Editorial: Extract cross-document swap algo out

[noamr]

The cross-document deactivation part of the navigation algorithm is an indentation-hell of lambdas. Refactoring it to a couple of top-level algos instead.

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/browsing-the-web.html ( diff )
/dom.html ( diff )
/infrastructure.html ( diff )

[domenic]

Suggested change

	<p>To <dfn>deactivate a document for a cross-document navigation</dfn>, run these steps given a
	<code>Document</code> <var>displayedDocument</var>, a <span>user navigation involvement</span>
	<var>userNavigationInvolvement</var>, a <span>source snapshot params</span>
	<var>sourceSnapshotParams</var>, a <span>session history entry</span> <var>targetEntry</var>, a
	<code>NavigationType</code> <var>navigationType</var>, and <var>afterPotentialUnloads</var>, which
	is an algorithm that receives no argument:
	<p>To <dfn>deactivate a document for a cross-document navigation</dfn> given a
	<code>Document</code> <var>displayedDocument</var>, a <span>user navigation involvement</span>
	<var>userNavigationInvolvement</var>, a <span>source snapshot params</span>
	<var>sourceSnapshotParams</var>, a <span>session history entry</span> <var>targetEntry</var>, a
	<code>NavigationType</code> <var>navigationType</var>, and <var>afterPotentialUnloads</var>, which
	is an algorithm that receives no argument:

[domenic]

I forgot to say, this is a big improvement, so thank you for doing this. Removing a level of indirection around the unload steps makes it a bit hard to match up the old and new versions, but greatly improves clarity.

[domenic]

I don't think we can check these things from inside the session history traversal queue. Snapshotting beforehand seemed more correct to me?

[noamr]

The way this works in Chromium is that we put a flag on the document that's readable from the traversal queue and change it when the css changes. So I think specing it like this is more accurate?

Also sourceSnapshotParams are about the source document, so they are the wrong concept here IIUC. They are often null.

[domenic]

Sounds like you need to spec that process, of updating such a flag. Right now it looks like it's crawling through the list of CSS rules and doing style computation from the traversal queue...

[noamr]

Done, see w3c/csswg-drafts#10078 and new revision

[domenic]

This new version looks great, thank you for doing that.

Although, I wonder if it'd be better to call into the CSS spec once instead of twice? I.e. instead of

If displayedDocument's can initiate outbound view transition is true, then set potentiallyTriggerViewTransition to the result of calling can navigation trigger a cross-document view-transition? given displayedDocument's origin...

something like

Set potentiallyTriggerViewTransition to the result of calling can navigation trigger a cross-document view transition? given displayedDocument, ...

[noamr]

Yea at this point this would be better, I wrote it the other way when we used the snapshot--params

[noamr]

See new revision.

[domenic]

This new version looks great, thank you for doing that.

Although, I wonder if it'd be better to call into the CSS spec once instead of twice? I.e. instead of

If displayedDocument's can initiate outbound view transition is true, then set potentiallyTriggerViewTransition to the result of calling can navigation trigger a cross-document view-transition? given displayedDocument's origin...

something like

Set potentiallyTriggerViewTransition to the result of calling can navigation trigger a cross-document view transition? given displayedDocument, ...