[css-ruby] Computing writing-mode for inter-character ruby from Xidorn Quan on 2015-02-25 (www-style@w3.org from February 2015) (original) (raw)

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.