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Re: [CSS3-text] text-underline-position and superscript

From: Ambrose LI <ambrose.li@gmail.com>
Date: Sun, 26 Dec 2010 09:00:20 -0500
Message-ID: <AANLkTikQiMmzcKLE-HwOyc5BwieYM1=D0gAed9CiRT6A@mail.gmail.com>
To: Koji Ishii <kojiishi@gluesoft.co.jp>
Cc: "Belov, Charles" <Charles.Belov@sfmta.com>, "www-style@w3.org" <www-style@w3.org>
Sorry for following up on myself again. I'll blame it being early
morning, but let me reorganize myself a bit and restate how the two
ideas are related:

==================================================

There are two generalized principles common to Charles' and my ideas,
and the two general principles are that:

1. We need some way to specify that, in some situations, no matter
what the glyph-specific underline position is, we want to keep a
constant underline position for some logical grouping of characters.

(1a) For superscript/subscripts: underlines don't move up/down due to
the super/subscripting

(1b) For Chinese: underlines don't move up/down when there are Latin
or other non-CJK characters in the sequence

2. As a corollary of the above, we need some way to specify that
underlines are always visually disjoint if they are semantically
marked up as separate.

(2a) For superscripts/subscripts: The logical markup is provided by
SUP or SUB and we make it clear that we want the underlines to move
up/down along with the super/subscript

(2b) For Chinese: The logical markup is provided by U and we make it
clear that the two adjacent underlines should never run into each
other

(2c) The Chinese use case could also potentially be useful for
non-Chinese situations

What Charles proposed are ways to specify how the constant underline
position in #1 should be determined, and to specify how a non-constant
underline position in #2 can be explicitly specified for superscripts
and subscripts. Perhaps there can be ways to get rid of the proposed
keywords, but his proposal is a good analysis (without considering the
requirements for the Chinese typography) of what we will need to deal
with when we need the browser to figure out a constant position for
the underlining.

Charles did not explicitly specify a use case for "pixel positioning",
but I suggested it as a possible fix for incorrect underline position
in Chinese. The above also shows that the counter-proposal of
correcting the underline positions in CJK fonts (which still should be
corrected, since this affects also word processors) alone will not be
a complete fix to the Chinese problem. Personally, I envision "pixel
positioning" to be usable as a workaround for both problem #1, and
problem #2 when we are dealing specifically with superscripts and
subscripts; it may not be a perfect solution but this could be what
Charles had in mind, *especially* if you don't want the proposed
additional keywords.

-- 
cheers,
-ambrose

does anyone know how to fix Snow Leopard? it broke input method
switching and is causing many typing mistakes and is very annoying
Received on Sunday, 26 December 2010 14:00:48 GMT

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