[csswg-drafts] [scroll-animations] Unclamped start and end element-based offsets are hard to work with (#4327)

flackr has just created a new issue for https://github.com/w3c/csswg-drafts:

== [scroll-animations] Unclamped start and end element-based offsets are hard to work with ==
This issue is separating out a particular concern in https://github.com/WICG/scroll-animations/issues/51 where offsets can be outside the scrollable range which means that your animation will start partway through, a distance depending on the geometry of the page. In https://flackr.github.io/scroll-timeline/demo/parallax/unclamped.html you can see that this has made animations at the start and end of the scroller start / end partway through the animation.

I think as a developer this unclamped behavior is hard to reason about (i.e. I have to use a different parallax boundary for elements which start on screen from those which scroll into view - but that's dependent on the size of the viewport). This seems to eliminate some of the benefits of element-based offsets as the developer has to again worry about resizing / shifting of elements.

I think that we should clamp offsets outside of the scroll range (as in https://flackr.github.io/scroll-timeline/demo/parallax/ ) for better developer ergonomics.

Please view or discuss this issue at https://github.com/w3c/csswg-drafts/issues/4327 using your GitHub account

Received on Wednesday, 18 September 2019 15:35:20 UTC