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Re: XBL2: First Thoughts and Use Cases

From: Boris Zbarsky <bzbarsky@MIT.EDU>
Date: Tue, 14 Dec 2010 21:34:06 -0800
Message-ID: <4D08534E.6020800@mit.edu>
To: "Tab Atkins Jr." <jackalmage@gmail.com>
CC: Dimitri Glazkov <dglazkov@google.com>, public-webapps <public-webapps@w3.org>
On 12/14/10 4:50 PM, Tab Atkins Jr. wrote:
> I wasn't thinking of positioning the port with respect to explicit
> shadow children.  That sounds like something that could be simplified
> by punting - change the template language so that you can only set
> output ports on childless elements (use a void element for output
> ports in the template, which becomes an empty container in the
> shadow?)

That ends up creating extra elements, right?  The common use cases I've 
seen do in fact have the port as a child of an element with explicit 
shadow children.

Note that with flexbox layout having to insert an element like that 
means that some layouts become impossible.

> Hierarchy error.  Shadow nodes need to be bound to their specific
> shadow tree.  Anything else is psychotic, as you say.  ^_^

OK, good so far!  ;)

>> 4.  Nodes are added or removed from the DOM which affect the position of a
>> particular output port in its parent node.
>
> I'm not sure I understand.  Can you elaborate with a trivial example?
> I've got a few things in mind that you could possible mean, but I'd
> rather not guess.

Using XBL1 syntax, because I can't recall what the XBL2 one is off the 
top of my head:

<content>
   <div>
     <span></span>
     <children/>
     <span></span>
   </div>
<content>

And then you remove the first span.

>> Gecko doesn't have live templates; just mutable shadows.
>
> Okay.  So you do something similar to what I've described with
> instantiating the template into data structures, just limited to the
> C++ side of the code?

I'm not sure what you mean by "limited to the C++ side of the code".

The way Gecko's implementation "works" if one can call it that is that 
there is the template DOM and then the shadow DOM.  The shadow DOM is 
created by cloning the template DOM, more or less.  Output ports are 
kept track of on the template DOM.  When you insert a node as a child 
under the bind element, you find the right port in the template DOM, 
then try to find the corresponding location in the (possibly mutated) 
shadow DOM.  This clearly doesn't work very well!

-Boris
Received on Wednesday, 15 December 2010 05:34:42 GMT

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