Bottom and Top Margin Issues with IntersectionObserver

[snewcomer]

Issue

RAF

Currently we use bottom to determine when we are in-viewport here. This wasn't documented but ppl used it to start fetching before reaching the sentinel element.

IntersectionObserver

bottom actually extends the "capturing frame" of your root. So in the case a user passed bottom: 500, in fact, top is actually what we need for IntersectionObserver. However, positive rootMargin does not seem to even add inset/outset margin anyways. I'll try to put together a codepen. Overflow:hidden / auto may be the culprit.