专注模式：从带 mdg_reader 的地址打开时，等 B站 页面接管完再放进字幕栏

extension/content.js

@@ -337,6 +337,8 @@ const UNNAMED_SUBTITLE = "未命名字幕";
 const READER_FOLLOW_IDLE_MS = 1000;
 // Between two tries to mount the player after focus mode opened without one.
 const PLAYER_RETRY_MS = 500;
+// How long after navigation focus mode waits for the page to be hydrated (pageHydrating).
+const HYDRATE_WAIT_MS = 10000;
 // Smaller than this is a thumbnail or a preview, not the player.
 const MIN_PLAYER = { width: 240, height: 120 };
 // The appearance settings focus mode changes itself; a change to them does not touch the note.
@@ -1621,6 +1623,10 @@ async function ensureReaderPlayerMounted({ retries = 1, delayMs = 100, forceLayo
     if (!isReaderMode()) {
       return false;
     }
+    if (pageHydrating()) {
+      await sleep(delayMs);
+      continue;
+    }
     const video = getRuntimeVideoElement();
     const playerHost = findReaderPlayerHost(video);
     if (video && playerHost) {
@@ -1706,6 +1712,14 @@ async function ensureReaderPlayerMounted({ retries = 1, delayMs = 100, forceLayo
   return false;
 }
 
+// B站 hands its server-rendered page to the client only after load (Vue then drops data-server-rendered). Focus mode
+// put into the page before that leaves the page's own part switching dead for the visit (列表、下一个、自动连播), so the
+// mount waits; past HYDRATE_WAIT_MS it goes ahead, in case a page keeps the marker.
+function pageHydrating() {
+  const marks = reader().hydrating || [];
+  return Boolean(marks.length && document.querySelector(sel(marks))) && performance.now() < HYDRATE_WAIT_MS;
+}
+
 function queueEnsureReaderPlayerMounted() {
   if (!state.readingViewOpen || state.readingPlayerMountTimer) {
     return;

extension/content.selftest.js

@@ -172,13 +172,15 @@ const settle = async () => {
     state.subtitleBody = [];
     state.subtitles = [{ id: "1", url: "u" }];
     const body = gate("raw");
+    const site = t.currentSite;
     t.currentSite = () => ({ fetchRaw: () => body.promise, parseSegments: () => [{ from: 0, to: 1, content: "旧视频" }] });
     const switching = t.switchSubtitle("u");
     await settle();
     t.clipRuns.next();
     body.open();
     await assert.rejects(switching, (e) => e.message === "视频已切换，请刷新网页后重试");
     assert.deepStrictEqual(state.subtitleBody, [], "the new video keeps an empty body");
+    t.currentSite = site;
   }
 
   // G4: the note's AI turns and triage extras read for the old video are dropped once it changed.
@@ -759,6 +761,31 @@ const settle = async () => {
     Object.assign(t, keep);
   }
 
+  // V8: on a B站 page not hydrated yet (data-server-rendered still there) the mount puts nothing into the page: that
+  // left B站's own part switching dead. Past HYDRATE_WAIT_MS after navigation it mounts anyway.
+  {
+    const names = ["getRuntimeVideoElement", "findReaderPlayerHost", "dismissReaderMiniPlayer", "bindReadingViewVideo", "moveReadingMainInline", "normalizeReaderPlayerContainer", "clearNativeReaderFloatingStyles", "hasNativeReaderPlayerLayoutIssue", "bindReaderPlayerControlsHover", "bindReaderLayout", "layoutReaderPlayerHost", "cleanupReaderPlayerHostNode", "setReaderPlayerControlsVisible", "ensureReaderPlayerControlsRecovered", "queueEnsureReaderPlayerControlsRecovered"];
+    const keep = Object.fromEntries(names.map((k) => [k, t[k]]));
+    const [query, perf] = [t.document.querySelector, t.performance];
+    t.document.querySelector = (s) => (s === "[data-server-rendered]" ? {} : null);
+    for (const [name, now, mounted, moved] of [["hydrating", 3000, false, 0], ["marker kept past the wait", 10001, true, 1]]) {
+      for (const f of names) t[f] = () => {};
+      let moves = 0;
+      t.performance = { ...perf, now: () => now };
+      t.getRuntimeVideoElement = () => ({ removeAttribute() {}, setAttribute() {}, closest: () => null });
+      t.findReaderPlayerHost = () => ({ classList: { add() {} } });
+      t.hasNativeReaderPlayerLayoutIssue = () => false;
+      t.moveReadingMainInline = () => moves++;
+      t.stepReader("mark");
+      t.stepReader("enter");
+      assert.deepStrictEqual([await real.ensureReaderPlayerMounted({ retries: 2, delayMs: 1 }), moves], [mounted, moved], name);
+      t.stepReader("close");
+    }
+    Object.assign(t, keep, { performance: perf });
+    t.document.querySelector = query;
+    state.readingPlayerHost = null;
+  }
+
   // 跟随已停 shows after a manual scroll only while playing. Following stays off while the reader is away from the
   // playing line, however long; it resumes once the line is back in view and the reader has let go, or at 回到当前.
   {
@@ -1523,7 +1550,6 @@ const settle = async () => {
     const was = { href: t.location.href, hostname: t.location.hostname, ...Object.fromEntries(["site", "videoId", "videoDuration", "subtitles"].map((k) => [k, state[k]])) };
     t.location.href = "https://www.youtube.com/watch?v=dQw4w9WgXcQ";
     t.location.hostname = "www.youtube.com";
-    t.currentSite = () => t.MdgSites.matchSite(t.location.href); // the real one (a test above stubs it)
     Object.assign(state, { site: "youtube", videoId: "dQw4w9WgXcQ", videoDuration: 0 });
     const url = "https://www.youtube.com/api/timedtext?v=dQw4w9WgXcQ&lang=en";
     state.subtitles = [{ id: "en", lang: "en", url }];

extension/sites.js

@@ -553,6 +553,8 @@
       playerLayout: [".bpx-player-container", ".bpx-docker", ".bpx-player-video-area", ".bpx-player-primary-area", ".bpx-player-inner", ".scroll-sticky", "#bilibili-player", "#playerWrap", ".player-wrap"],
       // /video/ and /list/, 番剧 (#bilibili-player-wrap), 活动页 (.festival-video-player).
       playerWrap: ["#playerWrap", ".player-wrap", "#bilibili-player-wrap", ".festival-video-player"],
+      // The server-rendered page until the client takes it over (content.js pageHydrating).
+      hydrating: ["[data-server-rendered]"],
       miniPlayer: [".bpx-player-mini-warp", ".bpx-player-mini-close"],
       miniClose: [".bpx-player-mini-close"],
       endingPanel: [".bpx-player-ending-panel", ".bpx-player-ending-related"],