[css-ruby] text-orientation of bopomofo annotation

[upsuper]

Copy from my email to www-style:

I propose that we should add "text-orientation: upright" to the "rt:lang(zh-TW)" rule.

The reason is that, all the tone marks in bopomofo (U+02CA, U+02C7, U+02CB, U+02D9) have Vertical_Orientation property "R" while the bopomofo characters are all "U". It means, without explicitly setting text-orientation to upright, the text run would break between them, which makes it impossible to use font feature to place the tone mark properly.

[upsuper]

Reply from @fantasai:

I think it would make more sense to have Unicode update UTR50 to make these characters upright in mixed-orientation text (or otherwise tailor it within CSS as a whole). It's not just a problem with ruby.

[upsuper]

Reply from me:

Well, that could be tricky, because those characters might also be used with latin scripts. I'm not sure anyway.

Koji, any thoughts?

[upsuper]

Reply from @kojiishi:

Unified code points tend to be controversial, and I'm not sure how much common these code points are in Latin usages. I can ask at Unicode ML.

[upsuper]

Reply from @fantasai:

Latin mostly uses the combining-mark form, rather than the modifier letter form. Also for mixed vertical text, we're biased mostly towards CJK usage (which bopomofo counts as). So I think we're okay.

Still would like Unicode signoff, too, of course.

[upsuper]

Reply from @kojiishi:

One confirmation; if we were to propose a change, should the first tone mark also included? From wikipedia[1], I understand Bopomofo does not use the first tone mark but Pinyin does.

Better to include but not required for Bopomofo usages?

[1] https://en.wikipedia.org/wiki/Bopomofo#Tonal_marks

[upsuper]

Reply from me:

The bopomofo handbook [1] from Taiwan says that, the first tone "can be omitted" [2]. I read this as a recommendation instead of a requirement, and thus I'd suggest if we do this change, we should also include the first tone, although it may not be used as usual as other four tones.

[1] http://www.edu.tw/files/site_content/M0001/juyin/ (Chinese)
[2] http://www.edu.tw/files/site_content/M0001/juyin/tt4.htm?open (Chinese)

[xfq]

FYI - see recommendation from ucd-dev in F5.

It will be discussed in UTC next week.

[frivoal]

@xfq, it looks like UTC planned to agree with @fantasai, but I don't know where to find the actual conclusion. Could you supply a link to those? If they did, that would solve the issue.

Either way, this really is a Unicode thing, so while it is a very relevant question in general, for the purpose of css-ruby as a spec, it is out of scope, we should close.