`inView` lifecycle method

[aantusahaa]

Is your feature request related to a problem? Please describe.
Not really a problem. Rather a convenience thing.

Describe the solution you'd like
A method namely inView() that will run whenever the component came into the viewport. It could use IntersectionObserver behind the scene.

Describe alternatives you've considered
Currently, I can use an component around the component I want to listen to.

How important is this feature to you?
For me, it will be a welcoming feature. Whatever projects I do more often than not it involves some use of IntersectionObserver.

[bluwy]

How actually do we detect that a component comes into the viewport? IntersectionObserver relies on observing a DOM element. Since a component can have multiple root elements, should we trigger the inView lifecycle when at least one element enters the view, or only when all of them enters?

There seems to be a lot of unknowns here, which I think should be handled off to a library or a custom action, like svelte-inview.

[aantusahaa]

Since a component can have multiple root elements, should we trigger the inView lifecycle when at least one element enters the view, or only when all of them enters?

We could define that in some sort of config object or even in the DOM elements itself.

I wasn't aware of svelte-inview . Thanks for that.

[bluwy]

We could define that if some sort of config object or even in the DOM elements itself.

Sounds like a perfect use case for a Svelte action :) Personally I find the API from svelte-inview much easier to work with, than having an inView lifecycle function. If anything, Svelte could instead provide these actions by default, which tracked at sveltejs/rfcs#24

[tanhauhau]

you can implement your own action, and there's no plan of having any built-in actions within Svelte right now.