[Bug 22390] [Shadow]: Support ':context()' pseudo class.

https://www.w3.org/Bugs/Public/show_bug.cgi?id=22390

--- Comment #6 from Hayato Ito <hayato@chromium.org> ---
(In reply to comment #5)
> (In reply to comment #4)
> > In the f2f on this last Friday, we decided that :host should *not* allow
> > combinators, as Tab noted.
> > 
> > The idea is that from a given shadowRoot, it's important to be able to glean
> > some information about the composed tree (for example, does it match an
> > important theming selector), but it's brittle to rely on composed tree
> > structure (is A inside of B) because its details may change and shouldn't be
> > known to a given shadowRoot.
> > 
> > Hayato-san, in your document, it looks like you're proposing that :host
> > allow combinators as long as they match within the host scope. That's an
> > interesting restriction and addresses the concern above, but my sense is
> > that the additional expressiveness is offset by the arcane host scope
> > matching behavior.
> 
> Yes, we do *not* want combinators, even if they're just parent or descendant
> combinators.  We're matching against the fully composed ancestor list, which
> includes the shadow trees of any enclosing components, and we don't want to
> expose the details of those trees more than necessary.

Okay. I don't have a strong opinion for that.

While we lose a power of a combinator, we get a power to match against the
fully composed ancestor list. It would be enough in practical cases. Sounds
good to me.

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Received on Tuesday, 25 June 2013 02:31:12 UTC