In whatwg/html#5510 I'm trying to specify <img loading=lazy> in terms of IntersectionObserver as per discussion in whatwg/html#5236

The desired behavior for lazy-loading is to dynamically change the rootMargin in response to things like scrolling and network changes. See whatwg/html#5408 (comment)

Since IntersectionObserver only allows setting the rootMargin upon initialization, this would require one of

• Register a new IntersectionObserver and observe all the same elements as the old one, and get rid of the old one. This seems bad, but I assume is what a JS polyfill would have to do?
• Have the browser internally update the rootMargin even though the public API doesn't allow for it.

I think the second option seems better, but per the extensible web manifesto we try to have web features be explained by lower-level APIs without having special magic that isn't accessible to web developers.

Are there issues with modifying the rootMargin after initialization?