[mediaqueries] MQs and seamless iframes

Should a seamless iframe resolve its MQs in its normal context, or in
the context of the outer page?

I think the latter.  For one thing, we avoid some possible circularity
issues today due to the fact that iframes are replaced elements, and
aren't sized according to their contents.  That means we can resolve
the width MQs without issue.

However, a seamless iframe's width *does* depend on its content.  This
obviously causes issues.

Another possible issue (and one that is relevant today, see
<https://codereview.chromium.org/18360007/>) is that some things like
the initial font size can vary based on the origin, and that is
detectable in MQs.  Should a seamless iframe use the initial font size
of its origin, or of the outer origin?

More widely, what about other conditional rules, most specifically @document?

I think it makes the most sense to declare that, for the purpose of
all conditional rules, seamless iframes are treated as being in the
outer page.

~TJ

Received on Thursday, 11 July 2013 21:10:40 UTC