[css-view-transitions-1] Which skipping reason does "View transition page-visibility change steps" use?

[nt1m]

https://drafts.csswg.org/css-view-transitions-1/#page-visibility-change-steps

If document’s active view transition is not null, then skip document’s active view transition.

I noticed this while implementing in WebKit, the current spec doesn't say which reason / exception to pass to the skip the view transition algorithm.

cc @noamr @khushalsagar

[nt1m]

I also noticed another bug in the spec:

In https://drafts.csswg.org/css-view-transitions-1/#ViewTransition-prepare

If document’s visibility state is "hidden", then skip transition with an "InvalidStateError" DOMException, and return.

We should be returning the transition here, instead of returning nothing.

[css-meeting-bot]

The CSS Working Group just discussed [css-view-transitions-1] Which skipping reason does "View transition page-visibility change steps" use?, and agreed to the following:

• RESOLVED: Use "InvalidStateError" when skipping the view transition due to document not visible
• RESOLVED: Fix algorithm error, always return transition object
• RESOLVED: Publish CRD of css-view-transitions-1

The full IRC log of that discussion

<fantasai> s/Topic/Subtopic/
<fantasai> ntim: implementing recent resolution to skip transition when document is hidden
<fantasai> ntim: we didn't define the reason/exception to pass
<khush_> q+
<fantasai> ntim: also noticed that the algorithm to prepare the view transition returns nothing
<fantasai> ntim: in the case where it skips the transition
<fantasai> s/transition/transition because it's hidden/
<fantasai> ntim: seems it should return the transition
<astearns> ack khush_
<fantasai> ntim: seems like a bugfix issue?
<fantasai> khush_: I think that was a typo, that algorithm should return transition
<fantasai> khush_: wrt reasonable exception to use, the other spot we use "InvalidStateError" which seems like reasonable error code for invisibility
<vmpstr> +1
<fantasai> ntim: sgtm
<fantasai> astearns: anyone else?
<fantasai> RESOLVED: Use "InvalidStateError" when skipping the view transition due to document not visible
<fantasai> vmpstr: If transition is skipped, algorithm steps should still return 'transition'
<fantasai> khush_: it's an error in the spec, should be returning that in al cases
<fantasai> RESOLVED: Fix algorithm error, always return transition object
<astearns> ack fantasai
<fantasai> fantasai: do we need to publish a new CR?
<fantasai> khush_: If there's other issues to batch up, can batch up. Otherwise ok to republish
<fantasai> ntim: I look at ED when I implement, so fine either way
<fantasai> fantasai: It's a problem if the ED is more reliable than the /TR copy, so let's do a CRD.
<fantasai> astearns: proposed to update draft with all resolutions and update CRD of VT1
<fantasai> RESOLVED: Publish CRD of css-view-transitions-1