fix rainbow breaks compound emojis

res/css/views/elements/_RichText.scss

@@ -80,6 +80,7 @@ a.mx_Pill {
     // and scale with the size of the surrounding text
     font-size: calc(18 / 14 * 1em);
     vertical-align: bottom;
+    font-family: Segoe UI Symbol;
 }
 
 .mx_Markdown_BOLD {

src/utils/colour.ts

@@ -14,10 +14,12 @@ See the License for the specific language governing permissions and
 limitations under the License.
 */
 
+import { split } from 'lodash';
+
 export function textToHtmlRainbow(str: string): string {
     const frequency = (2 * Math.PI) / str.length;
 
-    return Array.from(str)
+    return split(str, '')
         .map((c, i) => {
             if (c === " ") {
                 return c;

test/utils/colour-test.ts

@@ -0,0 +1,24 @@
+/*
+Copyright 2021 Šimon Brandner <[email protected]>
+
+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 { textToHtmlRainbow } from "../../src/utils/colour";
+
+describe("textToHtmlRainbow", () => {
+    it('correctly transform text to html without splitting the emoji in two', () => {
+        expect(textToHtmlRainbow('🐻')).toBe('<font color="#ff00be">🐻</font>');
+        expect(textToHtmlRainbow('🐕‍🦺')).toBe('<font color="#ff00be">🐕‍🦺</font>');
+    });
+});