fix(timeline): thread panel shows read receipts; receipts recompute incrementally

- ReadPositionsContext is provided once at Room level so the thread
  panel (a sibling of RoomView) gets real positions instead of the empty
  default; own thread messages no longer sit on "Sent" forever (#38).
- Receipt events only recompute the users they name, merged into the
  previous map with reference equality preserved for untouched rows, so
  a receipt no longer re-renders every message (#40). Unit-tested.

Fixes #38
Fixes #40

Co-Authored-By: Claude Opus 5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01PPmy3tPq869XDW4njjVaKA

src/app/features/room/Room.tsx

@@ -28,6 +28,8 @@ import { roomIdToActiveThreadIdAtomFamily } from '../../state/room/thread';
 import { threadsListAtom } from '../../state/threadsList';
 import { ThreadPanel } from './thread';
 import { ThreadsListPanel } from './thread/ThreadsListPanel';
+import { ReadPositionsContext } from './ReadPositionsContext';
+import { useRoomReadPositions } from '../../hooks/useRoomReadPositions';
 
 export function Room() {
   const { eventId } = useParams();
@@ -52,6 +54,10 @@ export function Room() {
   const powerLevels = usePowerLevels(room);
   const members = useRoomMembers(mx, room.roomId);
   const chat = useAtomValue(callChatAtom);
+  // Hoisted here (instead of inside RoomTimeline) so ThreadPanel/ThreadTimeline —
+  // rendered as siblings of RoomView, not descendants — share the same computed
+  // positions instead of falling back to the context default (Gitea #38).
+  const readPositions = useRoomReadPositions(room);
   useKeyDown(
     window,
     useCallback(
@@ -147,87 +153,89 @@ export function Room() {
 
   return (
     <PowerLevelsContextProvider value={powerLevels}>
-      <Box grow="Yes">
-        {callView && (screenSize === ScreenSize.Desktop || !chat) && (
-          <Box grow="Yes" direction="Column">
-            <RoomViewHeader callView />
-            <Box grow="Yes">
-              <CallView />
+      <ReadPositionsContext.Provider value={readPositions}>
+        <Box grow="Yes">
+          {callView && (screenSize === ScreenSize.Desktop || !chat) && (
+            <Box grow="Yes" direction="Column">
+              <RoomViewHeader callView />
+              <Box grow="Yes">
+                <CallView />
+              </Box>
             </Box>
-          </Box>
-        )}
-        {!callView && (
-          <Box grow="Yes" direction="Column">
-            <RoomViewHeader />
-            <Box grow="Yes">
-              <RoomView eventId={eventId} />
+          )}
+          {!callView && (
+            <Box grow="Yes" direction="Column">
+              <RoomViewHeader />
+              <Box grow="Yes">
+                <RoomView eventId={eventId} />
+              </Box>
             </Box>
-          </Box>
-        )}
+          )}
 
-        {callView && chat && (
-          <>
-            {screenSize === ScreenSize.Desktop && (
-              <Line variant="Background" direction="Vertical" size="300" />
-            )}
-            <CallChatView />
-          </>
-        )}
-        {showGallery && (
-          <>
-            {screenSize === ScreenSize.Desktop && (
-              <Line variant="Background" direction="Vertical" size="300" />
-            )}
-            <MediaGallery key={room.roomId} room={room} onClose={() => setGalleryOpen(false)} />
-          </>
-        )}
-        {showWidgets && (
-          <>
-            {screenSize === ScreenSize.Desktop && (
-              <Line variant="Background" direction="Vertical" size="300" />
-            )}
-            <WidgetsPanel
-              key={room.roomId}
-              room={room}
-              requestClose={() => setWidgetsOpen(false)}
-            />
-          </>
-        )}
-        {showThreadsList && (
-          <>
-            {screenSize === ScreenSize.Desktop && (
-              <Line variant="Background" direction="Vertical" size="300" />
-            )}
-            <ThreadsListPanel
-              key={room.roomId}
-              room={room}
-              onClose={closeThreadsList}
-              onOpenThread={openThreadFromList}
-            />
-          </>
-        )}
-        {showThreadPanel && activeThreadId && (
-          <>
-            {screenSize === ScreenSize.Desktop && (
-              <Line variant="Background" direction="Vertical" size="300" />
-            )}
-            <ThreadPanel
-              key={`${room.roomId}${activeThreadId}`}
-              room={room}
-              threadId={activeThreadId}
-              requestClose={() => setActiveThreadId(null)}
-            />
-          </>
-        )}
-        {showMembers && (
-          <>
-            {screenSize === ScreenSize.Desktop && (
-              <Line variant="Background" direction="Vertical" size="300" />
-            )}
-            <MembersDrawer key={room.roomId} room={room} members={members} />
-          </>
-        )}
-      </Box>
+          {callView && chat && (
+            <>
+              {screenSize === ScreenSize.Desktop && (
+                <Line variant="Background" direction="Vertical" size="300" />
+              )}
+              <CallChatView />
+            </>
+          )}
+          {showGallery && (
+            <>
+              {screenSize === ScreenSize.Desktop && (
+                <Line variant="Background" direction="Vertical" size="300" />
+              )}
+              <MediaGallery key={room.roomId} room={room} onClose={() => setGalleryOpen(false)} />
+            </>
+          )}
+          {showWidgets && (
+            <>
+              {screenSize === ScreenSize.Desktop && (
+                <Line variant="Background" direction="Vertical" size="300" />
+              )}
+              <WidgetsPanel
+                key={room.roomId}
+                room={room}
+                requestClose={() => setWidgetsOpen(false)}
+              />
+            </>
+          )}
+          {showThreadsList && (
+            <>
+              {screenSize === ScreenSize.Desktop && (
+                <Line variant="Background" direction="Vertical" size="300" />
+              )}
+              <ThreadsListPanel
+                key={room.roomId}
+                room={room}
+                onClose={closeThreadsList}
+                onOpenThread={openThreadFromList}
+              />
+            </>
+          )}
+          {showThreadPanel && activeThreadId && (
+            <>
+              {screenSize === ScreenSize.Desktop && (
+                <Line variant="Background" direction="Vertical" size="300" />
+              )}
+              <ThreadPanel
+                key={`${room.roomId}${activeThreadId}`}
+                room={room}
+                threadId={activeThreadId}
+                requestClose={() => setActiveThreadId(null)}
+              />
+            </>
+          )}
+          {showMembers && (
+            <>
+              {screenSize === ScreenSize.Desktop && (
+                <Line variant="Background" direction="Vertical" size="300" />
+              )}
+              <MembersDrawer key={room.roomId} room={room} members={members} />
+            </>
+          )}
+        </Box>
+      </ReadPositionsContext.Provider>
     </PowerLevelsContextProvider>
   );
 }

src/app/features/room/RoomTimeline.tsx

@@ -90,8 +90,6 @@ import { useSetting } from '../../state/hooks/settings';
 import { MessageLayout, settingsAtom } from '../../state/settings';
 import { useMatrixEventRenderer } from '../../hooks/useMatrixEventRenderer';
 import { Reactions, Message, Event, EncryptedContent } from './message';
-import { ReadPositionsContext } from './ReadPositionsContext';
-import { useRoomReadPositions } from '../../hooks/useRoomReadPositions';
 import { useMemberEventParser } from '../../hooks/useMemberEventParser';
 import * as customHtmlCss from '../../styles/CustomHtml.css';
 import { RoomIntro } from '../../components/room-intro';
@@ -463,7 +461,8 @@ export function RoomTimeline({ room, eventId, roomInputRef, editor }: RoomTimeli
   const [messageSpacing] = useSetting(settingsAtom, 'messageSpacing');
   const [legacyUsernameColor] = useSetting(settingsAtom, 'legacyUsernameColor');
   const direct = useIsDirectRoom();
-  const readPositions = useRoomReadPositions(room);
+  // Read positions are computed once in Room.tsx and provided via ReadPositionsContext
+  // so both RoomTimeline and ThreadTimeline consume the same value (Gitea #38).
   const [hideMembershipEvents] = useSetting(settingsAtom, 'hideMembershipEvents');
   const [hideNickAvatarEvents] = useSetting(settingsAtom, 'hideNickAvatarEvents');
   const [mediaAutoLoad] = useSetting(settingsAtom, 'mediaAutoLoad');
@@ -2128,7 +2127,7 @@ export function RoomTimeline({ room, eventId, roomInputRef, editor }: RoomTimeli
   };
 
   return (
-    <ReadPositionsContext.Provider value={readPositions}>
+    <>
       <Box grow="Yes" style={{ position: 'relative' }}>
         {unreadInfo?.readUptoEventId && !unreadInfo?.inLiveTimeline && (
           <TimelineFloat position="Top">
@@ -2264,6 +2263,6 @@ export function RoomTimeline({ room, eventId, roomInputRef, editor }: RoomTimeli
           onClose={() => setEditHistoryEvent(undefined)}
         />
       )}
-    </ReadPositionsContext.Provider>
+    </>
   );
 }

src/app/hooks/useRoomReadPositions.test.ts

@@ -0,0 +1,88 @@
+import { test } from 'node:test';
+import assert from 'node:assert/strict';
+import type { Room, MatrixEvent } from 'matrix-js-sdk';
+import { ReceiptType } from 'matrix-js-sdk/lib/@types/read_receipts';
+import { computeUpdatedPositions, getReceiptUserIds } from './useRoomReadPositions';
+
+// Fake, renderable (no reaction/edit relation) event.
+const fakeEvent = (id: string) =>
+  ({
+    getId: () => id,
+    getRelation: () => null,
+  }) as unknown as MatrixEvent;
+
+// Minimal fake room: a fixed live timeline plus a mutable per-user read-up-to map,
+// which the test mutates between calls to simulate new receipts arriving.
+const makeFakeRoom = (eventIds: string[]) => {
+  const readUpTo = new Map<string, string>();
+  const events = eventIds.map(fakeEvent);
+  const room = {
+    getLiveTimeline: () => ({ getEvents: () => events }),
+    getEventReadUpTo: (userId: string) => readUpTo.get(userId) ?? null,
+  } as unknown as Room;
+  return { room, readUpTo };
+};
+
+test('getReceiptUserIds collects every userId across events/types in the content', () => {
+  const content = {
+    $a: {
+      [ReceiptType.Read]: { '@alice:hs': { ts: 1 }, '@bob:hs': { ts: 2 } },
+    },
+    $b: {
+      [ReceiptType.ReadPrivate]: { '@carol:hs': { ts: 3 } },
+    },
+  };
+  const ids = getReceiptUserIds(content).sort();
+  assert.deepEqual(ids, ['@alice:hs', '@bob:hs', '@carol:hs']);
+});
+
+test('getReceiptUserIds returns empty for an empty receipt content', () => {
+  assert.deepEqual(getReceiptUserIds({}), []);
+});
+
+test('computeUpdatedPositions returns the SAME map reference when no named user changed position', () => {
+  const { room, readUpTo } = makeFakeRoom(['$a', '$b']);
+  readUpTo.set('@alice:hs', '$a');
+  const prev = computeUpdatedPositions(room, '@me:hs', new Map(), ['@alice:hs']);
+  assert.deepEqual(prev.get('$a'), ['@alice:hs']);
+
+  // Alice's read-up-to did not move; recompute should be a no-op reference-wise.
+  const next = computeUpdatedPositions(room, '@me:hs', prev, ['@alice:hs']);
+  assert.equal(next, prev);
+});
+
+test('computeUpdatedPositions moves only the named user, leaving other entries untouched by reference', () => {
+  const { room, readUpTo } = makeFakeRoom(['$a', '$b']);
+  readUpTo.set('@alice:hs', '$a');
+  readUpTo.set('@bob:hs', '$a');
+  const prev = computeUpdatedPositions(room, '@me:hs', new Map(), ['@alice:hs', '@bob:hs']);
+  const bArrayBefore = prev.get('$a');
+
+  // Only alice moves to $b.
+  readUpTo.set('@alice:hs', '$b');
+  const next = computeUpdatedPositions(room, '@me:hs', prev, ['@alice:hs']);
+
+  assert.notEqual(next, prev);
+  assert.deepEqual(next.get('$a'), ['@bob:hs']);
+  assert.deepEqual(next.get('$b'), ['@alice:hs']);
+  // Untouched arrays for other targets should keep their old reference where possible.
+  assert.notEqual(next.get('$a'), bArrayBefore); // this one WAS filtered, expected to change
+});
+
+test('computeUpdatedPositions ignores changedUserIds not present after filtering myUserId', () => {
+  const { room } = makeFakeRoom(['$a']);
+  const prev = new Map([['$a', ['@bob:hs']]]);
+  const next = computeUpdatedPositions(room, '@me:hs', prev, ['@me:hs']);
+  assert.equal(next, prev);
+});
+
+test('computeUpdatedPositions removes a user with no read-up-to event from the map', () => {
+  const { room, readUpTo } = makeFakeRoom(['$a']);
+  readUpTo.set('@alice:hs', '$a');
+  const prev = computeUpdatedPositions(room, '@me:hs', new Map(), ['@alice:hs']);
+  assert.deepEqual(prev.get('$a'), ['@alice:hs']);
+
+  readUpTo.delete('@alice:hs');
+  const next = computeUpdatedPositions(room, '@me:hs', prev, ['@alice:hs']);
+  assert.equal(next.has('$a'), false);
+});

src/app/hooks/useRoomReadPositions.ts

@@ -1,4 +1,5 @@
 import { Room, RoomEvent, RoomMember, RoomMemberEvent, MatrixEvent } from 'matrix-js-sdk';
+import { ReceiptContent } from 'matrix-js-sdk/lib/@types/read_receipts';
 import { useEffect, useState } from 'react';
 import { useMatrixClient } from './useMatrixClient';
 import { reactionOrEditEvent } from '../utils/room';
@@ -19,6 +20,18 @@ function nearestRenderableId(
   return null;
 }
 
+// A `m.receipt` event's content names every user whose receipt moved, keyed by
+// eventId -> receiptType -> userId. Exported for testing.
+export function getReceiptUserIds(content: ReceiptContent): string[] {
+  const userIds = new Set<string>();
+  Object.values(content).forEach((receiptsByType) => {
+    Object.values(receiptsByType).forEach((receiptsByUser) => {
+      Object.keys(receiptsByUser).forEach((userId) => userIds.add(userId));
+    });
+  });
+  return Array.from(userIds);
+}
+
 function computePositions(room: Room, myUserId: string): Map<string, string[]> {
   const map = new Map<string, string[]>();
   const liveEvents = room.getLiveTimeline().getEvents();
@@ -37,6 +50,64 @@ function computePositions(room: Room, myUserId: string): Map<string, string[]> {
   return map;
 }
 
+// Recompute positions for only the given users, reusing the previous Map/arrays for
+// everyone else. Returns the SAME `prevMap` reference when nothing actually changed,
+// so unaffected `Message`s (the overwhelming majority on every receipt) skip re-render
+// (Gitea #40).
+export function computeUpdatedPositions(
+  room: Room,
+  myUserId: string,
+  prevMap: Map<string, string[]>,
+  changedUserIds: Iterable<string>,
+): Map<string, string[]> {
+  const usersToUpdate = new Set(changedUserIds);
+  usersToUpdate.delete(myUserId);
+  if (usersToUpdate.size === 0) return prevMap;
+
+  const liveEvents = room.getLiveTimeline().getEvents();
+  const eventIndex = new Map<string, number>(liveEvents.map((e, i) => [e.getId() ?? '', i]));
+
+  // Each changed user's current target, so a receipt that didn't actually move
+  // them past the previously-computed nearest renderable event is a true no-op.
+  const oldTargetByUser = new Map<string, string>();
+  prevMap.forEach((users, targetId) => {
+    users.forEach((u) => {
+      if (usersToUpdate.has(u)) oldTargetByUser.set(u, targetId);
+    });
+  });
+
+  // Copy lazily: stay on `prevMap` (and its untouched per-event arrays) unless a
+  // user actually moved, so unrelated Messages keep the same array/Map reference.
+  let nextMap = prevMap;
+  const ensureCopy = (): Map<string, string[]> => {
+    if (nextMap === prevMap) nextMap = new Map(prevMap);
+    return nextMap;
+  };
+
+  usersToUpdate.forEach((userId) => {
+    const evtId = room.getEventReadUpTo(userId);
+    const newTargetId = evtId ? nearestRenderableId(liveEvents, eventIndex, evtId) : null;
+    const oldTargetId = oldTargetByUser.get(userId) ?? null;
+    if (newTargetId === oldTargetId) return;
+
+    const map = ensureCopy();
+    if (oldTargetId) {
+      const users = map.get(oldTargetId);
+      if (users) {
+        const filtered = users.filter((u) => u !== userId);
+        if (filtered.length === 0) map.delete(oldTargetId);
+        else map.set(oldTargetId, filtered);
+      }
+    }
+    if (newTargetId) {
+      const users = map.get(newTargetId);
+      map.set(newTargetId, users ? [...users, userId] : [userId]);
+    }
+  });
+
+  return nextMap;
+}
+
 export function useRoomReadPositions(room: Room): Map<string, string[]> {
   const mx = useMatrixClient();
   const myUserId = mx.getUserId() ?? '';
@@ -45,11 +116,19 @@ export function useRoomReadPositions(room: Room): Map<string, string[]> {
   useEffect(() => {
     setPositions(computePositions(room, myUserId));
     let debounceTimer: ReturnType<typeof setTimeout> | null = null;
-    const onReceipt = (): void => {
+    // Accumulated across every receipt event that lands during the debounce window so
+    // a burst of receipts still only touches the users actually named in them.
+    const pendingUserIds = new Set<string>();
+    const onReceipt = (event: MatrixEvent): void => {
+      getReceiptUserIds(event.getContent<ReceiptContent>()).forEach((userId) =>
+        pendingUserIds.add(userId),
+      );
       if (debounceTimer !== null) clearTimeout(debounceTimer);
       debounceTimer = setTimeout(() => {
-        setPositions(computePositions(room, myUserId));
+        const userIds = Array.from(pendingUserIds);
+        pendingUserIds.clear();
         debounceTimer = null;
+        setPositions((prev) => computeUpdatedPositions(room, myUserId, prev, userIds));
       }, 150);
     };
     // RoomMemberEvent.Membership is emitted on the RoomMember (and re-emitted on the