From eacf28317e93430c7309402e124d2b25fb927e93 Mon Sep 17 00:00:00 2001
From: Nolan Lawson <nolan@nolanlawson.com>
Date: Tue, 16 Jan 2018 23:16:15 -0800
Subject: [PATCH] more progress on infinite scroll

---
 routes/_components/Layout.html          | 43 +++++++++++++++++++++++--
 routes/_components/Timeline.html        |  7 ++--
 routes/_components/VirtualList.html     | 40 +++++++----------------
 routes/_components/VirtualListItem.html |  3 +-
 routes/_utils/virtualListStore.js       | 16 ++-------
 5 files changed, 61 insertions(+), 48 deletions(-)

diff --git a/routes/_components/Layout.html b/routes/_components/Layout.html
index 0d5da5e3..54491424 100644
--- a/routes/_components/Layout.html
+++ b/routes/_components/Layout.html
@@ -1,16 +1,55 @@
+<:Window bind:innerHeight='innerHeight'/>
 <Nav page={{page}} />
 
-<div class="container">
+<div class="container" on:scroll="onScroll(event)" ref:node>
   <main>
     <slot></slot>
   </main>
 </div>
 <script>
 	import Nav from './Nav.html';
+	import { virtualListStore } from '../_utils/virtualListStore'
+
+  import throttle from 'lodash/throttle'
+  const THROTTLE_DELAY = 500
 
 	export default {
+	  oncreate() {
+      this.observe('innerHeight', throttle(() => {
+        // respond to window resize events
+        this.store.set({
+          offsetHeight: this.refs.node.offsetHeight
+        })
+      }, THROTTLE_DELAY))
+	    this.store.set({
+        scrollTop: this.refs.node.scrollTop,
+        scrollHeight: this.refs.node.scrollHeight,
+        offsetHeight: this.refs.node.offsetHeight
+      })
+    },
 		components: {
 			Nav
-		}
+		},
+    store: () => virtualListStore,
+    events: {
+      scroll(node, callback) {
+        const onScroll = throttle(callback, THROTTLE_DELAY)
+        node.addEventListener('scroll', onScroll);
+
+        return {
+          teardown() {
+            node.removeEventListener('scroll', onScroll);
+          }
+        };
+      }
+    },
+    methods: {
+		  onScroll(event) {
+		    this.store.set({
+          scrollTop: event.target.scrollTop,
+          scrollHeight: event.target.scrollHeight
+        })
+      }
+    }
 	};
 </script>
\ No newline at end of file
diff --git a/routes/_components/Timeline.html b/routes/_components/Timeline.html
index 387b5610..7533eb9a 100644
--- a/routes/_components/Timeline.html
+++ b/routes/_components/Timeline.html
@@ -18,7 +18,7 @@
 
   let i = -1
 
-  const createData = () => fixture.slice(0, 5).map(_ => ({
+  const createData = () => fixture.slice(0, 20).map(_ => ({
     key: `${++i}`,
     props: _
   }))
@@ -37,7 +37,10 @@
       splice: splice,
       addMoreItems() {
         console.log('addMoreItems')
-        this.splice('statuses', this.get('statuses').length, 0, ...createData())
+        let statuses = this.get('statuses')
+        if (statuses) {
+          this.splice('statuses', statuses.length, 0, ...createData())
+        }
       }
     }
   }
diff --git a/routes/_components/VirtualList.html b/routes/_components/VirtualList.html
index 321a31ff..6a905475 100644
--- a/routes/_components/VirtualList.html
+++ b/routes/_components/VirtualList.html
@@ -1,5 +1,4 @@
-<:Window bind:innerHeight='innerHeight'/>
-<div class="virtual-list" style="height: {{$height}}px;">
+<div class="virtual-list">
   <!-- <div class="virtual-list-viewport" ref:viewport></div> -->
   {{#each $visibleItems as item @key}}
   <VirtualListItem :component
@@ -17,46 +16,24 @@
 <script>
   import VirtualListItem from './VirtualListItem'
   import { virtualListStore } from '../_utils/virtualListStore'
-  import throttle from 'lodash/throttle'
 
-  const THROTTLE_TIME = 500
   const DISTANCE_FROM_BOTTOM_TO_FIRE = 400
 
   export default {
     oncreate () {
-      let container = document.body.querySelector('.container')
-      this.observe('innerHeight', throttle(() => {
-        // respond to window resize events
-        this.store.set({
-          offsetHeight: container.offsetHeight
-        })
-      }, THROTTLE_TIME))
       this.observe('items', (items) => {
         this.store.set({
-          'items': items
+          items: items
         })
       })
-      this.store.observe('distanceFromBottom', distanceFromBottom => {
-        console.log('distanceFromBottom', distanceFromBottom)
-        if (distanceFromBottom >= 0 &&
+
+      this.observe('distanceFromBottom', (distanceFromBottom) => {
+        //console.log('distanceFromBottom', distanceFromBottom)
+        if (distanceFromBottom > 0 && // hack: the first it's reported, it's always 0
             distanceFromBottom <= DISTANCE_FROM_BOTTOM_TO_FIRE) {
           this.fire('scrollToBottom')
         }
       })
-      container.addEventListener('scroll', throttle((e) => {
-        this.store.set({
-          scrollTop: e.target.scrollTop,
-          scrollHeight: e.target.scrollHeight
-        }, {
-          leading: false,
-          trailing: true
-        })
-      }, THROTTLE_TIME))
-      this.store.set({
-        scrollTop: container.scrollTop,
-        scrollHeight: container.scrollHeight,
-        offsetHeight: container.offsetHeight
-      })
     },
     data: () => ({
       component: null
@@ -64,6 +41,11 @@
     store: () => virtualListStore,
     components: {
       VirtualListItem
+    },
+    computed: {
+      distanceFromBottom: ($scrollHeight, $scrollTop, $offsetHeight) => {
+        return $scrollHeight - $scrollTop - $offsetHeight
+      }
     }
   }
 </script>
\ No newline at end of file
diff --git a/routes/_components/VirtualListItem.html b/routes/_components/VirtualListItem.html
index fad96839..ce65e08c 100644
--- a/routes/_components/VirtualListItem.html
+++ b/routes/_components/VirtualListItem.html
@@ -35,7 +35,8 @@
     oncreate() {
       let key = this.get('key')
       onIntersectionCallbacks[key] = entry => {
-        updateItemHeights[key] = entry.boundingClientRect.height
+        let rect = entry.boundingClientRect
+        updateItemHeights[key] = rect.height
         promise.then(() => {
           // update all item heights in one microtask batch for better perf
           let updatedKeys = Object.keys(updateItemHeights)
diff --git a/routes/_utils/virtualListStore.js b/routes/_utils/virtualListStore.js
index 0caff675..ed9121c4 100644
--- a/routes/_utils/virtualListStore.js
+++ b/routes/_utils/virtualListStore.js
@@ -27,7 +27,7 @@ virtualListStore.compute('visibleItems',
         continue // below the area we want to render
       }
     } else {
-      if (currentOffset > (scrollTop + offsetHeight + renderBuffer)) {
+      if (currentOffset > (scrollTop + height + renderBuffer)) {
         break // above the area we want to render
       }
     }
@@ -35,24 +35,12 @@ virtualListStore.compute('visibleItems',
       offset: currentOffset,
       props: props,
       key: key,
-      index: i,
-      height: height
+      index: i
     })
   }
   return visibleItems
 })
 
-virtualListStore.compute('distanceFromBottom',
-    ['scrollHeight', 'scrollTop', 'offsetHeight'],
-    (scrollHeight, scrollTop, offsetHeight) => {
-  if (typeof scrollHeight === 'undefined' ||
-      typeof scrollTop === 'undefined' ||
-      typeof offsetHeight === 'undefined') {
-    return -1
-  }
-  return scrollHeight - scrollTop - offsetHeight
-})
-
 virtualListStore.compute('height', ['items', 'itemHeights'], (items, itemHeights) => {
   let sum = 0
   let i = -1