Add "system" theme setting for MacOS

permissions_popup_preload.js

@@ -1,9 +1,11 @@
 /* global window */
 
-const { ipcRenderer } = require('electron');
+const { ipcRenderer, remote } = require('electron');
 const url = require('url');
 const i18n = require('./js/modules/i18n');
 
+const { systemPreferences } = remote.require('electron');
+
 const config = url.parse(window.location.toString(), true).query;
 const { locale } = config;
 const localeMessages = ipcRenderer.sendSync('locale-data');
@@ -12,6 +14,25 @@ window.getVersion = () => config.version;
 window.theme = config.theme;
 window.i18n = i18n.setup(locale, localeMessages);
 
+function setSystemTheme() {
+  window.systemTheme = systemPreferences.isDarkMode() ? 'dark' : 'light';
+}
+
+setSystemTheme();
+
+window.subscribeToSystemThemeChange = fn => {
+  if (!systemPreferences.subscribeNotification) {
+    return;
+  }
+  systemPreferences.subscribeNotification(
+    'AppleInterfaceThemeChangedNotification',
+    () => {
+      setSystemTheme();
+      fn();
+    }
+  );
+};
+
 require('./js/logging');
 
 window.closePermissionsPopup = () =>
@@ -19,6 +40,8 @@ window.closePermissionsPopup = () =>
 
 window.getMediaPermissions = makeGetter('media-permissions');
 window.setMediaPermissions = makeSetter('media-permissions');
+window.getThemeSetting = makeGetter('theme-setting');
+window.setThemeSetting = makeSetter('theme-setting');
 
 function makeGetter(name) {
   return () =>