Fix: Video Room Chat Header Button Removed (#11911)

* "@vector-im/compound-design-tokens": "^0.1.0"

* add chat button to room header for video rooms

* cleanup useEffect, comments

* comment

src/components/views/rooms/RoomHeader.tsx

@@ -50,6 +50,7 @@ import { formatCount } from "../../../utils/FormattingUtils";
 import RightPanelStore from "../../../stores/right-panel/RightPanelStore";
 import { Linkify, topicToHtml } from "../../../HtmlUtils";
 import PosthogTrackers from "../../../PosthogTrackers";
+import { VideoRoomChatButton } from "./RoomHeader/VideoRoomChatButton";
 
 /**
  * A helper to transform a notification color to the what the Compound Icon Button
@@ -215,6 +216,9 @@ export default function RoomHeader({
                     </Tooltip>
                 )}
 
+                {/* Renders nothing when room is not a video room */}
+                <VideoRoomChatButton room={room} />
+
                 <Tooltip label={_t("common|threads")}>
                     <IconButton
                         indicator={notificationColorToIndicator(threadNotifications)}

src/components/views/rooms/RoomHeader/VideoRoomChatButton.tsx

@@ -0,0 +1,75 @@
+/*
+Copyright 2023 The Matrix.org Foundation C.I.C.
+
+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, { useContext } from "react";
+import { Icon as ChatIcon } from "@vector-im/compound-design-tokens/icons/chat-solid.svg";
+import { Room } from "matrix-js-sdk/src/matrix";
+import { IconButton, Tooltip } from "@vector-im/compound-web";
+
+import { isVideoRoom as calcIsVideoRoom } from "../../../../utils/video-rooms";
+import { _t } from "../../../../languageHandler";
+import { useEventEmitterState } from "../../../../hooks/useEventEmitter";
+import { NotificationStateEvents } from "../../../../stores/notifications/NotificationState";
+import { NotificationColor } from "../../../../stores/notifications/NotificationColor";
+import { RightPanelPhases } from "../../../../stores/right-panel/RightPanelStorePhases";
+import { SDKContext } from "../../../../contexts/SDKContext";
+import { ButtonEvent } from "../../elements/AccessibleButton";
+
+/**
+ * Display a button to toggle timeline for video rooms
+ * @param room
+ * @returns for a video room: a button to toggle timeline in the right panel
+ *          otherwise null
+ */
+export const VideoRoomChatButton: React.FC<{ room: Room }> = ({ room }) => {
+    const sdkContext = useContext(SDKContext);
+
+    const isVideoRoom = calcIsVideoRoom(room);
+
+    const notificationState = isVideoRoom ? sdkContext.roomNotificationStateStore.getRoomState(room) : undefined;
+    const notificationColor = useEventEmitterState(
+        notificationState,
+        NotificationStateEvents.Update,
+        () => notificationState?.color,
+    );
+
+    if (!isVideoRoom) {
+        return null;
+    }
+
+    const displayUnreadIndicator =
+        !!notificationColor &&
+        [NotificationColor.Bold, NotificationColor.Grey, NotificationColor.Red].includes(notificationColor);
+
+    const onClick = (event: ButtonEvent): void => {
+        // stop event propagating up and triggering RoomHeader bar click
+        // which will open RoomSummary
+        event.stopPropagation();
+        sdkContext.rightPanelStore.showOrHidePanel(RightPanelPhases.Timeline);
+    };
+
+    return (
+        <Tooltip label={_t("right_panel|video_room_chat|title")}>
+            <IconButton
+                aria-label={_t("right_panel|video_room_chat|title")}
+                onClick={onClick}
+                indicator={displayUnreadIndicator ? "default" : undefined}
+            >
+                <ChatIcon />
+            </IconButton>
+        </Tooltip>
+    );
+};