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Re: [CSS3 Text] text-underline-position

From: Keiko Hiraide <hiraide@antenna.co.jp>
Date: Wed, 22 Dec 2010 10:00:06 +0900
To: "www-style@w3.org" <www-style@w3.org>
Message-Id: <20101222100006.885A.71209412@antenna.co.jp>
> 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?

AH Formatter implements the underline auto a little lower (about 0.1em) position 
based on the position of alphabetic baseline. It is not a position of "under". 
Although underlinePosition information on OpenType is not being used now, it is 
being examined to use the information in the further version of Formatter. 

Only the information on "underlinePosition" exists in OpenType and there is especially
 no "underline position for Japanese" in OpenType.
http://www.microsoft.com/typography/otspec/post.htm


It is thought that in most cases, the default position is enough for the under line position
for Japanese  language. (If the default is unfavorable and  you would like to put the
under line under em-box, you only have to specify text-underline-position: under).

Thank you,

Keiko Hiraide
Antenna House, Inc. 
Web: www.antennahouse.com



On Mon, 20 Dec 2010 22:40:09 -0500
Koji Ishii <kojiishi@gluesoft.co.jp> wrote:

> 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 Wednesday, 22 December 2010 01:00:07 GMT

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