[Webkit-unassigned] [Bug 87805] [Shadow DOM] <style> inside Shadow subtree should be scoped inside the subtree.

[bugzilla-daemon at webkit.org]

https://bugs.webkit.org/show_bug.cgi?id=87805





--- Comment #9 from Takashi Sakamoto <tasak at google.com>  2012-06-07 20:59:54 PST ---
Thank you for answering my question.

(In reply to comment #7)
> (In reply to comment #6)
> > Thank you for reviewing.
> > 
> > I will recreate a patch. However I would like to ask one question. We cannot rely on inDocument() to determine whether style elements are registered or not?

> 
> I am not sure what you mean by "style elements are registered" here. If you mean "registered with a scoping node", then obviously no. when inDocument() == false, the node should not be registered with any scoping node, but when inDocument() == true, it may or may not be registered with a scoping node.
> 
> If you mean something else, you may have to explain it a bit more :)
> 
> > If using scoped() and m_isRegisteredWithScopingNode in the same way (=the original code's way), I think, we cannot determine where the style was registered when scoped attribute is changed to be true. I tested this by the following example:
> > 
> >    <style id="mystyle" scoped>div { color: red };</style>
> > 
> >    var style = document.getElementById("mystyle");
> >    style.setAttribute("scoped", "a"); // parseAttribute is invoked with !value.isNull
> >    style.setAttribute("scoped", "b"); // parseAttribute is invoked with !value.isNull
> >    style.setAttribute("scoped", "c"); // parseAttribute is invoked with !value.isNull
> >    style.setAttribute("scoped", "d"); // parseAttribute is invoked with !value.isNull
> 
> I don't understand what you're testing here. Can you explain a bit more?

I mean, if I can expect that parseAttribute is invoked if and only if an attribute value is actually changed, i.e. from false to true or from true to false. If so, we can determine old scoped value from current scoped value.
However, the above test shows that it doesn't depend on whether scoped attribute's bool value changes or not.

> > During HTMLStyleElement::parseAttribute, we can only know whether currently scoped or not and whether currently in shadow tree or not. So we cannot determine:
> > 
> >   (a) [old] in shadow DOM subtree and not scoped --> [new] in shadow DOM subtree and scoped
> >   (b) [old] in shadow DOM subtree and scoped --> [new] in shadow DOM subtree and scoped
> > 
> > In the case (b), we don't need to update. But in the case (a), we have to remove the style from shadow root. However in the both case, m_isRegisteredWithScopingNode is true, scoped() is true and isInShadowTree() is true.
> 
> So, what you need is a knowledge of how the scoping came about: whether by virtue of just being in shadow DOM subtree, or with a scoped attribute. I think I understand.
> 
> > 
> > This is the reason why I removed m_isRegisteredWithScopingNode and I added the layout test, setAttribute("scoped", "scoped") for already scoped style.
> > 
> > I think, there are several ways to fix the above issue:
> > (1) modifying scoped() to see m_scoped, i.e. bool scoped() { return m_scoped; }
> 
> This is wrong. scoped() should always reflect the attribute value.
> 
> > (2) modifying the type of m_isRegisteredWithScopingNode from bool to enum { NotRegistered, RegisteredAsScoped, RegisteredInShadowTree }.
> 
> This seems good.
> 
> > (3) adding a new boolean flag to find where a style element was registered, e.g. m_isRegisteredInShadowRoot or something.
> 
> Here, you will always have one invalid combination, which seems like a bad thing.

I see. I added the enum.

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