fixes and functions

static/js/theme.js

@@ -7,11 +7,15 @@
  * See LICENSE file in repository root for details.
  */
 const STORAGE_KEY = "rustpad:theme";
-const DEFAULT_THEME = "dark";
 const THEMES = new Set(["dark", "light"]);
+const systemThemeQuery = window.matchMedia("(prefers-color-scheme: light)");
+
+function systemTheme() {
+  return systemThemeQuery.matches ? "light" : "dark";
+}
 
 function normalizeTheme(value) {
-  return THEMES.has(value) ? value : DEFAULT_THEME;
+  return THEMES.has(value) ? value : systemTheme();
 }
 
 function updateBrowserChrome(theme) {
@@ -42,5 +46,13 @@ export function applySessionTheme(session) {
 }
 
 window.addEventListener("storage", event => {
-  if (event.key === STORAGE_KEY && event.newValue) applyTheme(event.newValue, { persist: false });
+  if (event.key !== STORAGE_KEY) return;
+  applyTheme(THEMES.has(event.newValue) ? event.newValue : systemTheme(), { persist: false });
+});
+
+systemThemeQuery.addEventListener("change", () => {
+  try {
+    if (THEMES.has(localStorage.getItem(STORAGE_KEY))) return;
+  } catch { }
+  applyTheme(systemTheme(), { persist: false });
 });