Add generic element context menu / popover.

src/components/views/context_menus/GenericElementContextMenu.js

@@ -0,0 +1,30 @@
+/*
+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.
+*/
+
+'use strict';
+
+import React from 'react';
+import PropTypes from 'prop-types';
+
+export default class GenericElementContextMenu extends React.Component {
+    static PropTypes = {
+        element: PropTypes.element.isRequired,
+    };
+
+    render() {
+        return <div>{ this.props.element }</div>;
+    }
+}

src/skins/vector/css/matrix-react-sdk/views/rooms/_MessageComposer.scss

@@ -258,7 +258,11 @@ limitations under the License.
     overflow: hidden;
 }
 
-// Set z-index for popovers
-.another-react-popover-container {
-    z-index: 1000;
+.mx_StickersContentPlaceholder {
+    display: flex;
+    flex-grow: 1;
+    flex-direction: column;
+    align-items: center;
+    justify-content: center;
+    text-align: center;
 }