Upstream Shadow DOM spec to DOM/HTML Standard

[hayatoito]

Eventually, we should upstream Shadow DOM spec into DOM/HTML Standard.

Let's use this issue to discuss how we should proceed. That might not happen soon, but I hope we can start in the near future.

[domenic]

I took a quick look.

• SD section 2 could probably be moved into a subsection of DOM section 2
• We'd probably create a new top-level section in DOM for shadow DOM. Maybe after "nodes". Maybe at the end.
• SD sections 3 and 4 would move into the new top-level section.
• SD section 5 would need some work. It needs to be integrated into DOM section 3.
  • "In each algorithm in this section, the Window must be considered as if it were the parent node of the Document so that the Window also receives an event." I am pretty sure HTML has a similar sentence, but I cannot find it easily...
  • UI Events, Touch Events, and HTML will need patches for shadow DOM 5.5-5.9
• SD section 6 mostly gets upstreamed into HTML, some in Editing maybe.
• SD section 7 goes into HTML, creating several new element categories for 7.1, and changing the processing algorithms as in 7.2.
• SD section 8 goes into the new DOM top-level section on shadow DOMs
  • Some of the interface members on ShadowRoot need to go into other specs as partial interface definitions: activeElement and styleShets in HTML, element(s)FromPoint in CSSOM, innerHTML in DOM P&S, a few others... I think only host is left, actually.
  • I guess the definition of HTMLSlotElement and assignedSlot go in the HTML spec?
  • The blocklist of elements you cannot attachShadow too goes in HTML, or maybe becomes a DOM concept which HTML references.
• SD section 9 goes into a subsection of the new DOM top-level section on shadow DOMs

We should check with @annevk, but I would be OK with gradually moving over pieces, leaving pointers from the current spec into their new destinations. The trick is figuring out what are good chunks of work to do that in. For example, we could move over the HTMLSlotElement and assignedSlot stuff in one chunk and have it reference the shadow DOM spec until it's fully integrated. We could move over the conceptual stuff in another chunk. Etc.

[annevk]

I think a good place to start would be the "in a document" versus "in a x document" checks in the HTML standard. That is once the pieces that is actually biting implementers. I forgot what we decided on for x.

I think it's a good idea to do things in pieces.

[hayatoito]

As far as I know, for x, there are several candidates:

• in a document deeply: That's defined in Shadow DOM spec: http://w3c.github.io/webcomponents/spec/shadow/#dfn-in-a-document-deeply

However, in #362, I proposed connectedToDocument / disconnectedFromDocument.

The pros of in a document deeply is that it can be used as a replacement of both in a document and inserted into a document / removed from a document.

e.g.

• If the node is in a document deeply, ...
• When the node is inserted into a document deeply, ..

But if we use connected to a document, it might be confusing?

e.g.

• If the node is connected to a document, ...
• When the node gets connected into a document, ..

[annevk]

Isn't the problem with "deep" that if you have a closed shadow tree those nodes would be excluded, as is the case with deepPath? Would it not be "composed"?

[hayatoito]

So far, I do not feel any trouble by using the term of "deep" in the Shadow DOM spec.

When I have to consider a closed shadow tree, I am using "unclosed node" or "unclosed tree" in defining the behavior of a closed tree. That seems successful, so far. I do not have any trouble.

"composed" might be confusing because the Shadow DOM spec has a well defined concept of "composed tree". "in a document deeply" and "in a composed tree" are different concept.

But, I am fine with using composed here because it sounds more intuitive, I think.

Thus, the candidates would be:

1. in a composed document

   It might be confusing, due to the existing concept of composed tree. We might want to rename composed tree to something else, e.g. flattened tree, if we use "in a composed document" here.

2. in a document deeply.

3. connected to a document

[annevk]

So you are saying that deepPath uses the deep document, restricted to unclosed nodes?

I don't understand what the conceptual difference would be between "composed document" and "deep document" if deep document was not restricted to unclosed nodes. Which nodes would be in the former that are not in the latter? Or vice versa?

[hayatoito]

Sorry for confusing.

So you are saying that deepPath uses the deep document, restricted to unclosed nodes?

Basically, yes. (Though the spec does not use the term of "deep document")

• There is no concept of "deep document" nor "composed document" in the spec.
• The term of "in a composed document" is born in this thread and I meant we can use this new term as a replacement of "in a document deeply", if we want to avoid the term of "deep"
• There are concepts of "tree of trees", "in a document deeply" and "composed tree" in the Shadow DOM spec. Those are well defined terms.

I am thinking that we can replace existing terms with more understandable terms:

• "Tree of trees whose root tree is a document tree" => "composed document"
• "in a document deeply" => "in a composed document"
• "composed tree" => We might want to rename this to something else.

Note that "deepPath()" is only web-exposed API which uses the term of "deep". I am not sure how we should rename this or keep this as is.

[annevk]

My thinking with respect to the "deep" terminology was that it would be exactly like "composed", but restricted to "unclosed" nodes.

So most standards would operate on "composed documents", but APIs would be restricted to either "documents" or "deep documents", depending on the use case.

There was also the case of nodes that would not end up in the composed tree and how to address them. I don't think we had a solution for that.

[rniwa]

How about "in a connected tree scope" where "tree scope" refers to either a Document or a shadow root which is a node's ancestor, and "connected" means the tree scope is either a document or its host is "in a connected tree scope".

[hayatoito]

My thinking with respect to the "deep" terminology was that it would be exactly like "composed", but restricted to "unclosed" nodes.

I'm okay to use the deep terminology in this sense. But the current Shadow DOM spec does not follow this rule, e.g. "deep child": http://w3c.github.io/webcomponents/spec/shadow/#dfn-deep-child

If we reserve the "deep" terminology for this purpose, "deep child" or other similar terminologies should bee renamed to something, such as "composed child" ?

So most standards would operate on "composed documents", but APIs would be restricted to either "documents" or "deep documents", depending on the use case.

I am fine with this idea, basically. From my experience, most standards could operate on "a composed document". It's rare case that APIs would be restricted to "deep documents".

There was also the case of nodes that would not end up in the composed tree and how to address them. I don't think we had a solution for that.

"in a composed document, but not in a document composed tree" could work, I think.
http://w3c.github.io/webcomponents/spec/shadow/#dfn-document-composed-tree

It this is too long, we have to invent yet another terminology as an alias for this long condition.

[annevk]

@hayatoito yeah, "deep child" would have to become "composed child".

@rniwa is "connected" a replacement term for "composed" or "deep" (with "deep" meaning "composed" excluding "closed")?

[rniwa]

"connected" would mean it's in the document or your shadow root's host is in the document regardless of whether any of shadow root inside which you reside is closed or not. So I think it corresponds to "composed" in your terminology.