forked from cybrespace/pinafore
66 lines
1.8 KiB
HTML
66 lines
1.8 KiB
HTML
<div class="virtual-list-item {{shown ? 'shown' : ''}}"
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virtual-list-key="{{key}}"
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ref:node
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style="transform: translate3d(0, {{offset}}px, 0);"
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>
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<:Component {component} virtualProps="{{props}}" />
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</div>
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<style>
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.virtual-list-item {
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position: absolute;
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top: 0;
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opacity: 0;
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pointer-events: none;
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}
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.shown {
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opacity: 1;
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pointer-events: auto;
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}
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</style>
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<script>
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import { virtualListStore } from '../_utils/virtualListStore'
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let updateItemHeights = {}
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let promise = Promise.resolve()
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let onIntersectionCallbacks = {}
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let intersectionObserver = new IntersectionObserver(entries => {
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entries.forEach(entry => {
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let key = entry.target.getAttribute('virtual-list-key')
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onIntersectionCallbacks[key](entry)
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})
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})
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export default {
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oncreate() {
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let key = this.get('key')
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onIntersectionCallbacks[key] = entry => {
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updateItemHeights[key] = entry.boundingClientRect.height
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promise.then(() => {
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// update all item heights in one microtask batch for better perf
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let updatedKeys = Object.keys(updateItemHeights)
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if (!updatedKeys.length) {
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return
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}
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// batch all updates to itemHeights for better perf
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let itemHeights = this.store.get('itemHeights')
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for (key of updatedKeys) {
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itemHeights[key] = updateItemHeights[key]
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}
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this.store.set({
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itemHeights: itemHeights
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})
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updateItemHeights = {}
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})
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}
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intersectionObserver.observe(this.refs.node)
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},
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ondestroy() {
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intersectionObserver.unobserve(this.refs.node)
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},
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store: () => virtualListStore,
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computed: {
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'shown': ($itemHeights, key) => $itemHeights[key] > 0
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}
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}
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</script> |