Only display rooms in the sliding window

Buggy: some rooms disappear entirely for some reason.

src/domain/session/SessionViewModel.js

@@ -41,6 +41,7 @@ export class SessionViewModel extends ViewModel {
             invites: this._sessionContainer.session.invites,
             rooms: this._sessionContainer.session.rooms,
             compareFn: this._sessionContainer.sync.compare.bind(this._sessionContainer.sync),
+            includeRoomFn: this._sessionContainer.sync.includeRoom.bind(this._sessionContainer.sync),
         })));
         this._settingsViewModel = null;
         this._roomViewModelObservable = null;

src/domain/session/leftpanel/LeftPanelViewModel.js

@@ -19,6 +19,7 @@ import {ViewModel} from "../../ViewModel.js";
 import {RoomTileViewModel} from "./RoomTileViewModel.js";
 import {InviteTileViewModel} from "./InviteTileViewModel.js";
 import {RoomFilter} from "./RoomFilter.js";
+import {FilteredMap} from "../../../observable/map/FilteredMap.js";
 import {ApplyMap} from "../../../observable/map/ApplyMap.js";
 import {addPanelIfNeeded} from "../../navigation/index.js";
 import { PlaceholderRoomTileViewModel } from "./PlaceholderRoomTileViewModel.js";
@@ -26,9 +27,13 @@ import { PlaceholderRoomTileViewModel } from "./PlaceholderRoomTileViewModel.js"
 export class LeftPanelViewModel extends ViewModel {
     constructor(options) {
         super(options);
-        const {rooms, invites, compareFn} = options;
+        const {rooms, invites, compareFn, includeRoomFn} = options;
         this._tileViewModelsMap = this._mapTileViewModels(rooms, invites);
-        this._tileViewModelsFilterMap = new ApplyMap(this._tileViewModelsMap);
+        this._tileViewModelsSlidingWindow = new FilteredMap(this._tileViewModelsMap, (r, roomId) => {
+            const include = includeRoomFn(roomId);
+            return include;
+        });
+        this._tileViewModelsFilterMap = new ApplyMap(this._tileViewModelsSlidingWindow);
         this._tileViewModels = this._tileViewModelsFilterMap.sortValues((a, b) => a.compare(b));
         this._currentTileVM = null;
         this._setupNavigation();

src/matrix/Sync3.ts

@@ -128,7 +128,7 @@ export class Sync3 {
         this.status = new ObservableValue(SyncStatus.Stopped);
         this.error = null;
         // Hydrogen only has 1 list currently (no DM section) so we only need 1 range
-        this.ranges = [[0, 49]];
+        this.ranges = [[0, 4]];
         this.roomIndexToRoomId = {};
         this.roomIdToRoomIndex = {};
     }
@@ -155,7 +155,11 @@ export class Sync3 {
         }
     }
 
-    compare(roomIdA: string, roomIdB: string) {
+    includeRoom(roomId: string): boolean {
+        return this.roomIdToRoomIndex[roomId] !== undefined;
+    }
+
+    compare(roomIdA: string, roomIdB: string): number {
         if (roomIdA === roomIdB) {
             return 0;
         }
@@ -325,6 +329,9 @@ export class Sync3 {
             await syncTxn.complete(log);
 
             // Sync v3 specific
+            // work out which rooms are no longer being tracked (they'll be deleted in indexToRoom but exist in this.roomIndexToRoomId)
+            // and then force update those rooms to force the FilteredMap to re-evalute to remove them from the left panel room list
+            const deletedRoomIDs = deletedElements(Object.values(this.roomIndexToRoomId), Object.values(indexToRoom));
             // atomically move all the rooms to their new positions
             // We need to do this BEFORE calling afterSync as that causes the room list to be sorted
             // which eventually causes Sync3.compare to be called, so we need it to be using the latest
@@ -335,6 +342,17 @@ export class Sync3 {
                 const index = Number(indexStr);
                 this.roomIdToRoomIndex[indexToRoom[index]] = index;
             });
+            if (deletedRoomIDs.length > 0) {
+                console.log("DELETED ", deletedRoomIDs);
+            }
+
+            // now force update rooms which fell off the sliding window
+            deletedRoomIDs.forEach((roomId) => {
+                let room = this.session.rooms.get(roomId);
+                room.forceRefresh();
+            })
+
+            // END sync v3 specific
 
             // update in-memory structs
             // this.session.afterSync(); // ???
@@ -528,6 +546,19 @@ const indexInRange = (ranges: number[][], i: number) => {
     return isInRange;
 };
 
+// returns the elements which exist in old but not in new
+const deletedElements = (oldArr: string[], newArr: string[]): string[] => {
+    let set = {};
+    oldArr.forEach((k) => {
+        set[k] = true;
+    });
+    newArr.forEach((k) => {
+        delete set[k];
+    })
+
+    return Object.keys(set);
+}
+
 export function tests() {
     return {
         "processSyncOps": assert => {

src/matrix/room/BaseRoom.js

@@ -76,6 +76,11 @@ export class BaseRoom extends EventEmitter {
         return retryTimelineEntries;
     }
 
+    // Forcibly update this room in collections
+    forceRefresh() {
+        this._emitUpdate();
+    }
+
     /**
      * Used for retrying decryption from other sources than sync, like key backup.
      * @internal

src/observable/list/SortedMapList.js

@@ -63,7 +63,20 @@ export class SortedMapList extends BaseObservableList {
 
     onRemove(key, value) {
         const pair = {key, value};
-        const idx = sortedIndex(this._sortedPairs, pair, this._comparator);
+        // Don't call sortedIndex as it does a binary search for the removed item.
+        // Whilst that is faster than the O(n) search we're doing here, it's not valid to compare
+        // removed items as the system may have no ability to compare them at this point.
+        let idx = -1;
+        for (let i = 0; i < this._sortedPairs.length; i++) {
+            if (this._sortedPairs[i].key === key) {
+                idx = i;
+                break;
+            }
+        }
+        if (idx === -1) {
+            return;
+        }
+        console.log("removing ", key, idx, value);
         // assert key === this._sortedPairs[idx].key;
         this._sortedPairs.splice(idx, 1);
         this.emitRemove(idx, value);