	    default))))
  (let ((pos (unencodable-char-position (point) (point-max) coding-system)))
    (if pos
	(goto-char (1+ pos))
      (message "All following characters are encodable by %s" coding-system))
    pos))


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(defvar last-coding-system-specified nil
  "Most recent coding system explicitly specified by the user when asked.
This variable is set whenever Emacs asks the user which coding system
to use in order to write a file.  If you set it to nil explicitly,
then call `write-region', then afterward this variable will be non-nil
only if the user was explicitly asked and specified a coding system.")

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(defvar select-safe-coding-system-accept-default-p nil
  "If non-nil, a function to control the behaviour of coding system selection.
The meaning is the same as the argument ACCEPT-DEFAULT-P of the
function `select-safe-coding-system' (which see).  This variable
overrides that argument.")

(defun select-safe-coding-system (from to &optional default-coding-system
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				       accept-default-p file)
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  "Ask a user to select a safe coding system from candidates.
The candidates of coding systems which can safely encode a text
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between FROM and TO are shown in a popup window.  Among them, the most
proper one is suggested as the default.

The list of `buffer-file-coding-system' of the current buffer and the
most preferred coding system (if it corresponds to a MIME charset) is
treated as the default coding system list.  Among them, the first one
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that safely encodes the text is normally selected silently and
returned without any user interaction.  See also the command
`prefer-coding-system'.

However, the user is queried if the chosen coding system is
inconsistent with what would be selected by `set-auto-coding' from
coding cookies &c. if the contents of the region were read from a
file.  (That could lead to data corruption in a file subsequently
re-visited and edited.)
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Optional 3rd arg DEFAULT-CODING-SYSTEM specifies a coding system or a
list of coding systems to be prepended to the default coding system
list.
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Optional 4th arg ACCEPT-DEFAULT-P, if non-nil, is a function to
determine the acceptability of the silently selected coding system.
It is called with that coding system, and should return nil if it
should not be silently selected and thus user interaction is required.

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Optional 5th arg FILE is the file name to use for this purpose.
That is different from `buffer-file-name' when handling `write-region'
\(for example).

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The variable `select-safe-coding-system-accept-default-p', if
non-nil, overrides ACCEPT-DEFAULT-P.
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Kludgy feature: if FROM is a string, the string is the target text,
and TO is ignored."
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  (if (and default-coding-system
	   (not (listp default-coding-system)))
      (setq default-coding-system (list default-coding-system)))

  ;; Change elements of the list to (coding . base-coding).
  (setq default-coding-system
	(mapcar (function (lambda (x) (cons x (coding-system-base x))))
		default-coding-system))

  ;; If buffer-file-coding-system is not nil nor undecided, append it
  ;; to the defaults.
  (if buffer-file-coding-system
      (let ((base (coding-system-base buffer-file-coding-system)))
	(or (eq base 'undecided)
	    (assq buffer-file-coding-system default-coding-system)
	    (rassq base default-coding-system)
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	    (setq default-coding-system
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		  (append default-coding-system
			  (list (cons buffer-file-coding-system base)))))))

  ;; If the most preferred coding system has the property mime-charset,
  ;; append it to the defaults.
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  (let ((tail coding-category-list)
	preferred base)
    (while (and tail
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		(not (setq preferred (symbol-value (car tail)))))
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      (setq tail (cdr tail)))
    (and (coding-system-p preferred)
	 (setq base (coding-system-base preferred))
	 (coding-system-get preferred 'mime-charset)
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	 (not (assq preferred default-coding-system))
	 (not (rassq base default-coding-system))
	 (setq default-coding-system
	       (append default-coding-system (list (cons preferred base))))))

  (if select-safe-coding-system-accept-default-p
      (setq accept-default-p select-safe-coding-system-accept-default-p))

  (let ((codings (find-coding-systems-region from to))
	(coding-system nil)
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	(bufname (buffer-name))
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	safe rejected unsafe)
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    (if (eq (car codings) 'undecided)
	;; Any coding system is ok.
	(setq coding-system t)
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      ;; Classify the defaults into safe, rejected, and unsafe.
      (dolist (elt default-coding-system)
	(if (memq (cdr elt) codings)
	    (if (and (functionp accept-default-p)
		     (not (funcall accept-default-p (cdr elt))))
		(push (car elt) rejected)
	      (push (car elt) safe))
	  (push (car elt) unsafe)))
      (if safe
	  (setq coding-system (car (last safe)))))

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    ;; If all the defaults failed, ask a user.
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    (when (not coding-system)
      ;; At first, if some defaults are unsafe, record at most 11
      ;; problematic characters and their positions for them by turning
      ;;	(CODING ...)
      ;; into
      ;;	((CODING (POS . CHAR) (POS . CHAR) ...) ...)
      (if unsafe
	  (if (stringp from)
	      (setq unsafe
		    (mapcar #'(lambda (coding)
				(cons coding
				      (mapcar #'(lambda (pos)
						  (cons pos (aref from pos)))
					      (unencodable-char-position
					       0 (length from) coding
					       11 from))))
			    unsafe))
	    (setq unsafe 
		  (mapcar #'(lambda (coding)
			      (cons coding
				    (mapcar #'(lambda (pos)
						(cons pos (char-after pos)))
					    (unencodable-char-position
					     from to coding 11))))
			  unsafe))))
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      ;; Change each safe coding system to the corresponding
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      ;; mime-charset name if it is also a coding system.  Such a name
      ;; is more friendly to users.
      (let ((l codings)
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	    mime-charset)
	(while l
	  (setq mime-charset (coding-system-get (car l) 'mime-charset))
	  (if (and mime-charset (coding-system-p mime-charset))
	      (setcar l mime-charset))
	  (setq l (cdr l))))

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      ;; Don't offer variations with locking shift, which you
      ;; basically never want.
      (let (l)
	(dolist (elt codings (setq codings (nreverse l)))
	  (unless (or (eq 'coding-category-iso-7-else
			  (coding-system-category elt))
		      (eq 'coding-category-iso-8-else
			  (coding-system-category elt)))
	    (push elt l))))

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      (let ((window-configuration (current-window-configuration)))
	(save-excursion
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	  ;; If some defaults are unsafe, make sure the offending
	  ;; buffer is displayed.
	  (when (and unsafe (not (stringp from)))
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	    (pop-to-buffer bufname)
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	    (goto-char (apply 'min (mapcar #'(lambda (x) (car (cadr x)))
					   unsafe))))
	  ;; Then ask users to select one from CODINGS while showing
	  ;; the reason why none of the defaults are not used.
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	  (with-output-to-temp-buffer "*Warning*"
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	    (save-excursion
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	      (set-buffer standard-output)
	      (if (not default-coding-system)
		  (insert "No default coding systems to try for "
			  (if (stringp from)
			      (format "string \"%s\"." from)
			    (format "buffer `%s'." bufname)))
		(insert
		 "These default coding systems were tried to encode"
		 (if (stringp from)
		     (concat " \"" (if (> (length from) 10)
				       (concat (substring from 0 10) "...\"")
				     (concat from "\"")))
		   (format " text\nin the buffer `%s'" bufname))
		 ":\n")
		(let ((pos (point))
		      (fill-prefix "  "))
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		  (mapc #'(lambda (x) (princ "  ") (princ (car x)))
			default-coding-system)
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		  (insert "\n")
		  (fill-region-as-paragraph pos (point)))
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		(when rejected
		  (insert "These safely encodes the target text,
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but it is not recommended for encoding text in this context,
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e.g., for sending an email message.\n ")
		  (mapc #'(lambda (x) (princ " ") (princ x)) rejected)
		  (insert "\n"))
		(when unsafe
		  (insert (if rejected "And the others" 
			    "However, each of them")
			  " encountered these problematic characters:\n")
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		  (mapc
		   #'(lambda (coding)
		       (insert (format "  %s:" (car coding)))
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		       (let ((i 0)
			     (func1
			      #'(lambda (bufname pos)
				  (when (buffer-live-p (get-buffer bufname))
				    (pop-to-buffer bufname)
				    (goto-char pos))))
			     (func2
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			      #'(lambda (bufname pos coding)
				  (when (buffer-live-p (get-buffer bufname))
				    (pop-to-buffer bufname)
				    (if (< (point) pos)
					(goto-char pos)
				      (forward-char 1)
				      (search-unencodable-char coding)
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				      (forward-char -1))))))
			 (dolist (elt (cdr coding))
			   (insert " ")
			   (if (stringp from)
			       (insert (if (< i 10) (cdr elt) "..."))
			     (if (< i 10)
				 (insert-text-button
				  (cdr elt)
				  :type 'help-xref
				  'help-echo
				  "mouse-2, RET: jump to this character"
				  'help-function func1
				  'help-args (list bufname (car elt)))
			       (insert-text-button
				"..."
				:type 'help-xref
				'help-echo
				"mouse-2, RET: next unencodable character"
				'help-function func2
				'help-args (list bufname (car elt)
						 (car coding)))))
			   (setq i (1+ i))))
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		       (insert "\n"))
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		   unsafe)
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		  (insert "\
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The first problematic character is at point in the displayed buffer,\n"
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			  (substitute-command-keys "\
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and \\[universal-argument] \\[what-cursor-position] will give information about it.\n"))))
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	      (insert (if safe
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			  "\nSelect the above, or "
			"\nSelect ")
		      "\
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one of the following safe coding systems, or edit the buffer:\n")
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	      (let ((pos (point))
		    (fill-prefix "  "))
		(mapcar (function (lambda (x) (princ "  ") (princ x)))
			codings)
		(insert "\n")
		(fill-region-as-paragraph pos (point)))))

	  ;; Read a coding system.
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	  (if safe
	      (setq codings (append safe codings)))
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	  (let* ((safe-names (mapcar (lambda (x) (list (symbol-name x)))
				     codings))
		 (name (completing-read
			(format "Select coding system (default %s): "
				(car codings))
			safe-names nil t nil nil
			(car (car safe-names)))))
	    (setq last-coding-system-specified (intern name)
		  coding-system last-coding-system-specified)))
	(kill-buffer "*Warning*")
	(set-window-configuration window-configuration)))
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    (if (vectorp (coding-system-eol-type coding-system))
	(let ((eol (coding-system-eol-type buffer-file-coding-system)))
	  (if (numberp eol)
	      (setq coding-system
		    (coding-system-change-eol-conversion coding-system eol)))))

    (if (eq coding-system t)
	(setq coding-system buffer-file-coding-system))
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    ;; Check we're not inconsistent with what `coding:' spec &c would
    ;; give when file is re-read.
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    ;; But don't do this if we explicitly ignored the cookie
    ;; by using `find-file-literally'.
    (unless (or (stringp from) find-file-literally)
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      (let ((auto-cs (save-excursion
		       (save-restriction
			 (widen)
			 (narrow-to-region from to)
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			 (goto-char (point-min))
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			 (set-auto-coding (or file buffer-file-name "")
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					  (buffer-size))))))
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	(if (and auto-cs coding-system
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		 ;; Don't barf if writing a compressed file, say.
		 ;; This check perhaps isn't ideal, but is probably
		 ;; the best thing to do.
		 (not (auto-coding-alist-lookup (or file buffer-file-name "")))
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		 (not (coding-system-equal (coding-system-base coding-system)
					   (coding-system-base auto-cs))))
	    (unless (yes-or-no-p
		     (format "Selected encoding %s disagrees with \
%s specified by file contents.  Really save (else edit coding cookies \
and try again)? " coding-system auto-cs))
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	      (error "Save aborted")))))
    coding-system))
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(setq select-safe-coding-system-function 'select-safe-coding-system)

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(defun select-message-coding-system ()
  "Return a coding system to encode the outgoing message of the current buffer.
It at first tries the first coding system found in these variables
in this order:
  (1) local value of `buffer-file-coding-system'
  (2) value of `sendmail-coding-system'
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  (3) value of `default-sendmail-coding-system'
  (4) value of `default-buffer-file-coding-system'
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If the found coding system can't encode the current buffer,
or none of them are bound to a coding system,
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it asks the user to select a proper coding system."
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  (let ((coding (or (and (local-variable-p 'buffer-file-coding-system)
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			  buffer-file-coding-system)
		     sendmail-coding-system
		     default-sendmail-coding-system
		     default-buffer-file-coding-system)))
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    (if (eq coding 'no-conversion)
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	;; We should never use no-conversion for outgoing mail.
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	(setq coding nil))
    (if (fboundp select-safe-coding-system-function)
	(funcall select-safe-coding-system-function
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		 (point-min) (point-max) coding
		 (function (lambda (x) (coding-system-get x 'mime-charset))))
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      coding)))
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;;; Language support stuff.
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(defvar language-info-alist nil
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  "Alist of language environment definitions.
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Each element looks like:
	(LANGUAGE-NAME . ((KEY . INFO) ...))
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where LANGUAGE-NAME is a string, the name of the language environment,
KEY is a symbol denoting the kind of information, and
INFO is the data associated with KEY.
Meaningful values for KEY include

  documentation      value is documentation of what this language environment
			is meant for, and how to use it.
  charset	     value is a list of the character sets used by this
			language environment.
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  sample-text	     value is an expression which is evalled to generate
                        a line of text written using characters appropriate
                        for this language environment.
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  setup-function     value is a function to call to switch to this
			language environment.
  exit-function      value is a function to call to leave this
		        language environment.
  coding-system      value is a list of coding systems that are good
			for saving text written in this language environment.
			This list serves as suggestions to the user;
			in effect, as a kind of documentation.
  coding-priority    value is a list of coding systems for this language
			environment, in order of decreasing priority.
			This is used to set up the coding system priority
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			list when you switch to this language environment.
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  nonascii-translation
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		     value is a translation table to be set in the
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			variable `nonascii-translation-table' in this
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			language environment, or a character set from
			which `nonascii-insert-offset' is calculated.
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  input-method       value is a default input method for this language
			environment.
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  features           value is a list of features requested in this
			language environment.
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The following keys take effect only when multibyte characters are
globally disabled, i.e. the value of `default-enable-multibyte-characters'
is nil.

  unibyte-syntax     value is a library name to load to set
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			unibyte 8-bit character syntaxes for this
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			language environment.

  unibyte-display    value is a coding system to encode characters
			for the terminal.  Characters in the range
			of 160 to 255 display not as octal escapes,
			but as non-ASCII characters in this language
			environment.")
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(defun get-language-info (lang-env key)
  "Return information listed under KEY for language environment LANG-ENV.
KEY is a symbol denoting the kind of information.
For a list of useful values for KEY and their meanings,
see `language-info-alist'."
  (if (symbolp lang-env)
      (setq lang-env (symbol-name lang-env)))
  (let ((lang-slot (assoc-ignore-case lang-env language-info-alist)))
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    (if lang-slot
	(cdr (assq key (cdr lang-slot))))))

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(defun set-language-info (lang-env key info)
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  "Modify part of the definition of language environment LANG-ENV.
Specifically, this stores the information INFO under KEY
in the definition of this language environment.
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KEY is a symbol denoting the kind of information.
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INFO is the value for that information.
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For a list of useful values for KEY and their meanings,
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see `language-info-alist'."
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  (if (symbolp lang-env)
      (setq lang-env (symbol-name lang-env)))
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  (let (lang-slot key-slot)
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    (setq lang-slot (assoc lang-env language-info-alist))
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    (if (null lang-slot)		; If no slot for the language, add it.
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	(setq lang-slot (list lang-env)
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	      language-info-alist (cons lang-slot language-info-alist)))
    (setq key-slot (assq key lang-slot))
    (if (null key-slot)			; If no slot for the key, add it.
	(progn
	  (setq key-slot (list key))
	  (setcdr lang-slot (cons key-slot (cdr lang-slot)))))
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    (setcdr key-slot (purecopy info))))
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(defun set-language-info-alist (lang-env alist &optional parents)
  "Store ALIST as the definition of language environment LANG-ENV.
ALIST is an alist of KEY and INFO values.  See the documentation of
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`language-info-alist' for the meanings of KEY and INFO.
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Optional arg PARENTS is a list of parent menu names; it specifies
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where to put this language environment in the
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Describe Language Environment and Set Language Environment menus.
For example, (\"European\") means to put this language environment
in the European submenu in each of those two menus."
  (if (symbolp lang-env)
      (setq lang-env (symbol-name lang-env)))
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  (let ((describe-map describe-language-environment-map)
	(setup-map setup-language-environment-map))
    (if parents
	(let ((l parents)
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	      map parent-symbol parent prompt)
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	  (while l
	    (if (symbolp (setq parent-symbol (car l)))
		(setq parent (symbol-name parent))
	      (setq parent parent-symbol parent-symbol (intern parent)))
	    (setq map (lookup-key describe-map (vector parent-symbol)))
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	    ;; This prompt string is for define-prefix-command, so
	    ;; that the map it creates will be suitable for a menu.
	    (or map (setq prompt (format "%s Environment" parent)))
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	    (if (not map)
		(progn
		  (setq map (intern (format "describe-%s-environment-map"
					    (downcase parent))))
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		  (define-prefix-command map nil prompt)
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		  (define-key-after describe-map (vector parent-symbol)
		    (cons parent map) t)))
	    (setq describe-map (symbol-value map))
	    (setq map (lookup-key setup-map (vector parent-symbol)))
	    (if (not map)
		(progn
		  (setq map (intern (format "setup-%s-environment-map"
					    (downcase parent))))
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		  (define-prefix-command map nil prompt)
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		  (define-key-after setup-map (vector parent-symbol)
		    (cons parent map) t)))
	    (setq setup-map (symbol-value map))
	    (setq l (cdr l)))))
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    ;; Set up menu items for this language env.
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    (let ((doc (assq 'documentation alist)))
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      (when doc
	(define-key-after describe-map (vector (intern lang-env))
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	  (cons lang-env 'describe-specified-language-support) t)))
    (define-key-after setup-map (vector (intern lang-env))
      (cons lang-env 'setup-specified-language-environment) t)
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    (while alist
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      (set-language-info lang-env (car (car alist)) (cdr (car alist)))
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      (setq alist (cdr alist)))))
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(defun read-language-name (key prompt &optional default)
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  "Read a language environment name which has information for KEY.
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If KEY is nil, read any language environment.
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Prompt with PROMPT.  DEFAULT is the default choice of language environment.
This returns a language environment name as a string."
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  (let* ((completion-ignore-case t)
	 (name (completing-read prompt
				language-info-alist
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				(and key
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				     (function (lambda (elm) (and (listp elm) (assq key elm)))))
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				t nil nil default)))
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    (if (and (> (length name) 0)
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	     (or (not key)
		 (get-language-info name key)))
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	name)))