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Re: Imperative API for Node Distribution in Shadow DOM (Revisited)

From: Ryosuke Niwa <rniwa@apple.com>
Date: Mon, 27 Apr 2015 19:01:57 -0700
Cc: Olli Pettay <olli@pettay.fi>, Anne van Kesteren <annevk@annevk.nl>, WebApps WG <public-webapps@w3.org>, Erik Bryn <erik@erikbryn.com>, Dimitri Glazkov <dglazkov@google.com>
Message-id: <22E46D96-F8B7-4B86-B521-691B4ECA2479@apple.com>
To: Steve Orvell <sorvell@google.com>

> On Apr 27, 2015, at 5:43 PM, Steve Orvell <sorvell@google.com> wrote:
>> 
>> That might be an acceptable mode of operations. If you wanted to synchronously update your insertion points, rely on custom element's lifecycle callbacks and you can only support direct children for distribution. 
> 
> That's interesting, thanks for working through it. Given a `childrenChanged` callback, I think your first proposal `<content>.insertAt` and `<content>.remove` best supports a synchronous mental model. As you note, re-distribution is then the element author's responsibility. This would be done by listening to the synchronous `distributionChanged` event. That seems straightforward.
> 
> Mutations that are not captured in childrenChanged that can affect distribution would still be a problem, however. Given:
> 
>     <div id="host">
>       <div id="child"></div>
>     </div>
>     
>     child.setAttribute('slot', 'a');
>     host.offsetHeight;
> 
> Again, we are guaranteed that parent's offsetHeight includes any contribution that adding the slot attribute caused (e.g. via a #child[slot=a] rule)
> 
> If the `host` is a custom element that uses distribution, would it be possible to have this same guarantee?
> 
>     <x-foo id="host">
>       <div id="child"></div>
>     </x-foo>
>     
>     child.setAttribute('slot', 'a');
>     host.offsetHeight;

That's a good point. Perhaps we need to make childrenChanged optionally get called when attributes of child nodes are changed just like the way you can configure mutation observers to optionally monitor attribute changes.

- R. Niwa
Received on Tuesday, 28 April 2015 02:02:26 UTC

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