Initial cut of Pinned event card in the right panel

src/components/views/right_panel/RoomHeaderButtons.tsx

@@ -18,7 +18,9 @@ See the License for the specific language governing permissions and
 limitations under the License.
 */
 
-import React from 'react';
+import React from "react";
+import { Room } from "matrix-js-sdk/src/models/room";
+
 import {_t} from '../../../languageHandler';
 import HeaderButton from './HeaderButton';
 import HeaderButtons, {HeaderKind} from './HeaderButtons';
@@ -27,6 +29,8 @@ import {Action} from "../../../dispatcher/actions";
 import {ActionPayload} from "../../../dispatcher/payloads";
 import RightPanelStore from "../../../stores/RightPanelStore";
 import {replaceableComponent} from "../../../utils/replaceableComponent";
+import {useSettingValue} from "../../../hooks/useSettings";
+import { useReadPinnedEvents, usePinnedEvents } from './PinnedMessagesCard';
 
 const ROOM_INFO_PHASES = [
     RightPanelPhases.RoomSummary,
@@ -38,9 +42,35 @@ const ROOM_INFO_PHASES = [
     RightPanelPhases.Room3pidMemberInfo,
 ];
 
+const PinnedMessagesHeaderButton = ({ room, isHighlighted, onClick }) => {
+    const pinningEnabled = useSettingValue("feature_pinning");
+    const pinnedEvents = usePinnedEvents(pinningEnabled && room);
+    const readPinnedEvents = useReadPinnedEvents(pinningEnabled && room);
+    if (!pinningEnabled) return null;
+
+    let unreadIndicator;
+    if (pinnedEvents.some(id => !readPinnedEvents.has(id))) {
+        unreadIndicator = <div className="mx_RightPanel_pinnedMessagesButton_unreadIndicator" />;
+    }
+
+    return <HeaderButton
+        name="pinnedMessagesButton"
+        title={_t("Pinned Messages")}
+        isHighlighted={isHighlighted}
+        onClick={onClick}
+        analytics={["Right Panel", "Pinned Messages Button", "click"]}
+    >
+        { unreadIndicator }
+    </HeaderButton>;
+};
+
+interface IProps {
+    room?: Room;
+}
+
 @replaceableComponent("views.right_panel.RoomHeaderButtons")
-export default class RoomHeaderButtons extends HeaderButtons {
-    constructor(props) {
+export default class RoomHeaderButtons extends HeaderButtons<IProps> {
+    constructor(props: IProps) {
         super(props, HeaderKind.Room);
     }
 
@@ -80,8 +110,18 @@ export default class RoomHeaderButtons extends HeaderButtons {
         this.setPhase(RightPanelPhases.NotificationPanel);
     };
 
+    private onPinnedMessagesClicked = () => {
+        // This toggles for us, if needed
+        this.setPhase(RightPanelPhases.PinnedMessages);
+    };
+
     public renderButtons() {
         return <>
+            <PinnedMessagesHeaderButton
+                room={this.props.room}
+                isHighlighted={this.isPhase(RightPanelPhases.PinnedMessages)}
+                onClick={this.onPinnedMessagesClicked}
+            />
             <HeaderButton
                 name="notifsButton"
                 title={_t('Notifications')}