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[css-ruby] What does it mean for "ruby-position: inter-character" to force writing-mode to be vertical?

From: Daniel Holbert <dholbert@mozilla.com>
Date: Wed, 10 Dec 2014 14:36:52 -0800
Message-ID: <5488CB04.4000102@mozilla.com>
To: www-style <www-style@w3.org>
The CSS Ruby spec has the following text about ruby-position's
"inter-character" value:

  # "inter-character"
  #   [...] This value forces the 'writing-mode' of the
  #   ruby annotation to be vertical.
http://dev.w3.org/csswg/css-ruby/#valdef-ruby-position-inter-character
(Note: 'writing-mode' is a link to the definition of that CSS property.)

This spec text needs some clarification, I think. In particular, the
following things are unclear to me:

 (1) Does this spec-text influence the *computed value* of the
'writing-mode' property? (I hope not; there's added complexity when
properties influence other properties' computed values on the same element.)

 (2) If the answer to (1) is "yes" (I hope not): is this "writing-mode"
computed-value influence restricted to elements with "display:
ruby-text", or does this influence happen regardless of "display"?  e.g.
would <div style="display:block; ruby-position: inter-character"> be
forced to have a vertical writing-mode?

 (3) Which 'writing-mode' value should we actually use?  There are two
distinct vertical values for the "writing-mode" property: "vertical-rl"
and "vertical-lr" -- which of those should we use here?  (In practice,
maybe it doesn't matter, because elsewhere the spec says "There are no
line breaking opportunities within inter-character annotations", and I
think the "rl" vs. "lr" distinction would only matter if there are
linebreaks. Still -- we should explicitly mention that here,
particularly if we're linkifying 'writing-mode' to point to the
property-definition, because otherwise it just seems vague.)

 (4) Does this "forcing" apply to descendants of the ruby annotation?
e.g. if a ruby annotation has a child with "display:inline-block", is
that child *also* forced to have a vertical writing-mode?  (If the child
isn't forced: does it still get a vertical writing mode by default,
somehow? Presumably not through inheritance, unless the answer to (1)
was "yes".)

Thanks,
~Daniel
Received on Wednesday, 10 December 2014 22:37:20 UTC

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