Fast lyric fitting for long videos; Search tab returns to the home screen while playing

- fitLyricLines measures text on a canvas with the line's own font and writes
  every --fit after measuring (it used an in-list DOM probe and wrote inside
  the loop, re-laying-out the whole list per line). 1200 lines: 600 ms -> 28 ms;
  sizes match the old method within 1 px. Service mode on long sermons with
  hundreds of transcribed lines opened slowly enough on phones to look broken.
- Bottom-nav Search while something plays shows the home screen (playlist
  board / hero) over the player pane; the media keeps playing unseen and the
  mini bar brings the player back (its close button too, so there is always a
  way back). Starting another video restores the player.

frontend/app.js

@@ -1974,6 +1974,7 @@ const Player = {
     // instead of hijacking playback (longest window: save-before-playing).
     const seq = (this._loadSeq = (this._loadSeq || 0) + 1);
     showSpinner(true);
+    setHomeOverPlayer(false);
     els.placeholder.classList.add('hidden');
     // Revoke any previous OPFS blob URL to free memory
     if (_currentBlobUrl) {
@@ -2981,14 +2982,32 @@ function fitLyricLines(list, { maxShare = 0.17, maxPx = 160, minPx = 18, uniform
   const width = list.clientWidth * 0.92 * 0.97; // 4% side padding + slack
   const cap = Math.max(30, Math.min(list.clientHeight * maxShare, maxPx));
   const clamp = (px) => Math.max(minPx, Math.min(cap, px));
-  const probe = document.createElement('div');
+  // Text widths come from a canvas (no page layout at all) using the line's
-  probe.className = 'sl-line';
+  // own font; the in-list DOM probe stays as the fallback.
-  probe.style.cssText = 'position:absolute;left:0;top:0;visibility:hidden;white-space:nowrap;width:auto;padding:0;font-size:100px;transition:none';
+  const cs = getComputedStyle(rows[0]);
-  list.appendChild(probe);
+  const ctx2d = (fitLyricLines._c || (fitLyricLines._c = document.createElement('canvas'))).getContext('2d');
-  const widthAt = (px) => { probe.style.fontSize = px + 'px'; return probe.getBoundingClientRect().width; };
+  let probe = null;
+  let widthAt;
+  if (ctx2d && cs.fontFamily) {
+    const lsEm = (parseFloat(cs.letterSpacing) || 0) / (parseFloat(cs.fontSize) || 1); // letter-spacing in em
+    widthAt = (px) => {
+      ctx2d.font = `${cs.fontStyle} ${cs.fontWeight} ${px}px ${cs.fontFamily}`;
+      const t = widthAt.text;
+      return ctx2d.measureText(t).width + lsEm * px * Math.max(0, t.length - 1);
+    };
+  } else {
+    probe = document.createElement('div');
+    probe.className = 'sl-line';
+    probe.style.cssText = 'position:absolute;left:0;top:0;visibility:hidden;white-space:nowrap;width:auto;padding:0;font-size:100px;transition:none';
+    list.appendChild(probe);
+    widthAt = (px) => { probe.style.fontSize = px + 'px'; probe.textContent = widthAt.text; return probe.getBoundingClientRect().width; };
+  }
+  // Measure every line first and write the sizes afterwards: writing --fit
+  // inside the loop dirtied the list's layout, so each following measurement
+  // re-laid-out every line (O(n²) — seconds on a phone for a long sermon).
   const fits = [];
   for (const el of rows) {
-    probe.textContent = el.textContent;
+    widthAt.text = el.textContent;
     const w100 = widthAt(100);
     let px = cap;
     if (w100) {
@@ -2996,14 +3015,11 @@ function fitLyricLines(list, { maxShare = 0.17, maxPx = 160, minPx = 18, uniform
       const wEst = widthAt(est);
       px = Math.floor(clamp(wEst ? est * (width / wEst) : est));
     }
-    el.style.setProperty('--fit', px + 'px');
     fits.push(px);
   }
-  probe.remove();
+  if (probe) probe.remove();
-  if (uniform) {
+  const same = uniform ? Math.min(...fits) : 0;
-    const px = Math.min(...fits);
+  rows.forEach((el, i) => el.style.setProperty('--fit', (uniform ? same : fits[i]) + 'px'));
-    rows.forEach((el) => el.style.setProperty('--fit', px + 'px'));
-  }
 }
 
 // ============================================================================
@@ -7032,6 +7048,26 @@ function updateProgress() {
 // ============================================================================
 // Mini now-playing bar
 // ============================================================================
+// Home while playing: the Search tab brings back the home screen (playlist
+// board / hero) over the player pane, using the same look as "nothing playing"
+// (.empty). The media keeps playing — it is only made invisible, never removed
+// or paused — and the mini bar stays up to get back to it.
+function setHomeOverPlayer(on) {
+  const pane = els.playerPane;
+  if (!pane) return;
+  on = !!on && !!(current && current.meta);
+  if (pane.classList.contains('home-over') === on) return;
+  pane.classList.toggle('home-over', on);
+  pane.classList.toggle('empty', on);
+  if (els.placeholder) els.placeholder.classList.toggle('hidden', !on);
+  if (on) {
+    renderHomePlaylists();
+    showMiniBar();
+    const body = document.querySelector('.body');
+    if (body) body.scrollTo({ top: 0 });
+  }
+}
+
 function showMiniBar() {
   if (!current || !current.meta) return;
   $('miniTitle').textContent = current.meta.title;
@@ -10146,9 +10182,14 @@ function wireUI() {
     b.addEventListener('click', () => { view = { type: b.dataset.view }; render(); });
   });
 
-  // Bottom-nav (portrait PWA) — same view switching as sidebar nav
+  // Bottom-nav (portrait PWA) — same view switching as sidebar nav. Search
+  // while something plays also brings back the home screen (see setHomeOverPlayer).
   document.querySelectorAll('.bottom-nav-btn').forEach((b) => {
-    b.addEventListener('click', () => { view = { type: b.dataset.view }; render(); });
+    b.addEventListener('click', () => {
+      view = { type: b.dataset.view };
+      if (b.dataset.view === 'search') setHomeOverPlayer(true);
+      render();
+    });
   });
 
   els.newPlaylistBtn.addEventListener('click', () => newPlaylist(null));
@@ -10476,6 +10517,7 @@ document.querySelectorAll('.chip').forEach((c) => {
   // Mini now-playing bar
   $('miniPlayBtn').addEventListener('click', (e) => { e.stopPropagation(); Player.toggle(); });
   $('miniBar').addEventListener('click', () => {
+    setHomeOverPlayer(false);
     hideMiniBar();
     // Scroll the player into view if needed. In portrait PWA, scroll only the
     // .body pane (the designated scroll container) — scrollIntoView() also
@@ -10490,7 +10532,8 @@ document.querySelectorAll('.chip').forEach((c) => {
     e.stopPropagation();
     enterServiceMode();
   });
-  $('miniCloseBtn').addEventListener('click', (e) => { e.stopPropagation(); hideMiniBar(); });
+  // On the home screen the mini bar is the way back, so ✕ returns to the player.
+  $('miniCloseBtn').addEventListener('click', (e) => { e.stopPropagation(); setHomeOverPlayer(false); hideMiniBar(); });
 
   // Drag-to-reorder: prevent default on cards container
   els.cards.addEventListener('dragover', (e) => {

frontend/styles.css

@@ -4280,3 +4280,10 @@ body.landscape-fs .player-stage { touch-action: none; } /* fullscreen (real or t
 }
 .dl-act:hover { border-color: var(--accent); }
 .dl-act.danger:hover { border-color: #ff5a4f; color: #ff5a4f; }
+
+/* Home screen over a playing video (Search tab): media stays alive, unseen */
+.player-pane.home-over video,
+.player-pane.home-over #stageLyrics,
+.player-pane.home-over #artFallback { visibility: hidden; }
+.player-pane.home-over .related-panel { display: none; }
+.player-pane.home-over > :not(.player-stage) { display: none !important; }