pinafore/routes/_components/pseudoVirtualList/PseudoVirtualList.html

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<div class="pseudo-virtual-list {{shown ? '' : 'hidden'}}" on:initializedVisibleItems ref:node>
{{#each wrappedItems as wrappedItem, i @item}}
<PseudoVirtualListLazyItem
component="{{component}}"
index="{{i}}"
length="{{items.length}}"
makeProps="{{makeProps}}"
key="{{wrappedItem.item}}"
intersectionObserver="{{intersectionObserver}}"
hide="{{shouldHide(wrappedItem.item, intersectionStates)}}"
height="{{getHeight(wrappedItem.item, intersectionStates)}}"
on:renderedListItem="onRenderedListItem()"
/>
{{/each}}
</div>
<style>
.pseudo-virtual-list {
position: relative;
transition: opacity 0.25s linear;
}
</style>
<script>
import PseudoVirtualListLazyItem from './PseudoVirtualListLazyItem.html'
import { getRectFromEntry } from '../../_utils/getRectFromEntry'
import { mark, stop } from '../../_utils/marks'
export default {
oncreate() {
this.set({
intersectionObserver: new IntersectionObserver(this.onIntersection.bind(this), {
root: document.getElementsByClassName('container')[0], // TODO: fix this
rootMargin: '300% 0px'
}),
intersectionStates: {}
})
this.observe('allItemsHaveHeight', allItemsHaveHeight => {
console.log('allItemsHaveHeight', allItemsHaveHeight)
if (allItemsHaveHeight && !this.get('initialized')) {
this.set({initialized: true})
console.log('initializedVisibleItems')
this.fire('initializedVisibleItems')
}
})
},
ondestroy() {
let intersectionObserver = this.get('intersectionObserver')
if (intersectionObserver) {
intersectionObserver.disconnect()
}
},
data: () => ({
intersectionStates: {}
}),
helpers: {
shouldHide(key, intersectionStates) {
return !!(intersectionStates[key] && !intersectionStates[key].isIntersecting)
},
getHeight(key, intersectionStates) {
return intersectionStates[key] && intersectionStates[key].rect.height
}
},
methods: {
scrollToPosition(rect) {
if (this.get('scrolledToPosition')) {
return
}
this.set({scrolledToPosition: true})
console.log('scrollToPosition', rect)
// TODO: there should be some cleaner way to grab the container element
let container = document.getElementsByClassName('container')[0]
if (!container) {
return
}
let containerRect = container.getBoundingClientRect()
let scrollTop = rect.top - containerRect.top
if (scrollTop !== 0) {
requestAnimationFrame(() => {
console.log('setting scrollTop to ', scrollTop)
container.scrollTop = scrollTop
})
}
},
onIntersection(entries) {
mark('onIntersection')
let newIntersectionStates = {}
let scrollToItem = this.get('scrollToItem')
let intersectionStates = this.get('intersectionStates')
for (let entry of entries) {
let key = entry.target.getAttribute('pseudo-virtual-list-key')
let rect = getRectFromEntry(entry)
newIntersectionStates[key] = {
isIntersecting: entry.isIntersecting,
rect: rect
}
if (scrollToItem === key) {
this.scrollToPosition(rect)
}
}
intersectionStates = Object.assign(intersectionStates, newIntersectionStates)
this.set({intersectionStates: intersectionStates})
stop('onIntersection')
}
},
computed: {
wrappedItems: (items) => items.map(item => ({item: item})),
allItemsHaveHeight: (items, intersectionStates) => {
if (!items.length) {
return false
}
for (let item of items) {
if (!intersectionStates[item]) {
return false
}
}
return true
}
},
components: {
PseudoVirtualListLazyItem
}
}
</script>