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

   1                                             -*-mode: text; coding: utf-8;-*-
   2
   3 Copyright (C) 2002-2013 Free Software Foundation, Inc.
   4 See the end of the file for license conditions.
   5
   6 Problems, fixmes and other unicode-related issues
   7 -------------------------------------------------------------
   8
   9 Notes by fx to record various things of variable importance.  handa
  10 needs to check them -- don't take too seriously, especially with
  11 regard to completeness.
  12
  13  * SINGLE_BYTE_CHAR_P returns true for Latin-1 characters, which has
  14    undesirable effects.  E.g.:
  15    (multibyte-string-p (let ((s "x")) (aset s 0 ?£) s)) => nil
  16    (multibyte-string-p (concat [?£])) => nil
  17    (text-char-description ?£) => "M-#"
  18
  19         These examples are all fixed by the change of 2002-10-14, but
  20         there still exist questionable SINGLE_BYTE_CHAR_P in the
  21         code (keymap.c and print.c).
  22
  23  * Rationalize character syntax and its relationship to the Unicode
  24    database.  (Applies mainly to symbol an punctuation syntax.)
  25
  26  * Fontset handling and customization needs work.  We want to relate
  27    fonts to scripts, probably based on the Unicode blocks.  The
  28    presence of small-repertoire 10646-encoded fonts in XFree 4 is a
  29    pain, not currently worked round.
  30
  31         With the change on 2002-07-26, multiple fonts can be
  32         specified in a fontset for a specific range of characters.
  33         Each range can also be specified by script.  Before using
  34         ISO10646 fonts, Emacs checks their repertories to avoid such
  35         fonts that don't have a glyph for a specific character.
  36
  37         fx has worked on fontset customization, but was stymied by
  38         basic problems with the way the default face is dealt with
  39         (and something else, I think).  This needs revisiting.
  40
  41  * Work is also needed on charset and coding system priorities.
  42
  43  * The relevant bits of latin1-disp.el need porting (and probably
  44    re-naming/updating).  See also cyril-util.el.
  45
  46  * Quail files need more work now the encoding is largely irrelevant.
  47
  48  * What to do with the old coding categories stuff?
  49
  50  * The preferred-coding-system property of charsets should probably be
  51    junked unless it can be made more useful now.
  52
  53  * find-multibyte-characters needs looking at.
  54
  55  * Implement Korean cp949/UHC, BIG5-HKSCS and any other important missing
  56    charsets.
  57
  58  * Lazy-load tables for unify-charset somehow?
  59
  60         Actually, Emacs clears out all charset maps and unify-map just
  61         before dumping, and they are loaded again on demand by the
  62         dumped emacs.  But, those maps (char tables) generated while
  63         temacs is running can't be removed from the dumped emacs.
  64
  65  * iso-2022 charsets get unified on i/o.
  66
  67         With the change on 2003-01-06, decoding routines put `charset'
  68         property to decoded text, and iso-2022 encoder pay attention
  69         to it.  Thus, for instance, reading and writing by
  70         iso-2022-7bit preserve the original designation sequences.
  71         The property name `preferred-charset' may be better?
  72
  73         We may have to utilize this property to decide a font.
  74
  75  * Revisit locale processing: look at treating the language and
  76    charset parts separately.  (Language should affect things like
  77    spelling and calendar, but that's not a Unicode issue.)
  78
  79  * Handle Unicode combining characters usefully, e.g. diacritics, and
  80    handle more scripts specifically (à la Devanagari).  There are
  81    issues with canonicalization.
  82
  83  * We need tabular input methods, e.g. for maths symbols.  (Not
  84    specific to Unicode.)
  85
  86  * Need multibyte text in menus, e.g. for the above.  (Not specific to
  87    Unicode -- see Emacs etc/TODO, but now mostly works with gtk.)
  88
  89  * There's currently no support for Unicode normalization.
  90
  91  * Populate char-width-table correctly for Unicode characters and
  92    worry about what happens when double-width charsets covering
  93    non-CJK characters are unified.
  94
  95  * There are type errors lurking, e.g. in
  96    Fcheck_coding_systems_region.  Define ENABLE_CHECKING to find them.
  97
  98  * Old auto-save files, and similar files, such as Gnus drafts,
  99    containing non-ASCII characters probably won't be re-read correctly.
 100
 101
 102 Source file encoding
 103 --------------------
 104
 105 Most Emacs source files are encoded in UTF-8 (or in ASCII, which is a
 106 subset), but there are a few exceptions, listed below.  Perhaps
 107 someday many of these files will be converted to UTF-8, for
 108 convenience when using tools like 'grep -r', but this might need
 109 nontrivial changes to the build process.
 110
 111  * chinese-big5
 112
 113      These are verbatim copies of files taken from external sources.
 114      They haven't been converted to UTF-8.
 115
 116         leim/CXTERM-DIC/4Corner.tit
 117         leim/CXTERM-DIC/ARRAY30.tit
 118         leim/CXTERM-DIC/ECDICT.tit
 119         leim/CXTERM-DIC/ETZY.tit
 120         leim/CXTERM-DIC/PY-b5.tit
 121         leim/CXTERM-DIC/Punct-b5.tit
 122         leim/CXTERM-DIC/QJ-b5.tit
 123         leim/CXTERM-DIC/ZOZY.tit
 124         leim/MISC-DIC/CTLau-b5.html
 125         leim/MISC-DIC/cangjie-table.b5
 126
 127  * chinese-iso-8bit
 128
 129      These are verbatim copies of files taken from external sources.
 130      They haven't been converted to UTF-8.
 131
 132         leim/CXTERM-DIC/CCDOSPY.tit
 133         leim/CXTERM-DIC/Punct.tit
 134         leim/CXTERM-DIC/QJ.tit
 135         leim/CXTERM-DIC/SW.tit
 136         leim/CXTERM-DIC/TONEPY.tit
 137         leim/MISC-DIC/pinyin.map
 138         leim/MISC-DIC/CTLau.html
 139         leim/MISC-DIC/ziranma.cin
 140
 141  * cp850
 142
 143      This file contains non-ASCII characters in unibyte strings.  When
 144      editing a keyboard layout it's more convenient to see 'é' than
 145      '\202', and the MS-DOS compiler requires the single byte if a
 146      backslash escape is not being used.
 147
 148         src/msdos.c
 149
 150  * iso-2022-cn-ext
 151
 152      This file is externally generated from leim/MISC-DIC/cangjie-table.b5
 153      by Big5->CNS converter.  It hasn't been converted to UTF-8.
 154
 155         leim/MISC-DIC/cangjie-table.cns
 156
 157  * iso-latin-2
 158
 159      These files are processed by csplain, a program that requires
 160      Latin-2 input.  In 2012 the csplain maintainers started
 161      recommending UTF-8, but these files haven't been converted yet.
 162
 163         etc/refcards/cs-dired-ref.tex
 164         etc/refcards/cs-refcard.tex
 165         etc/refcards/cs-survival.tex
 166         etc/refcards/sk-dired-ref.tex
 167         etc/refcards/sk-refcard.tex
 168         etc/refcards/sk-survival.tex
 169
 170  * japanese-iso-8bit
 171
 172      SKK-JISYO.L is a verbatim copy of a file taken from an external source.
 173      It hasn't been converted to UTF-8.
 174
 175         leim/SKK-DIC/SKK-JISYO.L
 176
 177  * japanese-shift-jis
 178
 179      This is a verbatim copy of a file taken from an external source.
 180      It hasn't been converted to UTF-8.
 181
 182         admin/charsets/mapfiles/cns2ucsdkw.txt
 183
 184  * no-conversion
 185
 186      This file purposely contains arbitrary bytes interspersed within text,
 187      to test whether the Emacs distribution is corrupted.
 188
 189         lib-src/testfile
 190
 191  * iso-2022-7bit
 192
 193      This file switches between CJK charsets, which is not encoded in UTF-8.
 194
 195         etc/HELLO
 196
 197      Each of these files contains just one CJK charset, but Emacs
 198      currently has no easy way to specify set-charset-priority on a
 199      per-file basis, so converting any of these files to UTF-8 might
 200      change the file's appearance when viewed by an Emacs that is
 201      operating in some other language environment.
 202
 203         etc/tutorials/TUTORIAL.ja
 204         leim/quail/cyril-jis.el
 205         leim/quail/hanja-jis.el
 206         leim/quail/japanese.el
 207         leim/quail/py-punct.el
 208         leim/quail/pypunct-b5.el
 209         lisp/international/ja-dic-cnv.el
 210         lisp/international/ja-dic-utl.el
 211         lisp/international/kinsoku.el
 212         lisp/international/kkc.el
 213         lisp/international/titdic-cnv.el
 214         lisp/language/japan-util.el
 215         lisp/language/japanese.el
 216         lisp/term/x-win.el
 217
 218  * utf-8-emacs
 219
 220      These files contain characters that cannot be encoded in UTF-8.
 221
 222         leim/quail/tibetan.el
 223         leim/quail/ethiopic.el
 224         lisp/international/titdic-cnv.el
 225         lisp/language/tibetan.el
 226         lisp/language/tibet-util.el
 227         lisp/language/ind-util.el
 228
 229 \f
 230 This file is part of GNU Emacs.
 231
 232 GNU Emacs is free software: you can redistribute it and/or modify
 233 it under the terms of the GNU General Public License as published by
 234 the Free Software Foundation, either version 3 of the License, or
 235 (at your option) any later version.
 236
 237 GNU Emacs is distributed in the hope that it will be useful,
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 239 MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 240 GNU General Public License for more details.
 241
 242 You should have received a copy of the GNU General Public License
 243 along with GNU Emacs.  If not, see <http://www.gnu.org/licenses/>.