Re: [css-ruby] Computing writing-mode for inter-character ruby

On Mon, Feb 16, 2015 at 4:03 PM, Xidorn Quan <quanxunzhen@gmail.com> wrote:

>
> The current spec says:
>
> This value forces the computed value of writing-mode of the ruby
> annotation container to be vertical-rl.
>
> And according to the discussions in CSSWG F2F meeting in Sydney, because
> of the cyclic dependency between writing-mode and display, the spec should
> be changed to something like
>
> The writing-mode of a ruby annotation is computed to vertical-rl if the
> ruby-position of its container is inter-character.
>
> But both forms have a problem encountered from the inheriting rule of
> anonymous boxes. Since either ruby annotation or its container could be an
> anonymous box (but never both), in which case, its computed writing-mode
> value cannot be inherited by its descendants.
>
> I have no idea how to solve this. If the cyclic dependency above is
> allowed, though, probably we can say the writing-mode is computed to
> vertical-rl for both ruby annotation and ruby annotation container.
>

A more serious problem is that, actually the display value of an element
could affect what container it is in. If the writing-mode depends on what's
the container, it finally has to depend on the display value. Note that all
of ruby, rbc, rtc, rb, rt could be anonymous box according to the spec,
which means for "inter-character", it is impossible to know the
writing-mode before knowing the display value of an element.

- Xidorn