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RE: [CSS3 Text] text-underline-position and superscript

From: Belov, Charles <Charles.Belov@sfmta.com>
Date: Tue, 21 Dec 2010 11:49:53 -0800
Message-ID: <E17F75B6E86AE842A57B4534F82D03769C3479@MTAMAIL.muni.sfgov.org>
To: <www-style@w3.org>
alphabetic
The underline is aligned with the alphabetic baseline. In this case the
underline is likely to cross some descenders. 

under
The underline is aligned with the "bottom" (left in vertical writing)
edge of the element's em-box. In this case the underline usually does
not cross the descenders. This is sometimes called "accounting"
underline.

I am running into an issue in English with regard to text that is mixed
regular text and superscript text, where I want an unbroken underline.
In actual practice the underline jumps up to be immediately beneath the
superscript text.  I would hope this before-edge/after-edge could be
applied to the anchor tag to produce such an unbroken underline.  

What I'm looking for is basically alphabetical following the main
alphabetic content, that is, superscripting would be ignored for the
positioning of the underline.  However, the "under" proposal would not
seem to accomplish this, since it would not be immediately beneath the
letters, but rather further beneath.

Possibly there is a need for 

alpha-ignore-super
The underline is aligned with the alphabetic baseline without taking
superscript into account. In this case the underline is likely to cross
some descenders in non-superscripted text. 

I realize I can style the superscripted to not show an underline --
that's what I'm doing now -- but if there is underlined text both
preceding and following the superscripted text, then that produces an
undesired break in the underline.

And logically:

alpha-conform-sub
The underline is aligned with the alphabetic baseline.  The entire
underline is lowered to the position that would be required by
subscripted text, whether or not subscripted text is present in the
current underlined text. 

alpha-conform-if-sub
The underline is aligned with the alphabetic baseline.  If subscript is
present in the underlined portion, the entire underline is lowered to
the position required by the subscripted text. 

alpha-conform-line-if-sub
The underline is aligned with the alphabetic baseline.  If subscript is
present in an underlined portion anywhere on the current text line,
whether or not a subscript is present in the current underlined portion,
the entire underline is lowered to the position that would be required
by the subscripted text were it present in the current underlined
portion. 

Also, is there a reason that pixel-positioning of the underline is not
part of this proposal?

Hope this helps,
Charles Belov
SFMTA Webmaster
 
Received on Tuesday, 21 December 2010 19:54:03 GMT

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