fix(performance): bound media discovery work

extension/content/inject.js

@@ -128,7 +128,7 @@ var tc = {
       "subtitleNudgeEnabledByDefault",
       true
     ),
-    subtitleNudgeInterval: getSharedDefault("subtitleNudgeInterval", 50),
+    subtitleNudgeInterval: getSharedDefault("subtitleNudgeInterval", 250),
     subtitleNudgeAmount: getSharedDefault("subtitleNudgeAmount", 0.001),
     customButtonIcons: {}
   },
@@ -161,6 +161,7 @@ var YT_NATIVE_MIN = 0.25;
 var YT_NATIVE_MAX = 2.0;
 var YT_NATIVE_STEP = 0.05;
 var vscObservedRoots = new WeakSet();
+var vscObservedRootList = [];
 var vscConnectedScannedRoots = new WeakSet();
 var vscInitializedDocuments = new WeakSet();
 var vscSourceObjectIds = new WeakMap();
@@ -1608,21 +1609,6 @@ function scanNodeForMedia(node, parent, added) {
     observeRoot(node.shadowRoot);
   }
 
-  // Deep-scan descendant elements for shadow roots we haven't observed yet.
-  // This catches custom elements (like archive.org's <play-av>) whose shadow
-  // roots were created before our attachShadow patch was installed.
-  if (added && typeof node.querySelectorAll === "function") {
-    try {
-      var allElements = node.querySelectorAll("*");
-      for (var j = 0; j < allElements.length; j++) {
-        if (allElements[j].shadowRoot && !vscObservedRoots.has(allElements[j].shadowRoot)) {
-          observeRoot(allElements[j].shadowRoot);
-        }
-      }
-    } catch (e) {
-      // querySelectorAll may throw on detached or unusual nodes
-    }
-  }
 }
 
 function getScanNodeForRoot(root) {
@@ -1683,6 +1669,24 @@ function rescanOpenShadowRoots(root, visited, rescanObserved) {
   });
 }
 
+function rescanObservedMediaRoots(doc) {
+  var retainedRoots = [];
+  vscObservedRootList.forEach(function(root) {
+    if (!root || root.nodeType === Node.DOCUMENT_NODE) return;
+    var connected = Boolean(root.host ? root.host.isConnected : root.isConnected);
+    if (!connected) return;
+    retainedRoots.push(root);
+    if (
+      !doc ||
+      root.ownerDocument === doc ||
+      (root.host && root.host.ownerDocument === doc)
+    ) {
+      scanRootForMedia(root);
+    }
+  });
+  vscObservedRootList = retainedRoots;
+}
+
 function observeRoot(root) {
   if (!root) return;
 
@@ -1698,6 +1702,7 @@ function observeRoot(root) {
 
   if (!vscObservedRoots.has(root)) {
     vscObservedRoots.add(root);
+    vscObservedRootList.push(root);
     setupListener(root);
     attachMutationObserver(root);
     attachMediaDetectionListeners(root);
@@ -1765,24 +1770,34 @@ function installPageShadowBridge() {
     );
   }
 
-  function startPersistentShadowFallback() {
-    if (window.vscPersistentShadowFallbackTimer) return;
-    window.vscPersistentShadowFallbackTimer = setInterval(function() {
-      requestIdle(
-        function() {
-          if (!document.body) return;
-          rescanOpenShadowRoots(document, undefined, false);
-        },
-        { timeout: 2000 }
-      );
-    }, 30000);
+  function startBoundedShadowFallback() {
+    if (window.vscBoundedShadowFallbackStarted) return;
+    window.vscBoundedShadowFallbackStarted = true;
+    window.vscBoundedShadowFallbackTimers = [3000, 10000, 30000].map(
+      function(delay) {
+        return setTimeout(function() {
+          requestIdle(
+            function() {
+              if (
+                !document.body ||
+                (delay !== 3000 && window.vscPageShadowBridgeLoaded)
+              ) {
+                return;
+              }
+              rescanOpenShadowRoots(document, undefined, false);
+            },
+            { timeout: 2000 }
+          );
+        }, delay);
+      }
+    );
   }
 
   function handleBridgeFailure() {
     window.vscPageShadowBridgeRequested = false;
     window.vscPageShadowBridgeRetries =
       (Number(window.vscPageShadowBridgeRetries) || 0) + 1;
-    startPersistentShadowFallback();
+    startBoundedShadowFallback();
     if (window.vscPageShadowBridgeRetries > 3) return;
     clearTimeout(window.vscPageShadowBridgeRetryTimer);
     window.vscPageShadowBridgeRetryTimer = setTimeout(function() {
@@ -1815,10 +1830,6 @@ function installPageShadowBridge() {
       window.vscPageShadowBridgeLoaded = true;
       window.vscPageShadowBridgeRetries = 0;
       clearTimeout(window.vscPageShadowBridgeRetryTimer);
-      if (window.vscPersistentShadowFallbackTimer) {
-        clearInterval(window.vscPersistentShadowFallbackTimer);
-        window.vscPersistentShadowFallbackTimer = null;
-      }
     });
     bridge.addEventListener("error", function() {
       bridge.remove();
@@ -1826,6 +1837,9 @@ function installPageShadowBridge() {
     });
     window.vscPageShadowBridgeRequested = true;
     parent.appendChild(bridge);
+    // The bridge reports future roots, but cannot report roots that existed
+    // before the extension loaded. Keep one bounded initial discovery pass.
+    startBoundedShadowFallback();
   } catch (error) {
     handleBridgeFailure();
     log(`Unable to install page shadow bridge: ${error.message}`, 3);
@@ -1956,7 +1970,7 @@ function hydrateRuntimeSettings(rawStorage, options) {
       : getSharedDefault("subtitleNudgeEnabledByDefault", true);
   tc.settings.subtitleNudgeInterval = Math.min(
     1000,
-    Math.max(10, Number(storage.subtitleNudgeInterval) || 50)
+    Math.max(250, Number(storage.subtitleNudgeInterval) || 250)
   );
   tc.settings.subtitleNudgeAmount =
     Number(storage.subtitleNudgeAmount) ||
@@ -2810,7 +2824,7 @@ function setupControllerHostTracking(videoController, wrapper, mount) {
   var frameId = null;
   var geometryRetryTimer = null;
   var geometryRetryAttempts = 0;
-  var maxGeometryRetryAttempts = 40;
+  var maxGeometryRetryAttempts = 12;
   var update = function() {
     frameId = null;
     positionControllerHost(wrapper, videoController.video, mount);
@@ -4241,9 +4255,11 @@ function attachMutationObserver(root) {
       function() {
         var mutationsToProcess = pendingMutations.splice(0);
         mutationProcessingScheduled = false;
+        var controllerMountTargets = new Set();
 
         mutationsToProcess.forEach(function(mutation) {
           if (mutation.type === "childList") {
+            controllerMountTargets.add(mutation.target);
             mutation.addedNodes.forEach(function(node) {
               // Skip text nodes, comments, etc. — only elements can contain media
               if (node.nodeType !== Node.ELEMENT_NODE) return;
@@ -4254,14 +4270,6 @@ function attachMutationObserver(root) {
               scanNodeForMedia(node, node.parentNode || mutation.target, false);
             });
 
-            // Player gesture/click panes are frequently inserted after the
-            // video. Keep equal-z-index controller hosts last, and repair a
-            // host that the site removed independently of its media element.
-            tc.mediaElements.slice().forEach(function(video) {
-              if (!video || !video.vsc || !video.vsc.div) return;
-              if (video.vsc.controllerHostMount !== mutation.target) return;
-              remountControllerHost(video.vsc, mutation.target);
-            });
             return;
           }
 
@@ -4299,6 +4307,17 @@ function attachMutationObserver(root) {
           }
         });
 
+        // Reconcile once per batch, not once per mutation. Large news/social
+        // pages can emit hundreds of childList records in one render pass.
+        if (controllerMountTargets.size > 0) {
+          tc.mediaElements.slice().forEach(function(video) {
+            if (!video || !video.vsc || !video.vsc.div) return;
+            var mount = video.vsc.controllerHostMount;
+            if (!controllerMountTargets.has(mount)) return;
+            remountControllerHost(video.vsc, mount);
+          });
+        }
+
         // Document selectors do not cross shadow boundaries. A detached
         // custom-element host can therefore hide connected-looking media from
         // the removed subtree scan; prune by composed connectivity as a final
@@ -4414,26 +4433,12 @@ function initializeNow(doc, forceReinit = false) {
   attachKeydownListeners(doc);
   attachMediaTargetTracking(doc);
 
-  // Bounded fallback scans catch open page-world roots if a site's CSP blocked
-  // the bridge script. The event bridge handles the normal ongoing path.
-  if (!doc.vscDelayedShadowScanDone) {
-    doc.vscDelayedShadowScanDone = true;
-    [3000, 10000, 30000].forEach(function(delay) {
-      setTimeout(function() {
-        if (!doc.body) return;
-        try {
-          rescanOpenShadowRoots(doc);
-        } catch (e) {}
-      }, delay);
-    });
-  }
-
   if (forceReinit) {
     log("Force re-initialization requested", 4);
     // A root is normally scanned only once. A user-requested rescan must also
     // revisit media that was present but source-less during the initial scan.
     scanRootForMedia(doc);
-    rescanOpenShadowRoots(doc);
+    rescanObservedMediaRoots(doc);
     refreshAllControllerGeometry();
     if (tc.settings.rememberSpeed || tc.settings.forceLastSavedSpeed) {
       tc.mediaElements.slice().forEach(applyRememberedSpeedPolicy);

extension/options/options.html

@@ -427,15 +427,15 @@
           <div class="row">
             <label for="subtitleNudgeInterval"
               >Nudge interval (milliseconds)<br /><em
-                >How often to nudge: 10&ndash;1000. Smaller values are more
-                frequent. Default: 50.</em
+                >How often to nudge: 250&ndash;1000. Smaller values are more
+                frequent. Default: 250.</em
               >
             </label>
             <input
               id="subtitleNudgeInterval"
               type="text"
               value=""
-              placeholder="50"
+              placeholder="250"
             />
           </div>
         </section>
@@ -909,12 +909,12 @@
                     </div>
                     <div class="site-rule-option site-rule-option-field">
                       <label
-                        >Nudge interval (10&ndash;1000ms):<br /><em
-                          >How often to nudge: 10&ndash;1000. Smaller values are
-                          more frequent. Default: 50.</em
+                        >Nudge interval (250&ndash;1000ms):<br /><em
+                          >How often to nudge: 250&ndash;1000. Smaller values are
+                          more frequent. Default: 250.</em
                         ></label
                       >
-                      <input type="text" class="site-subtitleNudgeInterval" placeholder="50" />
+                      <input type="text" class="site-subtitleNudgeInterval" placeholder="250" />
                     </div>
                   </div>
                 </div>

extension/options/options.js

@@ -878,8 +878,8 @@ function save_options() {
     parseInt(document.getElementById("subtitleNudgeInterval").value, 10) ||
     tcDefaults.subtitleNudgeInterval;
 
-  if (settings.subtitleNudgeInterval < 10) {
-    settings.subtitleNudgeInterval = 10;
+  if (settings.subtitleNudgeInterval < 250) {
+    settings.subtitleNudgeInterval = 250;
   }
   if (settings.subtitleNudgeInterval > 1000) {
     settings.subtitleNudgeInterval = 1000;
@@ -1003,7 +1003,7 @@ function save_options() {
       rule.subtitleNudgeInterval = Math.min(
         1000,
         Math.max(
-          10,
+          250,
           Number.isFinite(nudgeIv) ? nudgeIv : settings.subtitleNudgeInterval
         )
       );

extension/shared/settings-core.js

@@ -149,9 +149,7 @@
       {
         title: "YouTube videos",
         pattern: "/^https:\\/\\/(www\\.)?youtube\\.com\\/(?!shorts\\/).*/",
-        enabled: true,
-        enableSubtitleNudge: true,
-        subtitleNudgeInterval: 50
+        enabled: true
       },
       {
         title: "YouTube Shorts",
@@ -176,7 +174,7 @@
     popupControllerButtons: DEFAULT_BUTTONS.slice(),
     enableSubtitleNudge: false,
     subtitleNudgeEnabledByDefault: true,
-    subtitleNudgeInterval: 50,
+    subtitleNudgeInterval: 250,
     subtitleNudgeAmount: 0.001
   };
 
@@ -359,7 +357,7 @@
       return clampFiniteNumber(value, 0, 200, undefined);
     }
     if (key === "subtitleNudgeInterval") {
-      return clampFiniteNumber(value, 10, 1000, undefined);
+      return clampFiniteNumber(value, 250, 1000, undefined);
     }
     if (key === "preferredSpeed") {
       return clampFiniteNumber(value, 0.0625, 16, undefined);
@@ -914,7 +912,7 @@
     });
     expanded.subtitleNudgeInterval = clampFiniteNumber(
       expanded.subtitleNudgeInterval,
-      10,
+      250,
       1000,
       DEFAULT_SETTINGS.subtitleNudgeInterval
     );

tests/inject-lifecycle.regression.test.js

@@ -154,7 +154,7 @@ describe("inject.js media/controller lifecycle regressions", () => {
     expect(shadowEvents).toBe(1);
   });
 
-  it("retries a blocked page bridge and keeps a persistent shadow fallback", async () => {
+  it("retries a blocked page bridge with bounded shadow fallback scans", async () => {
     vi.useFakeTimers();
     bootInject();
     const firstBridge = document.querySelector(
@@ -165,7 +165,9 @@ describe("inject.js media/controller lifecycle regressions", () => {
     firstBridge.dispatchEvent(new Event("error"));
 
     expect(window.vscPageShadowBridgeRequested).toBe(false);
-    expect(window.vscPersistentShadowFallbackTimer).not.toBeNull();
+    expect(window.vscBoundedShadowFallbackStarted).toBe(true);
+    expect(window.vscBoundedShadowFallbackTimers).toHaveLength(3);
+    expect(window.vscPersistentShadowFallbackTimer).toBeUndefined();
     await vi.advanceTimersByTimeAsync(250);
     expect(
       document.querySelector('script[src$="content/shadow-bridge.js"]')
@@ -513,6 +515,27 @@ describe("inject.js media/controller lifecycle regressions", () => {
     expect(mountA.querySelector(".vsc-controller")).toBeNull();
   });
 
+  it("reconciles a burst of player mutations only once per idle batch", async () => {
+    bootInject();
+    await settleLifecycle();
+
+    const { mount, wrapper } = createControlledVideo();
+    const originalAppendChild = mount.appendChild.bind(mount);
+    let controllerReorders = 0;
+    mount.appendChild = function(node) {
+      if (node === wrapper) controllerReorders += 1;
+      return originalAppendChild(node);
+    };
+
+    for (let index = 0; index < 25; index += 1) {
+      mount.appendChild(document.createElement("span"));
+    }
+    await settleLifecycle(8);
+
+    expect(controllerReorders).toBe(1);
+    expect(mount.lastElementChild).toBe(wrapper);
+  });
+
   it("suppresses a zero-size host and reveals it when the video becomes visible", async () => {
     bootInject();
     await settleLifecycle();

tests/inject.test.js

@@ -250,7 +250,9 @@ describe("inject runtime", () => {
     loadScript("extension/content/inject.js");
 
     // Fast-forward 3000ms for delayed rescan to trigger
-    vi.advanceTimersByTime(3000);
+    await vi.advanceTimersByTimeAsync(3000);
+    // The bounded discovery pass yields to an idle callback before traversing.
+    await vi.advanceTimersByTimeAsync(2000);
 
     for (let i = 0; i < 5; i += 1) {
       await flushAsyncWork();

tests/options.integration.test.js

@@ -236,7 +236,7 @@ describe("options page", () => {
     expect(savedSettings.controllerMarginTop).toBe(200);
     expect(savedSettings.controllerMarginBottom).toBe(0);
     expect(savedSettings.subtitleNudgeEnabledByDefault).toBe(false);
-    expect(savedSettings.subtitleNudgeInterval).toBe(10);
+    expect(savedSettings.subtitleNudgeInterval).toBe(250);
     expect(savedSettings.showPopupControlBar).toBe(false);
     expect(savedSettings.popupMatchHoverControls).toBe(false);
     expect(savedSettings.popupControllerButtons).toEqual(["rewind", "faster"]);
@@ -251,7 +251,7 @@ describe("options page", () => {
         controllerOpacity: 0,
         enableSubtitleNudge: true,
         subtitleNudgeEnabledByDefault: false,
-        subtitleNudgeInterval: 75,
+        subtitleNudgeInterval: 250,
         showPopupControlBar: false,
         popupControllerButtons: ["advance"]
       })

tests/settings-core.spec.js

@@ -34,6 +34,8 @@ describe("canonical settings storage", () => {
       })
     );
     expect(settings.shortcutTargetMode).toBe("closest");
+    expect(settings.subtitleNudgeInterval).toBe(250);
+    expect(settings.siteRules[0].enableSubtitleNudge).toBeUndefined();
   });
 
   it("round-trips global and site-specific shortcut targeting", () => {
@@ -228,7 +230,7 @@ describe("canonical settings storage", () => {
     expect(rule.rememberSpeed).toBe(false);
     expect(rule.forceLastSavedSpeed).toBe(true);
     expect(rule.controllerOpacity).toBe(1);
-    expect(rule.subtitleNudgeInterval).toBe(10);
+    expect(rule.subtitleNudgeInterval).toBe(250);
     expect(rule.preferredSpeed).toBe(16);
   });