Add auto-update setting and functionality

javascript/gallery.js

@@ -1271,6 +1271,43 @@ async function galleryClearInit() {
   }, 1000);
 }
 
+async function initGalleryAutoRefresh() {
+  const isModern = opts.theme_type?.toLowerCase() === 'modern';
+  let galleryTab = isModern ? document.getElementById('gallery_tabitem') : document.getElementById('tab_gallery');
+  let timeout = 0;
+  while (!galleryTab && timeout++ < 60) {
+    await new Promise((resolve) => { setTimeout(resolve, 1000); });
+    galleryTab = isModern ? document.getElementById('gallery_tabitem') : document.getElementById('tab_gallery');
+  }
+  if (!galleryTab) {
+    throw new Error('Timed out waiting for gallery tab element');
+  }
+  const displayNoneRegEx = /display:\s*none/;
+  async function galleryAutoRefresh(mutations) {
+    if (!opts.browser_gallery_autoupdate) return;
+    for (const mutation of mutations) {
+      switch (mutation.attributeName) {
+        case 'class':
+          if (mutation.oldValue.includes('hidden') && !mutation.target.classList.contains('hidden')) {
+            await updateFolders();
+            GalleryFolder.getActive()?.click();
+          }
+          break;
+        case 'style':
+          if (displayNoneRegEx.test(mutation.oldValue) && !displayNoneRegEx.test(mutation.target.style.display)) {
+            await updateFolders();
+            GalleryFolder.getActive()?.click();
+          }
+          break;
+        default:
+          break;
+      }
+    }
+  }
+  const galleryVisObserver = new MutationObserver(galleryAutoRefresh);
+  galleryVisObserver.observe(galleryTab, { attributeFilter: ['class', 'style'], attributeOldValue: true });
+}
+
 async function blockQueueUntilReady() {
   // Add block to maintenanceQueue until cache is ready
   maintenanceQueue.enqueue({