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RE: Adopting a Custom Element into Another Document

From: Domenic Denicola <d@domenic.me>
Date: Tue, 13 Jan 2015 19:43:13 +0000
To: Ryosuke Niwa <rniwa@apple.com>, Anne van Kesteren <annevk@annevk.nl>
CC: Webapps WG <public-webapps@w3.org>, Boris Zbarsky <bzbarsky@mit.edu>
Message-ID: <CY1PR0501MB13697B73BD1A0ADA170FEAC7DF400@CY1PR0501MB1369.namprd05.prod.outlook.com>
I imagine this has all been discussed before, but why do __proto__-munging when adopting cross document? That seems bizarre, and causes exactly these problems. When you put an object in a Map from another realm, it doesn't __proto__-munge it to that other realm's Object.prototype. Why is the tree data structure embodied by the DOM any different?

-----Original Message-----
From: Ryosuke Niwa [mailto:rniwa@apple.com] 
Sent: Tuesday, January 13, 2015 14:37
To: Anne van Kesteren
Cc: Webapps WG; Boris Zbarsky
Subject: Re: Adopting a Custom Element into Another Document

On Jan 13, 2015, at 11:27 AM, Anne van Kesteren <annevk@annevk.nl> wrote:

> On Tue, Jan 13, 2015 at 8:15 PM, Ryosuke Niwa <rniwa@apple.com> wrote:
>> By "the same thing", do you mean that they will manually change 
>> __proto__ themselves?
> 
> Yes.
> 
> 
>> Let's say we have MyElement that inherits from HTMLElement and we're 
>> adopting an instance of this element (let's call it myElement) from a 
>> document A to document B; MyElement is currently defined in A's 
>> global object.
>> 
>> I have two questions:
>> 
>> Why did we decide to let custom elements handle this themselves 
>> instead of doing it in the browser?
> 
> With two realms it's not a given that both realms use the same custom 
> element registry. (As you acknowledge.)

Okay.

>> When "myElement" is adopted into B, there is no guarantee that 
>> MyElement is also defined in B.  Does that mean MyElement may need to 
>> create another class, let us call this MyElementB, in the B's context 
>> that inherits from B's HTMLElement?
> 
> Well, if you control both realms I would assume you would give the same name.

I'm not sure I understand what you mean by that.  The name of the new class MyElementB isn't important.

Do you agree that the author has to create a new class in B if there is no definition of MyElement there?
But how do we even determine whether MyElement's defined in B?
And if did, how do we get the class's prototype?

>> Didn't Boris say Gecko needs to do this synchronously in order to 
>> enforce their security policy?
> 
> I don't think that's conclusive, though if it turns out that's the 
> case we would need different timing between normal and custom 
> elements, yes.

Great. Thanks for the clarification.

- R. Niwa


Received on Tuesday, 13 January 2015 19:43:41 UTC

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