Make theme toggle switch to opposite color when in auto mode

When clicking the toggle in auto mode, it now jumps to the opposite of
what's currently displayed (e.g. light if system is dark) instead of
always going to light next.

Author: ad-si

tests/cli/playground/script.js

@@ -55,7 +55,10 @@ function applyMode(mode) {
 applyMode(currentMode)
 
 document.getElementById("themeBtn").addEventListener("click", () => {
-  const next = THEME_MODES[(THEME_MODES.indexOf(currentMode) + 1) % THEME_MODES.length]
+  // From auto, jump to the opposite of what's currently shown
+  const next = currentMode === "auto"
+    ? (isDark() ? "light" : "dark")
+    : THEME_MODES[(THEME_MODES.indexOf(currentMode) + 1) % THEME_MODES.length]
   applyMode(next)
   if (next === "auto") {
     localStorage.removeItem(STORAGE_KEY_THEME)