code style theme chooser

web/react/utils/constants.jsx

@@ -304,6 +304,13 @@ module.exports = {
             uiName: 'Mention Highlight Link'
         }
     ],
+    CODE_THEMES: {
+        github: 'GitHub',
+        solarized_light: 'Solarized light',
+        monokai: 'Monokai',
+        solarized_dark: 'Solarized Dark'
+    },
+    DEFAULT_CODE_THEME: 'github',
     Preferences: {
         CATEGORY_DIRECT_CHANNEL_SHOW: 'direct_channel_show',
         CATEGORY_DISPLAY_SETTINGS: 'display_settings',

web/react/utils/utils.jsx

@@ -424,6 +424,11 @@ export function toTitleCase(str) {
 }
 
 export function applyTheme(theme) {
+    if (!theme.codeTheme) {
+        theme.codeTheme = Constants.DEFAULT_CODE_THEME;
+    }
+    updateCodeTheme(theme.codeTheme);
+
     if (theme.sidebarBg) {
         changeCss('.sidebar--left, .settings-modal .settings-table .settings-links, .sidebar--menu', 'background:' + theme.sidebarBg, 1);
     }
@@ -612,6 +617,27 @@ export function rgb2hex(rgbIn) {
     return '#' + hex(rgb[1]) + hex(rgb[2]) + hex(rgb[3]);
 }
 
+export function updateCodeTheme(theme) {
+    const path = '/static/css/highlight/' + theme + '.css';
+    const $link = $('link.code_theme');
+    if (path !== $link.attr('href')) {
+        changeCss('code.hljs', 'visibility: hidden');
+        var xmlHTTP = new XMLHttpRequest();
+        xmlHTTP.open('GET', path, true);
+        xmlHTTP.onload = function onLoad() {
+            $link.attr('href', path);
+            if (isBrowserFirefox()) {
+                $link.one('load', () => {
+                    changeCss('code.hljs', 'visibility: visible');
+                });
+            } else {
+                changeCss('code.hljs', 'visibility: visible');
+            }
+        };
+        xmlHTTP.send();
+    }
+}
+
 export function placeCaretAtEnd(el) {
     el.focus();
     if (typeof window.getSelection != 'undefined' && typeof document.createRange != 'undefined') {