Re: Shadow DOM: state of the distribution API

On Wed, May 6, 2015 at 2:05 AM, Anne van Kesteren <annevk@annevk.nl> wrote:

> It seems we have three contenders for the distribution API.
>
> 1) Synchronous, no flattening of <content>. A host element's shadow
> tree has a set of slots each exposed as a single <content> element to
> the outside. Host elements nested inside that shadow tree can only
> reuse slots from the outermost host element.
>
> 2) Synchronous, flattening of <content>. Any host element nested
> inside a shadow tree can get anything that is being distributed.
> (Distributed <content> elements are unwrapped and not distributed
> as-is.)
>
> 3) Lazy. A distinct global (similar to the isolated Shadow DOM story)
> is responsible for distribution so it cannot observe when distribution
> actually happens.
>
> The argument for 1 is that there are no (good?) use cases for 2 and
> that descendants can be distributed, not just children. The argument
> for 2 is that it can be used to implement <content select> and
> <content slot> without much difficulty. The argument for 3 is that
> distribution is a layout concept (despite also impacting non-UI events
> and DOM APIs).
>
> (1/2 also require something akin "nanotask" mutation observers.)
>
> As I said elsewhere it's not clear to me we should couple DOM and
> layout. The composed tree is distinct from the render tree. It's also
> not clear to me what 3 would look like. No concrete proposal has been
> made. What is clear to me given the experience with service workers is
> that introducing a new global environment is not simple and would
> likely set us back another couple of years.
>
> That leaves 1/2 and although Ryosuke and Tab have taken sides, neither
> has really backed up their story. I tried to explore 1 in
> https://lists.w3.org/Archives/Public/public-webapps/2015AprJun/0474.html
> but that did not get much traction. So... trying again.
>


To complement this email, here's the in-depth (and work-in-progress)
discussion of this:
https://github.com/w3c/webcomponents/blob/gh-pages/proposals/Imperative-API-for-Node-Distribution-in-Shadow-DOM.md