From 81f7ab16394df7a2ad18c5067202902a640e1c8d Mon Sep 17 00:00:00 2001
From: Alexander Zinchuk <alx.zinchuk@gmail.com>
Date: Wed, 12 May 2021 22:22:21 +0300
Subject: [PATCH] Infinite Scroll: Prevent scroll jumps in global search and
 member list

---
 src/components/left/search/ChatResults.tsx |  2 +
 src/components/right/Profile.tsx           |  2 +
 src/components/ui/InfiniteScroll.tsx       |  8 ++-
 src/components/ui/SimpleInfiniteScroll.tsx | 81 ----------------------
 4 files changed, 11 insertions(+), 82 deletions(-)
 delete mode 100644 src/components/ui/SimpleInfiniteScroll.tsx

diff --git a/src/components/left/search/ChatResults.tsx b/src/components/left/search/ChatResults.tsx
index 312915bc1..3f39dda15 100644
--- a/src/components/left/search/ChatResults.tsx
+++ b/src/components/left/search/ChatResults.tsx
@@ -187,6 +187,8 @@ const ChatResults: FC<OwnProps & StateProps & DispatchProps> = ({
       className="LeftSearch custom-scroll"
       items={foundMessages}
       onLoadMore={handleLoadMore}
+      // To prevent scroll jumps caused by delayed local results rendering
+      noScrollRestoreOnTop
       noFastList
     >
       {dateSearchQuery && (
diff --git a/src/components/right/Profile.tsx b/src/components/right/Profile.tsx
index 40f5ca571..f87eac467 100644
--- a/src/components/right/Profile.tsx
+++ b/src/components/right/Profile.tsx
@@ -314,6 +314,8 @@ const Profile: FC<OwnProps & StateProps & DispatchProps> = ({
       cacheBuster={cacheBuster}
       sensitiveArea={PROFILE_SENSITIVE_AREA}
       preloadBackwards={canRenderContents ? (resultType === 'members' ? MEMBERS_SLICE : SHARED_MEDIA_SLICE) : 0}
+      // To prevent scroll jumps caused by reordering member list
+      noScrollRestoreOnTop
       noFastList
       onLoadMore={getMore}
       onScroll={handleScroll}
diff --git a/src/components/ui/InfiniteScroll.tsx b/src/components/ui/InfiniteScroll.tsx
index 2cd357a25..43400abf2 100644
--- a/src/components/ui/InfiniteScroll.tsx
+++ b/src/components/ui/InfiniteScroll.tsx
@@ -18,6 +18,7 @@ type OwnProps = {
   preloadBackwards?: number;
   sensitiveArea?: number;
   noScrollRestore?: boolean;
+  noScrollRestoreOnTop?: boolean;
   noFastList?: boolean;
   cacheBuster?: any;
   children: any;
@@ -38,6 +39,7 @@ const InfiniteScroll: FC<OwnProps> = ({
   sensitiveArea = DEFAULT_SENSITIVE_AREA,
   // Used to turn off restoring scroll position (e.g. for frequently re-ordered chat or user lists)
   noScrollRestore = false,
+  noScrollRestoreOnTop = false,
   noFastList,
   // Used to re-query `listItemElements` if rendering is delayed by transition
   cacheBuster,
@@ -110,10 +112,14 @@ const InfiniteScroll: FC<OwnProps> = ({
       return;
     }
 
+    if (noScrollRestoreOnTop && container.scrollTop === 0) {
+      return;
+    }
+
     resetScroll(container, newScrollTop);
 
     state.isScrollTopJustUpdated = true;
-  }, [noScrollRestore, itemSelector, items, cacheBuster]);
+  }, [items, itemSelector, noScrollRestore, noScrollRestoreOnTop, cacheBuster]);
 
   const handleScroll = useCallback((e: UIEvent<HTMLDivElement>) => {
     if (loadMoreForwards && loadMoreBackwards) {
diff --git a/src/components/ui/SimpleInfiniteScroll.tsx b/src/components/ui/SimpleInfiniteScroll.tsx
deleted file mode 100644
index 458bded74..000000000
--- a/src/components/ui/SimpleInfiniteScroll.tsx
+++ /dev/null
@@ -1,81 +0,0 @@
-import { RefObject, UIEvent } from 'react';
-import { LoadMoreDirection } from '../../types';
-
-import React, {
-  FC, useCallback, useEffect, useMemo, useRef,
-} from '../../lib/teact/teact';
-
-import { debounce } from '../../util/schedulers';
-
-type OwnProps = {
-  ref?: RefObject<HTMLDivElement>;
-  className?: string;
-  onLoadMore: ({ direction }: { direction: LoadMoreDirection }) => void;
-  onScroll?: (e: UIEvent<HTMLDivElement>) => void;
-  items: any[];
-  sensitiveArea?: number;
-  preloadBackwards?: number;
-  children: any;
-};
-
-const DEFAULT_SENSITIVE_AREA = 1200;
-const DEFAULT_PRELOAD_BACKWARDS = 20;
-
-const SimpleInfiniteScroll: FC<OwnProps> = ({
-  ref,
-  className,
-  onLoadMore,
-  onScroll,
-  items,
-  sensitiveArea = DEFAULT_SENSITIVE_AREA,
-  preloadBackwards = DEFAULT_PRELOAD_BACKWARDS,
-  children,
-}: OwnProps) => {
-  // eslint-disable-next-line no-null/no-null
-  let containerRef = useRef<HTMLDivElement>(null);
-  if (ref) {
-    containerRef = ref;
-  }
-
-  // eslint-disable-next-line no-null/no-null
-  const anchorTopRef = useRef<number>(null);
-
-  // eslint-disable-next-line react-hooks/exhaustive-deps
-  const onLoadMoreDebounced = useMemo(() => debounce(onLoadMore, 1000, true, false), [onLoadMore, items]);
-
-  useEffect(() => {
-    if (!items || items.length < preloadBackwards) {
-      onLoadMoreDebounced({ direction: LoadMoreDirection.Backwards });
-    }
-  }, [items, onLoadMoreDebounced, preloadBackwards]);
-
-  const handleScroll = useCallback((e: UIEvent<HTMLDivElement>) => {
-    if (onScroll) {
-      onScroll(e);
-    }
-    const container = e.target as HTMLElement;
-    const anchor = container.firstElementChild;
-    if (!anchor) {
-      return;
-    }
-
-    const { scrollTop, scrollHeight, offsetHeight } = container;
-    const newAnchorTop = anchor.getBoundingClientRect().top;
-    const isNearBottom = scrollHeight - (scrollTop + offsetHeight) <= sensitiveArea;
-    const isMovingDown = typeof anchorTopRef.current === 'number' && newAnchorTop < anchorTopRef.current;
-
-    if (isNearBottom && isMovingDown) {
-      onLoadMoreDebounced({ direction: LoadMoreDirection.Backwards });
-    }
-
-    anchorTopRef.current = newAnchorTop;
-  }, [onLoadMoreDebounced, onScroll, sensitiveArea]);
-
-  return (
-    <div ref={containerRef} className={className} onScroll={handleScroll}>
-      {children}
-    </div>
-  );
-};
-
-export default SimpleInfiniteScroll;