[Bug 17590] [Shadow]: Specifying styling of host, light nodes with @host, /select/

https://www.w3.org/Bugs/Public/show_bug.cgi?id=17590

--- Comment #3 from Takashi Sakamoto <tasak@google.com> 2012-07-02 10:56:42 UTC ---
(In reply to comment #1)
> (In reply to comment #0)
> > What is the meaning of
> > 
> > <style scoped>
> > @host { ... }
> > </style>
> > 
> > in a shadow tree?
> 
> Right now, it's not mentioned that "scoped" affects anything, so I assumed that
> it's clear that @host only affects the shadow host, regardless of the value.

I would like to ask how to find matched scoped styles which contain @host
rules. For example,
there is some HTML document like:

<div id="host">
   <div id="child-a"></div>
   <div id="child-b"></div>
</div>

and a shadow root (attached to the div whose id is "host") is

<div>
   <style scoped>
      @host { color: red }
   </style>
   <content select=":first-child"></content>
</div>
<div>
   <style scoped>
      @host { color: blue }
   </style>
   <content></content>
</div>

We have to go up a DOM tree to find matched styles. So to find child-a or
child-b's style, we will go up the following tree:

   host------------------#shadow-root...
     |
     +----child-a
     |
     +----child-b

If we have no @host rules,  it is ok to look at child-a and host node to find
child-a's matched styles.
However, if the above "scoped" works, I think, we have to traverse in the
following way:

  host
     |
     +----#shadow-root
                |
                +-----div (has scoped @host rule)
                              |
                              +----- child-a (color: red)

Talking about child-b,  

  host
     |
     +----#shadow-root
                |
                +-----div (has scoped @host rule)
                              |
                              +----- child-b (color: blue)

If we cannot make @host rules "scoped", 

  host (color: blue)
     |
     +----child-a

  host (color: blue)
     |
     +----child-b

(in this case, we cannot change the color of child-b.) 

I'm not sure which is better for web developers. However according to an idea
of @host rules, i.e. web developers can change styles of host nodes,  I think,
they want to change styles per <content> (or <shadow>).

Best regards,
Takashi Sakamoto

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Received on Monday, 2 July 2012 10:56:48 UTC