Re: [css-text-decor][css-ruby] Underline position for Japanese text with ruby

On 06/26/2015 08:25 PM, Xidorn Quan wrote:
> Hi,
>
> Recently, Masayuki mentioned that, for Japanese, if a piece of
> text in vertical writing mode has both ruby and underline, the
> underline should be outside ruby annotation, like:
>
> 分わ|
> か　|
> る　|
>
> However, implementors who are not aware of this will tend to implement that as:
>
> 分|わ
> か|
> る|
>
> (This is actually the current behavior of Firefox Nightly)
>
> I know the current spec says the exact position of underline is
> UA-defined, but I guess it at least worths a note. Actually, I
> don't think this is a behavior could be covered by "UA-defined".
>
> As an implementor, I feel it looks hard to implement, but probably
> not something impossible.
>
> Also it seems to me this is not mentioned in JLReq. I guess we
> should also cc people there and ask their opinion about this.

Good point. I agree with asking the JLTF to put a clarification
into JLREQ--for this situation in both horizontal and vertical
text--and we should follow up by figuring out a good model for
handling this in CSS. I'm not 100% sure what that should be, as
there might also be cases where the underline should go between
the ruby and the base.

At the moment, I lean towards saying that underline specified
directly on a ruby container should be under the lowest level
of text, overline should be over the highest level of text, and
line-through should be applied to the base level.

Decorations specified on a descendant of the ruby container
should of course only apply within that descendant's level.

But for ancestors of the ruby container, I am less sure what the
correct answer should be.

~fantasai