From: Doug Ewell (dewell@adelphia.net)
Date: Tue Mar 13 2007 - 23:53:44 CST
Philippe Verdy <verdy underscore p at wanadoo dot fr> wrote:
> It would be better to have in Unicode some special ranges of control
> characters mapped to byte values that are part of unconverted CES
> sequences like in VT100, VT200 (and so on) protocols, or in other
> legacy terminal protocols (to encode colors, cursor control, or other
> rich text enhancements, or the encoding of user-defined bitmaps for
> custom characters or glyphs, notably used in some East-Asian Teletext
> systems, because trying to detect which character those bitmaps
> represent can be difficult, or even impossible, as they were really
> user-defined and local to the document containing those glyph
> definitions).
On no account do I wish to replace ISO 6429 with some other mechanism,
or introduce new coded characters to assist ISO 6429 handling. It
wouldn't work as intended anyway, and the experience with Plan 14 tags
shows how reluctant UTC would be to invent such "special control
characters."
I'm only asking for layer clarifications between ISO 6429 and various
Unicode/10646 representations.
> Consider sequences like:
> ESC, [, A, I, R
> (in a 7-bit or 8-bit encoded document prepared and sent on medias that
> support with VT100-like enhancement).
>
> Or even this one with Videotex:
> ESC, A, I, R
>
> Do they c ontain the English word "AIR" or the abbreviation "IR"
> (preceded by a ANSI/VT100-like color attribute)? How can we delimit
> the length of escape sequences?
That's easy if you've read ISO 6429 or the equivalent ECMA or ANSI
standard:
1B [30-3F]* [20-2F]* [40-7E]
The syntax is well-defined and unambiguous. In your first example, the
sequence ends with the letter A, and would move the cursor up one row
(if possible) before printing the letters "IR".
-- Doug Ewell * Fullerton, California, USA * RFC 4645 * UTN #14 http://users.adelphia.net/~dewell/ http://www1.ietf.org/html.charters/ltru-charter.html http://www.alvestrand.no/mailman/listinfo/ietf-languages
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