[css-contain-2] Incomplete event definition for ContentVisibilityAutoStateChanged

[tidoust]

Spec says that a ContentVisibilityAutoStateChanged event gets fired at an element. But ContentVisibilityAutoStateChanged is the name of the interface used by the event, not the name of the event itself. What is the name of the event that fires at the element?

Ideally, the spec would use the fire an event concept defined in DOM with wording similar to:

When the rendering state of an element with content-visibility: auto style changes and the element either becomes or stops being relevant to the user, the user agent must fire an event named contentvisibilityautostatechange at the Element using ContentVisibilityAutoStateChanged.

Also, if you're firing a new event on the Element interface, that interface should be extended to add an onevent event handler IDL attribute to meet the Always add event handlers design principle.

[Loirooriol]

Blink already shipped and Gecko is implementing, so if it has to be renamed, better do it soon.

[Loirooriol]

I mean, this is not clear from the top comment, but as stated in #7740

Apart from a few exceptions in old specs, events are always named with verbs in the present tense. Accordingly, this update switches the event type to contentvisibilityautostatechange instead of contentvisibilityautostatechanged and also renames the IDL interfaces. For what it's worth, this guidance does not yet appear in the TAG's API design principles but is considered for inclusion in w3ctag/design-principles#280

In particular, there is the change event which is not called changed.

[css-meeting-bot]

The CSS Working Group just discussed [css-contain-2] Incomplete event definition for ContentVisibilityAutoStateChanged.

The full IRC log of that discussion

<fantasai> Topic: [css-contain-2] Incomplete event definition for ContentVisibilityAutoStateChanged
<fantasai> github: https://github.com//issues/7603
<fantasai> oriol: This issue covers different things, but only want to discuss name of the event
<fantasai> oriol: contain introduced ContentVisiblityAutoStateChanged event
<fantasai> oriol: this is inconsistent naming, since other events they use the present tense and this is using past tense
<fantasai> oriol: there's even a proposed design principle in TAG about naming events about avoiding past tense
<fantasai> oriol: just some legacy events are using past tense
<fantasai> oriol: So should we align with this design principle?
<fantasai> oriol: This feature has already shipped in Blink in July or such
<fantasai> oriol: but maybe it could still be compatible to change or maybe Blink could support both for awhile or something like that
<fantasai> oriol: Firefox is implementing now, and WebKit has not implemented this property yet
<fantasai> florian: Do you want to change the name of the event and the object type or just the event?
<vmpstr> q+
<fantasai> oriol: It should be consistent
<flackr> I *think* this is the use counter for registrations: https://chromestatus.com/metrics/feature/timeline/popularity/4328
<emilio> ack emilio
<vmpstr> https://chromestatus.com/metrics/feature/popularity#ContentVisibilityAutoStateChangedHandlerRegistered
<Rossen_> ack vmpstr
<fantasai> vmpstr: On Chrome status there is 0.048% that register a handle for this event
<fantasai> vmpstr: it's a low usage but it's non-zero
<fantasai> Rossen_: is that above the threshold? Wasn't it 0.03%
<fantasai> vmpstr: Justification is that the state change has already happened, different from click event where you can preventDefault
<fantasai> vmpstr: but that's why it was named in the past tense
<flackr> Also animationstart, animationend, transitionstart, transitionend
<fantasai> oriol: form controls also have change event for afterwards, can't prevent change, and this event is in present
<emilio> Yeah, lots of precedents there, `visibilitychange` / `pageshow` / etc
<emilio> +1 for changing
<fantasai> Rossen_: Can we resolve to change, and if we get feedback strongly that this will be a problem, we can revisit?
<fantasai> Rossen_: from spec point of view, right thing to resolve is in favor of change
<fantasai> +1
<vmpstr> +1
<Rossen_> q?
<fantasai> RESOVLED: Change to present tense for ContentVisiblityAutoStateChanged (event and object)