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Sebastian Markbåge
605a880c8c
We added support for `onScrollEnd` in #26789 but it only works in Chrome and Firefox. Safari still doesn't support `scrollend` and there's no indication that they will anytime soon so this polyfills it. While I don't particularly love our synthetic event system this tries to stay within the realm of how our other polyfills work. This implements all `onScrollEnd` events as a plugin. The basic principle is to first feature detect the `onscrollend` DOM property to see if there's native support and otherwise just use the native event. Then we listen to `scroll` events and set a timeout. If we don't get any more scroll events before the timeout we fire `onScrollEnd`. Basically debouncing it. If we're currently pressing down on touch or a mouse then we wait until it is lifted such as if you're scrolling with a finger or using the scrollbars on desktop but isn't currently moving. If we do get any native events even though we're in polyfilling mode, we use that as an indication to fire the `onScrollEnd` early. Part of the motivation is that this becomes extra useful pair for https://github.com/facebook/react/pull/32422. We also probably need these events to coincide with other gesture related internals so you're better off using our polyfill so they're synced.