pinafore/routes/_components/VirtualListItem.html

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<div class="virtual-list-item {{shown ? 'shown' : ''}}"
virtual-list-key="{{key}}"
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ref:node
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style="transform: translateY({{offset}}px);" >
<:Component {component} virtualProps="{{props}}" virtualIndex="{{index}}" virtualLength="{{$numItems}}"
on:recalculateHeight="doRecalculateHeight()"/>
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</div>
<style>
.virtual-list-item {
position: absolute;
top: 0;
opacity: 0;
pointer-events: none;
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/* will-change: transform; */ /* causes jank in mobile Firefox */
}
.virtual-list-item.shown {
opacity: 1;
pointer-events: auto;
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}
</style>
<script>
import { virtualListStore } from '../_utils/virtualListStore'
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import { AsyncLayout } from '../_utils/AsyncLayout'
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const keyGetter = node => node.getAttribute('virtual-list-key')
const asyncLayout = new AsyncLayout(keyGetter)
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export default {
oncreate() {
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let key = this.get('key')
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asyncLayout.observe(key, this.refs.node, (rect) => {
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// update all item heights in one microtask batch for better perf
this.store.batchUpdate('itemHeights', key, rect.height)
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})
},
ondestroy() {
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let key = this.get('key')
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asyncLayout.unobserve(key, this.refs.node)
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},
store: () => virtualListStore,
computed: {
'shown': ($itemHeights, key) => $itemHeights[key] > 0
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},
methods: {
doRecalculateHeight() {
let tempAsyncLayout = new AsyncLayout(keyGetter)
let key = this.get('key')
tempAsyncLayout.observe(key, this.refs.node, (rect) => {
tempAsyncLayout.disconnect()
// update all item heights in one microtask batch for better perf
this.store.batchUpdate('itemHeights', key, rect.height)
})
}
}
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}
</script>