Keep screen awake during slideshow via Wake Lock API

Acquire a screen wake lock when the slideshow is playing; release on
pause or page hide; re-acquire when the tab returns to the foreground.
Failures are silently ignored so older browsers degrade gracefully.

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

1 files changed, 16 insertions, 1 deletions

diff --git a/public/js/slideshow.js b/public/js/slideshow.js
index 7df0955..b8e2a11 100644
--- a/public/js/slideshow.js
+++ b/public/js/slideshow.js
@@ -4,6 +4,17 @@ let ssIdx     = 0;
 let ssTimer   = null;
 let ssPlaying = true;
 let ssQueue   = SS_ENTRIES.slice();
+let wakeLock  = null;
+
+async function acquireWakeLock() {
+  if (!('wakeLock' in navigator) || document.hidden) return;
+  try { wakeLock = await navigator.wakeLock.request('screen'); } catch (_) {}
+}
+
+function releaseWakeLock() {
+  wakeLock?.release();
+  wakeLock = null;
+}
 
 const img   = document.getElementById('ss-img');
 const vid   = document.getElementById('ss-video');
@@ -87,7 +98,8 @@ function ssPrev() {
 function ssToggle() {
   ssPlaying = !ssPlaying;
   btn.textContent = ssPlaying ? '⏸ Pause' : '▶ Play';
-  if (ssPlaying) ssSchedule(); else clearTimeout(ssTimer);
+  if (ssPlaying) { ssSchedule(); acquireWakeLock(); }
+  else           { clearTimeout(ssTimer); releaseWakeLock(); }
 }
 
 // ── Shuffle ────────────────────────────────────────────────────────────────────
@@ -140,11 +152,13 @@ document.addEventListener('fullscreenchange',       onFsChange);
 document.addEventListener('webkitfullscreenchange', onFsChange);
 
 // Pause timer while tab is hidden; reschedule fresh on return so no burst catch-up.
+// Wake lock is auto-released by the browser on hide; re-acquire on return.
 document.addEventListener('visibilitychange', () => {
   if (document.hidden) {
     clearTimeout(ssTimer);
   } else if (ssPlaying) {
     ssSchedule();
+    acquireWakeLock();
   }
 });
 
@@ -190,6 +204,7 @@ if (ssParams.get('shuffle') === '1') {
 if (ssQueue.length > 0) {
   ssShow(0, true);
   ssSchedule();
+  acquireWakeLock();
 }
 
 // Browsers require a live user gesture for requestFullscreen — entering it