Clarify root rect with overflow and padding.

emilio commented 2 years ago

https://w3c.github.io/IntersectionObserver/#intersectionobserver-root-intersection-rectangle says to use the "content area" when the element has scrollable overflow, however this seems wrong when there's padding.

WebKit and Blink implement the spec to the letter.
Firefox implements what I think is better behavior: The intersection root rect is the scrollport rect, not the content rect.

Unless I'm missing something, the intent of the spec is to not include the scrollbar and borders, but I believe the correct behavior is Firefox's.

@miketaylr @szager-chromium do you agree?

miketaylr commented 2 years ago

With my webdev hat on, I find Firefox's implementation to be less surprising. @szager-chromium WDYT?

emilio commented 1 year ago

Cc @tcaptan-cr, wonder if there's any opinion here. I think this is an obvious spec bug / oversight.

tcaptan-cr commented 1 year ago

Cc @tcaptan-cr, wonder if there's any opinion here. I think this is an obvious spec bug / oversight.

I agree that the scrollport rect would be better.

w3c / IntersectionObserver