add scroll top container component

src/app/components/scroll-top-container/ScrollTopContainer.tsx

@@ -0,0 +1,35 @@
+import React, { RefObject, useCallback, useState } from 'react';
+import { Box, as } from 'folds';
+import classNames from 'classnames';
+import * as css from './style.css';
+import {
+  getIntersectionObserverEntry,
+  useIntersectionObserver,
+} from '../../hooks/useIntersectionObserver';
+
+export const ScrollTopContainer = as<
+  'div',
+  {
+    scrollRef?: RefObject<HTMLElement>;
+    anchorRef: RefObject<HTMLElement>;
+  }
+>(({ className, scrollRef, anchorRef, ...props }, ref) => {
+  const [onTop, setOnTop] = useState(true);
+
+  useIntersectionObserver(
+    useCallback(
+      (intersectionEntries) => {
+        if (!anchorRef.current) return;
+        const entry = getIntersectionObserverEntry(anchorRef.current, intersectionEntries);
+        if (entry) setOnTop(entry.isIntersecting);
+      },
+      [anchorRef]
+    ),
+    useCallback(() => ({ root: scrollRef?.current }), [scrollRef]),
+    useCallback(() => anchorRef.current, [anchorRef])
+  );
+
+  if (onTop) return null;
+
+  return <Box className={classNames(css.ScrollTopContainer, className)} {...props} ref={ref} />;
+});

src/app/components/scroll-top-container/index.ts

@@ -0,0 +1 @@
+export * from './ScrollTopContainer';

src/app/components/scroll-top-container/style.css.ts

@@ -0,0 +1,20 @@
+import { keyframes, style } from '@vanilla-extract/css';
+import { config } from 'folds';
+
+const ScrollContainerAnime = keyframes({
+  '0%': {
+    transform: `translate(-50%, -100%) scale(0)`,
+  },
+  '100%': {
+    transform: `translate(-50%, 0) scale(1)`,
+  },
+});
+
+export const ScrollTopContainer = style({
+  position: 'absolute',
+  top: config.space.S200,
+  left: '50%',
+  transform: 'translateX(-50%)',
+  zIndex: 1,
+  animation: `${ScrollContainerAnime} 100ms`,
+});

src/app/organisms/room/MembersDrawer.tsx

@@ -39,10 +39,6 @@ import { openInviteUser, openProfileViewer } from '../../../client/action/naviga
 import * as css from './MembersDrawer.css';
 import { useRoomMembers } from '../../hooks/useRoomMembers';
 import { useMatrixClient } from '../../hooks/useMatrixClient';
-import {
-  getIntersectionObserverEntry,
-  useIntersectionObserver,
-} from '../../hooks/useIntersectionObserver';
 import { Membership } from '../../../types/matrix/room';
 import { UseStateProvider } from '../../components/UseStateProvider';
 import {
@@ -60,6 +56,7 @@ import { getMxIdLocalPart } from '../../utils/matrix';
 import { useSetting } from '../../state/hooks/settings';
 import { settingsAtom } from '../../state/settings';
 import { millify } from '../../plugins/millify';
+import { ScrollTopContainer } from '../../components/scroll-top-container';
 
 export const MembershipFilters = {
   filterJoined: (m: RoomMember) => m.membership === Membership.Join,
@@ -190,8 +187,6 @@ export function MembersDrawer({ room }: MembersDrawerProps) {
   const membershipFilter = membershipFilterMenu[membershipFilterIndex] ?? membershipFilterMenu[0];
   const sortFilter = sortFilterMenu[sortFilterIndex] ?? sortFilterMenu[0];
 
-  const [onTop, setOnTop] = useState(true);
-
   const typingMembers = useAtomValue(
     useMemo(() => selectRoomTypingMembersAtom(room.roomId, roomIdToTypingMembersAtom), [room])
   );
@@ -235,16 +230,6 @@ export function MembersDrawer({ room }: MembersDrawerProps) {
     overscan: 10,
   });
 
-  useIntersectionObserver(
-    useCallback((intersectionEntries) => {
-      if (!scrollTopAnchorRef.current) return;
-      const entry = getIntersectionObserverEntry(scrollTopAnchorRef.current, intersectionEntries);
-      if (entry) setOnTop(entry.isIntersecting);
-    }, []),
-    useCallback(() => ({ root: scrollRef.current }), []),
-    useCallback(() => scrollTopAnchorRef.current, [])
-  );
-
   const handleSearchChange: ChangeEventHandler<HTMLInputElement> = useDebounce(
     useCallback(
       (evt) => {
@@ -446,20 +431,18 @@ export function MembersDrawer({ room }: MembersDrawerProps) {
               </Box>
             </Box>
 
-            {!onTop && (
-              <Box className={css.DrawerScrollTop}>
-                <IconButton
-                  onClick={() => virtualizer.scrollToOffset(0)}
-                  variant="Surface"
-                  radii="Pill"
-                  outlined
-                  size="300"
-                  aria-label="Scroll to Top"
-                >
-                  <Icon src={Icons.ChevronTop} size="300" />
-                </IconButton>
-              </Box>
-            )}
+            <ScrollTopContainer scrollRef={scrollRef} anchorRef={scrollTopAnchorRef}>
+              <IconButton
+                onClick={() => virtualizer.scrollToOffset(0)}
+                variant="Surface"
+                radii="Pill"
+                outlined
+                size="300"
+                aria-label="Scroll to Top"
+              >
+                <Icon src={Icons.ChevronTop} size="300" />
+              </IconButton>
+            </ScrollTopContainer>
 
             {!fetchingMembers && !result && processMembers.length === 0 && (
               <Text style={{ padding: config.space.S300 }} align="Center">

src/app/pages/client/inbox/Notifications.tsx

@@ -1,5 +1,17 @@
 import React, { useCallback, useEffect, useRef, useState } from 'react';
-import { Avatar, Box, Chip, Header, Icon, Icons, Scroll, Text, config, toRem } from 'folds';
+import {
+  Avatar,
+  Box,
+  Chip,
+  Header,
+  Icon,
+  IconButton,
+  Icons,
+  Scroll,
+  Text,
+  config,
+  toRem,
+} from 'folds';
 import { useSearchParams } from 'react-router-dom';
 import { INotification, INotificationsResponse, Method } from 'matrix-js-sdk';
 import { useVirtualizer } from '@tanstack/react-virtual';
@@ -12,6 +24,7 @@ import { SequenceCard } from '../../../components/sequence-card';
 import { RoomAvatar } from '../../../components/room-avatar';
 import { nameInitials } from '../../../utils/common';
 import { getRoomAvatarUrl } from '../../../utils/room';
+import { ScrollTopContainer } from '../../../components/scroll-top-container';
 
 type RoomNotificationsGroup = {
   roomId: string;
@@ -94,6 +107,7 @@ export function Notifications() {
   const [searchParams, setSearchParams] = useSearchParams();
   const notificationsSearchParams = getNotificationsSearchParams(searchParams);
   const scrollRef = useRef<HTMLDivElement>(null);
+  const scrollTopAnchorRef = useRef<HTMLDivElement>(null);
 
   const onlyHighlight = notificationsSearchParams.only === 'highlight';
   const setOnlyHighlighted = (highlight: boolean) => {
@@ -146,12 +160,12 @@ export function Notifications() {
         </Box>
       </PageHeader>
 
-      <Box grow="Yes">
+      <Box style={{ position: 'relative' }} grow="Yes">
         <Scroll ref={scrollRef} hideTrack visibility="Hover">
           <PageContent>
             <PageContentCenter>
               <Box direction="Column" gap="200">
-                <Box direction="Column" gap="100">
+                <Box ref={scrollTopAnchorRef} direction="Column" gap="100">
                   <span data-spacing-node />
                   <Text size="L400">Filter</Text>
                   <Box gap="200">
@@ -187,6 +201,18 @@ export function Notifications() {
                     </Chip>
                   </Box>
                 </Box>
+                <ScrollTopContainer scrollRef={scrollRef} anchorRef={scrollTopAnchorRef}>
+                  <IconButton
+                    onClick={() => virtualizer.scrollToOffset(0)}
+                    variant="Surface"
+                    radii="Pill"
+                    outlined
+                    size="300"
+                    aria-label="Scroll to Top"
+                  >
+                    <Icon src={Icons.ChevronTop} size="300" />
+                  </IconButton>
+                </ScrollTopContainer>
                 <div
                   style={{
                     position: 'relative',
@@ -198,6 +224,8 @@ export function Notifications() {
                     if (!group) return null;
                     const groupRoom = mx.getRoom(group.roomId);
                     if (!groupRoom) return null;
+                    // TODO: instead of null return empty div to measure element
+                    // extract scroll to top floating btn component from MemberDrawer component
 
                     return (
                       <Box