split out header from RoomSubList and let it update separately

By moving the header into its own RoomSubListHeader, we can refresh it explicitly
by poking it by the new constantTimeDispatcher without re-rendering the whole stack
of room tiles

*UNTESTED*

src/components/structures/RoomSubListHeader.js

@@ -0,0 +1,116 @@
+/*
+Copyright 2017 Vector Creations 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.
+*/
+
+'use strict';
+
+var React = require('react');
+var ReactDOM = require('react-dom');
+var classNames = require('classnames');
+var sdk = require('matrix-react-sdk')
+var dis = require('matrix-react-sdk/lib/dispatcher');
+var MatrixClientPeg = require('matrix-react-sdk/lib/MatrixClientPeg');
+var RoomNotifs = require('matrix-react-sdk/lib/RoomNotifs');
+var AccessibleButton = require('matrix-react-sdk/lib/components/views/elements/AccessibleButton');
+var ConstantTimeDispatcher = require('matrix-react-sdk/lib/ConstantTimeDispatcher');
+
+module.exports = React.createClass({
+    displayName: 'RoomSubListHeader',
+
+    propTypes: {
+        label: React.PropTypes.string.isRequired,
+        tagName: React.PropTypes.string,
+        roomCount: React.PropTypes.string,
+        collapsed: React.PropTypes.bool.isRequired, // is LeftPanel collapsed?
+        isIncomingCallRoom: React.PropTypes.bool,
+        hidden: React.PropTypes.bool,
+        onHeaderClick: React.PropTypes.func,
+    },
+
+    getDefaultProps: function() {
+        return {
+            onHeaderClick: function() {}, // NOP
+        };
+    },
+
+    componentWillMount: function() {
+        constantTimeDispatcher.register("RoomSubList.refreshHeader", this.props.tagName, this.onRefresh);
+    },
+
+    componentWillUnmount: function() {
+        constantTimeDispatcher.unregister("RoomSubList.refreshHeader", this.props.tagName, this.onRefresh);
+    },
+
+    onRefresh: function() {
+        this.forceUpdate();
+    },
+
+    render: function() {
+        var TintableSvg = sdk.getComponent("elements.TintableSvg");
+
+        var subListNotifications = this.roomNotificationCount();
+        var subListNotifCount = subListNotifications[0];
+        var subListNotifHighlight = subListNotifications[1];
+
+        var chevronClasses = classNames({
+            'mx_RoomSubList_chevron': true,
+            'mx_RoomSubList_chevronRight': this.props.hidden,
+            'mx_RoomSubList_chevronDown': !this.props.hidden,
+        });
+
+        var badgeClasses = classNames({
+            'mx_RoomSubList_badge': true,
+            'mx_RoomSubList_badgeHighlight': subListNotifHighlight,
+        });
+
+        var badge;
+        if (subListNotifCount > 0) {
+            badge = <div className={badgeClasses}>{ FormattingUtils.formatCount(subListNotifCount) }</div>;
+        }
+        else if (subListNotifHighlight) {
+            badge = <div className={badgeClasses}>!</div>;   
+        }
+
+        // When collapsed, allow a long hover on the header to show user
+        // the full tag name and room count
+        var title;
+        if (this.props.collapsed) {
+            title = this.props.label;
+            if (roomCount !== '') {
+                title += " [" + roomCount + "]";
+            }
+        }
+
+        if (this.props.isIncomingCallRoom) {
+            var IncomingCallBox = sdk.getComponent("voip.IncomingCallBox");
+            incomingCall = <IncomingCallBox className="mx_RoomSubList_incomingCall" incomingCall={ this.props.incomingCall }/>;
+        }
+
+        var tabindex = this.props.searchFilter === "" ? "0" : "-1";
+
+        return (
+            <div className="mx_RoomSubList_labelContainer" title={ title } ref="header">
+                <AccessibleButton onClick={ this.onClick } className="mx_RoomSubList_label" tabIndex={tabindex}>
+                    { this.props.collapsed ? '' : this.props.label }
+                    <div className="mx_RoomSubList_roomCount">{ roomCount }</div>
+                    <div className={chevronClasses}></div>
+                    { badge }
+                    { incomingCall }
+                </AccessibleButton>
+            </div>
+        );
+    },
+});
+