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