From 729356394e30672832f176a338eade2b1f3de51c Mon Sep 17 00:00:00 2001
From: "J. Ryan Stinnett" <jryans@gmail.com>
Date: Fri, 15 Jan 2021 13:54:38 +0000
Subject: [PATCH] Use room-specific listeners for message previews

This should be a bit faster (since we now only notify one tile instead of all
for each update). It also resolves the max listener warning.

Fixes https://github.com/vector-im/element-web/issues/15121
---
 src/components/views/rooms/RoomTile.tsx     | 22 ++++++++++++++++++---
 src/stores/room-list/MessagePreviewStore.ts | 10 +++++++---
 2 files changed, 26 insertions(+), 6 deletions(-)

diff --git a/src/components/views/rooms/RoomTile.tsx b/src/components/views/rooms/RoomTile.tsx
index a241a13991..2ad10c79c8 100644
--- a/src/components/views/rooms/RoomTile.tsx
+++ b/src/components/views/rooms/RoomTile.tsx
@@ -29,7 +29,7 @@ import ActiveRoomObserver from "../../../ActiveRoomObserver";
 import { _t } from "../../../languageHandler";
 import { ChevronFace, ContextMenuTooltipButton } from "../../structures/ContextMenu";
 import { DefaultTagID, TagID } from "../../../stores/room-list/models";
-import { MessagePreviewStore, ROOM_PREVIEW_CHANGED } from "../../../stores/room-list/MessagePreviewStore";
+import { MessagePreviewStore } from "../../../stores/room-list/MessagePreviewStore";
 import DecoratedRoomAvatar from "../avatars/DecoratedRoomAvatar";
 import { ALL_MESSAGES, ALL_MESSAGES_LOUD, MENTIONS_ONLY, MUTE } from "../../../RoomNotifs";
 import { MatrixClientPeg } from "../../../MatrixClientPeg";
@@ -99,7 +99,10 @@ export default class RoomTile extends React.PureComponent<IProps, IState> {
 
         ActiveRoomObserver.addListener(this.props.room.roomId, this.onActiveRoomUpdate);
         this.dispatcherRef = defaultDispatcher.register(this.onAction);
-        MessagePreviewStore.instance.on(ROOM_PREVIEW_CHANGED, this.onRoomPreviewChanged);
+        MessagePreviewStore.instance.on(
+            MessagePreviewStore.getPreviewChangedEventName(this.props.room),
+            this.onRoomPreviewChanged,
+        );
         this.notificationState = RoomNotificationStateStore.instance.getRoomState(this.props.room);
         this.notificationState.on(NOTIFICATION_STATE_UPDATE, this.onNotificationUpdate);
         this.roomProps = EchoChamber.forRoom(this.props.room);
@@ -128,6 +131,16 @@ export default class RoomTile extends React.PureComponent<IProps, IState> {
         if (prevProps.showMessagePreview !== this.props.showMessagePreview && this.showMessagePreview) {
             this.setState({messagePreview: this.generatePreview()});
         }
+        if (prevProps.room?.roomId !== this.props.room?.roomId) {
+            MessagePreviewStore.instance.off(
+                MessagePreviewStore.getPreviewChangedEventName(prevProps.room),
+                this.onRoomPreviewChanged,
+            );
+            MessagePreviewStore.instance.on(
+                MessagePreviewStore.getPreviewChangedEventName(this.props.room),
+                this.onRoomPreviewChanged,
+            );
+        }
     }
 
     public componentDidMount() {
@@ -140,9 +153,12 @@ export default class RoomTile extends React.PureComponent<IProps, IState> {
     public componentWillUnmount() {
         if (this.props.room) {
             ActiveRoomObserver.removeListener(this.props.room.roomId, this.onActiveRoomUpdate);
+            MessagePreviewStore.instance.off(
+                MessagePreviewStore.getPreviewChangedEventName(this.props.room),
+                this.onRoomPreviewChanged,
+            );
         }
         defaultDispatcher.unregister(this.dispatcherRef);
-        MessagePreviewStore.instance.off(ROOM_PREVIEW_CHANGED, this.onRoomPreviewChanged);
         this.notificationState.off(NOTIFICATION_STATE_UPDATE, this.onNotificationUpdate);
         CommunityPrototypeStore.instance.off(UPDATE_EVENT, this.onCommunityUpdate);
     }
diff --git a/src/stores/room-list/MessagePreviewStore.ts b/src/stores/room-list/MessagePreviewStore.ts
index 2803f0a23e..38e56881cc 100644
--- a/src/stores/room-list/MessagePreviewStore.ts
+++ b/src/stores/room-list/MessagePreviewStore.ts
@@ -30,7 +30,7 @@ import { UPDATE_EVENT } from "../AsyncStore";
 
 // Emitted event for when a room's preview has changed. First argument will the room for which
 // the change happened.
-export const ROOM_PREVIEW_CHANGED = "room_preview_changed";
+const ROOM_PREVIEW_CHANGED = "room_preview_changed";
 
 const PREVIEWS = {
     'm.room.message': {
@@ -84,6 +84,10 @@ export class MessagePreviewStore extends AsyncStoreWithClient<IState> {
         return MessagePreviewStore.internalInstance;
     }
 
+    public static getPreviewChangedEventName(room: Room): string {
+        return `${ROOM_PREVIEW_CHANGED}:${room?.roomId}`;
+    }
+
     /**
      * Gets the pre-translated preview for a given room
      * @param room The room to get the preview for.
@@ -150,7 +154,7 @@ export class MessagePreviewStore extends AsyncStoreWithClient<IState> {
                 // We've muted the underlying Map, so just emit that we've changed.
                 this.previews.set(room.roomId, map);
                 this.emit(UPDATE_EVENT, this);
-                this.emit(ROOM_PREVIEW_CHANGED, room);
+                this.emit(MessagePreviewStore.getPreviewChangedEventName(room), room);
             }
             return; // we're done
         }
@@ -158,7 +162,7 @@ export class MessagePreviewStore extends AsyncStoreWithClient<IState> {
         // At this point, we didn't generate a preview so clear it
         this.previews.set(room.roomId, new Map<TagID|TAG_ANY, string|null>());
         this.emit(UPDATE_EVENT, this);
-        this.emit(ROOM_PREVIEW_CHANGED, room);
+        this.emit(MessagePreviewStore.getPreviewChangedEventName(room), room);
     }
 
     protected async onAction(payload: ActionPayload) {