;;; iso-pc.el --- Work with Texts in ISO-8859-1 charset on an IBM-PC
;;; using Codepage 850

;; Author: Carsten Leonhardt <leo@arioch.tng.oche.de>

;; Version 0.4 - November 18, 1995, 15:00 CET

;; Copyright (c) 1995 Carsten Leonhardt

;; This 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.

;; This code is distributed in the hope that it will be useful, but WITHOUT
;; ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
;; FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License
;; for more details.

;; You should have received a copy of the GNU General Public License along
;; with GNU Emacs; see the file COPYING.  If not, write to the Free
;; Software Foundation, 675 Mass Ave, Cambridge, MA 02139, USA.

;;;
;;; Commentary:
;;
;; This code sets Emacs up to work on texts using ISO-8859-1 (Latin-1)
;; characters on IBM-PCs using the Codepage 850
;;
;; If you load this file, characters will still be displayed as CP-850 chars,
;; to display them as ISO-8859-1 chars, you have to call 'iso-pc-enable' or
;; 'iso-pc'.
;;
;; There are three functions you can call:
;;
;; 'iso-pc'
;;
;;   Used to toggle between ISO-8859-1 mode and CP-850 mode.
;;   Very handy if bound to a key.
;;
;; 'iso-pc-enable'
;;
;;   Enables the ISO-8859-1 mode
;;
;; 'iso-pc-disable'
;;
;;   Disables the ISO-8859-1 mode and leaves you with your CP-850 characters

;;;
;;; Limitations:
;;
;; When using Gnus 5.0, changing the display tables doesn't affect the
;; display in the Summary Buffer. So you should enable the ISO-8859-1
;; before entering the Summary Buffer if you want it to be displayed as
;; ISO-8859-1 text.
;;
;; If you enter a character from the keyboard which does not exist in
;; ISO-8859-1 (these are those stupid box drawings signs, the 'dutch
;; guilder sign', the dotless i and the greek mu), you'll get a space
;; instead.
;;
;; If ISO-8859-1 characters are displayed, the control characters from 128
;; to 159 are displayed as an abbreviation of the name of the character in
;; curly brackets (like '{SS2}').

;;;
;;; To install:
;;
;; First put this file somewhere into your loadpath.
;;
;; To enable the switching, put the following line into your ~/.emacs:
;;
;; (load "iso-pc")
;;
;; You should ensure that _all_ characters are displayed (the default will
;; not display character 255, which is a y with diaresis in the CP-850
;; charset) by also adding the following line to your ~/.emacs
;;
;; (standard-display-8bit 128 255)
;;
;; You might want Emacs to know the lowercase-uppercase relation of the 
;; newly aquired characters by adding the following to your ~/.emacs
;;
;; (require 'iso-syntax)
;;
;; I find it convenient to be able to switch between the two display-modes
;; with a simple key-combination (C-^ is pretty quick on my german keyboard)
;;
;; (global-set-key "" 'iso-pc)

;;; Code:

(require 'disp-table)

(defvar iso-pc-enabled nil
  "This variable is used to determine the state in which iso-pc currently is.
t means translation is enabled, nil means translation is disabled.
See function iso-pc for a little more information")

(defun iso-pc-enable-keyboard ()
  "Enable translation from keyboard to ISO-8859-1"
  (let ((the-table (make-string 256 0)))
    (let ((i 0))
      (while (< i 256)
	(aset the-table i i)
	(setq i (1+ i))))
;;; Insert ISO-8859-1 codes instead of CP850 codes
;;;
;;; Are the capital letters with grave correct ?
;;;
;;; if you see the described characters, you look at this file with ISO-8859-1
    (aset the-table ?\200 ?\�) ;; C with cedilla
    (aset the-table ?\201 ?\�) ;; u with diaresis
    (aset the-table ?\202 ?\�) ;; e with acute
    (aset the-table ?\203 ?\�) ;; a with circumflex
    (aset the-table ?\204 ?\�) ;; a with diaresis
    (aset the-table ?\205 ?\�) ;; a with grave
    (aset the-table ?\206 ?\�) ;; a with ring
    (aset the-table ?\207 ?\�) ;; c with cedilla
    (aset the-table ?\210 ?\�) ;; e with circumflex
    (aset the-table ?\211 ?\�) ;; e with diaresis
    (aset the-table ?\212 ?\�) ;; e with grave
    (aset the-table ?\213 ?\�) ;; i with diaresis
    (aset the-table ?\214 ?\�) ;; i with circumflex
    (aset the-table ?\215 ?\�) ;; i with grave
    (aset the-table ?\216 ?\�) ;; A with diaresis
    (aset the-table ?\217 ?\�) ;; A with ring
    (aset the-table ?\220 ?\�) ;; E with acute
    (aset the-table ?\221 ?\�) ;; ae
    (aset the-table ?\222 ?\�) ;; AE
    (aset the-table ?\223 ?\�) ;; o with circumflex
    (aset the-table ?\224 ?\�) ;; o with diaresis
    (aset the-table ?\225 ?\�) ;; o with grave
    (aset the-table ?\226 ?\�) ;; u with circumflex
    (aset the-table ?\227 ?\�) ;; u with grave
    (aset the-table ?\230 ?\�) ;; y with diaresis
    (aset the-table ?\231 ?\�) ;; O with diaresis
    (aset the-table ?\232 ?\�) ;; U with diaresis
    (aset the-table ?\233 ?\�) ;; o with stroke
    (aset the-table ?\234 ?\�) ;; pound sign
    (aset the-table ?\235 ?\�) ;; O with stroke
    (aset the-table ?\236 ?\�) ;; multiplication sign
    (aset the-table ?\237 ?\ ) ;; dutch guilder sign (no iso-equivalent)
    (aset the-table ?\240 ?\�) ;; a with acute
    (aset the-table ?\241 ?\�) ;; i with acute
    (aset the-table ?\242 ?\�) ;; o with acute
    (aset the-table ?\243 ?\�) ;; u with acute
    (aset the-table ?\244 ?\�) ;; n with tilde
    (aset the-table ?\245 ?\�) ;; N with tilde
    (aset the-table ?\246 ?\�) ;; feminine ordinal indicator
    (aset the-table ?\247 ?\�) ;; masculine ordinal indicator
    (aset the-table ?\250 ?\�) ;; inverted question mark
    (aset the-table ?\251 ?\�) ;; registered sign
    (aset the-table ?\252 ?\�) ;; not sign
    (aset the-table ?\253 ?\�) ;; vulgar fraction one half
    (aset the-table ?\254 ?\�) ;; vulgar fraction one quarter
    (aset the-table ?\255 ?\�) ;; inverted exclamation mark
    (aset the-table ?\256 ?\�) ;; <<
    (aset the-table ?\257 ?\�) ;; >>
    (aset the-table ?\260 ?\ ) ;; light shade (non-iso)
    (aset the-table ?\261 ?\ ) ;; medium shade (non-iso)
    (aset the-table ?\262 ?\ ) ;; dark shade (non-iso)
    (aset the-table ?\263 ?\ ) ;; box drawings light vertical (non-iso)
    (aset the-table ?\264 ?\ ) ;; box drawings light vertical and left (non-iso)
    (aset the-table ?\265 ?\�) ;; A with acute
    (aset the-table ?\266 ?\�) ;; A with circumflex
    (aset the-table ?\267 ?\�) ;; A with grave
    (aset the-table ?\270 ?\�) ;; copyright sign
    (aset the-table ?\271 ?\ ) ;; (non-iso)
    (aset the-table ?\272 ?\ ) ;; (non-iso)
    (aset the-table ?\273 ?\ ) ;; (non-iso)
    (aset the-table ?\274 ?\ ) ;; (non-iso)
    (aset the-table ?\275 ?\�) ;; cent sign
    (aset the-table ?\276 ?\�) ;; yen sign
    (aset the-table ?\277 ?\ ) ;; (non-iso)
    (aset the-table ?\300 ?\ ) ;; (non-iso)
    (aset the-table ?\301 ?\ ) ;; (non-iso)
    (aset the-table ?\302 ?\ ) ;; (non-iso)
    (aset the-table ?\303 ?\ ) ;; (non-iso)
    (aset the-table ?\304 ?\ ) ;; (non-iso)
    (aset the-table ?\305 ?\ ) ;; (non-iso)
    (aset the-table ?\306 ?\�) ;; a with tilde
    (aset the-table ?\307 ?\�) ;; A with tilde
    (aset the-table ?\310 ?\ ) ;; (non-iso)
    (aset the-table ?\311 ?\ ) ;; (non-iso)
    (aset the-table ?\312 ?\ ) ;; (non-iso)
    (aset the-table ?\313 ?\ ) ;; (non-iso)
    (aset the-table ?\314 ?\ ) ;; (non-iso)
    (aset the-table ?\315 ?\ ) ;; (non-iso)
    (aset the-table ?\316 ?\ ) ;; (non-iso)
    (aset the-table ?\317 ?\�) ;; currency sign
    (aset the-table ?\320 ?\�) ;; eth (icelandic)
    (aset the-table ?\321 ?\�) ;; ETH (icelandic)
    (aset the-table ?\322 ?\�) ;; E with circumflex
    (aset the-table ?\323 ?\�) ;; E with diaresis
    (aset the-table ?\324 ?\�) ;; E with grave
    (aset the-table ?\325 ?\ ) ;; i dotless (non-iso)
    (aset the-table ?\326 ?\�) ;; I with acute
    (aset the-table ?\327 ?\�) ;; I with circumflex
    (aset the-table ?\330 ?\�) ;; I with diaresis
    (aset the-table ?\331 ?\ ) ;; (non-iso)
    (aset the-table ?\332 ?\ ) ;; (non-iso)
    (aset the-table ?\333 ?\ ) ;; (non-iso)
    (aset the-table ?\334 ?\ ) ;; (non-iso)
    (aset the-table ?\335 ?\�) ;; broken bar
    (aset the-table ?\336 ?\�) ;; I with grave
    (aset the-table ?\337 ?\ ) ;; (non-iso)
    (aset the-table ?\340 ?\�) ;; O with acute
    (aset the-table ?\341 ?\�) ;; sharp s
    (aset the-table ?\342 ?\�) ;; O with circumflex
    (aset the-table ?\343 ?\�) ;; O with grave
    (aset the-table ?\344 ?\�) ;; o with tilde
    (aset the-table ?\345 ?\�) ;; O with tilde
    (aset the-table ?\346 ?\ ) ;; mu (greek) (non-iso)
    (aset the-table ?\347 ?\�) ;; THORN (icelandic)
    (aset the-table ?\350 ?\�) ;; thorn (icelandic)
    (aset the-table ?\351 ?\�) ;; U with acute
    (aset the-table ?\352 ?\�) ;; U with circumflex
    (aset the-table ?\353 ?\�) ;; U with grave
    (aset the-table ?\354 ?\�) ;; y with acute
    (aset the-table ?\355 ?\�) ;; Y with acute
    (aset the-table ?\356 ?\ ) ;; em dash (non-iso)
    (aset the-table ?\357 ?\�) ;; acute accent
    (aset the-table ?\360 ?\�) ;; soft hyphen
    (aset the-table ?\361 ?\�) ;; plus-minus sign
    (aset the-table ?\362 ?\ ) ;; (non-iso)
    (aset the-table ?\363 ?\�) ;; vulgar fraction three quarters
    (aset the-table ?\364 ?\�) ;; pilcrow sign
    (aset the-table ?\365 ?\�) ;; section sign
    (aset the-table ?\366 ?\�) ;; division sign
    (aset the-table ?\367 ?\ ) ;; ogonek (non-iso)
    (aset the-table ?\370 ?\�) ;; degree sign
    (aset the-table ?\371 ?\�) ;; diaresis
    (aset the-table ?\372 ?\ ) ;; dot above (non-iso)
    (aset the-table ?\373 ?\�) ;; superscript one
    (aset the-table ?\374 ?\�) ;; superscript three
    (aset the-table ?\375 ?\�) ;; superscript two
    (aset the-table ?\376 ?\ ) ;; (non-iso)
    (aset the-table ?\377 ?\�) ;; no-break space
    (setq keyboard-translate-table the-table)))

(defun iso-pc-enable-display ()
  "Enable translation from ISO-8859-1 to display"
;;; if you see the described signs, you are looking at this file with CP850

  (standard-display-ascii 128 "{PAD}")   ; 
  (standard-display-ascii 129 "{HOP}")   ; 
  (standard-display-ascii 130 "{BPH}")   ; 
  (standard-display-ascii 131 "{NBH}")   ; 
  (standard-display-ascii 132 "{IND}")   ; 
  (standard-display-ascii 133 "{NEL}")   ; 
  (standard-display-ascii 134 "{SSA}")   ; 
  (standard-display-ascii 135 "{ESA}")   ; 
  (standard-display-ascii 136 "{HTS}")   ; 
  (standard-display-ascii 137 "{HTJ}")   ; 
  (standard-display-ascii 138 "{VTS}")   ; 
  (standard-display-ascii 139 "{PLD}")   ; 
  (standard-display-ascii 140 "{PLU}")   ; 
  (standard-display-ascii 141 "{RI}")   ; 
  (standard-display-ascii 142 "{SS2}")   ; 
  (standard-display-ascii 143 "{SS3}")   ; 
  (standard-display-ascii 144 "{DCS}")   ; 
  (standard-display-ascii 145 "{PU1}")   ; 
  (standard-display-ascii 146 "{PU2}")   ; 
  (standard-display-ascii 147 "{STS}")   ; 
  (standard-display-ascii 148 "{CCH}")   ; 
  (standard-display-ascii 149 "{MW}")   ; 
  (standard-display-ascii 150 "{SPA}")   ; 
  (standard-display-ascii 151 "{EPA}")   ; 
  (standard-display-ascii 152 "{SOS}")   ; 
  (standard-display-ascii 153 "{SGCI}")   ; 
  (standard-display-ascii 154 "{SCI}")   ; 
  (standard-display-ascii 155 "{CSI}")   ; 
  (standard-display-ascii 156 "{ST}")   ; 
  (standard-display-ascii 157 "{OSC}")   ; 
  (standard-display-ascii 158 "{PM}")   ; 
  (standard-display-ascii 159 "{APC}")   ; 
  (standard-display-ascii 160 "�")   ; NBSP (no-break space)
  (standard-display-ascii 161 "�")   ; inverted exclamation mark
  (standard-display-ascii 162 "�")   ; cent sign
  (standard-display-ascii 163 "�")   ; pound sign
  (standard-display-ascii 164 "�")   ; general currency sign
  (standard-display-ascii 165 "�")   ; yen sign
  (standard-display-ascii 166 "�")   ; broken vertical line
  (standard-display-ascii 167 "�")   ; section sign
  (standard-display-ascii 168 "�")   ; diaeresis
  (standard-display-ascii 169 "�")   ; copyright sign
  (standard-display-ascii 170 "�")   ; ordinal indicator, feminine
  (standard-display-ascii 171 "�")   ; left angle quotation mark
  (standard-display-ascii 172 "�")   ; not sign
  (standard-display-ascii 173 "�")   ; soft hyphen
  (standard-display-ascii 174 "�")   ; registered sign
  (standard-display-ascii 175 "{=}") ; macron
  (standard-display-ascii 176 "�")   ; degree sign
  (standard-display-ascii 177 "�")   ; plus or minus sign
  (standard-display-ascii 178 "�")   ; superscript two
  (standard-display-ascii 179 "�")   ; superscript three
  (standard-display-ascii 180 "�")   ; acute accent
  (standard-display-ascii 181 "{u}") ; micro sign
  (standard-display-ascii 182 "�")   ; pilcrow
  (standard-display-ascii 183 "{.}") ; middle dot
  (standard-display-ascii 184 "{,}") ; cedilla
  (standard-display-ascii 185 "�")   ; superscript one
  (standard-display-ascii 186 "�")   ; ordinal indicator, masculine
  (standard-display-ascii 187 "�")   ; right angle quotation mark
  (standard-display-ascii 188 "�")   ; fraction one-quarter
  (standard-display-ascii 189 "�")   ; fraction one-half
  (standard-display-ascii 190 "�")   ; fraction three-quarters
  (standard-display-ascii 191 "�")   ; inverted question mark
  (standard-display-ascii 192 "�")   ; A with grave accent
  (standard-display-ascii 193 "�")  ; A with acute accent
  (standard-display-ascii 194 "�")  ; A with circumflex accent
  (standard-display-ascii 195 "�")  ; A with tilde
  (standard-display-ascii 196 "�") ; A with diaeresis or umlaut mark
  (standard-display-ascii 197 "�")  ; A with ring
  (standard-display-ascii 198 "�")  ; AE diphthong
  (standard-display-ascii 199 "�")  ; C with cedilla
  (standard-display-ascii 200 "�")  ; E with grave accent
  (standard-display-ascii 201 "�")  ; E with acute accent
  (standard-display-ascii 202 "�")  ; E with circumflex accent
  (standard-display-ascii 203 "�") ; E with diaeresis or umlaut mark
  (standard-display-ascii 204 "�")  ; I with grave accent
  (standard-display-ascii 205 "�")  ; I with acute accent
  (standard-display-ascii 206 "�")  ; I with circumflex accent
  (standard-display-ascii 207 "�") ; I with diaeresis or umlaut mark
  (standard-display-ascii 208 "�")  ; D with stroke, Icelandic eth
  (standard-display-ascii 209 "�")  ; N with tilde
  (standard-display-ascii 210 "�")  ; O with grave accent
  (standard-display-ascii 211 "�")  ; O with acute accent
  (standard-display-ascii 212 "�")  ; O with circumflex accent
  (standard-display-ascii 213 "�")  ; O with tilde
  (standard-display-ascii 214 "�") ; O with diaeresis or umlaut mark
  (standard-display-ascii 215 "�")   ; multiplication sign
  (standard-display-ascii 216 "�")  ; O with slash
  (standard-display-ascii 217 "�")  ; U with grave accent
  (standard-display-ascii 218 "�")  ; U with acute accent
  (standard-display-ascii 219 "�")  ; U with circumflex accent
  (standard-display-ascii 220 "�") ; U with diaeresis or umlaut mark
  (standard-display-ascii 221 "�")  ; Y with acute accent
  (standard-display-ascii 222 "�")  ; capital thorn, Icelandic
  (standard-display-ascii 223 "�")  ; small sharp s, German
  (standard-display-ascii 224 "�")  ; a with grave accent
  (standard-display-ascii 225 "�")  ; a with acute accent
  (standard-display-ascii 226 "�")  ; a with circumflex accent
  (standard-display-ascii 227 "�")  ; a with tilde
  (standard-display-ascii 228 "�") ; a with diaeresis or umlaut mark
  (standard-display-ascii 229 "�")  ; a with ring
  (standard-display-ascii 230 "�")  ; ae diphthong
  (standard-display-ascii 231 "�")  ; c with cedilla
  (standard-display-ascii 232 "�")  ; e with grave accent
  (standard-display-ascii 233 "�")  ; e with acute accent
  (standard-display-ascii 234 "�")  ; e with circumflex accent
  (standard-display-ascii 235 "�") ; e with diaeresis or umlaut mark
  (standard-display-ascii 236 "�")  ; i with grave accent
  (standard-display-ascii 237 "�")  ; i with acute accent
  (standard-display-ascii 238 "�")  ; i with circumflex accent
  (standard-display-ascii 239 "�") ; i with diaeresis or umlaut mark
  (standard-display-ascii 240 "�")  ; d with stroke, Icelandic eth
  (standard-display-ascii 241 "�")  ; n with tilde
  (standard-display-ascii 242 "�")  ; o with grave accent
  (standard-display-ascii 243 "�")  ; o with acute accent
  (standard-display-ascii 244 "�")  ; o with circumflex accent
  (standard-display-ascii 245 "�")  ; o with tilde
  (standard-display-ascii 246 "�") ; o with diaeresis or umlaut mark
  (standard-display-ascii 247 "�")   ; division sign
  (standard-display-ascii 248 "�")  ; o with slash
  (standard-display-ascii 249 "�")  ; u with grave accent
  (standard-display-ascii 250 "�")  ; u with acute accent
  (standard-display-ascii 251 "�")  ; u with circumflex accent
  (standard-display-ascii 252 "�") ; u with diaeresis or umlaut mark
  (standard-display-ascii 253 "�")  ; y with acute accent
  (standard-display-ascii 254 "�")  ; small thorn, Icelandic
  (standard-display-ascii 255 "�") ; small y with diaeresis or umlaut mark
  )

(defun iso-pc-disable ()
  "Disable all translation, display and accept characters in native way.  If
called non-interactively, a 'redraw-display' may be necessary"
  (interactive)
  (setq keyboard-translate-table nil)
  (standard-display-8bit 128 255)
  (setq iso-pc-enabled nil)
  (message "Now CP850 characters are displayed and accepted"))

(defun iso-pc-enable ()
  "Enable Translation of display and keyboard to behave as if working with
ISO-8859-1. If called non-interactively, a 'redraw-display' may be
necessary"
(interactive)
  (iso-pc-enable-display)
  (iso-pc-enable-keyboard)
  (setq iso-pc-enabled t)
  (message "Now ISO-8859-1 characters are displayed and accepted"))

(defun iso-pc ()
  "Work with Texts in ISO-8859-1 charset on an IBM-PC using Codepage 850.
This function toggles between conversion and normal,
according to the value of iso-pc-enabled"
  (interactive)
  (if iso-pc-enabled
      (iso-pc-disable)
    (iso-pc-enable)
    )
  (redraw-display))

;;; I don't think this is really needed...
(provide 'iso-pc)

;;; iso-pc.el ends here