[css-position][css-sticky] Provide an easing option between an elements states when using position sticky

[Sandstedt]

To make the animation of an elements default position and it's sticky position more smooth, it would be great to provide an easing option when using position: sticky.

In the current implementation it looks very static and mechanic when scrolling on a page using sticky elements. By providing and easing curve, the animation could become smooth and organic, or bouncy and fun, or just a mechaning animation using a linear easing.

Current spec: https://www.w3.org/TR/css-position-3/#stickypos-insets

(Will soon create a video comparing the current state of the spec and how it could look with easing applied)

[jonjohnjohnson]

I think things like this fall less under position:sticky and more under the new houdini specs. I'd suggest checking them out, specifically the css-animation-worklet and scroll timelines. Also check out the current issues relating to scroll animation/timeline things https://github.com/w3c/csswg-drafts/issues?q=is%3Aissue+scroll+timeline. With scroll timelines we won't just have easing options for that inset position, but we'll also have transitions easing through other properties like transform/opacity/etc.