[Bug 27775] [Shadow]: Define the behavior of *closed* shadow trees.

https://www.w3.org/Bugs/Public/show_bug.cgi?id=27775

Dylan Barrell <dylan@barrell.com> changed:

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--- Comment #11 from Dylan Barrell <dylan@barrell.com> ---
(In reply to Philip Jägenstedt from comment #3)
> It would be nice to have closed shadow trees, which the the shadow-piercing
> combinator '>>>' cannot reach into and whose internal structure is otherwise
> entirely opaque to the containing document. Things like <video controls>
> would then be closed.
> 
> We could perhaps also allow script-created shadow trees to be closed,
> although defaulting to open.

I would strongly caution to not allow scripts to create closed trees from two
perspectives:

1) How do you do testing into a closed tree in an end-to-end testing
environment like Webdriver? I have already encountered occasions where Angular
2 end-to-end testing is complicated by the shadow DOM. Making the shadow DOM
totally opaque would further complicate this unless you provide a testing API -
in which case what is to stop someone from mis-using the testing API to reach
inside the shadow DOM.

2) How do you do custom validations of entire documents for things like
accessibility when the dependencies of ARIA roles and attributes can cross
shadow root boundaries. One way to do this would be to expose the composed tree
through an API but failure to expose the composed tree with the ability to
create non-standard components that are 100% opaque make this sort of
validation impossible.

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Received on Tuesday, 10 March 2015 21:44:19 UTC