Mouse enter leave

[jquense]

Updated version of #5762 maybe there is a new failing test tho with fiber?

cc @nhunzaker

[nhunzaker]

Thanks for reviving this! On the surface, this looks great. Looks like CI is just failing because of a linting issue.

I'll be able to dig in for a deeper review on Friday. I'll setup a DOM test fixture and do some browser QA. From there, we just need to figure out what's going on with Fiber.

@spicyj Could you take a look at this?

[jquense]

If I'm remembering correctly from way back when I originally did this, the other approach is to use the plugin add/remove listener hooks to circumvent the top level delegate for the polyfill (and attach a listener directly to the node). This may be a preferable approach judging from @sebmarkbage comment in the old PR.

[jquense]

So I'm revisiting this. From what I can tell native mouseenter and mouseleave are supported on all modern (and not modern) browsers. https://developer.mozilla.org/en-US/docs/Web/Events/mouseleave

Why is there a polyfill to begin with? Can we just remove at this point?

[sebmarkbage]

WebKit browsers (including Chrome at the time) didn't get support for it until late 2013. After React. There was also a long tail of upgrades that took a while but I think we can remove it now.

Similarly focusin/out wasn't supported in Firefox until this year(!) but once it has enough adoption we can kill the polyfilling around that too. However, that one is a bit different since we have slightly different behavior.

Also, Portals currently support bubbling through to the parent. That can be replicated in other ways though (e.g. redispatching the event).

[jquense]

Also, Portals currently support bubbling through to the parent. That can be replicated in other ways though (e.g. redispatching the event).

This is a killer feature for dealing with focus in fixed position dropdowns btw 👍

If we remove the polyfill we can rely on the normal event dispatch methods vs the fun custom one for ME, does that handle the portal case automatically or does it need to be handled further up or down?

[sebmarkbage]

Another feature of portals is that the events don't fire when you move between the parent and the portal. That bit might need a bit more complicated logic.

[gaearon]

Closing as stale.