pinafore/routes/_components/virtualList/VirtualList.html

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<VirtualListContainer :realm >
<div class="virtual-list {{shown ? '' : 'hidden'}}" style="height: {{$height}}px;">
<VirtualListHeader component="{{headerComponent}}" virtualProps="{{headerProps}}" shown="{{$showHeader}}"/>
{{#if $visibleItems}}
{{#each $visibleItems as visibleItem @key}}
<VirtualListLazyItem :component
offset="{{visibleItem.offset}}"
makeProps="{{makeProps}}"
key="{{visibleItem.key}}"
index="{{visibleItem.index}}"
/>
{{/each}}
{{/if}}
{{#if $showFooter}}
<VirtualListFooter component="{{footerComponent}}" />
{{/if}}
</div>
</VirtualListContainer>
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<style>
.virtual-list {
position: relative;
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transition: opacity 0.25s linear;
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}
</style>
<script>
import VirtualListContainer from './VirtualListContainer.html'
import VirtualListLazyItem from './VirtualListLazyItem'
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import VirtualListFooter from './VirtualListFooter.html'
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import VirtualListHeader from './VirtualListHeader.html'
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import { virtualListStore } from './virtualListStore'
import throttle from 'lodash/throttle'
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import { mark, stop } from '../../_utils/marks'
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const DISTANCE_FROM_BOTTOM_TO_FIRE = 400
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const SCROLL_EVENT_THROTTLE = 1000
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export default {
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oncreate () {
this.fireScrollToBottom = throttle(() => {
this.fire('scrollToBottom')
}, SCROLL_EVENT_THROTTLE)
this.fireScrollToTop = throttle(() => {
this.fire('scrollToTop')
}, SCROLL_EVENT_THROTTLE)
this.observe('showFooter', showFooter => {
mark('set showFooter')
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this.store.setForRealm({showFooter: showFooter})
mark('set showFooter')
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})
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this.observe('showHeader', showHeader => {
mark('set showHeader')
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this.store.setForRealm({showHeader: showHeader})
stop('set showHeader')
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})
this.observe('itemsStringified', (itemsStringified) => {
let items = typeof itemsStringified === 'undefined' ? undefined :
JSON.parse(itemsStringified)
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mark('set items')
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this.store.setForRealm({items: items})
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stop('set items')
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})
this.observe('allVisibleItemsHaveHeight', allVisibleItemsHaveHeight => {
if (allVisibleItemsHaveHeight) {
this.fire('initializedVisibleItems')
}
})
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let observedOnce = false
this.observe('distanceFromBottom', (distanceFromBottom) => {
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if (!observedOnce) {
observedOnce = true // TODO: the first time is always 0... need better way to handle this
return
}
if (distanceFromBottom >= 0 &&
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distanceFromBottom <= DISTANCE_FROM_BOTTOM_TO_FIRE) {
this.fireScrollToBottom()
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}
})
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this.observe('distanceFromTop', (distanceFromTop) => {
if (distanceFromTop === 0) {
this.fireScrollToTop()
}
})
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},
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data: () => ({
component: null
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}),
store: () => virtualListStore,
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components: {
VirtualListContainer,
VirtualListLazyItem,
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VirtualListFooter,
VirtualListHeader
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},
computed: {
distanceFromBottom: ($scrollHeight, $scrollTop, $offsetHeight) => {
return $scrollHeight - $scrollTop - $offsetHeight
},
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distanceFromTop: ($scrollTop) => $scrollTop,
// TODO: bug in svelte store, shouldn't need to do this
allVisibleItemsHaveHeight: ($allVisibleItemsHaveHeight) => $allVisibleItemsHaveHeight,
// hack to avoid getting called too often
itemsStringified: (items) => JSON.stringify(items)
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}
}
</script>