Spec review for Snap Events

[DavMila]

こんにちは TAG-さん!

I'm requesting a TAG review of Snap Events.

CSS scroll snap points are often used as a mechanism to create interactive scroll "selection" components, giving authors control over what areas of its content a scrolling container can settle. This proposal adds 2 JavaScript events, “snapchanging” and “snapchanged”, which fire in response to the scrolling/snapping of containers which snap. snapchanging is a JavaScript event that aims to let the web page know, as early as possible, that a scrolling operation will result in a change in the element the container being scrolled is snapped to. snapchanged is a JavaScript event that fires when a scrolling operation is complete and the scroller has snapped to a different element than it was previously snapped to.

• Explainer¹ (minimally containing user needs and example code):
  Snapchanged: https://github.com/argyleink/ScrollSnapExplainers/tree/main/js-snapChanged
  Snapchanging: https://github.com/argyleink/ScrollSnapExplainers/tree/main/js-snapChanging

• Specification URL: https://drafts.csswg.org/css-scroll-snap-2/#snap-events

• Tests: [wpt folder(s), if available]
  https://wpt.fyi/results/css/css-scroll-snap-2/snapchanging
  https://wpt.fyi/results/css/css-scroll-snap-2/snapchanged

• User research: [url to public summary/results of research]
  N/A

• Security and Privacy self-review²:
  As indicated in the explainer, there are no known privacy or security issues.

• GitHub repo (if you prefer feedback filed there):

• Primary contacts (and their relationship to the specification):

  • David Awogbemila (@DavMila), Google
  • Robert Flack (@flackr), Google

• Organization(s)/project(s) driving the specification: CSSWG

• Key pieces of existing multi-stakeholder (e.g. developers, implementers, civil society) support, review or discussion of this specification:

  • Chromium comments: [url]
  • Mozilla comments: Snap Events mozilla/standards-positions#1008
  • WebKit comments: Snap Events WebKit/standards-positions#333

• External status/issue trackers for this specification (publicly visible, e.g. Chrome Status):

  • snapchanging chromestatus
  • snapchanged chromestatus

Further details:

• I have reviewed the TAG's Web Platform Design Principles
• Relevant time constraints or deadlines: Interested in shipping when possible
• The group where the work on this specification is currently being done: CSSWG
• The group where standardization of this work is intended to be done (if current group is a community group or other incubation venue):
• Major unresolved issues with or opposition to this specification:
  • csswg-drafts issue #10173: Should snap events fired at the document bubble?
  • csswg-drafts issue #10175: Should pseudo-elements show up as null SnapEvent.snapTargetBlock/Inline?
  • csswg-drafts issue #9697: Use present tense for snap event names.
• This work is being funded by: Google

[martinthomson]

Discussed with @hober. This looks like it is on track. The choices made all seem appropriate.

Thanks for the detailed explainer.