pinafore/routes/_components/VirtualListItem.html

<div class="virtual-list-item"
     ref:node
     style="transform: translate3d(0, {{itemOffset}}px, 0);"
     data-virtual-index="{{index}}"
     data-virtual-key="{{key}}"
>
  <:Component {component} virtualProps="{{props}}" />
</div>
<style>
  .virtual-list-item {
    position: absolute;
    top: 0;
    will-change: transform;
  }
</style>
<script>
  import { virtualListStore } from '../_utils/virtualListStore'

  export default {
    oncreate() {
      let itemHeights = this.store.get('itemHeights')
      itemHeights[this.get('key')] = this.refs.node.offsetHeight
      this.store.set({itemHeights: itemHeights})
    },
    computed: {
      itemOffset: ($itemOffsets, key) => {
        return $itemOffsets[key] || 0
      }
    },
    store: () => virtualListStore
  }
</script>