From fd15fc39849ccecb562f8488e987a1fbb95f52eb Mon Sep 17 00:00:00 2001
From: Travis Ralston <travpc@gmail.com>
Date: Thu, 23 Jul 2020 22:24:07 -0600
Subject: [PATCH] Ensure message previews update when needed

In 9969b01c5f5270aec26eae32732c07b42d42ad9a we stopped updating the sublist whenever we felt like it, which indirectly froze message previews for room tiles (badges, unread state, etc were unaffected because that is managed by a different store). To fix this, we simply have to listen for changes and perform an update.
---
 src/components/views/rooms/RoomTile.tsx     | 10 +++++++++-
 src/stores/room-list/MessagePreviewStore.ts |  6 ++++++
 2 files changed, 15 insertions(+), 1 deletion(-)

diff --git a/src/components/views/rooms/RoomTile.tsx b/src/components/views/rooms/RoomTile.tsx
index 3265316c67..2c4d1d0163 100644
--- a/src/components/views/rooms/RoomTile.tsx
+++ b/src/components/views/rooms/RoomTile.tsx
@@ -35,7 +35,7 @@ import {
     MenuItem,
 } from "../../structures/ContextMenu";
 import { DefaultTagID, TagID } from "../../../stores/room-list/models";
-import { MessagePreviewStore } from "../../../stores/room-list/MessagePreviewStore";
+import { MessagePreviewStore, ROOM_PREVIEW_CHANGED } from "../../../stores/room-list/MessagePreviewStore";
 import DecoratedRoomAvatar from "../avatars/DecoratedRoomAvatar";
 import {
     getRoomNotifsState,
@@ -128,6 +128,7 @@ export default class RoomTile extends React.Component<IProps, IState> {
 
         ActiveRoomObserver.addListener(this.props.room.roomId, this.onActiveRoomUpdate);
         this.dispatcherRef = defaultDispatcher.register(this.onAction);
+        MessagePreviewStore.instance.on(ROOM_PREVIEW_CHANGED, this.onRoomPreviewChanged);
     }
 
     private get showContextMenu(): boolean {
@@ -150,6 +151,7 @@ export default class RoomTile extends React.Component<IProps, IState> {
             ActiveRoomObserver.removeListener(this.props.room.roomId, this.onActiveRoomUpdate);
         }
         defaultDispatcher.unregister(this.dispatcherRef);
+        MessagePreviewStore.instance.off(ROOM_PREVIEW_CHANGED, this.onRoomPreviewChanged);
     }
 
     private onAction = (payload: ActionPayload) => {
@@ -160,6 +162,12 @@ export default class RoomTile extends React.Component<IProps, IState> {
         }
     };
 
+    private onRoomPreviewChanged = (room: Room) => {
+        if (this.props.room && room.roomId === this.props.room.roomId) {
+            this.forceUpdate(); // we don't have any state to set, so just complain that we need an update
+        }
+    };
+
     private scrollIntoView = () => {
         if (!this.roomTileRef.current) return;
         this.roomTileRef.current.scrollIntoView({
diff --git a/src/stores/room-list/MessagePreviewStore.ts b/src/stores/room-list/MessagePreviewStore.ts
index f61488c3bb..2803f0a23e 100644
--- a/src/stores/room-list/MessagePreviewStore.ts
+++ b/src/stores/room-list/MessagePreviewStore.ts
@@ -28,6 +28,10 @@ import { StickerEventPreview } from "./previews/StickerEventPreview";
 import { ReactionEventPreview } from "./previews/ReactionEventPreview";
 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 PREVIEWS = {
     'm.room.message': {
         isState: false,
@@ -146,6 +150,7 @@ 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);
             }
             return; // we're done
         }
@@ -153,6 +158,7 @@ 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);
     }
 
     protected async onAction(payload: ActionPayload) {