admin/notes/unicode

   1                                             -*-mode: text; coding: latin-1;-*-
   2
   3 Copyright (C) 2002, 2003, 2004, 2005, 2006, 2007, 2008
   4   Free Software Foundation, Inc.
   5 See the end of the file for license conditions.
   6
   7 Problems, fixmes and other unicode-related issues
   8 -------------------------------------------------------------
   9
  10 Notes by fx to record various things of variable importance.  handa
  11 needs to check them -- don't take too seriously, especially with
  12 regard to completeness.
  13
  14  * SINGLE_BYTE_CHAR_P returns true for Latin-1 characters, which has
  15    undesirable effects.  E.g.:
  16    (multibyte-string-p (let ((s "x")) (aset s 0 ?£) s)) => nil
  17    (multibyte-string-p (concat [?£])) => nil
  18    (text-char-description ?£) => "M-#"
  19
  20         These examples are all fixed by the change of 2002-10-14, but
  21         there still exist questionable SINGLE_BYTE_CHAR_P in the
  22         code (keymap.c and print.c).
  23
  24  * Rationalize character syntax and its relationship to the Unicode
  25    database.  (Applies mainly to symbol an punctuation syntax.)
  26
  27  * Fontset handling and customization needs work.  We want to relate
  28    fonts to scripts, probably based on the Unicode blocks.  The
  29    presence of small-repertoire 10646-encoded fonts in XFree 4 is a
  30    pain, not currently worked round.
  31
  32         With the change on 2002-07-26, multiple fonts can be
  33         specified in a fontset for a specific range of characters.
  34         Each range can also be specified by script.  Before using
  35         ISO10646 fonts, Emacs checks their repertories to avoid such
  36         fonts that don't have a glyph for a specific character.
  37
  38         fx has worked on fontset customization, but was stymied by
  39         basic problems with the way the default face is dealt with
  40         (and something else, I think).  This needs revisiting.
  41
  42  * Work is also needed on charset and coding system priorities.
  43
  44  * The relevant bits of latin1-disp.el need porting (and probably
  45    re-naming/updating).  See also cyril-util.el.
  46
  47  * Quail files need more work now the encoding is largely irrelevant.
  48
  49  * What to do with the old coding categories stuff?
  50
  51  * The preferred-coding-system property of charsets should probably be
  52    junked unless it can be made more useful now.
  53
  54  * find-multibyte-characters needs looking at.
  55
  56  * Implement Korean cp949/UHC, BIG5-HKSCS and any other important missing
  57    charsets.
  58
  59  * Lazy-load tables for unify-charset somehow?
  60
  61         Actually, Emacs clears out all charset maps and unify-map just
  62         before dumping, and they are loaded again on demand by the
  63         dumped emacs.  But, those maps (char tables) generated while
  64         temacs is running can't be removed from the dumped emacs.
  65
  66  * Translation tables for {en,de}code currently aren't supported.
  67
  68         This should be fixed by the changes of 2002-10-14.
  69
  70  * Defining CCL coding systems currently doesn't work.
  71
  72         This should be fixed by the changes of 2003-01-30.
  73
  74  * iso-2022 charsets get unified on i/o.
  75
  76         With the change on 2003-01-06, decoding routines put `charset'
  77         property to decoded text, and iso-2022 encoder pay attention
  78         to it.  Thus, for instance, reading and writing by
  79         iso-2022-7bit preserve the original designation sequences.
  80         The property name `preferred-charset' may be better?
  81
  82         We may have to utilize this property to decide a font.
  83
  84  * Revisit locale processing: look at treating the language and
  85    charset parts separately.  (Language should affect things like
  86    spelling and calendar, but that's not a Unicode issue.)
  87
  88  * Handle Unicode combining characters usefully, e.g. diacritics, and
  89    handle more scripts specifically (à la Devanagari).  There are
  90    issues with canonicalization.
  91
  92  * Bidi is a separate issue with no support currently.
  93
  94  * We need tabular input methods, e.g. for maths symbols.  (Not
  95    specific to Unicode.)
  96
  97  * Need multibyte text in menus, e.g. for the above.  (Not specific to
  98    Unicode -- see Emacs etc/TODO, but now mostly works with gtk.)
  99
 100  * There's currently no support for Unicode normalization.
 101
 102  * Populate char-width-table correctly for Unicode characters and
 103    worry about what happens when double-width charsets covering
 104    non-CJK characters are unified.
 105
 106  * Emacs 20/21 .elc files are currently not loadable.  It may or may
 107    not be possible to do this properly.
 108
 109         With the change on 2002-07-24, elc files generated by Emacs
 110         20.3 and later are correctly loaded (including those
 111         containing multibyte characters and compressed).  But, elc
 112         files generated by 20.2 and the primer are still not loadable.
 113         Is it really worth working on it?
 114
 115  * Rmail won't work with non-ASCII text.  Encoding issues for Babyl
 116    files need sorting out, but rms says Babyl will go before this is
 117    released.
 118
 119  * Gnus still needs some attention, and we need to get changes
 120    accepted by Gnus maintainers...
 121
 122  * There are type errors lurking, e.g. in
 123    Fcheck_coding_systems_region.  Define ENABLE_CHECKING to find them.
 124
 125  * You can grep the code for lots of fixmes.
 126
 127  * Old auto-save files, and similar files, such as Gnus drafts,
 128    containing non-ASCII characters probably won't be re-read correctly.
 129
 130 \f
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