Re: Mozilla and the Shadow DOM

On Wed, Apr 15, 2015 at 6:30 AM, Anne van Kesteren <annevk@annevk.nl> wrote:

> On Wed, Apr 8, 2015 at 8:17 AM, Anne van Kesteren <annevk@annevk.nl>
> wrote:
> > * Multiple shadow roots. We'd like to retain this feature.
> > Although it has complexity, we've heard from both Firefox UI and
> > Firefox OS application developers that the moment your library gets
> > sophisticated, you want this for extensibility.
>
> I was asked to provide a use case for our stance. One that we've found
> with Firefox OS is custom dialogs, quoting Wilson Page:
>
> # I have an <x-dialog> component. It takes care of transitioning
> # in and out of the viewport and appropriate styling contained
> # elements (<h1>, <button>, <p>).
> #
> # I want to be able to extend this component to produce
> # <x-dialog-alert>. In this case extending the prototype alone
> # isn't enough, I need to also be able to extend the markup
> # and styling of <x-dialog>.
> #
> # At the point of creation <x-dialog-alert> can add a second
> # ShadowRoot that allows it to compose its own content
> # inside that of the 'old' <x-dialog> ShadowRoot. Without this
> # <x-dialog-alert> would have to duplicate all the markup, style
> # and interaction code again.
>
>
I don't think you need to duplicate anything. The super class can still
fill in the original shadow root, then the subclass can modify it. This is
the same concept of the prototype inheritance, your methods will shadow the
super class methods, but you can just call them and then extend the
behavior.

This is also the reason the created and attached callbacks are on the
prototype. So you can call super and use the parent behavior by shared
protocol.

- E