Fix LHN flickers on web

src/components/LHNOptionsList/LHNOptionsList.tsx

@@ -17,6 +17,7 @@ import usePrevious from '@hooks/usePrevious';
 import useTheme from '@hooks/useTheme';
 import useThemeStyles from '@hooks/useThemeStyles';
 import {isValidDraftComment} from '@libs/DraftCommentUtils';
+import getPlatform from '@libs/getPlatform';
 import {getIOUReportIDOfLastAction, getLastMessageTextForReport} from '@libs/OptionsListUtils';
 import {getOriginalMessage, getSortedReportActionsForDisplay, isMoneyRequestAction} from '@libs/ReportActionsUtils';
 import {canUserPerformWriteAction} from '@libs/ReportUtils';
@@ -31,7 +32,7 @@ import type {LHNOptionsListProps, RenderItemProps} from './types';
 const keyExtractor = (item: string) => `report_${item}`;
 
 function LHNOptionsList({style, contentContainerStyles, data, onSelectRow, optionMode, shouldDisableFocusOptions = false, onFirstItemRendered = () => {}}: LHNOptionsListProps) {
-    const {saveScrollOffset, getScrollOffset} = useContext(ScrollOffsetContext);
+    const {saveScrollOffset, getScrollOffset, saveScrollIndex, getScrollIndex} = useContext(ScrollOffsetContext);
     const flashListRef = useRef<FlashList<string>>(null);
     const route = useRoute();
 
@@ -49,6 +50,9 @@ function LHNOptionsList({style, contentContainerStyles, data, onSelectRow, optio
     const {translate, preferredLocale} = useLocalize();
     const estimatedListSize = useLHNEstimatedListSize();
     const shouldShowEmptyLHN = data.length === 0;
+    const estimatedItemSize = optionMode === CONST.OPTION_MODE.COMPACT ? variables.optionRowHeightCompact : variables.optionRowHeight;
+    const platform = getPlatform();
+    const isWebOrDesktop = platform === CONST.PLATFORM.WEB || platform === CONST.PLATFORM.DESKTOP;
 
     // When the first item renders we want to call the onFirstItemRendered callback.
     // At this point in time we know that the list is actually displaying items.
@@ -237,14 +241,17 @@ function LHNOptionsList({style, contentContainerStyles, data, onSelectRow, optio
                 return;
             }
             saveScrollOffset(route, e.nativeEvent.contentOffset.y);
+            if (isWebOrDesktop) {
+                saveScrollIndex(route, Math.floor(e.nativeEvent.contentOffset.y / estimatedItemSize));
+            }
         },
-        [route, saveScrollOffset],
+        [estimatedItemSize, isWebOrDesktop, route, saveScrollIndex, saveScrollOffset],
     );
 
     const onLayout = useCallback(() => {
         const offset = getScrollOffset(route);
 
-        if (!(offset && flashListRef.current)) {
+        if (!(offset && flashListRef.current) || isWebOrDesktop) {
             return;
         }
 
@@ -255,7 +262,7 @@ function LHNOptionsList({style, contentContainerStyles, data, onSelectRow, optio
             }
             flashListRef.current.scrollToOffset({offset});
         });
-    }, [route, flashListRef, getScrollOffset]);
+    }, [getScrollOffset, route, isWebOrDesktop]);
 
     return (
         <View style={[style ?? styles.flex1, shouldShowEmptyLHN ? styles.emptyLHNWrapper : undefined]}>
@@ -279,12 +286,13 @@ function LHNOptionsList({style, contentContainerStyles, data, onSelectRow, optio
                     testID="lhn-options-list"
                     keyExtractor={keyExtractor}
                     renderItem={renderItem}
-                    estimatedItemSize={optionMode === CONST.OPTION_MODE.COMPACT ? variables.optionRowHeightCompact : variables.optionRowHeight}
+                    estimatedItemSize={estimatedItemSize}
                     extraData={extraData}
                     showsVerticalScrollIndicator={false}
                     onLayout={onLayout}
                     onScroll={onScroll}
                     estimatedListSize={estimatedListSize}
+                    initialScrollIndex={isWebOrDesktop ? getScrollIndex(route) : undefined}
                 />
             )}
         </View>

src/components/ScrollOffsetContextProvider.tsx

@@ -1,13 +1,12 @@
 import type {ParamListBase} from '@react-navigation/native';
 import React, {createContext, useCallback, useEffect, useMemo, useRef} from 'react';
-import {withOnyx} from 'react-native-onyx';
+import {useOnyx} from 'react-native-onyx';
 import usePrevious from '@hooks/usePrevious';
 import type {PlatformStackRouteProp} from '@libs/Navigation/PlatformStackNavigation/types';
 import type {NavigationPartialRoute, State} from '@libs/Navigation/types';
 import NAVIGATORS from '@src/NAVIGATORS';
 import ONYXKEYS from '@src/ONYXKEYS';
 import SCREENS from '@src/SCREENS';
-import type {PriorityMode} from '@src/types/onyx';
 
 type ScrollOffsetContextValue = {
     /** Save scroll offset of flashlist on given screen */
@@ -16,23 +15,26 @@ type ScrollOffsetContextValue = {
     /** Get scroll offset value for given screen */
     getScrollOffset: (route: PlatformStackRouteProp<ParamListBase>) => number | undefined;
 
+    /** Save scroll index of flashlist on given screen */
+    saveScrollIndex: (route: PlatformStackRouteProp<ParamListBase>, scrollIndex: number) => void;
+
+    /** Get scroll index value for given screen */
+    getScrollIndex: (route: PlatformStackRouteProp<ParamListBase>) => number | undefined;
+
     /** Clean scroll offsets of screen that aren't anymore in the state */
     cleanStaleScrollOffsets: (state: State) => void;
 };
 
-type ScrollOffsetContextProviderOnyxProps = {
-    /** The chat priority mode */
-    priorityMode: PriorityMode;
-};
-
-type ScrollOffsetContextProviderProps = ScrollOffsetContextProviderOnyxProps & {
+type ScrollOffsetContextProviderProps = {
     /** Actual content wrapped by this component */
     children: React.ReactNode;
 };
 
 const defaultValue: ScrollOffsetContextValue = {
     saveScrollOffset: () => {},
     getScrollOffset: () => undefined,
+    saveScrollIndex: () => {},
+    getScrollIndex: () => undefined,
     cleanStaleScrollOffsets: () => {},
 };
 
@@ -46,7 +48,8 @@ function getKey(route: PlatformStackRouteProp<ParamListBase> | NavigationPartial
     return `${route.name}-global`;
 }
 
-function ScrollOffsetContextProvider({children, priorityMode}: ScrollOffsetContextProviderProps) {
+function ScrollOffsetContextProvider({children}: ScrollOffsetContextProviderProps) {
+    const [priorityMode] = useOnyx(ONYXKEYS.NVP_PRIORITY_MODE);
     const scrollOffsetsRef = useRef<Record<string, number>>({});
     const previousPriorityMode = usePrevious(priorityMode);
 
@@ -87,23 +90,32 @@ function ScrollOffsetContextProvider({children, priorityMode}: ScrollOffsetConte
         }
     }, []);
 
+    const saveScrollIndex: ScrollOffsetContextValue['saveScrollIndex'] = useCallback((route, scrollIndex) => {
+        scrollOffsetsRef.current[getKey(route)] = scrollIndex;
+    }, []);
+
+    const getScrollIndex: ScrollOffsetContextValue['getScrollIndex'] = useCallback((route) => {
+        if (!scrollOffsetsRef.current) {
+            return;
+        }
+        return scrollOffsetsRef.current[getKey(route)];
+    }, []);
+
     const contextValue = useMemo(
         (): ScrollOffsetContextValue => ({
             saveScrollOffset,
             getScrollOffset,
             cleanStaleScrollOffsets,
+            saveScrollIndex,
+            getScrollIndex,
         }),
-        [saveScrollOffset, getScrollOffset, cleanStaleScrollOffsets],
+        [saveScrollOffset, getScrollOffset, cleanStaleScrollOffsets, saveScrollIndex, getScrollIndex],
     );
 
     return <ScrollOffsetContext.Provider value={contextValue}>{children}</ScrollOffsetContext.Provider>;
 }
 
-export default withOnyx<ScrollOffsetContextProviderProps, ScrollOffsetContextProviderOnyxProps>({
-    priorityMode: {
-        key: ONYXKEYS.NVP_PRIORITY_MODE,
-    },
-})(ScrollOffsetContextProvider);
+export default ScrollOffsetContextProvider;
 
 export {ScrollOffsetContext};