58 lines
2.1 KiB
HTML
58 lines
2.1 KiB
HTML
{#if props}
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<VirtualListItem {component}
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{offset}
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{props}
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{key}
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{index}
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/>
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{/if}
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<script>
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import VirtualListItem from './VirtualListItem'
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import { mark, stop } from '../../_utils/marks'
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import { scheduleIdleTask } from '../../_utils/scheduleIdleTask'
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import { createPriorityQueue } from '../../_utils/createPriorityQueue'
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import { isMobile } from '../../_utils/userAgent/isMobile'
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// In Svelte's implementation of lists, these VirtualListLazyItems can be
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// created in any order. By default in fact it seems to do it in reverse
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// order, which we don't really want, because then items render in a janky
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// way, with the last ones first and then replaced by the first ones,
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// resulting in a UI that looks like a deck of cards being shuffled.
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// This functions waits a microtask and then ensures that the callbacks
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// are called by index, in ascending order.
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const priorityQueue = createPriorityQueue()
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export default {
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async oncreate () {
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const { makeProps, key, index } = this.get()
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if (makeProps) {
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await priorityQueue(index)
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const props = await makeProps(key)
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const setProps = () => {
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mark('VirtualListLazyItem set props')
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this.set({ props: props })
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stop('VirtualListLazyItem set props')
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}
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// On mobile, render in rIC for maximum input responsiveness. The reason we do
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// different behavior for desktop versus mobile is:
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// 1. On desktop, the scrollbar is really distracting as it changes size. It may
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// even cause issues for people with vestibular disorders (see also prefers-reduced-motion).
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// 2. On mobile, the CPU is generally slower, so we want better input responsiveness.
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// TODO: someday we can use isInputPending as a better way to break up work
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// https://www.chromestatus.com/feature/5719830432841728
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if (isMobile()) {
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scheduleIdleTask(setProps)
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} else {
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setProps()
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}
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}
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},
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data: () => ({
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props: undefined
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}),
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components: {
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VirtualListItem
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}
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}
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</script>
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