[css-ruby] How does ruby interact with ligatures/shaping?

How should ruby interact with ligatures and shaping (and even
combining marks)?

In particular, if two adjacent ruby-bases, or a ruby-base adjacent
to something outside the ruby, form ligatures or connect to the
adjacent text?  Similar for adjacent ruby-texts?

I'm inclined to think they should not interact (i.e., always
separate text) since large ruby-bases can separate ruby-texts, and
large ruby-texts can separate ruby-bases.  This makes things easier.
I'm not sure how much the use cases for these things intersect,
although if they do (e.g., Korean written in decomposed Hangul with
what could be part of one jamo in one ruby base and part in another)
I'm not at all convinced that combining would even be the right
behavior.

In any case, I think the spec should specify what happens, perhaps
in http://dev.w3.org/csswg/css-ruby/#ruby-layout .

-David

-- 
𝄞   L. David Baron                         http://dbaron.org/   𝄂
𝄢   Mozilla                          https://www.mozilla.org/   𝄂
             Before I built a wall I'd ask to know
             What I was walling in or walling out,
             And to whom I was like to give offense.
               - Robert Frost, Mending Wall (1914)