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Allow dynamically changing rootMargin #428
Description
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
IntersectionObserverand 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
rootMargineven 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?
Activity
domfarolino commentedon May 8, 2020
This seems reasonable, but also I don't think it should block whatwg/html#5510
zcorpan commentedon May 18, 2020
Agreed. I think it doesn't need to block fixing whatwg/html#5408 either, we could temporarily violate the extensible web manifesto here. But fixing this first certainly seems nicer to me!
emilio commentedon Oct 19, 2020
I don't think there'd be an issue allowing this.
zcorpan commentedon Oct 29, 2020
There will be a TPAC breakout session tomorrow (30 October 14:00–15:00 UTC) to discuss this issue.
https://www.w3.org/2020/10/TPAC/breakout-schedule.html#intersectionobserver
zcorpan commentedon Oct 30, 2020
The breakout starts in ~20 minutes. Agenda and meeting notes here: https://docs.google.com/document/d/1SXwbMiwOUkLPXSM_klk4q9mFEanbIH8IAgTM80cCMXU/edit?usp=sharing
asakusuma commentedon Sep 22, 2021
@zcorpan I read the meeting notes, has someone proposed an API here to allow
rootMarginmutation?Another use case here is top navbars that change size.
zcorpan commentedon Sep 23, 2021
@asakusuma The API we gravitated towards was to allow assigning to
rootMargin(and @smfr suggested also allow changingthresholdsfor symmetry).In metonym/svelte-intersection-observer#12 (comment) @dysfunc also explains a use case for this feature. The implementation in
svelte-intersection-observervalidates that there is a web developer need for this feature.cc @chrishtr
Allow setting rootMargin and thresholds
zcorpan commentedon Oct 21, 2021
PRs: #485 (
thresholds), #486 (rootMargin)Allow setting rootMargin