[css-scroll-snap-2] snapChanged and snapChanging events are confusing and incomplete

[dontcallmedom]

https://drafts.csswg.org/css-scroll-snap-2/#snap-events seems two describe two new events, snapChanged and snapChanging.

Confusingly, it describes them as "event handler" with an event type of scroll, but I'm not sure what this is supposed to mean.

This misses an IDL fragment that describes on… event handler (presumably on the HTMLElement interface, but maybe GlobalEventHandlers if the events are supposed to bubble).

The vast majority of event names are purely lowercase, so the event should probably be snapchanged and snapchanging.

[bakura10]

Adding on that, JS seems to always have used present tense (input events: change, blur), page events (pagehide), window events (resize)... would it be more sense to replace "snapchange" by "snapchanged" ? I agree snapchanged better reflect what it happens, but for consistency reason I think standard events should follow standard casing and naming logic.

[zcorpan]

The table seems to use the same structure as in https://html.spec.whatwg.org/multipage/webappapis.html#event-handlers-on-elements%2C-document-objects%2C-and-window-objects but confusingly defines "snapChanged" and "snapChanging" as an event handlers for scroll events (on which objects?). i.e.:

obj.snapChanged = e => console.assert(e.type === "scroll")

It looks like implementation has started in Chromium, so addressing the naming at least would be good.
https://bugs.chromium.org/p/chromium/issues/detail?id=1456339
https://bugs.chromium.org/p/chromium/issues/detail?id=1494892

[zcorpan]

The implemented SnapEvent interface is also not specified.

[flackr]

@DavMila is working on improving the spec for these on #9515

[zcorpan]

Why are new events needed, vs adding the snap information to the existing scroll and scrollend events?

[DavMila]

For snapchanging, I'd say I think it's better as a separate event form scroll so a developer doesn't have to have an event listener run on every scroll event just to know whether something snap-related is happening.
For snapchanged, I think modifying scrollend would work except that snapchanged could be invoked by a layout change as well.
(I acknowledge that spec still doesn't say much about these events.)

[zcorpan]

OK, thanks.

Since there was a comment about the naming, I'd like to suggest event names that are more consistent with scroll and scrollend:

• scrollsnap
• scrollsnapend

This would make them appear next to scroll in autocomplete and docs etc.

[DavMila]

I filed this issue so the working group can come to a resolution on the naming at some point.

[flackr]

Is this resolved now? I think @DavMila articulated why it's useful to have separate events #7442 (comment), we agreed on and updated the names #9697, and the event handlers have been called out in the appendix https://drafts.csswg.org/css-scroll-snap-2/#event-handlers though should be added to the html spec, but it's not uncommon to start in the appendix of the related spec.

[dontcallmedom]

re event handler, I think #10344 still needs consideration - but otherwise, my side of the issue has been addressed