code.delx.au - gnu-emacs/blob - admin/notes/unicode

   1                                             -*-mode: text; coding: utf-8;-*-
   2
   3 Copyright (C) 2002-2016 Free Software Foundation, Inc.
   4 See the end of the file for license conditions.
   5
   6 Importing a new Unicode Standard version into Emacs
   7 -------------------------------------------------------------
   8
   9 Emacs uses the following files from the Unicode Character Database
  10 (a.k.a. "UCD):
  11
  12   . UnicodeData.txt
  13   . Blocks.txt
  14   . BidiMirroring.txt
  15   . BidiBrackets.txt
  16   . IVD_Sequences.txt
  17
  18 First, these files need to be copied into admin/unidata/, and then
  19 Emacs should be rebuilt for them to take effect.  Rebuilding Emacs
  20 updates several derived files elsewhere in the Emacs source tree,
  21 mainly in lisp/international/.
  22
  23 When Emacs is rebuilt for the first time after importing the new
  24 files, pay attention to any warning or error messages.  In particular,
  25 admin/unidata/unidata-gen.el will complain if UnicodeData.txt defines
  26 new bidirectional attributes of characters, because unidata-gen.el,
  27 bidi.c and dispextern.h need to be updated in that case; failure to do
  28 so will cause aborts in redisplay.
  29
  30 Next, review the changes in UnicodeData.txt vs the previous version
  31 used by Emacs.  Any changes, be it introduction of new scripts or
  32 addition of codepoints to existing scripts, might need corresponding
  33 changes in the data used for filling the category-table, case-table,
  34 and char-width-table.  The additional scripts should cause automatic
  35 updates in charscript.el, but it is a good idea to look at the results
  36 and see if any changes in admin/unidata/blocks.awk are required.
  37
  38 Any new scripts added by UnicodeData.txt will also need updates to
  39 script-representative-chars defined in fontset.el, and also the list
  40 of OTF script tags in otf-script-alist, whose source is on this page:
  41
  42   https://www.microsoft.com/typography/otspec/scripttags.htm
  43
  44 Other databases in fontset.el might also need to be updated as needed.
  45
  46 The function 'ucs-names', defined in lisp/international/mule-cmds.el,
  47 might need to be updated because it knows about used and unused ranges
  48 of Unicode codepoints, which a new release of the Unicode Standard
  49 could change.
  50
  51 Problems, fixmes and other unicode-related issues
  52 -------------------------------------------------------------
  53
  54 Notes by fx to record various things of variable importance.  Handa
  55 needs to check them -- don't take too seriously, especially with
  56 regard to completeness.
  57
  58  * SINGLE_BYTE_CHAR_P returns true for Latin-1 characters, which has
  59    undesirable effects.  E.g.:
  60    (multibyte-string-p (let ((s "x")) (aset s 0 ?£) s)) => nil
  61    (multibyte-string-p (concat [?£])) => nil
  62    (text-char-description ?£) => "M-#"
  63
  64         These examples are all fixed by the change of 2002-10-14, but
  65         there still exist questionable SINGLE_BYTE_CHAR_P in the
  66         code (keymap.c and print.c).
  67
  68  * Rationalize character syntax and its relationship to the Unicode
  69    database.  (Applies mainly to symbol an punctuation syntax.)
  70
  71  * Fontset handling and customization needs work.  We want to relate
  72    fonts to scripts, probably based on the Unicode blocks.  The
  73    presence of small-repertoire 10646-encoded fonts in XFree 4 is a
  74    pain, not currently worked round.
  75
  76         With the change on 2002-07-26, multiple fonts can be
  77         specified in a fontset for a specific range of characters.
  78         Each range can also be specified by script.  Before using
  79         ISO10646 fonts, Emacs checks their repertories to avoid such
  80         fonts that don't have a glyph for a specific character.
  81
  82         fx has worked on fontset customization, but was stymied by
  83         basic problems with the way the default face is dealt with
  84         (and something else, I think).  This needs revisiting.
  85
  86  * Work is also needed on charset and coding system priorities.
  87
  88  * The relevant bits of latin1-disp.el need porting (and probably
  89    re-naming/updating).  See also cyril-util.el.
  90
  91  * Quail files need more work now the encoding is largely irrelevant.
  92
  93  * What to do with the old coding categories stuff?
  94
  95  * The preferred-coding-system property of charsets should probably be
  96    junked unless it can be made more useful now.
  97
  98  * find-multibyte-characters needs looking at.
  99
 100  * Implement Korean cp949/UHC, BIG5-HKSCS and any other important missing
 101    charsets.
 102
 103  * Lazy-load tables for unify-charset somehow?
 104
 105         Actually, Emacs clears out all charset maps and unify-map just
 106         before dumping, and they are loaded again on demand by the
 107         dumped emacs.  But, those maps (char tables) generated while
 108         temacs is running can't be removed from the dumped emacs.
 109
 110  * iso-2022 charsets get unified on i/o.
 111
 112         With the change on 2003-01-06, decoding routines put the 'charset'
 113         property onto decoded text, and iso-2022 encoder pay attention
 114         to it.  Thus, for instance, reading and writing by
 115         iso-2022-7bit preserve the original designation sequences.
 116         The property name 'preferred-charset' may be better?
 117
 118         We may have to utilize this property to decide a font.
 119
 120  * Revisit locale processing: look at treating the language and
 121    charset parts separately.  (Language should affect things like
 122    spelling and calendar, but that's not a Unicode issue.)
 123
 124  * Handle Unicode combining characters usefully, e.g. diacritics, and
 125    handle more scripts specifically (à la Devanagari).  There are
 126    issues with canonicalization.
 127
 128  * We need tabular input methods, e.g. for maths symbols.  (Not
 129    specific to Unicode.)
 130
 131  * Need multibyte text in menus, e.g. for the above.  (Not specific to
 132    Unicode -- see Emacs etc/TODO, but now mostly works with gtk.)
 133
 134  * There's currently no support for Unicode normalization.
 135
 136  * Populate char-width-table correctly for Unicode characters and
 137    worry about what happens when double-width charsets covering
 138    non-CJK characters are unified.
 139
 140  * There are type errors lurking, e.g. in
 141    Fcheck_coding_systems_region.  Define ENABLE_CHECKING to find them.
 142
 143  * Old auto-save files, and similar files, such as Gnus drafts,
 144    containing non-ASCII characters probably won't be re-read correctly.
 145
 146
 147 Source file encoding
 148 --------------------
 149
 150 Most Emacs source files are encoded in UTF-8 (or in ASCII, which is a
 151 subset), but there are a few exceptions, listed below.  Perhaps
 152 someday many of these files will be converted to UTF-8, for
 153 convenience when using tools like 'grep -r', but this might need
 154 nontrivial changes to the build process.
 155
 156  * chinese-big5
 157
 158      These are verbatim copies of files taken from external sources.
 159      They haven't been converted to UTF-8.
 160
 161         leim/CXTERM-DIC/4Corner.tit
 162         leim/CXTERM-DIC/ARRAY30.tit
 163         leim/CXTERM-DIC/ECDICT.tit
 164         leim/CXTERM-DIC/ETZY.tit
 165         leim/CXTERM-DIC/PY-b5.tit
 166         leim/CXTERM-DIC/Punct-b5.tit
 167         leim/CXTERM-DIC/QJ-b5.tit
 168         leim/CXTERM-DIC/ZOZY.tit
 169         leim/MISC-DIC/CTLau-b5.html
 170         leim/MISC-DIC/cangjie-table.b5
 171
 172  * chinese-iso-8bit
 173
 174      These are verbatim copies of files taken from external sources.
 175      They haven't been converted to UTF-8.
 176
 177         leim/CXTERM-DIC/CCDOSPY.tit
 178         leim/CXTERM-DIC/Punct.tit
 179         leim/CXTERM-DIC/QJ.tit
 180         leim/CXTERM-DIC/SW.tit
 181         leim/CXTERM-DIC/TONEPY.tit
 182         leim/MISC-DIC/CTLau.html
 183         leim/MISC-DIC/pinyin.map
 184         leim/MISC-DIC/ziranma.cin
 185
 186  * cp850
 187
 188      This file contains non-ASCII characters in unibyte strings.  When
 189      editing a keyboard layout it's more convenient to see 'é' than
 190      '\202', and the MS-DOS compiler requires the single byte if a
 191      backslash escape is not being used.
 192
 193         src/msdos.c
 194
 195  * iso-2022-cn-ext
 196
 197      This file is externally generated from leim/MISC-DIC/cangjie-table.b5
 198      by Big5->CNS converter.  It hasn't been converted to UTF-8.
 199
 200         leim/MISC-DIC/cangjie-table.cns
 201
 202  * japanese-iso-8bit
 203
 204      SKK-JISYO.L is a verbatim copy of a file taken from an external source.
 205      It hasn't been converted to UTF-8.
 206
 207         leim/SKK-DIC/SKK-JISYO.L
 208
 209  * japanese-shift-jis
 210
 211      This is a verbatim copy of a file taken from an external source.
 212      It hasn't been converted to UTF-8.
 213
 214         admin/charsets/mapfiles/cns2ucsdkw.txt
 215
 216  * iso-2022-7bit
 217
 218      This file switches between CJK charsets, which is not encoded in UTF-8.
 219
 220         etc/HELLO
 221
 222      Each of these files contains just one CJK charset, but Emacs
 223      currently has no easy way to specify set-charset-priority on a
 224      per-file basis, so converting any of these files to UTF-8 might
 225      change the file's appearance when viewed by an Emacs that is
 226      operating in some other language environment.
 227
 228         etc/tutorials/TUTORIAL.ja
 229         lisp/international/ja-dic-cnv.el
 230         lisp/international/ja-dic-utl.el
 231         lisp/international/kinsoku.el
 232         lisp/international/kkc.el
 233         lisp/international/titdic-cnv.el
 234         lisp/language/japan-util.el
 235         lisp/language/japanese.el
 236         lisp/leim/quail/cyril-jis.el
 237         lisp/leim/quail/hanja-jis.el
 238         lisp/leim/quail/japanese.el
 239         lisp/leim/quail/py-punct.el
 240         lisp/leim/quail/pypunct-b5.el
 241
 242      This file contains just Chinese characters, and has same problem.
 243      Also, it contains characters that cannot be encoded in UTF-8.
 244
 245         lisp/international/titdic-cnv.el
 246
 247  * utf-8-emacs
 248
 249      These files contain characters that cannot be encoded in UTF-8.
 250
 251         lisp/language/ethio-util.el
 252         lisp/language/ethiopic.el
 253         lisp/language/ind-util.el
 254         lisp/language/tibet-util.el
 255         lisp/language/tibetan.el
 256         lisp/leim/quail/ethiopic.el
 257         lisp/leim/quail/tibetan.el
 258
 259  * binary files
 260
 261      These files contain binary data, and are not text files.
 262      Some of the entries in this list are patterns, and stand for any
 263      files with the listed extension.
 264
 265         *.gz
 266         *.icns
 267         *.ico
 268         *.pbm
 269         *.pdf
 270         *.png
 271         *.sig
 272         etc/e/eterm-color
 273         etc/package-keyring.gpg
 274         msdos/emacs.pif
 275         nextstep/GNUstep/Emacs.base/Resources/emacs.tiff
 276         nt/icons/hand.cur
 277
 278 \f
 279 This file is part of GNU Emacs.
 280
 281 GNU Emacs is free software: you can redistribute it and/or modify
 282 it under the terms of the GNU General Public License as published by
 283 the Free Software Foundation, either version 3 of the License, or
 284 (at your option) any later version.
 285
 286 GNU Emacs is distributed in the hope that it will be useful,
 287 but WITHOUT ANY WARRANTY; without even the implied warranty of
 288 MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 289 GNU General Public License for more details.
 290
 291 You should have received a copy of the GNU General Public License
 292 along with GNU Emacs.  If not, see <http://www.gnu.org/licenses/>.