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202 lines
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Plaintext
202 lines
8.0 KiB
Plaintext
-*-mode: text; coding: latin-1;-*-
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Problems, fixmes and other issues in the emacs-unicode branch
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-------------------------------------------------------------
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Notes by fx to record various things of variable importance. handa
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needs to check them -- don't take too seriously, especially with
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regard to completeness.
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_Do take seriously that you don't want this branch unless you're
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actually working on it; you risk your data by actually using it._ If
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you just want to edit Unicode and/or unify iso-8859 et al, see the
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existing support and the extra stuff at
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<URL:ftp://dlpx1.dl.ac.uk/fx/emacs/Mule>, mostly now in the CVS trunk.
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(Editing support is mostly orthogonal to the internal representation.)
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* SINGLE_BYTE_CHAR_P returns true for Latin-1 characters, which has
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undesirable effects. E.g.:
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(multibyte-string-p (let ((s "x")) (aset s 0 ?£) s)) => nil
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(multibyte-string-p (concat [?£])) => nil
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(text-char-description ?£) => "M-#"
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These examples are all fixed by the change of 2002-10-14, but
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there still exist questionalble SINGLE_BYTE_CHAR_P in the
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code (keymap.c and print.c).
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* Rationalize character syntax and its relationship to the Unicode
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database. (Applies mainly to symbol an punctuation syntax.)
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* Fontset handling and customization needs work. We want to relate
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fonts to scripts, probably based on the Unicode blocks. The
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presence of small-repertoire 10646-encoded fonts in XFree 4 is a
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pain, not currently worked round.
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With the change on 2002-07-26, multiple fonts can be
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specified in a fontset for a specific range of characters.
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Each range can also be specified by script. Before using
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ISO10646 fonts, Emacs checks their repertories to avoid such
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fonts that don't have a glyph for a specific character.
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fx has worked on fontset customization, but was stymied by
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basic problems with the way the default face is dealt with
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(and something else, I think). This needs revisiting.
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* Work is also needed on charset and coding system priorities.
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* The relevant bits of latin1-disp.el need porting (and probably
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re-naming/updating). See also cyril-util.el.
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* Quail files need more work now the encoding is largely irrelevant.
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* What to do with the old coding categories stuff?
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* The preferred-coding-system property of charsets should probably be
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junked unless it can be made more useful now.
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* find-multibyte-characters needs looking at.
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* Implement Korean cp949/UHC, BIG5-HKSCS and any other important missing
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charsets.
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* Lazy-load tables for unify-charset somehow?
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Actually, Emacs clear out all charset maps and unify-map just
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before dumping, and their are loaded again on demand the
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dumped emacs. But, those maps (char tables) generated while
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temacs is running can't be get rid of from the dumped emacs.
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* Translation tables for {en,de}code currently aren't supported.
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This should be fixed by the changes of 2002-10-14.
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* Defining CCL coding systems currently doesn't work.
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This should be fixed by the changes of 2003-01-30.
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* iso-2022 charsets get unified on i/o.
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With the change on 2003-01-06, decoding routines put `charset'
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property to decoded text, and iso-2022 encoder pay attention
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to it. Thus, for instance, reading and writing by
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iso-2022-7bit preserve the original designation sequences.
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The property name `preferred-charset' may be better?
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We may have to utilize this property to decide a font.
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* Revisit locale processing: look at treating the language and
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charset parts separately. (Language should affect things like
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speling and calendar, but that's not a Unicode issue.)
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* Handle Unicode combining characters usefully, e.g. diacritics, and
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handle more scripts specifically (à la Devanagari). There are
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issues with canonicalization.
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* Bidi is a separate issue with no support currently.
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* We need tabular input methods, e.g. for maths symbols. (Not
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specific to Unicode.)
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* Need multibyte text in menus, e.g. for the above. (Not specific to
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Unicode -- see Emacs etc/TODO, but now mostly works with gtk.)
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* There's currently no support for Unicode normalization.
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* Populate char-width-table correctly for Unicode chanaracters and
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worry about what happens when double-width charsets covering
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non-CJK characters are unified.
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* Emacs 20/21 .elc files are currently not loadable. It may or may
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not be possible to do this properly.
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With the change on 2002-07-24, elc files generated by Emacs
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20.3 and later are correctly loaded (including those
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containing multibyte characters and compressed). But, elc
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files generated by 20.2 and the primer are still not loadable.
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Is it really worth working on it?
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* Rmail won't work with non-ASCII text. Encoding issues for Babyl
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files need sorting out, but rms says Babyl will go before this is
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released.
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* Gnus still needs some attention, and we need to get changes
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accepted by Gnus maintainers...
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* There are type errors lurking, e.g. in
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Fcheck_coding_systems_region. Define ENABLE_CHECKING to find them.
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* You can grep the code for lots of fixmes.
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* Old auto-save files, and similar files, such as Gnus drafts,
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containing non-ASCII characters probably won't be re-read correctly.
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New font handling mechanism with font backend method
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----------------------------------------------------
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This branch now contains new codes for handling fonts by multiple font
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backends. The old font handling codes still exist completely parallel
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to the new codes, and the new codes are used only when you configure
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Emacs with the argument "--enable-font-backend".
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Which font backends to use can be specified by X resource
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"FontBackend". For instance, if you want to use Xft fonts only,
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Emacs.FontBackend: xft
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will work. If this resource is not set, Emacs tries to use all font
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backends available on your graphic device.
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The configure script, if invoked with "--enable-font-backend", checks
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if libraries freetype and fontconfig exist. If they are both
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available, macro "USE_FONT_BACKEND" is defined in src/config.h. In
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that case, the existing of Xft library is checked too.
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The new files are:
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font.h -- header providing font-backend related structures
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(most important ones are "struct font" and "struct
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font_driver"), macros, and etc.
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font.c -- main font handling code.
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xfont.c -- font-driver on X for X core fonts.
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ftfont.c -- generic font-driver for FreeType fonts providing
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device-independent methods of struct font_driver.
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xftfont.c -- font-driver on X using Xft for FreeType fonts
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utilizing methods provided by ftfont.c.
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ftxfont.c -- font-driver on X directly using FreeType fonts
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utilizing methods provided by ftfont.c.
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w32font.c -- font driver on w32 using Windows native fonts,
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corresponding to xfont.c
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So we already have codes for X. For the other systems (w32 and mac),
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it seems that we need these files:
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atmfont.c -- font-driver on mac using ATM fonts, corresponding
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to xfont.c
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As BDF fonts are currently used on w32, we may also implement these:
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bdffont.c -- generic font-driver for BDF fonts, corresponding to
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ftfont.c
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bdfw32font.c -- font-driver on w32 using BDF fonts,
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corresponding to ftxfont.c
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But, as FreeType already supports BDF fonts, if FreeType and
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Fontconfig are also available on w32, what we need may be:
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ftw32font.c -- font-driver on w32 directly using FreeType fonts
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utilizing methods provided by ftfont.c.
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And, for those to work, macterm.c and macfns.c must be changed by the
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similar way as xterm.c and xfns.c (the parts "#ifdef USE_FONT_BACKEND"
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... "#endif" should be checked).
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It may be interesting if Emacs supports a frame buffer directly and
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have these font driver.
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ftfbfont.c -- font-driver on FB for FreeType fonts.
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bdffbfont.c -- font-driver on FB for BDF fonts.
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Note: The fontset related codes are not yet matuared to work well with
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the font backend method. So, for instance, even if you start Emacs
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as something like this:
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% emacs -fn tahoma
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Non-ASCII Latin characters will not be displayed by the font "tahoma".
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In such a case, please try this:
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(set-fontset-font "fontset-default" 'latin '("tahoma" . "unicode-bmp"))
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