Defering calculations for determining if user scrolled to bottom or not. slight delay improves the accuracy in responsive view (#5244)

1 files changed, 9 insertions, 7 deletions

diff --git a/webapp/components/post_view/components/post_list.jsx b/webapp/components/post_view/components/post_list.jsx
index 7550db348..3584e9923 100644
--- a/webapp/components/post_view/components/post_list.jsx
+++ b/webapp/components/post_view/components/post_list.jsx
@@ -120,17 +120,10 @@ export default class PostList extends React.Component {
                 break;
             }
         }
-        this.wasAtBottom = this.isAtBottom();
         if (!this.jumpToPostNode && childNodes.length > 0) {
             this.jumpToPostNode = childNodes[childNodes.length - 1];
         }
 
-        // --- --------
-
-        this.props.postListScrolled(this.isAtBottom());
-        this.prevScrollHeight = this.refs.postlist.scrollHeight;
-        this.prevOffsetTop = this.jumpToPostNode.offsetTop;
-
         this.updateFloatingTimestamp();
 
         if (!this.state.isScrolling) {
@@ -139,6 +132,15 @@ export default class PostList extends React.Component {
             });
         }
 
+        // Postpone all DOM related calculations to next frame.
+        // scrollHeight etc might return wrong data at this point
+        setTimeout(() => {
+            this.wasAtBottom = this.isAtBottom();
+            this.props.postListScrolled(this.isAtBottom());
+            this.prevScrollHeight = this.refs.postlist.scrollHeight;
+            this.prevOffsetTop = this.jumpToPostNode.offsetTop;
+        }, 0);
+
         this.scrollStopAction.fireAfter(Constants.SCROLL_DELAY);
     }