If I try to summarise it (sorry I am not actively using my own lib).

The current behavior (before this PR) is to consider element not in the viewport when their height and width is 0.

With your change, they will now be considered in the viewport as soon as they are in the viewport, no matter their height.

If I get this right, I am down for the change and we can move forward, let me know

For me, you summarized well the problem.

👍 to merge, and to release a major version

Tests are failing now, I cannot really understand why but there's something to dig here (run them locally with npm run dev)

It's because Travis doesn't expose the Saucelabs credentials to branches created by people who don't own the repo.

Either you'll have to run them yourself directly, or you can push this branch up to another branch in this repository and open a new pull request, at which point Travis should pass the credentials along happily.

I did run them myself and they are failing, just added one fix (cc @tzi we broke this contains method)

Only two failing tests now:

The testing stack is only good in dev mode for now (travis and saucelabs are too brittle and may need an update on the tested browsers).

@tzi At some point you opened this #9

That's the tests that are failing so I am wondering if this current PR still works for you?

@vvo You totally right. I didn't make the link... Sorry 😞

In theory, this library should not test visibility, but only test if an element is in the viewport.
So this PR seems great, but if you try the example example/invisible-element.html it will always find a display: none element as in the Viewport.

That's a problem.
For example, if you want to lazyload images stacked in horizontal containers AND to lazyload the containers stacked vertically (like the netflix UI). The images that are in not-already-loaded containers could load because there are not displayed.

We should actually replace the old isVisible method in isDisplayed.
Here is a proposition with a complementary example tzi@8fff59e
@cusspvz What do you think?

Cheers,
Thomas.