Put always-on-screen widgets in top left

always-on-screen widgets now appear in the top-left where the
call preview normally is if you're not in the room that they're in.

Fixes https://github.com/vector-im/riot-web/issues/7007
Based off https://github.com/matrix-org/matrix-react-sdk/pull/2053

src/components/views/elements/PersistentApp.js

@@ -0,0 +1,88 @@
+/*
+Copyright 2018 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.
+*/
+
+import React from 'react';
+import PropTypes from 'prop-types';
+import RoomViewStore from '../../../stores/RoomViewStore';
+import ActiveWidgetStore from '../../../stores/ActiveWidgetStore';
+import WidgetUtils from '../../../utils/WidgetUtils';
+import sdk from '../../../index';
+import MatrixClientPeg from '../../../MatrixClientPeg';
+
+module.exports = React.createClass({
+    displayName: 'PersistentApp',
+
+    getInitialState: function() {
+        return {
+            roomId: RoomViewStore.getRoomId(),
+        };
+    },
+
+    componentWillMount: function() {
+        this._roomStoreToken = RoomViewStore.addListener(this._onRoomViewStoreUpdate);
+    },
+
+    componentWillUnmount: function() {
+        if (this._roomStoreToken) {
+            this._roomStoreToken.remove();
+        }
+    },
+
+    _onRoomViewStoreUpdate: function(payload) {
+        if (RoomViewStore.getRoomId() === this.state.roomId) return;
+        this.setState({
+            roomId: RoomViewStore.getRoomId(),
+        });
+    },
+
+    render: function() {
+        if (ActiveWidgetStore.getPersistentWidgetId()) {
+            const persistentWidgetInRoomId = ActiveWidgetStore.getRoomId(ActiveWidgetStore.getPersistentWidgetId());
+            if (this.state.roomId !== persistentWidgetInRoomId) {
+                const persistentWidgetInRoom = MatrixClientPeg.get().getRoom(persistentWidgetInRoomId);
+                // get the widget data
+                const appEvent = WidgetUtils.getRoomWidgets(persistentWidgetInRoom).find((ev) => {
+                    return ev.getStateKey() === ActiveWidgetStore.getPersistentWidgetId();
+                });
+                const app = WidgetUtils.makeAppConfig(
+                    appEvent.getStateKey(), appEvent.getContent(), appEvent.sender, persistentWidgetInRoomId,
+                );
+                const capWhitelist = WidgetUtils.getCapWhitelistForAppTypeInRoomId(app.type, persistentWidgetInRoomId);
+                const AppTile = sdk.getComponent('elements.AppTile');
+                return <AppTile
+                    key={app.id}
+                    id={app.id}
+                    url={app.url}
+                    name={app.name}
+                    type={app.type}
+                    fullWidth={true}
+                    room={persistentWidgetInRoom}
+                    userId={MatrixClientPeg.get().credentials.userId}
+                    show={true}
+                    creatorUserId={app.creatorUserId}
+                    widgetPageTitle={(app.data && app.data.title) ? app.data.title : ''}
+                    waitForIframeLoad={app.waitForIframeLoad}
+                    whitelistCapabilities={capWhitelist}
+                    showDelete={false}
+                    showMinimise={false}
+                    miniMode={true}
+                />;
+            }
+        }
+        return null;
+    },
+});
+