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[css3-fonts][css-variables][css-counter-styles-3][css3-values] Case sensitivity of user-defined identifiers

From: Tab Atkins Jr. <jackalmage@gmail.com>
Date: Wed, 26 Sep 2012 17:34:09 -0700
Message-ID: <CAAWBYDCpFoUPubXaL5bQ_e+f8h3iKvZ76CafiL2xuGN6e-BEGA@mail.gmail.com>
To: www-style list <www-style@w3.org>
At the last F2F we discussed the issue of the case of user-defined
identifiers.  CSS-defined idents are all case-insensitive; however,
they are also all within the ASCII range, so it's very trivial to
define what that means.  User-defined idents can contain all of
Unicode, which potentially makes the problem much larger.  Currently,
we define that user-defined idents are case-sensitive, but that's not
easily compatible with several things we're doing where user-defined
idents mix with CSS-defined idents, or where something that was
previous CSS-defined is reinterpreted into a user-defined one in the
UA stylesheet.

So, at the F2F we agreed to make user-defined idents case-insensitive,
but deferred defining exactly what that means until we get some more
research on what's necessary/possible.

There are a few reasonable options:

1. ASCII case-insensitivity.  This is the minimal change to be
compatible with CSS-defined idents migrating to being user-defined.
However, it's very limited - if you write an ident in a language other
than English, you may very well run up against casing issues that
should be "obvious" to solve.

2. Latin1 case-insenstivity.  This allows case-insensitivity within
all the "English-like" languages, so that, for example, an accented
lowercase letter is equal to its uppercase version.

3. Unicode case-insensitivity.  I'm not very familiar with the
possibility-space here, but I'm told there are algorithms for doing
case-folding in Unicode.  We specifically need one that can
*canonicalize* a string into a comparable form, so we can turn it into
an atomic string and do fast comparisons later, rather than one that
can only be used to compare two strings.

jdaggett was supposed to look into option 3 and report back.  John,
any progress?  This is a blocking issue for both Variables and Counter
Styles.

~TJ
Received on Thursday, 27 September 2012 00:34:56 GMT

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