From 7f53920598db083455408ae73e99e058695bcf95 Mon Sep 17 00:00:00 2001
From: Alexander Skvortsov <38059171+askvortsov1@users.noreply.github.com>
Date: Wed, 17 Feb 2021 10:36:30 -0500
Subject: [PATCH] Various iOS scroll improvements (#2548)

* Don't update scrubber while post pages loading

This alleviates the scrubber bouncing around when scrolling up on iOS

* Throttle loadMore loadPrevious

Throttle loadMore and loadPrevious functions to alleviate skipping over pages and pages of posts during one scroll. This sometimes happens on iOS
---
 framework/core/js/src/forum/components/PostStream.js  | 4 +---
 framework/core/js/src/forum/states/PostStreamState.js | 8 ++++++--
 2 files changed, 7 insertions(+), 5 deletions(-)

diff --git a/framework/core/js/src/forum/components/PostStream.js b/framework/core/js/src/forum/components/PostStream.js
index c121b37ca..cf5a43d1c 100644
--- a/framework/core/js/src/forum/components/PostStream.js
+++ b/framework/core/js/src/forum/components/PostStream.js
@@ -146,12 +146,10 @@ export default class PostStream extends Component {
    * @param {Integer} top
    */
   onscroll(top = window.pageYOffset) {
-    if (this.stream.paused) return;
+    if (this.stream.paused || this.stream.pagesLoading) return;
 
     this.updateScrubber(top);
 
-    if (this.stream.pagesLoading) return;
-
     this.loadPostsIfNeeded(top);
 
     // Throttle calculation of our position (start/end numbers of posts in the
diff --git a/framework/core/js/src/forum/states/PostStreamState.js b/framework/core/js/src/forum/states/PostStreamState.js
index 1adf6b293..b93ec9143 100644
--- a/framework/core/js/src/forum/states/PostStreamState.js
+++ b/framework/core/js/src/forum/states/PostStreamState.js
@@ -1,3 +1,4 @@
+import { throttle } from 'lodash-es';
 import anchorScroll from '../../common/utils/anchorScroll';
 
 class PostStreamState {
@@ -49,6 +50,9 @@ class PostStreamState {
      */
     this.forceUpdateScrubber = false;
 
+    this.loadNext = throttle(this._loadNext, 300);
+    this.loadPrevious = throttle(this._loadPrevious, 300);
+
     this.show(includedPosts);
   }
 
@@ -187,7 +191,7 @@ class PostStreamState {
   /**
    * Load the next page of posts.
    */
-  loadNext() {
+  _loadNext() {
     const start = this.visibleEnd;
     const end = (this.visibleEnd = this.sanitizeIndex(this.visibleEnd + this.constructor.loadCount));
 
@@ -210,7 +214,7 @@ class PostStreamState {
   /**
    * Load the previous page of posts.
    */
-  loadPrevious() {
+  _loadPrevious() {
     const end = this.visibleStart;
     const start = (this.visibleStart = this.sanitizeIndex(this.visibleStart - this.constructor.loadCount));