From bfe0f1255a3edc89c19511ae8b09edc6ec1ee8c6 Mon Sep 17 00:00:00 2001
From: Nolan Lawson <nolan@nolanlawson.com>
Date: Wed, 17 Jan 2018 19:41:37 -0800
Subject: [PATCH] implement batchUpdate()

---
 routes/_components/VirtualListItem.html | 28 ++----------------------
 routes/_utils/virtualListStore.js       | 29 +++++++++++++++++++++++++
 2 files changed, 31 insertions(+), 26 deletions(-)

diff --git a/routes/_components/VirtualListItem.html b/routes/_components/VirtualListItem.html
index 4ba0dbc8..ee986bc2 100644
--- a/routes/_components/VirtualListItem.html
+++ b/routes/_components/VirtualListItem.html
@@ -21,44 +21,20 @@
 <script>
   import { virtualListStore } from '../_utils/virtualListStore'
   import { AsyncLayout } from '../_utils/AsyncLayout'
-  import { mark, stop } from '../_utils/marks'
-
-  let updateItemHeights = {}
-  let promise = Promise.resolve()
 
   const asyncLayout = new AsyncLayout(node => node.getAttribute('virtual-list-key'))
 
   export default {
     oncreate() {
       let key = this.get('key')
-      // TODO: implement batchUpdate
-      // TODO: fix resize on media
       asyncLayout.observe(key, this.refs.node, (rect) => {
-        updateItemHeights[key] = rect.height
-        promise = promise.then(() => {
-          // update all item heights in one microtask batch for better perf
-          let updatedKeys = Object.keys(updateItemHeights)
-          if (!updatedKeys.length) {
-            return
-          }
-          mark('batch update VirtualListItem')
-          // batch all updates to itemHeights for better perf
-          let itemHeights = this.store.get('itemHeights')
-          for (key of updatedKeys) {
-            itemHeights[key] = updateItemHeights[key]
-          }
-          this.store.set({
-            itemHeights: itemHeights
-          })
-          updateItemHeights = {}
-          stop('batch update VirtualListItem')
-        })
+        // update all item heights in one microtask batch for better perf
+        this.store.batchUpdate('itemHeights', key, rect.height)
       })
     },
     ondestroy() {
       let key = this.get('key')
       asyncLayout.unobserve(key, this.refs.node)
-      delete updateItemHeights[key]
     },
     store: () => virtualListStore,
     computed: {
diff --git a/routes/_utils/virtualListStore.js b/routes/_utils/virtualListStore.js
index d89d38ac..8867457e 100644
--- a/routes/_utils/virtualListStore.js
+++ b/routes/_utils/virtualListStore.js
@@ -2,6 +2,35 @@ import { Store } from 'svelte/store.js'
 import { mark, stop } from '../_utils/marks'
 
 class VirtualListStore extends Store {
+  constructor(obj) {
+    super(obj)
+    this._batches = {}
+  }
+
+  batchUpdate(key, subKey, value) {
+    let batch = this._batches[key]
+    if (!batch) {
+      batch = this._batches[key] = {}
+    }
+    batch[subKey] = value
+
+    requestAnimationFrame(() => {
+      let updatedKeys = Object.keys(batch)
+      if (!updatedKeys.length) {
+        return
+      }
+      mark('batchUpdate()')
+      let obj = this.get(key)
+      for (let otherKey of updatedKeys) {
+        obj[otherKey] = batch[otherKey]
+      }
+      delete this._batches[key]
+      let toSet = {}
+      toSet[key] = obj
+      this.set(toSet)
+      stop('batchUpdate()')
+    })
+  }
 }
 
 const virtualListStore = new VirtualListStore({