Migrate RoomScrollStateStore to TypeScript

src/@types/global.d.ts

@@ -46,6 +46,7 @@ import { VoiceRecordingStore } from "../stores/VoiceRecordingStore";
 import PerformanceMonitor from "../performance";
 import UIStore from "../stores/UIStore";
 import { SetupEncryptionStore } from "../stores/SetupEncryptionStore";
+import { RoomScrollStateStore } from "../stores/RoomScrollStateStore";
 
 declare global {
     interface Window {
@@ -87,6 +88,7 @@ declare global {
         mxPerformanceEntryNames: any;
         mxUIStore: UIStore;
         mxSetupEncryptionStore?: SetupEncryptionStore;
+        mxRoomScrollStateStore?: RoomScrollStateStore;
     }
 
     interface Document {

src/components/structures/RoomView.tsx

@@ -42,7 +42,7 @@ import eventSearch, { searchPagination } from '../../Searching';
 import MainSplit from './MainSplit';
 import RightPanel from './RightPanel';
 import RoomViewStore from '../../stores/RoomViewStore';
-import RoomScrollStateStore from '../../stores/RoomScrollStateStore';
+import RoomScrollStateStore, { ScrollState } from '../../stores/RoomScrollStateStore';
 import WidgetEchoStore from '../../stores/WidgetEchoStore';
 import SettingsStore from "../../settings/SettingsStore";
 import { Layout } from "../../settings/Layout";
@@ -1577,7 +1577,7 @@ export default class RoomView extends React.Component<IProps, IState> {
     // get the current scroll position of the room, so that it can be
     // restored when we switch back to it.
     //
-    private getScrollState() {
+    private getScrollState(): ScrollState {
         const messagePanel = this.messagePanel;
         if (!messagePanel) return null;
 

src/stores/RoomScrollStateStore.js

@@ -1,50 +0,0 @@
-/*
-Copyright 2017 New Vector Ltd
-
-Licensed under the Apache License, Version 2.0 (the "License");
-you may not use this file except in compliance with the License.
-You may obtain a copy of the License at
-
-    http://www.apache.org/licenses/LICENSE-2.0
-
-Unless required by applicable law or agreed to in writing, software
-distributed under the License is distributed on an "AS IS" BASIS,
-WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
-See the License for the specific language governing permissions and
-limitations under the License.
-*/
-
-/**
- * Stores where the user has scrolled to in each room
- */
-class RoomScrollStateStore {
-    constructor() {
-        // A map from room id to scroll state.
-        //
-        // If there is no special scroll state (ie, we are following the live
-        // timeline), the scroll state is null. Otherwise, it is an object with
-        // the following properties:
-        //
-        //    focussedEvent: the ID of the 'focussed' event. Typically this is
-        //        the last event fully visible in the viewport, though if we
-        //        have done an explicit scroll to an explicit event, it will be
-        //        that event.
-        //
-        //    pixelOffset: the number of pixels the window is scrolled down
-        //        from the focussedEvent.
-        this._scrollStateMap = {};
-    }
-
-    getScrollState(roomId) {
-        return this._scrollStateMap[roomId];
-    }
-
-    setScrollState(roomId, scrollState) {
-        this._scrollStateMap[roomId] = scrollState;
-    }
-}
-
-if (global.mx_RoomScrollStateStore === undefined) {
-    global.mx_RoomScrollStateStore = new RoomScrollStateStore();
-}
-export default global.mx_RoomScrollStateStore;

src/stores/RoomScrollStateStore.ts

@@ -0,0 +1,53 @@
+/*
+Copyright 2017 New Vector Ltd
+
+Licensed under the Apache License, Version 2.0 (the "License");
+you may not use this file except in compliance with the License.
+You may obtain a copy of the License at
+
+    http://www.apache.org/licenses/LICENSE-2.0
+
+Unless required by applicable law or agreed to in writing, software
+distributed under the License is distributed on an "AS IS" BASIS,
+WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+See the License for the specific language governing permissions and
+limitations under the License.
+*/
+
+export interface ScrollState {
+    focussedEvent: string;
+    pixelOffset: number;
+}
+
+/**
+ * Stores where the user has scrolled to in each room
+ */
+export class RoomScrollStateStore {
+    // A map from room id to scroll state.
+    //
+    // If there is no special scroll state (ie, we are following the live
+    // timeline), the scroll state is null. Otherwise, it is an object with
+    // the following properties:
+    //
+    //    focussedEvent: the ID of the 'focussed' event. Typically this is
+    //        the last event fully visible in the viewport, though if we
+    //        have done an explicit scroll to an explicit event, it will be
+    //        that event.
+    //
+    //    pixelOffset: the number of pixels the window is scrolled down
+    //        from the focussedEvent.
+    private scrollStateMap = new Map<string, ScrollState>();
+
+    public getScrollState(roomId: string): ScrollState {
+        return this.scrollStateMap.get(roomId);
+    }
+
+    setScrollState(roomId: string, scrollState: ScrollState): void {
+        this.scrollStateMap.set(roomId, scrollState);
+    }
+}
+
+if (window.mxRoomScrollStateStore === undefined) {
+    window.mxRoomScrollStateStore = new RoomScrollStateStore();
+}
+export default window.mxRoomScrollStateStore;