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Fix timeline items being rerendered constantly #1055

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Merged
7w1 merged 1 commit into from
Jul 11, 2026
+131 −94
Merged

Fix timeline items being rerendered constantly #1055

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5 changes: 5 additions & 0 deletions .changeset/stop-silly-rerenders.md
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Original file line number Diff line number Diff line change
@@ -0,0 +1,5 @@
---
default: patch
---

Fixed the entire timeline being rerendered every time you scroll :P
220 changes: 126 additions & 94 deletions src/app/features/room/RoomTimeline.tsx
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Original file line number Diff line number Diff line change
Expand Up @@ -7,6 +7,7 @@ import {
useMemo,
useRef,
useState,
memo,
} from 'react';
import type { Editor } from 'slate';
import { useAtomValue, useSetAtom } from 'jotai';
Expand Down Expand Up @@ -48,7 +49,7 @@ import { useSpaceOptionally } from '$hooks/useSpace';
import { useMediaAuthentication } from '$hooks/useMediaAuthentication';
import { useIgnoredUsers } from '$hooks/useIgnoredUsers';
import { useImagePackRooms } from '$hooks/useImagePackRooms';
import { settingsAtom, MessageLayout } from '$state/settings';
import { settingsAtom, MessageLayout, type MessageSpacing } from '$state/settings';
import { useHiddenEventSettings, useSetting } from '$state/hooks/settings';
import { nicknamesAtom } from '$state/nicknames';
import { useRoomAbbreviationsContext } from '$hooks/useRoomAbbreviations';
Expand Down Expand Up @@ -103,6 +104,116 @@ const getDayDividerText = (ts: number) => {
return timeDayMonthYear(ts);
};

const MemoizedTimelineItem = memo(function MemoizedTimelineItem({
eventData,
index,
showLoadingPlaceholders,
canPaginateBack,
backPaginationJSX,
room,
messageLayout,
messageSpacing,
renderMatrixEvent,
}: {
eventData: ProcessedEvent | undefined;
index: number;
showLoadingPlaceholders: boolean;
canPaginateBack: boolean;
backPaginationJSX: ReactNode | undefined;
room: Room;
messageLayout: MessageLayout;
messageSpacing: MessageSpacing;
renderMatrixEvent: ReturnType<typeof useTimelineEventRenderer>;
}) {
if (showLoadingPlaceholders) {
return (
<MessageBase key={`placeholder-${index}`}>
{messageLayout === MessageLayout.Compact ? <CompactPlaceholder /> : <DefaultPlaceholder />}
</MessageBase>
);
}

if (!eventData) {
if (index === 0 && !canPaginateBack) {
return (
<Fragment key="intro-and-first">
{backPaginationJSX}
<div
style={{
padding: `${config.space.S700} ${config.space.S400} ${config.space.S600} ${messageLayout === MessageLayout.Compact ? config.space.S400 : toRem(64)}`,
}}
>
<RoomIntro room={room} />
</div>
</Fragment>
);
}
if (index === 0) return <Fragment key="first">{backPaginationJSX}</Fragment>;
return <Fragment key={index} />;
}

const renderedEvent = renderMatrixEvent(
eventData.mEvent.getType(),
typeof eventData.mEvent.getStateKey() === 'string',
eventData.id,
eventData.mEvent,
eventData.itemIndex,
eventData.timelineSet,
eventData.collapsed
);

const showDividers = renderedEvent !== null;

const dividers = showDividers ? (
<>
{eventData.willRenderDayDivider && (
<MessageBase space={messageSpacing}>
<TimelineDivider variant="Surface">
<Badge as="span" size="500" variant="Secondary" fill="None" radii="300">
<Text size="L400">{getDayDividerText(eventData.mEvent.getTs())}</Text>
</Badge>
</TimelineDivider>
</MessageBase>
)}
{eventData.willRenderNewDivider && (
<MessageBase space={messageSpacing}>
<TimelineDivider style={{ color: color.Success.Main }} variant="Inherit">
<Badge as="span" size="500" variant="Success" fill="Solid" radii="300">
<Text size="L400">New Messages</Text>
</Badge>
</TimelineDivider>
</MessageBase>
)}
</>
) : null;

if (index === 0) {
return (
<Fragment key="first-item-block">
{!canPaginateBack && (
<div
style={{
padding: `${config.space.S700} ${config.space.S400} ${config.space.S600} ${messageLayout === MessageLayout.Compact ? config.space.S400 : toRem(64)}`,
}}
>
<RoomIntro room={room} />
</div>
)}
{backPaginationJSX}
{dividers}
{renderedEvent}
</Fragment>
);
}

return (
<Fragment key={eventData.id}>
{dividers}
{renderedEvent}
</Fragment>
);
});

export type RoomTimelineProps = {
room: Room;
eventId?: string;
Expand Down Expand Up @@ -903,99 +1014,20 @@ export function RoomTimeline({
}}
onScroll={handleVListScroll}
>
{(eventData, index) => {
if (showLoadingPlaceholders) {
return (
<MessageBase key={`placeholder-${index}`}>
{messageLayout === MessageLayout.Compact ? (
<CompactPlaceholder />
) : (
<DefaultPlaceholder />
)}
</MessageBase>
);
}

if (!eventData) {
if (index === 0 && !timelineSync.canPaginateBack) {
return (
<Fragment key="intro-and-first">
{backPaginationJSX}
<div
style={{
padding: `${config.space.S700} ${config.space.S400} ${config.space.S600} ${messageLayout === MessageLayout.Compact ? config.space.S400 : toRem(64)}`,
}}
>
<RoomIntro room={room} />
</div>
</Fragment>
);
}
if (index === 0) return <Fragment key="first">{backPaginationJSX}</Fragment>;
return <Fragment key={index} />;
}

const renderedEvent = renderMatrixEvent(
eventData.mEvent.getType(),
typeof eventData.mEvent.getStateKey() === 'string',
eventData.id,
eventData.mEvent,
eventData.itemIndex,
eventData.timelineSet,
eventData.collapsed
);

const showDividers = renderedEvent !== null;

const dividers = showDividers ? (
<>
{eventData.willRenderDayDivider && (
<MessageBase space={messageSpacing}>
<TimelineDivider variant="Surface">
<Badge as="span" size="500" variant="Secondary" fill="None" radii="300">
<Text size="L400">{getDayDividerText(eventData.mEvent.getTs())}</Text>
</Badge>
</TimelineDivider>
</MessageBase>
)}
{eventData.willRenderNewDivider && (
<MessageBase space={messageSpacing}>
<TimelineDivider style={{ color: color.Success.Main }} variant="Inherit">
<Badge as="span" size="500" variant="Success" fill="Solid" radii="300">
<Text size="L400">New Messages</Text>
</Badge>
</TimelineDivider>
</MessageBase>
)}
</>
) : null;

if (index === 0) {
return (
<Fragment key="first-item-block">
{!timelineSync.canPaginateBack && (
<div
style={{
padding: `${config.space.S700} ${config.space.S400} ${config.space.S600} ${messageLayout === MessageLayout.Compact ? config.space.S400 : toRem(64)}`,
}}
>
<RoomIntro room={room} />
</div>
)}
{backPaginationJSX}
{dividers}
{renderedEvent}
</Fragment>
);
}

return (
<Fragment key={eventData.id}>
{dividers}
{renderedEvent}
</Fragment>
);
}}
{(eventData, index) => (
<MemoizedTimelineItem
key={eventData ? eventData.id : `placeholder-${index}`}
eventData={eventData}
index={index}
showLoadingPlaceholders={showLoadingPlaceholders}
canPaginateBack={timelineSync.canPaginateBack}
backPaginationJSX={backPaginationJSX}
room={room}
messageLayout={messageLayout}
messageSpacing={messageSpacing}
renderMatrixEvent={renderMatrixEvent}
/>
)}
</VList>
</div>

Expand Down
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