Fix “slow mode” issues (#11859)

* Fix weird scroll-jumping behavior with pending items

* Treat pending items as unread items

* Fix scroll position being altered because of the “X new items” button

1 files changed, 9 insertions, 1 deletions

diff --git a/app/javascript/mastodon/components/scrollable_list.js b/app/javascript/mastodon/components/scrollable_list.js
index 0bf817923..253646ed0 100644
--- a/app/javascript/mastodon/components/scrollable_list.js
+++ b/app/javascript/mastodon/components/scrollable_list.js
@@ -172,8 +172,9 @@ export default class ScrollableList extends PureComponent {
     const someItemInserted = React.Children.count(prevProps.children) > 0 &&
       React.Children.count(prevProps.children) < React.Children.count(this.props.children) &&
       this.getFirstChildKey(prevProps) !== this.getFirstChildKey(this.props);
+    const pendingChanged = (prevProps.numPending > 0) !== (this.props.numPending > 0);
 
-    if (someItemInserted && (this.getScrollTop() > 0 || this.mouseMovedRecently)) {
+    if (pendingChanged || someItemInserted && (this.getScrollTop() > 0 || this.mouseMovedRecently)) {
       return this.getScrollHeight() - this.getScrollTop();
     } else {
       return null;
@@ -261,6 +262,13 @@ export default class ScrollableList extends PureComponent {
   handleLoadPending = e => {
     e.preventDefault();
     this.props.onLoadPending();
+    // Prevent the weird scroll-jumping behavior, as we explicitly don't want to
+    // scroll to top, and we know the scroll height is going to change
+    this.scrollToTopOnMouseIdle = false;
+    this.lastScrollWasSynthetic = false;
+    this.clearMouseIdleTimer();
+    this.mouseIdleTimer = setTimeout(this.handleMouseIdle, MOUSE_IDLE_DELAY);
+    this.mouseMovedRecently = true;
   }
 
   render () {