ubuntu-based-kiosk/kiosk-app/slideshow.html

<!DOCTYPE html>
<html>
<head>
<meta charset="utf-8">
<title>Slideshow</title>
<!-- Shown for a site that's a local folder - see slideshow.js. The item
     list arrives from main.js via window.kioskSlideshow.update(); a Word
     document's bytes are requested by setting the page title (see
     TITLE_REQUEST in slideshow.js) and arrive via kioskSlideshow.docData(). -->
<style>
  html, body { margin: 0; height: 100%; background: #000; overflow: hidden; cursor: none; }
  .slide {
    position: absolute; inset: 0; overflow: hidden;
    opacity: 0; transition-property: opacity;
  }
  .slide.show { opacity: 1; }
  .slide img { width: 100%; height: 100%; object-fit: contain; display: block; }
  .slide.doc { background: #666; }
  #msg {
    position: absolute; inset: 0; display: flex; align-items: center; justify-content: center;
    color: #888; font: 24px sans-serif; text-align: center; padding: 2em; box-sizing: border-box;
  }
</style>
<script src="node_modules/jszip/dist/jszip.min.js"></script>
<script src="node_modules/docx-preview/dist/docx-preview.min.js"></script>
<script src="docx-render.js"></script>
</head>
<body>
<div class="slide" id="a"></div>
<div class="slide" id="b"></div>
<div id="msg">Loading slideshow…</div>
<script>
(() => {
  const TITLE = 'Slideshow';
  const TITLE_REQUEST = 'kiosk-slideshow-need:';
  const layers = [document.getElementById('a'), document.getElementById('b')];
  const msg = document.getElementById('msg');
  let front = 0;
  let order = [];
  let pos = -1;
  let timer = null;
  let scrollAnim = null;
  let state = null;
  let generation = 0;                  // bumps on every (re)start, cancels stale work
  const docCache = new Map();          // url -> { mtime, bytes }
  const pendingDocs = new Map();       // url -> { resolve, reject, timeout }

  const keyOf = (it) => it && `${it.type}:${it.url}:${it.mtime || ''}`;

  function shuffled(list) {
    const a = list.slice();
    for (let i = a.length - 1; i > 0; i--) {
      const j = Math.floor(Math.random() * (i + 1));
      [a[i], a[j]] = [a[j], a[i]];
    }
    return a;
  }

  function stopTimers() {
    clearTimeout(timer);
    cancelAnimationFrame(scrollAnim);
    scrollAnim = null;
  }

  function showMessage(text) {
    stopTimers();
    msg.textContent = text;
    msg.style.display = 'flex';
    layers.forEach((l) => { l.classList.remove('show'); l.innerHTML = ''; });
  }

  // Ask main.js for a document's bytes (see slideshow.js); cached by mtime
  // so a document is only re-read when it changed on disk.
  function getDocBytes(item) {
    const hit = docCache.get(item.url);
    if (hit && hit.mtime === item.mtime) return Promise.resolve(hit.bytes);
    return new Promise((resolve, reject) => {
      const timeout = setTimeout(() => {
        pendingDocs.delete(item.url);
        document.title = TITLE;
        reject(new Error('timed out reading the file'));
      }, 20000);
      pendingDocs.set(item.url, { resolve, reject, timeout, mtime: item.mtime });
      // main.js notices title *changes*; every answer (or timeout) puts it
      // back to TITLE, so each request is a change.
      document.title = TITLE_REQUEST + item.url;
    });
  }

  // Fill `layer` with `item`, resolving once it's ready to fade in.
  async function prepare(layer, item) {
    layer.innerHTML = '';
    layer.scrollTop = 0;
    layer.classList.toggle('doc', item.type === 'docx');
    if (item.type === 'image') {
      const img = new Image();
      img.style.objectFit = state.options.fit;
      await new Promise((resolve, reject) => {
        img.onload = resolve;
        img.onerror = () => reject(new Error('unreadable image'));
        img.src = item.url;
      });
      layer.appendChild(img);
      return;
    }
    if (!KioskDocx.available()) throw new Error('Word document viewer missing');
    const bytes = await getDocBytes(item);
    const zoomEl = document.createElement('div');
    layer.appendChild(zoomEl);
    const cls = await KioskDocx.render(bytes, zoomEl);
    // One page: show all of it at once. Longer: fit the width and let
    // autoScroll() move through it.
    if (KioskDocx.isSinglePage(zoomEl, cls)) {
      KioskDocx.fitPage(zoomEl, cls, window.innerWidth, window.innerHeight);
      zoomEl.style.display = 'flex';
      zoomEl.style.justifyContent = 'center';
    } else {
      KioskDocx.fit(zoomEl, cls, window.innerWidth);
    }
  }

  // A document taller than the screen scrolls smoothly top to bottom
  // during its time on screen: holds at the top for the first 15%,
  // reaches the bottom at 85%, then holds.
  function autoScroll(layer, seconds) {
    const distance = layer.scrollHeight - layer.clientHeight;
    if (distance <= 4) return;
    const start = performance.now();
    const total = seconds * 1000;
    const step = (now) => {
      const t = Math.min(Math.max(((now - start) / total - 0.15) / 0.7, 0), 1);
      const eased = t < 0.5 ? 2 * t * t : 1 - Math.pow(-2 * t + 2, 2) / 2;
      layer.scrollTop = distance * eased;
      if (t < 1) scrollAnim = requestAnimationFrame(step);
    };
    scrollAnim = requestAnimationFrame(step);
  }

  async function next(attempts = 0) {
    stopTimers();
    if (!order.length) return;
    if (attempts >= order.length) { showMessage('None of the files in this folder could be shown.'); return; }
    const gen = generation;
    pos = (pos + 1) % order.length;
    if (pos === 0 && state.options.shuffle && order.length > 1) order = shuffled(order);
    const item = order[pos];
    const back = layers[1 - front];
    try {
      await prepare(back, item);
    } catch (e) {
      console.warn('[SLIDESHOW] Skipping', item.url, '-', e.message || e);
      if (gen === generation) next(attempts + 1);
      return;
    }
    if (gen !== generation) return;   // folder changed while loading
    msg.style.display = 'none';
    const old = layers[front];
    back.classList.add('show');
    old.classList.remove('show');
    front = 1 - front;
    // Free the old slide (a rendered document can be large) once faded out.
    setTimeout(() => { if (!old.classList.contains('show')) old.innerHTML = ''; },
      state.options.transition * 1000 + 100);
    const seconds = item.type === 'docx' ? state.options.docInterval : state.options.interval;
    if (item.type === 'docx') autoScroll(back, seconds);
    // A lone document still cycles, so its scroll starts over from the top.
    if (order.length > 1 || item.type === 'docx') timer = setTimeout(next, seconds * 1000);
  }

  window.kioskSlideshow = {
    update(s) {
      const first = !state;
      const sameItems = state && JSON.stringify(state.items) === JSON.stringify(s.items);
      const currentKey = keyOf(order[pos]);
      state = s;
      layers.forEach((l) => { l.style.transitionDuration = s.options.transition + 's'; });
      layers.forEach((l) => l.querySelectorAll('img').forEach((img) => { img.style.objectFit = s.options.fit; }));
      // Drop cached documents that left the folder.
      for (const url of docCache.keys()) {
        if (!s.items.some((it) => it.url === url)) docCache.delete(url);
      }
      if (!s.items.length) {
        order = [];
        generation++;
        showMessage(s.exists ? `No images or documents in ${s.dir}` : `Folder not found: ${s.dir}`);
        return;
      }
      if (sameItems && !first) return;
      // Folder changed: keep showing the current item if it's still there
      // unchanged and carry on from it, otherwise restart from the top.
      generation++;
      order = s.options.shuffle ? shuffled(s.items) : s.items.slice();
      const keep = currentKey ? order.findIndex((it) => keyOf(it) === currentKey) : -1;
      if (keep >= 0 && !first) {
        pos = keep;
        clearTimeout(timer);
        const it = order[pos];
        const seconds = it.type === 'docx' ? s.options.docInterval : s.options.interval;
        if (order.length > 1 || it.type === 'docx') timer = setTimeout(next, seconds * 1000);
      } else {
        pos = -1;
        next();
      }
    },

    docData(url, d) {
      const p = pendingDocs.get(url);
      if (!p) return;
      pendingDocs.delete(url);
      clearTimeout(p.timeout);
      document.title = TITLE;
      if (d.error) { p.reject(new Error(d.error)); return; }
      const bytes = KioskDocx.base64ToBytes(d.data);
      docCache.set(url, { mtime: p.mtime, bytes });
      // Keep at most 10 documents' bytes around.
      while (docCache.size > 10) docCache.delete(docCache.keys().next().value);
      p.resolve(bytes);
    },
  };
})();
</script>
</body>
</html>