On 1/7/15 9:51 AM, Anne van Kesteren wrote:
That is what I meant. Otherwise in order to support new Element()
you'd have to support an ever growing set of more specific objects as
well and layering is out of the window.
Do you mean layering of implementations or specifications? For
specifications, here's one way this could work with reasonable layering.
DOM provides the following bits:
1) A registry mapping (namespace, localname) pairs to abstract
operations that allocate an object.
2) Abstract operations that can be used by specifications built on top
of DOM to register abstract operations in this registry.
3) An abstract operation that takes a list of internal slot names and
returns an object which has those internal slots, plus the internal
slots all elements have, plus probably the ordinary object internal
slots from ES6, depending on whether Web IDL assumes these are ordinary
objects. I thought ES6 had this sort of abstract operation already, but
I don't see anything like it; in any case the only issue here is that
this requires implementations of DOM and specifications built on top of
it to agree internally on what "internal slot" means for elements, I agree.
Specifications that define elements on top of DOM provide the following
bits:
4) An abstract operation that creates an uninitialized version of their
element, via calling the thing defined in #3.
5) Registration of the abstract operation defined in #4 with the
registry defined in #1, whether that happens at global-setup time or
when the element definition is encountered or whatever.
An implementation that wants to just implement core DOM but not things
built on on top of it can skip all of this machinery. An implementation
that wants to support DOM but not everything on top of it (e.g. support
MathML but not HTML or something) just supports the bits it wants and
the registry ends up not having stuff in it that it has in other
implementations. Seems ok to me.
Now some questions:
* Did I cover your concern about "have to support an ever growing set of
more specific objects"? If not, can you explain what the concern is?
* Without a mechanism like the above, how would one go about supporting
document.createElement(NS) as it exists on the web.
However, that does indeed seem like a lot of work and it's not clear
whether that actually pays off in the end :-(
That's hard to say without knowing what the desired payoff is.
-Boris
