perf(presenter): smooth navigation via postMessage (no reload, no flicker)

Problem: Switching slides reset iframe.src each time, causing visible
flicker (white flash → load → render) on every navigation.

Solution: load each preview iframe ONCE, then use postMessage for all
subsequent slide changes. The iframe stays mounted; only .is-active
class toggles between slides inside it.

Changes:
- runtime.js preview mode: now exposes a showSlide() function and
  listens for window.message events of type 'preview-goto'. Also
  posts 'preview-ready' to parent on init so the presenter window
  knows when each iframe is loaded.
- presenter window: tracks iframeReady state per iframe; first frame
  renders via iframe.src = ?preview=N (one-time), all subsequent
  navigation goes through postPreviewGoto() → postMessage. Notes,
  meta, and timer update directly without touching iframes.
- Init no longer calls update(idx) which used to reset iframe.src;
  instead inits notes/meta/count once and lets the load→ready flow
  populate previews.

Docs synced to match new architecture:
- SKILL.md: describes 4 magnetic cards, draggable/resizable, with
  the iframe ?preview=N pattern explained for AI consumers
- references/presenter-mode.md: updated ASCII diagram to show 4
  cards, removed old 58%/35% layout description, added explanation
  for why previews are pixel-perfect (iframe loads same HTML) and
  why navigation is flicker-free (postMessage, not reload)
- presenter-mode-reveal README: updated 4-card description

SKILL.md

@@ -24,7 +24,7 @@ One command, no build. Pure static HTML/CSS/JS with only CDN webfonts.
 - **31 layouts** (`templates/single-page/*.html`) with realistic demo data
 - **27 CSS animations** (`assets/animations/animations.css`) via `data-anim`
 - **20 canvas FX animations** (`assets/animations/fx/*.js`) via `data-fx` — particle-burst, confetti-cannon, firework, starfield, matrix-rain, knowledge-graph (force-directed), neural-net (pulses), constellation, orbit-ring, galaxy-swirl, word-cascade, letter-explode, chain-react, magnetic-field, data-stream, gradient-blob, sparkle-trail, shockwave, typewriter-multi, counter-explosion
-- **Keyboard runtime** (`assets/runtime.js`) — arrows, T (theme), A (anim), F/O, **S (presenter view: current + next + large speaker script + timer)**, N (legacy notes drawer), R (reset timer)
+- **Keyboard runtime** (`assets/runtime.js`) — arrows, T (theme), A (anim), F/O, **S (presenter mode: magnetic-card popup with CURRENT / NEXT / SCRIPT / TIMER cards)**, N (notes drawer), R (reset timer in presenter)
 - **FX runtime** (`assets/animations/fx-runtime.js`) — auto-inits `[data-fx]` on slide enter, cleans up on leave
 - **Showcase decks** for themes / layouts / animations / full-decks gallery
 - **Headless Chrome render script** for PNG export
@@ -43,7 +43,17 @@ See [references/presenter-mode.md](references/presenter-mode.md) for the full au
 2. **每页 150–300 字** — 2–3 分钟/页的节奏
 3. **用口语，不用书面语** — "因此"→"所以"，"该方案"→"这个方案"
 
-All full-deck templates support the S key presenter view (it's built into `runtime.js`). **S opens a separate popup window** — the original page stays as the audience view, and the popup shows current/next slide (CSS scale at 1920×1080 design resolution, pixel-perfect) + large speaker script + timer. The two windows sync navigation via BroadcastChannel.
+All full-deck templates support the S key presenter mode (it's built into `runtime.js`). **S opens a new popup window with 4 magnetic cards**:
+- 🔵 **CURRENT** — pixel-perfect iframe preview of the current slide
+- 🟣 **NEXT** — pixel-perfect iframe preview of the next slide
+- 🟠 **SPEAKER SCRIPT** — large-font 逐字稿 (scrollable)
+- 🟢 **TIMER** — elapsed time + slide counter + prev/next/reset buttons
+
+Each card is **draggable by its header** and **resizable by the bottom-right corner handle**. Card positions/sizes persist to `localStorage` per deck. A "Reset layout" button restores the default arrangement.
+
+**Why the previews are pixel-perfect**: each preview is an `<iframe>` that loads the actual deck HTML with a `?preview=N` query param; `runtime.js` detects this and renders only slide N with no chrome. So the preview uses the **same CSS, theme, fonts, and viewport as the audience view** — colors and layout are guaranteed identical.
+
+**Smooth navigation**: on slide change, the presenter window sends `postMessage({type:'preview-goto', idx:N})` to each iframe. The iframe just toggles `.is-active` between slides — **no reload, no flicker**. The two windows also stay in sync via `BroadcastChannel`.
 
 Only `presenter-mode-reveal` is designed from the ground up around the feature with proper example 逐字稿 on every slide.
 
@@ -197,9 +207,10 @@ capture, runtime.js exposes `#/N` deep-links, and render.sh iterates 1..N.
 ```
 ←  →  Space  PgUp  PgDn  Home  End    navigate
 F                                       fullscreen
-S                                       open presenter window (new popup: current + next + script + timer)
+S                                       open presenter window (magnetic cards: current/next/script/timer)
 N                                       quick notes drawer (bottom overlay)
 R                                       reset timer (in presenter window)
+?preview=N                              URL param — force preview-only mode (single slide, no chrome)
 O                                       slide overview grid
 T                                       cycle themes (reads data-themes attr)
 A                                       cycle demo animation on current slide

assets/runtime.js

@@ -48,23 +48,33 @@
 
     /* ===== Preview-only mode: show one slide, hide everything else ===== */
     if (isPreviewMode) {
-      slides.forEach((s, i) => {
+      function showSlide(i) {
-        s.classList.toggle('is-active', i === previewOnlyIdx);
+        slides.forEach((s, j) => {
-        if (i !== previewOnlyIdx) {
+          const active = (j === i);
-          s.style.display = 'none';
+          s.classList.toggle('is-active', active);
-        } else {
+          s.style.display = active ? '' : 'none';
-          s.style.opacity = '1';
+          if (active) {
-          s.style.transform = 'none';
+            s.style.opacity = '1';
-          s.style.pointerEvents = 'auto';
+            s.style.transform = 'none';
-        }
+            s.style.pointerEvents = 'auto';
-      });
+          }
+        });
+      }
+      showSlide(previewOnlyIdx);
       /* Hide chrome that the presenter shouldn't see in preview */
       const hideSel = '.progress-bar, .notes-overlay, .overview, .notes, aside.notes, .speaker-notes';
       document.querySelectorAll(hideSel).forEach(el => { el.style.display = 'none'; });
-      /* Also add a data attr so templates can style preview mode if needed */
       document.documentElement.setAttribute('data-preview', '1');
       document.body.setAttribute('data-preview', '1');
-      /* Don't register key handlers, don't start broadcast channel, don't auto-hash */
+      /* Listen for postMessage from parent presenter window to switch slides
+       * WITHOUT reloading — this eliminates flicker during navigation. */
+      window.addEventListener('message', function(e) {
+        if (!e.data || e.data.type !== 'preview-goto') return;
+        const n = parseInt(e.data.idx, 10);
+        if (n >= 0 && n < slides.length) showSlide(n);
+      });
+      /* Signal to parent that preview iframe is ready */
+      try { window.parent && window.parent.postMessage({ type: 'preview-ready' }, '*'); } catch(e) {}
       return;
     }
 
@@ -596,22 +606,49 @@
     });
   });
 
-  /* ===== Update content ===== */
+  /* ===== Preview iframe ready tracking =====
+   * Each iframe loads the deck ONCE with ?preview=1 on init. Subsequent
+   * slide changes are sent via postMessage('preview-goto') so the iframe
+   * just toggles visibility of a different .slide — no reload, no flicker.
+   */
+  var iframeReady = { cur: false, nxt: false };
+  window.addEventListener('message', function(e) {
+    if (!e.data || e.data.type !== 'preview-ready') return;
+    if (e.source === iframeCur.contentWindow) {
+      iframeReady.cur = true;
+      postPreviewGoto(iframeCur, idx);
+      rescaleIframe(iframeCur);
+    } else if (e.source === iframeNxt.contentWindow) {
+      iframeReady.nxt = true;
+      postPreviewGoto(iframeNxt, idx + 1 < total ? idx + 1 : idx);
+      rescaleIframe(iframeNxt);
+    }
+  });
+
+  function postPreviewGoto(iframe, n) {
+    try {
+      iframe.contentWindow.postMessage({ type: 'preview-goto', idx: n }, '*');
+    } catch(e) {}
+  }
+
+  /* ===== Update content =====
+   * Smooth (no-reload) navigation: send postMessage to iframes instead of
+   * resetting src. Iframes stay loaded, just switch visible .slide.
+   */
   function update(n) {
     n = Math.max(0, Math.min(total - 1, n));
     idx = n;
 
-    /* Current preview iframe */
+    /* Current preview — postMessage (smooth) */
-    var curUrl = deckUrl + '?preview=' + (n + 1) + '&_ts=' + Date.now();
+    if (iframeReady.cur) postPreviewGoto(iframeCur, n);
-    iframeCur.src = curUrl;
     curMeta.textContent = (n + 1) + '/' + total;
 
-    /* Next preview iframe */
+    /* Next preview */
     if (n + 1 < total) {
       iframeNxt.style.display = '';
       var endEl = document.querySelector('#card-nxt .preview-end');
       if (endEl) endEl.remove();
-      iframeNxt.src = deckUrl + '?preview=' + (n + 2) + '&_ts=' + Date.now();
+      if (iframeReady.nxt) postPreviewGoto(iframeNxt, n + 1);
       nxtMeta.textContent = (n + 2) + '/' + total;
     } else {
       iframeNxt.style.display = 'none';
@@ -631,9 +668,6 @@
 
     /* Timer count */
     timerCount.textContent = (n + 1) + ' / ' + total;
-
-    /* Re-fit after src change */
-    setTimeout(rescaleAll, 200);
   }
 
   /* ===== Timer ===== */
@@ -685,9 +719,19 @@
   iframeCur.addEventListener('load', function(){ rescaleIframe(iframeCur); });
   iframeNxt.addEventListener('load', function(){ rescaleIframe(iframeNxt); });
 
-  /* ===== Init ===== */
+  /* ===== Init =====
+   * Load each iframe ONCE with the deck file. After they post
+   * 'preview-ready', all subsequent navigation is via postMessage
+   * (smooth, no reload, no flicker).
+   */
   applyLayout(readLayout());
-  update(idx);
+  iframeCur.src = deckUrl + '?preview=' + (idx + 1);
+  if (idx + 1 < total) iframeNxt.src = deckUrl + '?preview=' + (idx + 2);
+  /* Initialize notes/timer/count without touching iframes */
+  notesBody.innerHTML = slideMeta[idx].notes || '<span class="empty">（这一页还没有逐字稿）</span>';
+  curMeta.textContent = (idx + 1) + '/' + total;
+  nxtMeta.textContent = (idx + 2) + '/' + total;
+  timerCount.textContent = (idx + 1) + ' / ' + total;
 })();
 </` + `script>
 </body></html>`;

references/presenter-mode.md

@@ -126,28 +126,41 @@ html-ppt 的 **S 键演讲者视图是 `runtime.js` 内置的，所有 full-deck
 
 ## 演讲者视图显示的内容
 
-按 `S` 键后，**弹出一个独立的演讲者窗口**（原页面保持观众视图不变）：
+按 `S` 键后，**弹出一个独立的演讲者窗口**（原页面保持观众视图不变）。演讲者窗口是 **4 个独立的磁吸卡片**：
 
 ```
- 观众窗口（原页面）           演讲者窗口（新弹窗）
+ 观众窗口（原页面）           演讲者窗口（磁吸卡片）
-┌──────────────────┐    ┌────────────────────────┬──────────────────────┐
+┌─────────────────┐   ┌─────────────────────┬──────────────────┐
-│                  │    │                        │  NEXT                │
+│                 │   │ 🔵 CURRENT         │ 🟣 NEXT            │
-│   正常 slide     │    │    CURRENT             │  [下一页缩放预览]    │
+│  正常 slide     │   │ ━━━━━━━━━━━━━━━━ │ ━━━━━━━━━━━━━ │
-│   全屏展示       │◄──►│    [当前页缩放预览]    ├──────────────────────┤
+│  全屏展示       │◄►│                   │  iframe preview   │
-│                  │sync│    1920×1080 → scale() │  SPEAKER SCRIPT      │
+│                 │   │  iframe preview   │  （下一页）         │
-│                  │    │                        │  [大字号逐字稿]      │
+│                 │   │  （当前页）        ├──────────────────┤
-│                  │    │                        │  [可滚动]            │
+│                 │   │                   │ 🟠 SPEAKER SCRIPT  │
-│                  │    │                        ├──────────────────────┤
+│                 │   │                   │ ━━━━━━━━━━━━━ │
-│                  │    │                        │  ⏱ 12:34  3 / 8  💡  │
+│                 │   ├─────────────────────┤  [大字号逐字稿]   │
-└──────────────────┘    └────────────────────────┴──────────────────────┘
+│                 │   │ 🟢 TIMER           │  [可滚动]         │
+│                 │   │ ⏱ 12:34   3 / 8 │                   │
+│                 │   │ [← Prev][Next →]  │                   │
+└─────────────────┘   └─────────────────────┴──────────────────┘
        ↑ BroadcastChannel 双向同步翻页 ↑
 ```
 
-- **左侧 58%**：当前页 — 在 1920×1080 设计尺寸下渲染后 CSS scale 缩放，排版与观众端一致
+卡片交互规则：
-- **右上 35%**：下一页预览 — 同样 scale 缩放，帮助准备过渡
+- **拖动卡片 header**（带彩色圆点和标题的顶部条）→ 移动卡片位置
-- **右中**：逐字稿，字号 18px，高对比度，可滚动
+- **拖动卡片右下角的三角手柄** → 调整卡片大小
-- **右下**：计时器 + 页码 + 当前页标题 + 键位提示
+- **位置/尺寸自动保存到 localStorage**，下次打开恢复
-- **两窗口同步**：在任一窗口按 ← → 翻页，另一个窗口自动同步
+- 底部 "重置布局" 按钮恢复默认排列
+
+卡片内容：
+- 🔵 **CURRENT** — 当前页 **像素级完美预览**（iframe 加载原 HTML 文件的 `?preview=N` 模式，错色不可能）
+- 🟣 **NEXT** — 下一页预览，同样像素级完美
+- 🟠 **SPEAKER SCRIPT** — 逐字稿，字号 18px，支持 `<strong>` (橘色加粗)、`<em>` (蓝色强调)、`<code>` 等 inline 样式
+- 🟢 **TIMER** — 计时器不会丢失焦点，带切页按钮
+
+两窗口同步：在任一窗口按 ← → 翻页，另一个窗口自动同步（BroadcastChannel）。
+
+丝滑翻页：iframe 只加载一次，后续翻页用 `postMessage` 切换可见的 slide，**不重新加载、不闪烁**。
 
 ## 键盘快捷键（演讲者模式）
 
@@ -169,7 +182,9 @@ html-ppt 的 **S 键演讲者视图是 `runtime.js` 内置的，所有 full-deck
 4. 在任一窗口按 ← → 翻页，两边自动同步
 5. 演讲者窗口里看逐字稿 + 下一页 + 计时器
 
-> 💡 html-ppt 的演讲者模式会**弹出一个独立的新窗口**。原页面保持观众视图不变，只受翻页控制。两个窗口通过 BroadcastChannel 双向同步。演讲者窗口中的当前页/下一页预览使用 CSS `transform: scale()` 在 1920×1080 设计分辨率下缩放渲染，保证排版与观众端完全一致。
+> 💡 **为什么预览像素级完美**：每个预览是一个 `<iframe>`，它加载的就是同一个 deck HTML 文件，只是 URL 多了 `?preview=N` 参数。`runtime.js` 检测到这个参数时只渲染第 N 页、隐藏所有 chrome。**iframe 使用与观众视图完全相同的 CSS、主题、字体和 viewport**——颜色和排版保证一致。外层用 CSS `transform: scale()` 把 1920×1080 缩到卡片宽高，等比缩放不变形。
+
+> 💡 **为什么不闪烁**：iframe 初次加载后就常驻，翻页时 presenter 窗口通过 `postMessage({type:'preview-goto', idx:N})` 告诉 iframe 切换到第 N 页。iframe 内的 runtime.js 只切换 `.is-active` class，**不重新加载、不渲染白屏**。
 
 ## 常见错误
 

templates/full-decks/presenter-mode-reveal/README.md

@@ -1,6 +1,6 @@
 # presenter-mode-reveal · 演讲者模式模板
 
-一份专为**带逐字稿的技术分享**设计的 full-deck 模板。核心卖点是真正可用的**演讲者视图 (Presenter View)**：当前页 + 下页预览 + 大字号逐字稿 + 计时器，全部集成在 `runtime.js` 里，零依赖。
+一份专为**带逐字稿的技术分享**设计的 full-deck 模板。核心卖点是真正可用的**磁吸卡片式演讲者视图**：当前页 iframe 预览 + 下页 iframe 预览 + 大字号逐字稿 + 计时器，4 个卡片可任意拖拽/缩放，全部集成在 `runtime.js` 里，零依赖。
 
 ## 使用场景
 
@@ -78,6 +78,23 @@ presenter-mode-reveal/
 - **改样式**：只动 `style.css`，不要碰根目录的 `assets/base.css`
 - **加动效**：在元素上加 `data-anim="fade-up"` 等（参考 `references/animations.md`）
 
+## 演讲者窗口的 4 个卡片
+
+按 `S` 后弹出的窗口里有：
+
+- 🔵 **CURRENT** — 当前页 iframe 预览（加载 `?preview=N` 模式，像素级完美，与观众端同 CSS/主题/字体）
+- 🟣 **NEXT** — 下一页预览，帮助准备过渡
+- 🟠 **SPEAKER SCRIPT** — 大字号逐字稿，可滚动
+- 🟢 **TIMER** — 经过时间 + 页码 + Prev/Next/Reset 按钮
+
+卡片操作：
+- **拖卡片头**（彩色圆点 + 标题的顶部条）→ 移动卡片
+- **拖卡片右下角** → 调整大小
+- 位置 + 尺寸自动存 localStorage，下次打开恢复
+- 底部 "重置布局" 按钮可恢复默认卡片排列
+
+翻页丝滑：iframe 只加载一次，后续翻页通过 `postMessage` 切换内部 slide，**不重新加载不闪烁**。两窗口通过 `BroadcastChannel` 双向同步。
+
 ## 注意事项
 
 - **观众永远看不到 `.notes` 内容** — CSS 默认 `display:none`，只在演讲者视图里可见