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72 lines
2.3 KiB
Plaintext
72 lines
2.3 KiB
Plaintext
Unicode support in busybox
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There are several scenarios where we need to handle unicode
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correctly.
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Shell input
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We want to correctly handle input of unicode characters.
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There are several problems with it. Just handling input
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as sequence of bytes would break any editing. This was fixed
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and now lineedit operates on the array of wchar_t's.
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But we also need to handle the following problematic moments:
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* It is unreasonable to expect that output device supports
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_any_ unicode chars. Perhaps we need to avoid printing
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those chars which are not supported by output device.
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Examples: chars which are not present in the font,
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chars which are not assigned in unicode,
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combining chars (especially trying to combine bad pairs:
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a_chinese_symbol + "combining grave accent" = ??!)
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* We need to account for the fact that unicode chars have
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different widths: 0 for combining chars, 1 for usual,
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2 for ideograms (are there 3+ wide chars?).
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* Bidirectional handling. If user wants to echo a phrase
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in Hebrew, he types: echo "srettel werbeH"
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Editors (vi, ed)
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This case is a bit similar to "shell input", but unlike shell,
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editors may encounder many more unexpected unicode sequences
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(try to load a random binary file...), and they need to preserve
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them, unlike shell which can afford to drop bogus input.
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more, less
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Need to correctly display any input file. Ideally, with
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ASCII/unicode/filtered_unicode option or keyboard switch.
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Note: need to handle tabs and backspaces specially
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(bksp is for manpage compat).
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cut, fold, watch
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May need ability to cut unicode string to specified number of wchars
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and/or to specified screen width. Need to handle tabs specially.
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sed, awk, grep
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Handle unicode-aware regexp match
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ls (multi-column display)
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ls will fail to line up columnar output if it will not account
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for character widths (and maybe filter out some of them, see
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above). OTOH, non-columnar views (ls -1, ls -l, ls | car)
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should NOT filter out bad unicode (but need to filter out
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control chars (coreutils does that). Note that unlike more/less,
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tabs and backspaces need not special handling.
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top, ps
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Need to perform filtering similar to ls.
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Filename display (in error messages and elsewhere)
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Need to perform filtering similar to ls.
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TODO: write an email to Asmus Freytag (asmus@unicode.org),
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author of http://unicode.org/reports/tr11/
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