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RE: [CSS3 Text] text-underline-position

From: Koji Ishii <kojiishi@gluesoft.co.jp>
Date: Mon, 20 Dec 2010 22:40:09 -0500
To: Keiko Hiraide <hiraide@antenna.co.jp>, "www-style@w3.org" <www-style@w3.org>
CC: "CJK discussion (public-i18n-cjk@w3.org)" <public-i18n-cjk@w3.org>
Message-ID: <A592E245B36A8949BDB0A302B375FB4E0AA8B1BF0C@MAILR001.mail.lan>
Thank you for your valuable feedback.

If I understand correctly, you're talking about two issues. One is about 'before-edge' and 'after-edge'. As you pointed out, they are gone in the current WD, so I don't think we need to worry about that.

I'm more curious about the other one you mentioned:

> I have a very good feeling in the behavior that the
> underline position with "auto" makes the position a
> little lower than that with "alphabetic" in the horizontal
> writing mode

Although current WD defines 'auto' as UA dependent, I think this should be added as an example so that implementers know how to implement a good underline rendering method for CJK.

Can you please share with us how you implement "make the position a little lower" in AH Formatter? Do you use the same position as "under", information from OpenType font, or any heuristic value?


Regards,
Koji

-----Original Message-----
From: www-style-request@w3.org [mailto:www-style-request@w3.org] On Behalf Of Keiko Hiraide
Sent: Monday, December 20, 2010 6:32 PM
To: www-style@w3.org
Subject: [CSS3 Text] text-underline-position

Hello,

After formatting a sample of  text-under-position  with AH Formatter, I have a very good feeling in the behavior that the underline position with "auto"
makes the position a little lower than that with "alphabetic" in the horizontal writing mode. However, because "before-edge" and "after edge" are drawn outside of "line-height", it moves to the next line, then it is not easy to recognize to which line under line is drawn. Will the interpretation that "before-edge" 
and "after-edge" are drawn inside of "line-height" be impossible?

Also, in vertical writing mode, "auto" is being interpreted as "before-edge", which is OK. But the underline overflows to the next line similarly in horizontal writing mode. Will the interpretation that "before-edge" and "after-edge" are  drawn inside of "line-height" be unskillful?

Here is an example of text-underline-position formatted by AH Formatter.
http://www.antenna.co.jp/XML/img/underline.jpg

The current AH Formatter V5.2 adopts the values of 'before-edge' and 'after-edge'
according to;
http://www.w3.org/TR/2003/CR-css3-text-20030514/#text-underline-position

However, according to the recent spec;
http://www.w3.org/TR/css3-text/#text-underline-position/
I understand  if  'over' and 'under' are adopted and  refer to  'em-box',  the problem I pointed out will not be an issue.

If the values of 'before-edge' and 'after-edge' remain in the future, I suggest it better to add 'inside of ' as follows. 

before-edge
    the underline, if set, is aligned  inside of 'before-edge' of the line box.

after-edge
    the underline, if set, is aligned  inside of 'after-edge' 
baseline of the line box....

I think the underline of 'before-edge' and 'after-edge' should be processed  inside of line-height. 

Thank you,

Keiko Hiraide
Antenna House, Inc. 
Web: www.antennahouse.com
Received on Tuesday, 21 December 2010 03:43:31 GMT

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