pinafore/routes/_components/virtualList/VirtualList.html

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<VirtualListContainer {realm} {containerQuery} on:initialized on:noNeedToScroll >
<div class="virtual-list"
style="height: {$height}px;"
ref:node >
<VirtualListHeader component={headerComponent} virtualProps={headerProps} shown={$showHeader}/>
{#if $visibleItems}
{#each $visibleItems as visibleItem (visibleItem.key)}
<VirtualListLazyItem {component}
offset={visibleItem.offset}
{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;
}
</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-es/throttle'
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import { mark, stop } from '../../_utils/marks'
import isEqual from 'lodash-es/isEqual'
import { observe } from 'svelte-extras'
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const DISTANCE_FROM_BOTTOM_TO_FIRE = 800
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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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})
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this.observe('items', (newItems, oldItems) => {
if (!newItems || isEqual(newItems, oldItems)) {
return
}
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mark('set items')
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this.store.setForRealm({items: newItems})
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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('scrollTop', (scrollTop) => {
this.fire('scrollTopChanged', scrollTop)
if (scrollTop === 0) {
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this.fireScrollToTop()
}
this.calculateListOffset()
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})
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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 }) => {
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return $scrollHeight - $scrollTop - $offsetHeight
},
scrollTop: ({ $scrollTop }) => $scrollTop,
// TODO: bug in svelte store, shouldn't need to do this
allVisibleItemsHaveHeight: ({ $allVisibleItemsHaveHeight }) => $allVisibleItemsHaveHeight
},
methods: {
observe,
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calculateListOffset () {
// TODO: better way to get the offset top?
let node = this.refs.node
if (!node) {
return
}
mark('calculateListOffset')
let listOffset = node.offsetParent.offsetTop
this.store.setForRealm({listOffset})
stop('calculateListOffset')
}
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}
}
</script>