Use PresentationSourceType instead of url='_self'

[takumif]

No description provided.

[takumif]

Mark PTAL

[markafoltz]

This should be readonly as you shouldn't be able to change the source type on an existing connection.

[takumif]

It turns out that "Dictionaries must not be used as the type of an attribute" (spec), so we can't have PresentationSource be an attribute of PresentationConnection.

So I've added the fields directly to the PresentationConnection interface. We could wrap them into a separate interface but that feels like complication without much benefit right now.

[markafoltz]

From a WebIDL point of view, I do think there is benefit in declaring the mirroring parameters once in an interface, so those declarations don't have to be repeated.

[takumif]

I agree that the repetition isn't great.

PresentationConnection and PresentationSource are an interface and a dictionary respectively with basically the same set of fields, to achieve:

1. Not requiring the user to call a ctor for creating a PresentationSource
2. Working around WebIDL's restriction that a dictionary cannot be an interface attribute

I'm not sure if we can get rid of the duplication while maintaining the above two properties.

[markafoltz]

Can you check the WebIDL spec to see what our options are here?

[takumif]

Thus far I'm not seeing a cleaner way to do it. Implicit conversion from a JS object can be done with dictionaries but not interfaces. So we'd want PresentationSource to be a dictionary so that websites would be able to pass a JS object in rather than having to call a ctor.

However a dictionary cannot be used as an attribute nor can an interface inherit from a dictionary (or vice versa), so it seems to me that the parameters need to declared once each in a dictionary and an interface.

[markafoltz]

From a WebIDL point of view, I do think there is benefit in declaring the mirroring parameters once in an interface, so those declarations don't have to be repeated.

[markafoltz]

I don't think this can change to optional since it's mandatory in the current spec, as that would risk breaking current script.

[takumif]

You're right, changed. I suppose it can be an empty string rather than null when not used.

[markafoltz]

Can you check the WebIDL spec to see what our options are here?

[takumif]

The only change I made was to readonly attribute USVString url; in PresentationConnection. Sorry for all the noise from my attempt to rebase the branch.