[css-text-decor] Doesn't example 3 in text-underline-position break current UA behavior?

In EXAMPLE3 of text-underline-position 
<http://dev.w3.org/csswg/css-text-decor-3/#example-affafc32>, it 
suggests UA should use following style in its default UA style sheet:

:root:lang(ja), [lang|=ja],
:root:lang(ko), [lang|=ko] {
   text-underline-position: under right;
}

:root:lang(zh), [lang|=zh] {
   text-underline-position: under left;
}

This means that UA should use "under" for horizontal writing mode too. 
And even if it has some Western language contents (e.g., in 
<blockquote>), the underlines in it are rendered as "under". I think 
that |:root| is not necessary.

And also current CJK web pages are rendered as |text-underline-position: 
auto;|. So, if UA style sheel had the suggested style, rendering result 
of CJK web pages would be changed. So, I think that the possible value 
of text-underline-position should be [auto|under] || [left|right].

If not so, if there were the UA which supports text-underline-position 
but doesn't support vertical writing mode, web pages which have 
|text-underline-position: left;| or |text-underline-position: right;| 
only for vertical writing contents would be rendered with the underlines 
positioned "under" even though the contents are rendered horizontally.

-- 
Masayuki Nakano <masayuki@d-toybox.com>
Manager, Internationalization, Mozilla Japan.

Received on Monday, 11 May 2015 08:51:11 UTC