add screen to view a barcode isolated

static/rewards.js

@@ -0,0 +1,30 @@
+// Keep the screen awake while a rewards barcode is on screen so the cashier
+// can scan it without the display dimming or locking. This mirrors how wallet
+// apps behave when showing a barcode. The Screen Wake Lock API is best-effort:
+// it may be rejected (e.g. low battery) or auto-released when the tab is hidden,
+// so we re-acquire whenever the page becomes visible again.
+(function () {
+  var wakeLock = null;
+
+  function requestWakeLock() {
+    if (!("wakeLock" in navigator)) return;
+    navigator.wakeLock
+      .request("screen")
+      .then(function (sentinel) {
+        wakeLock = sentinel;
+      })
+      .catch(function () {
+        // Best-effort only; ignore failures (unsupported, low battery, etc.).
+      });
+  }
+
+  // Re-acquire if the lock was released (e.g. the tab was hidden) and the user
+  // returns to the page.
+  document.addEventListener("visibilitychange", function () {
+    if (document.visibilityState === "visible" && wakeLock === null) {
+      requestWakeLock();
+    }
+  });
+
+  requestWakeLock();
+})();