From ef206495cd137a0972233ebb56b49c01beffe56a Mon Sep 17 00:00:00 2001
From: Alexander Skvortsov <sasha.skvortsov109@gmail.com>
Date: Tue, 7 Jul 2020 19:06:12 -0400
Subject: [PATCH] Try calculating index before redraw to avoid calling redraw
 immediately after scroll

---
 js/src/forum/components/PostStream.js  | 7 ++-----
 js/src/forum/states/PostStreamState.js | 8 +++++---
 2 files changed, 7 insertions(+), 8 deletions(-)

diff --git a/js/src/forum/components/PostStream.js b/js/src/forum/components/PostStream.js
index 1746bddd6..0c72b2253 100644
--- a/js/src/forum/components/PostStream.js
+++ b/js/src/forum/components/PostStream.js
@@ -348,15 +348,12 @@ export default class PostStream extends Component {
       }
     }
 
-    return Promise.all([
-      $container.promise(),
-      this.state.loadPromise
-    ]).then(() => {
+    return Promise.all([$container.promise(), this.state.loadPromise])
+      .then(() => {
         m.redraw(true);
         return $(window).scrollTop($(`.PostStream-item[data-index=${$item.data('index')}]`).offset().top - this.getMarginTop());
       })
       .then(() => {
-        //if (this.state.locationType == 'number') this.updateScrubber();
         return this.calculatePosition();
       })
       .then(() => this.state.unpause());
diff --git a/js/src/forum/states/PostStreamState.js b/js/src/forum/states/PostStreamState.js
index ef2da1af3..0b4b565ed 100644
--- a/js/src/forum/states/PostStreamState.js
+++ b/js/src/forum/states/PostStreamState.js
@@ -20,10 +20,8 @@ class PostStreamState {
     this.loadPageTimeouts = {};
     this.pagesLoading = 0;
 
-    this.show(includedPosts);
-
     this.locationType = null;
-    this.index = (this.visibleEnd - this.visibleStart) / 2;
+    this.index = 0;
     this.number = 1;
 
     /**
@@ -39,6 +37,8 @@ class PostStreamState {
      * @type {String}
      */
     this.description = '';
+
+    this.show(includedPosts);
   }
 
   /**
@@ -125,6 +125,7 @@ class PostStreamState {
   show(posts) {
     this.visibleStart = posts.length ? this.discussion.postIds().indexOf(posts[0].id()) : 0;
     this.visibleEnd = this.sanitizeIndex(this.visibleStart + posts.length);
+    this.index = (this.visibleEnd - this.visibleStart) / 2;
   }
 
   /**
@@ -137,6 +138,7 @@ class PostStreamState {
   reset(start, end) {
     this.visibleStart = start || 0;
     this.visibleEnd = this.sanitizeIndex(end || this.constructor.loadCount);
+    this.index = (this.visibleEnd - this.visibleStart) / 2;
   }
 
   /**