Use interaction observer to detect viewport

[roderickhsiao]

We could probably try to integrate intersection observer and fallback to the original logic if the browser doesnt support it.

https://developer.mozilla.org/en-US/docs/Web/API/Intersection_Observer_API

Also there is issue that currently the scroll event is attached on window, so it might cause issue if the we are using overflow scroll

Support
https://caniuse.com/#feat=intersectionobserver

How do you think?

[kaesonho]

👍 makes totally sense to me, maybe just use polyfill to make make the logic even simpler?

[roderickhsiao]

sure, but I'm not pretty familiar with the logic and I dont have a working app using the viewport function. Do you think the functional test/unit test cover this case?