79 lines
1.9 KiB
JavaScript
79 lines
1.9 KiB
JavaScript
import { store } from '../_store/store'
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// via https://github.com/tootsuite/mastodon/blob/f59ed3a4fafab776b4eeb92f805dfe1fecc17ee3/app/javascript/mastodon/scroll.js
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const easingOutQuint = (x, t, b, c, d) =>
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c * ((t = t / d - 1) * t * t * t * t + 1) + b
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function smoothScrollPolyfill (node, key, target) {
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const startTime = Date.now()
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const offset = node[key]
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const gap = target - offset
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const duration = 1000
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let interrupt = false
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const step = () => {
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const elapsed = Date.now() - startTime
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const percentage = elapsed / duration
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if (interrupt) {
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return
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}
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if (percentage > 1) {
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cleanup()
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return
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}
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node[key] = easingOutQuint(0, elapsed, offset, gap, duration)
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requestAnimationFrame(step)
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}
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const cancel = () => {
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interrupt = true
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cleanup()
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}
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const cleanup = () => {
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node.removeEventListener('wheel', cancel)
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node.removeEventListener('touchstart', cancel)
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}
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node.addEventListener('wheel', cancel, { passive: true })
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node.addEventListener('touchstart', cancel, { passive: true })
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step()
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return cancel
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}
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function testSupportsSmoothScroll () {
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let supports = false
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try {
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let div = document.createElement('div')
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div.scrollTo({
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top: 0,
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get behavior () {
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supports = true
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return 'smooth'
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}
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})
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} catch (err) {} // Edge throws an error
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return supports
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}
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export const hasNativeSmoothScroll = process.browser && testSupportsSmoothScroll()
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export function smoothScroll (node, topOrLeft, horizontal) {
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if (store.get().reduceMotion) {
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// don't do smooth-scroll at all for users who prefer reduced motion
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node[horizontal ? 'scrollLeft' : 'scrollTop'] = topOrLeft
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} else if (hasNativeSmoothScroll) {
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return node.scrollTo({
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[horizontal ? 'left' : 'top']: topOrLeft,
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behavior: 'smooth'
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})
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} else {
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return smoothScrollPolyfill(node, horizontal ? 'scrollLeft' : 'scrollTop', topOrLeft)
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}
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}
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