横向画廊

把纵向滚动进度转换为画廊的横向位移。

09 / 22Horizontal gallery打开示例
D·03 横向画廊滚动驱动
0% · 起点
100% · 终点
  1. 使用场景

    系列作品展示。例如同一产品的三代设计依次横向进入画面,方便比较。

  2. 行为定义

    进度为 0 时看到首幅,进度为 1 时到达末幅。滚动和拖动都可以往返。

  3. 实现要点

    用画廊内容宽度减去可见宽度求出位移上限。尺寸变化后更新范围,逐帧只写 transform。

原生 HTML / CSS / JS

完整示例,可另存为 HTML 直接打开。

打开示例

查看源码
<!doctype html>
<html lang="zh-CN">
<head>
<meta charset="utf-8">
<meta name="viewport" content="width=device-width, initial-scale=1">
<title>横向画廊 · 原生示例</title>
<script>
  if (new URLSearchParams(location.search).get('theme') === 'dark') {
    document.documentElement.dataset.theme = 'dark';
  }
</script>
<style>
    :root {
      color-scheme: light;
      --page: #fbfaf7;
      --canvas: #edf3f6;
      --paper: #fff;
      --ink: #222c36;
      --line: #82939f;
      --mark: #b8412c;
      --selected: #fbe8e1;
      background: var(--page);
    }
    :root[data-theme="dark"] {
      color-scheme: dark;
      --page: #19222d;
      --canvas: #2b3c4d;
      --paper: #222e3c;
      --ink: #f6f5f1;
      --line: #8396a8;
      --mark: #ff9d7c;
      --selected: #2b3c4d;
    }
    * { box-sizing: border-box; }
    body { max-width: 720px; margin: 0 auto; padding: 24px; color: var(--ink); font: 16px/1.5 system-ui, sans-serif; }
    [hidden] { display: none !important; }
    .sticky { background: var(--page); }
    .stage { position: relative; overflow: hidden; aspect-ratio: 2 / 1; background: var(--canvas); }
    .art { display: block; width: 100%; height: 100%; }
    .strip { display: flex; width: 300%; height: 100%; transform: translateX(calc(var(--p) * (-200% / 3))); }
    .strip svg { display: block; flex: 0 0 calc(100% / 3); min-width: 0; height: 100%; }
    .scroll-mode .sticky { position: sticky; top: 0; }
    .scroll-mode .distance { height: 90vh; }
    .scroll-mode + p { min-height: 100vh; }
    .controls > div { display: flex; align-items: center; gap: 10px; margin-top: 10px; }
    input { flex: 1; min-width: 0; accent-color: var(--mark); }
    output { min-width: 4ch; text-align: end; }
    button { min-height: 44px; border: 1px solid var(--line); border-radius: 6px; background: var(--paper); color: var(--ink); }
    button[aria-pressed="true"] { border-color: var(--mark); background: var(--selected); }
    :focus-visible { outline: 2px solid var(--mark); outline-offset: 2px; }
</style>
<style>.demo-guide {
  display: flex;
  align-items: center;
  justify-content: space-between;
  gap: .5rem .9rem;
  min-inline-size: 0;
  margin-block: 0 .75rem;
  padding-block-end: .5rem;
  border-block-end: 1px solid var(--line-hi, #b8c4cd);
  color: var(--text-2, #434f5d);
  font-size: .8125rem;
  line-height: 1.5;
}

.trigger-stage > .demo-guide {
  margin: .35rem clamp(.85rem, 2.2vw, 1.4rem) 0;
}

.demo-guide [data-guide-caption] { margin: 0; }

.demo-guide > button[data-guide-replay] {
  flex: none;
  min-block-size: 44px;
  margin: 0;
  padding: .35rem .65rem;
  border: 1px solid var(--line-strong, #82939f);
  border-radius: 7px;
  background: var(--surface, #fff);
  color: var(--text, #222c36);
  font: inherit;
  font-weight: 550;
  cursor: pointer;
}

.demo-guide > button[data-guide-replay]:hover { border-color: var(--accent-text, #963324); }
.demo-guide > button[data-guide-replay]:focus-visible { outline: 2px solid var(--accent-text, #963324); outline-offset: 2px; }

.demo-guide-cursor {
  position: fixed;
  z-index: 20;
  inset: 0 auto auto 0;
  inline-size: 20px;
  block-size: 24px;
  pointer-events: none;
}

.demo-guide-cursor svg { display: block; inline-size: 100%; block-size: 100%; }
.demo-guide-cursor::before {
  position: absolute;
  inset: -7px auto auto -7px;
  inline-size: 18px;
  block-size: 18px;
  border: 2px solid var(--accent-text, #963324);
  border-radius: 50%;
  content: '';
  opacity: 0;
}
.demo-guide-cursor[data-press]::before { opacity: 1; }
@media (prefers-reduced-motion: reduce) { .demo-guide-cursor { display: none; } }
</style>
</head>
<body>
<h1>横向画廊</h1>
<p>拖动进度,或者切换到跟随页面滚动,比较开始与结束状态。</p>
<div class="track" style="--p:0">
    <div class="sticky">
      <div class="stage"><div class="strip" aria-hidden="true">
        <svg viewBox="0 0 600 300"><path fill="#39688b" d="M0 0h600v300H0z"/><path fill="none" stroke="#e8f3fa" stroke-width="25" d="M196 254V150a104 104 0 0 1 208 0v104"/></svg>
        <svg viewBox="0 0 600 300"><path fill="#fffdf8" d="M0 0h600v300H0z"/><path fill="#ef784d" d="m300 34 138 99-14 113-124-65-124 65-14-113z"/></svg>
        <svg viewBox="0 0 600 300"><path fill="#e8f3fa" d="M0 0h600v300H0z"/><circle cx="300" cy="150" r="96" fill="#39688b"/><ellipse cx="300" cy="150" rx="146" ry="36" transform="rotate(-22 300 150)" fill="none" stroke="#f7c98b" stroke-width="16"/></svg>
      </div></div>
      <div class="controls" hidden>
        <div class="range-row">
          <label for="progress">进度</label>
          <input id="progress" type="range" min="0" max="100" value="0">
          <output for="progress">0%</output>
        </div>
        <div class="steps" hidden>
          <button type="button" data-progress="0">起点</button>
          <button type="button" data-progress="1">终点</button>
        </div>
        <button class="scroll" type="button" aria-pressed="false">跟随页面滚动</button>
      </div>
      <p class="error" hidden>演示依赖未加载,请检查网络连接后刷新。</p>
    </div>
    <div class="distance" aria-hidden="true"></div>
</div>
<p>起点为 0%,终点为 100%。向上滚动可以反向观察同一过程。</p>

<script>
  (() => {
    const track = document.querySelector('.track');
    const sticky = document.querySelector('.sticky');
    const range = document.querySelector('#progress');
    const output = document.querySelector('output');
    const toggle = document.querySelector('.scroll');
    const motion = matchMedia('(prefers-reduced-motion: reduce)');
    let manual = Number(range.value) / 100;

    function showProgress(p) {
      range.value = Math.round(p * 100);
      output.value = range.value + '%';
    }
    
    let start = 0, distance = 1, frame = 0;
    function render(p) {
      track.style.setProperty('--p', p);
      showProgress(p);
    }
    function update() {
      if (!track.classList.contains('scroll-mode') || frame) return;
      frame = requestAnimationFrame(() => {
        frame = 0;
        if (track.classList.contains('scroll-mode')) {
          render(Math.max(0, Math.min(1, (scrollY - start) / distance)));
        }
      });
    }
    function connectScroll() {
      start = track.getBoundingClientRect().top + scrollY;
      distance = Math.max(1, track.offsetHeight - sticky.offsetHeight);
      update();
    }
    function disconnectScroll() {
      cancelAnimationFrame(frame);
      frame = 0;
    }
    window.addEventListener('scroll', update, { passive: true });
    window.addEventListener('resize', () => {
      if (track.classList.contains('scroll-mode')) connectScroll();
    });
  
    function setScroll(active) {
      track.classList.toggle('scroll-mode', active);
      toggle.setAttribute('aria-pressed', active);
      range.disabled = active;

      if (active) connectScroll();
      else {
        disconnectScroll();
        render(manual);
      }
    }
    function syncMotion() {
      document.querySelector('.range-row').hidden = motion.matches;
      document.querySelector('.steps').hidden = !motion.matches;
      toggle.hidden = motion.matches;
      if (motion.matches) {
        manual = manual < 0.5 ? 0 : 1;
        setScroll(false);
      }
    }

    toggle.addEventListener('click', () => setScroll(!track.classList.contains('scroll-mode')));
    track.addEventListener('formtempo:guide-reset', () => setScroll(false));
    range.addEventListener('input', () => {
      manual = Number(range.value) / 100;
      render(manual);
    });
    document.querySelectorAll('[data-progress]').forEach(button => {
      button.addEventListener('click', () => {
        manual = Number(button.dataset.progress);
        render(manual);
      });
    });
    motion.addEventListener('change', syncMotion);
    render(manual);
    syncMotion();
    document.querySelector('.controls').hidden = false;
  })();
</script>
<script>
(() => {
/** @param {number} duration @param {AbortSignal} signal @param {(progress: number) => void} [render] */
function guideBeat(duration, signal, render) {
  if (signal.aborted) return Promise.resolve();
  if (duration === 0) {
    render?.(1);
    return Promise.resolve();
  }

  return new Promise((resolve) => {
    let timer = 0;
    let frame = 0;
    const done = () => {
      clearTimeout(timer);
      cancelAnimationFrame(frame);
      signal.removeEventListener('abort', done);
      resolve(undefined);
    };
    signal.addEventListener('abort', done, { once: true });
    if (!render) {
      timer = window.setTimeout(done, duration);
      return;
    }

    const start = performance.now();
    const tick = (now) => {
      const progress = Math.min(1, (now - start) / duration);
      render(progress);
      if (progress === 1) done();
      else if (!signal.aborted) frame = requestAnimationFrame(tick);
    };
    frame = requestAnimationFrame(tick);
  });
}

/** @param {HTMLElement} root @param {import('./demo-guide-cases').DemoGuide} guide */
function bindDemoGuide(root, guide) {
  const view = root.querySelector(guide.view);
  if (!view || root.dataset.guideState || guide.steps.some(({ target }) => !root.querySelector(target))) return;

  const dock = guide.dock ? root.querySelector(guide.dock) : null;
  const bar = document.createElement('div');
  bar.className = 'demo-guide';
  bar.innerHTML = '<p data-guide-caption></p><button type="button" data-guide-replay>重播导览</button>';
  const caption = bar.querySelector('[data-guide-caption]');
  const replay = bar.querySelector('button');
  const heading = root === document.body ? root.querySelector('h1') : null;
  if (dock) dock.prepend(bar);
  else if (heading) heading.after(bar);
  else root.prepend(bar);

  const cursor = document.createElement('div');
  cursor.className = 'demo-guide-cursor';
  cursor.setAttribute('aria-hidden', 'true');
  cursor.hidden = true;
  cursor.innerHTML = '<svg viewBox="0 0 20 24" focusable="false"><path d="M2 2v17l4.8-4.5L10 21l3.2-1.6-3.2-6.2 6.6-.7L2 2Z" fill="#222c36" stroke="#fff" stroke-width="1.5" stroke-linejoin="round"/></svg>';
  document.body.append(cursor);

  const reduced = matchMedia('(prefers-reduced-motion: reduce)');
  const threshold = .5;
  const idleCaption = '导览在画面进入视口后播放一次。';
  const reducedCaption = '可重播关键状态,或直接操作。';
  const reset = guide.reset ? (root.matches(guide.reset) ? root : root.querySelector(guide.reset)) : null;
  const releaseTarget = guide.release ? root.querySelector(guide.release) : null;
  let autoPending = !reduced.matches;
  let inView = false;
  let playbackScroll = window.scrollY;
  /** @type {AbortController | undefined} */
  let run;
  /** @type {[number, number] | undefined} */
  let cursorPosition;

  root.dataset.guideState = 'idle';
  caption.textContent = reduced.matches ? reducedCaption : idleCaption;

  function hideCursor() {
    cursor.hidden = true;
    delete cursor.dataset.press;
    cursorPosition = undefined;
  }

  /** @param {PointerEvent} [pointer] */
  function stop(pointer) {
    autoPending = false;
    if (!run) return;
    run.abort();
    run = undefined;
    hideCursor();
    if (releaseTarget) {
      // A real pointer inside the target keeps its hover when the guide yields.
      if (pointer) sendPointer(releaseTarget, 'pointerenter', [pointer.clientX, pointer.clientY]);
      else sendPointer(releaseTarget, 'pointerleave', [0, 0]);
    }
    reset?.dispatchEvent(new Event('formtempo:guide-cancel'));
    root.dataset.guideState = 'interrupted';
    caption.textContent = '导览已停止,可以继续手动操作。';
  }

  /** @param {[number, number]} position */
  function moveCursor(position) {
    cursor.hidden = false;
    cursor.style.transform = `translate3d(${position[0]}px, ${position[1]}px, 0)`;
    cursorPosition = position;
  }

  /** @param {Element} target @param {readonly [number, number]} point */
  function location(target, [x, y]) {
    const rect = target.getBoundingClientRect();
    return /** @type {[number, number]} */ ([rect.left + rect.width * x, rect.top + rect.height * y]);
  }

  /** @param {Element} target @param {string} type @param {readonly [number, number]} position */
  function sendPointer(target, type, [clientX, clientY]) {
    target.dispatchEvent(new PointerEvent(type, { pointerType: 'mouse', clientX, clientY }));
  }

  /** @param {HTMLInputElement} slider @param {number} value */
  function setProgress(slider, value) {
    const next = Math.round(value);
    if (slider.valueAsNumber === next) return;
    slider.value = String(next);
    slider.dispatchEvent(new Event('input', { bubbles: true }));
  }

  /** @param {number} value */
  function showReducedProgress(value) {
    const options = Array.from(root.querySelectorAll('button[data-driven-step], button[data-scale-step], button[data-progress-step], button[data-progress]'));
    const percent = (button) => button.hasAttribute('data-progress')
      ? Number(button.getAttribute('data-progress')) * 100
      : Number(button.getAttribute('data-driven-step') ?? button.getAttribute('data-scale-step') ?? button.getAttribute('data-progress-step'));
    options.sort((a, b) => Math.abs(percent(a) - value) - Math.abs(percent(b) - value));
    if (options[0] instanceof HTMLButtonElement) options[0].click();
  }

  /** @param {import('./demo-guide-cases').DemoGuide['steps'][number]} step @param {AbortSignal} signal */
  async function playStep(step, signal) {
    const target = root.querySelector(step.target);
    if (!target) return;
    caption.textContent = step.text;
    const { action, value = 0, point = [.5, .5] } = step;

    if (action === 'progress' && target instanceof HTMLInputElement) {
      if (reduced.matches) {
        showReducedProgress(value);
      } else {
        const from = target.valueAsNumber;
        await guideBeat(step.duration ?? 0, signal, (progress) => {
          const current = from + (value - from) * progress;
          setProgress(target, current);
          moveCursor(location(target, [.04 + .92 * current / 100, .65]));
        });
      }
    } else {
      if (!reduced.matches) {
        const to = location(target, point);
        const [x, y] = point;
        const entry = x < .25 ? [-.08, y] : x > .75 ? [1.08, y] : [x, y < .5 ? -.08 : 1.08];
        const from = action === 'enter' ? location(target, /** @type {[number, number]} */ (entry))
          : cursorPosition ?? [to[0] + 26, to[1] + 19];
        const duration = action === 'leave' ? 200 : 340;
        await guideBeat(duration, signal, (progress) => {
          const t = 1 - (1 - progress) ** 3;
          const end = location(target, point);
          const position = /** @type {[number, number]} */ ([
            from[0] + (end[0] - from[0]) * t,
            from[1] + (end[1] - from[1]) * t,
          ]);
          moveCursor(position);
          if (action === 'move') sendPointer(target, 'pointermove', position);
        });
      }
      if (signal.aborted) return;

      if (action === 'click' && target instanceof HTMLElement) {
        if (!reduced.matches) {
          cursor.dataset.press = '';
          await guideBeat(125, signal);
          if (signal.aborted) return;
        }
        target.click();
        delete cursor.dataset.press;
      } else if (action === 'enter' || action === 'leave') {
        sendPointer(target, `pointer${action}`, location(target, point));
      }
    }

    await guideBeat(reduced.matches ? 600 : step.hold ?? 500, signal);
  }

  function bringViewIntoFrame() {
    const rect = view.getBoundingClientRect();
    const visibleHeight = Math.min(rect.bottom, window.innerHeight) - Math.max(rect.top, 0);
    if (visibleHeight < rect.height * threshold) view.scrollIntoView({ block: 'center', behavior: 'instant' });
  }

  async function start(replaying = false) {
    stop();
    const controller = new AbortController();
    const { signal } = controller;
    run = controller;
    root.dataset.guideState = 'playing';

    if (guide.ready) {
      caption.textContent = '正在等待视频就绪…';
      const deadline = performance.now() + 4000;
      while (!signal.aborted && !root.querySelector(guide.ready) && performance.now() < deadline &&
        !root.querySelector('[data-video-state="error"]')) {
        await guideBeat(90, signal);
      }
      if (signal.aborted) return;
      if (!root.querySelector(guide.ready)) {
        run = undefined;
        root.dataset.guideState = 'unavailable';
        caption.textContent = '视频暂未就绪,可以查看关键帧或重播。';
        return;
      }
    }

    reset?.dispatchEvent(new Event('formtempo:guide-reset'));
    if (replaying) bringViewIntoFrame();
    playbackScroll = window.scrollY;
    const steps = (reduced.matches && guide.reducedSteps) || guide.steps;
    for (const step of steps) {
      if (signal.aborted) return;
      await playStep(step, signal);
    }
    if (signal.aborted) return;

    run = undefined;
    hideCursor();
    root.dataset.guideState = 'complete';
    caption.textContent = '导览结束,可以继续手动操作。';
  }

  function tryAutoplay() {
    if (autoPending && inView && !document.hidden) void start();
  }

  if (typeof IntersectionObserver === 'function') {
    const observer = new IntersectionObserver(([entry]) => {
      inView = entry.intersectionRatio >= threshold;
      if (!entry.isIntersecting && run) stop();
      tryAutoplay();
    }, { threshold: [0, threshold] });
    observer.observe(view);
  }

  replay.addEventListener('click', () => {
    bringViewIntoFrame();
    void start(true);
  });

  const takeOver = (event) => {
    if (!event.isTrusted || replay.contains(event.target)) return;
    if (!run) {
      if (event.type === 'wheel' || !(event.target instanceof Element)) return;
      if (!event.target.closest('button, input') && !view.contains(event.target)) return;
    }
    const pointer = event instanceof PointerEvent && event.pointerType === 'mouse' && releaseTarget?.contains(event.target)
      ? event : undefined;
    stop(pointer);
  };
  for (const event of ['pointerdown', 'keydown', 'focusin', 'input', 'click', 'wheel']) {
    root.addEventListener(event, takeOver, { capture: true, passive: true });
  }
  if (guide.steps.some(({ action }) => action === 'enter' || action === 'move')) {
    view.addEventListener('pointermove', takeOver, { capture: true, passive: true });
  }
  if (guide.pageScrollInput) {
    window.addEventListener('scroll', () => {
      if (run && window.scrollY !== playbackScroll) stop();
    }, { passive: true });
  }
  document.addEventListener('visibilitychange', () => {
    if (document.hidden && run) stop();
    else tryAutoplay();
  });
  reduced.addEventListener('change', () => {
    if (!reduced.matches) return;
    const wasIdle = root.dataset.guideState === 'idle';
    stop();
    if (wasIdle) caption.textContent = reducedCaption;
  });
}

bindDemoGuide(document.body, {"view":".driven-stage, .track .stage","dock":".driven-sticky, .track .sticky","reset":"[data-driven], .track","steps":[{"text":"从首幅作品开始。","target":"input[type=\"range\"]","action":"progress","value":0,"duration":0,"hold":360},{"text":"进度向前,画廊横向移动到中间作品。","target":"input[type=\"range\"]","action":"progress","value":50,"duration":600,"hold":600},{"text":"进度到达终点,看到最后一幅。","target":"input[type=\"range\"]","action":"progress","value":100,"duration":600,"hold":360},{"text":"反向操作,回到中间作品。","target":"input[type=\"range\"]","action":"progress","value":50,"duration":600,"hold":360}],"reducedSteps":[{"text":"从首幅作品开始。","target":"input[type=\"range\"]","action":"progress","value":0,"duration":0,"hold":360},{"text":"进度到达终点,看到最后一幅。","target":"input[type=\"range\"]","action":"progress","value":100,"duration":600,"hold":360}]});
})();
</script>
</body>
</html>

GSAP 3.15.0

完整示例,从 CDN 加载指定版本。

打开示例

查看源码
<!doctype html>
<html lang="zh-CN">
<head>
<meta charset="utf-8">
<meta name="viewport" content="width=device-width, initial-scale=1">
<title>横向画廊 · GSAP示例</title>
<script>
  if (new URLSearchParams(location.search).get('theme') === 'dark') {
    document.documentElement.dataset.theme = 'dark';
  }
</script>
<style>
    :root {
      color-scheme: light;
      --page: #fbfaf7;
      --canvas: #edf3f6;
      --paper: #fff;
      --ink: #222c36;
      --line: #82939f;
      --mark: #b8412c;
      --selected: #fbe8e1;
      background: var(--page);
    }
    :root[data-theme="dark"] {
      color-scheme: dark;
      --page: #19222d;
      --canvas: #2b3c4d;
      --paper: #222e3c;
      --ink: #f6f5f1;
      --line: #8396a8;
      --mark: #ff9d7c;
      --selected: #2b3c4d;
    }
    * { box-sizing: border-box; }
    body { max-width: 720px; margin: 0 auto; padding: 24px; color: var(--ink); font: 16px/1.5 system-ui, sans-serif; }
    [hidden] { display: none !important; }
    .sticky { background: var(--page); }
    .stage { position: relative; overflow: hidden; aspect-ratio: 2 / 1; background: var(--canvas); }
    .art { display: block; width: 100%; height: 100%; }
    .strip { display: flex; width: 300%; height: 100%; transform: translateX(calc(var(--p) * (-200% / 3))); }
    .strip svg { display: block; flex: 0 0 calc(100% / 3); min-width: 0; height: 100%; }
    .scroll-mode .sticky { position: sticky; top: 0; }
    .scroll-mode .distance { height: 90vh; }
    .scroll-mode + p { min-height: 100vh; }
    .controls > div { display: flex; align-items: center; gap: 10px; margin-top: 10px; }
    input { flex: 1; min-width: 0; accent-color: var(--mark); }
    output { min-width: 4ch; text-align: end; }
    button { min-height: 44px; border: 1px solid var(--line); border-radius: 6px; background: var(--paper); color: var(--ink); }
    button[aria-pressed="true"] { border-color: var(--mark); background: var(--selected); }
    :focus-visible { outline: 2px solid var(--mark); outline-offset: 2px; }
</style>
<style>.demo-guide {
  display: flex;
  align-items: center;
  justify-content: space-between;
  gap: .5rem .9rem;
  min-inline-size: 0;
  margin-block: 0 .75rem;
  padding-block-end: .5rem;
  border-block-end: 1px solid var(--line-hi, #b8c4cd);
  color: var(--text-2, #434f5d);
  font-size: .8125rem;
  line-height: 1.5;
}

.trigger-stage > .demo-guide {
  margin: .35rem clamp(.85rem, 2.2vw, 1.4rem) 0;
}

.demo-guide [data-guide-caption] { margin: 0; }

.demo-guide > button[data-guide-replay] {
  flex: none;
  min-block-size: 44px;
  margin: 0;
  padding: .35rem .65rem;
  border: 1px solid var(--line-strong, #82939f);
  border-radius: 7px;
  background: var(--surface, #fff);
  color: var(--text, #222c36);
  font: inherit;
  font-weight: 550;
  cursor: pointer;
}

.demo-guide > button[data-guide-replay]:hover { border-color: var(--accent-text, #963324); }
.demo-guide > button[data-guide-replay]:focus-visible { outline: 2px solid var(--accent-text, #963324); outline-offset: 2px; }

.demo-guide-cursor {
  position: fixed;
  z-index: 20;
  inset: 0 auto auto 0;
  inline-size: 20px;
  block-size: 24px;
  pointer-events: none;
}

.demo-guide-cursor svg { display: block; inline-size: 100%; block-size: 100%; }
.demo-guide-cursor::before {
  position: absolute;
  inset: -7px auto auto -7px;
  inline-size: 18px;
  block-size: 18px;
  border: 2px solid var(--accent-text, #963324);
  border-radius: 50%;
  content: '';
  opacity: 0;
}
.demo-guide-cursor[data-press]::before { opacity: 1; }
@media (prefers-reduced-motion: reduce) { .demo-guide-cursor { display: none; } }
</style>
</head>
<body>
<h1>横向画廊</h1>
<p>拖动进度,或者切换到跟随页面滚动,比较开始与结束状态。</p>
<div class="track" style="--p:0">
    <div class="sticky">
      <div class="stage"><div class="strip" aria-hidden="true">
        <svg viewBox="0 0 600 300"><path fill="#39688b" d="M0 0h600v300H0z"/><path fill="none" stroke="#e8f3fa" stroke-width="25" d="M196 254V150a104 104 0 0 1 208 0v104"/></svg>
        <svg viewBox="0 0 600 300"><path fill="#fffdf8" d="M0 0h600v300H0z"/><path fill="#ef784d" d="m300 34 138 99-14 113-124-65-124 65-14-113z"/></svg>
        <svg viewBox="0 0 600 300"><path fill="#e8f3fa" d="M0 0h600v300H0z"/><circle cx="300" cy="150" r="96" fill="#39688b"/><ellipse cx="300" cy="150" rx="146" ry="36" transform="rotate(-22 300 150)" fill="none" stroke="#f7c98b" stroke-width="16"/></svg>
      </div></div>
      <div class="controls" hidden>
        <div class="range-row">
          <label for="progress">进度</label>
          <input id="progress" type="range" min="0" max="100" value="0">
          <output for="progress">0%</output>
        </div>
        <div class="steps" hidden>
          <button type="button" data-progress="0">起点</button>
          <button type="button" data-progress="1">终点</button>
        </div>
        <button class="scroll" type="button" aria-pressed="false">跟随页面滚动</button>
      </div>
      <p class="error" hidden>演示依赖未加载,请检查网络连接后刷新。</p>
    </div>
    <div class="distance" aria-hidden="true"></div>
</div>
<p>起点为 0%,终点为 100%。向上滚动可以反向观察同一过程。</p>
<script src="https://cdn.jsdelivr.net/npm/gsap@3.15.0/dist/gsap.min.js"></script>
<script src="https://cdn.jsdelivr.net/npm/gsap@3.15.0/dist/ScrollTrigger.min.js"></script>
<script>
  (() => {
    const track = document.querySelector('.track');
    const sticky = document.querySelector('.sticky');
    const range = document.querySelector('#progress');
    const output = document.querySelector('output');
    const toggle = document.querySelector('.scroll');
    const motion = matchMedia('(prefers-reduced-motion: reduce)');
    let manual = Number(range.value) / 100;

    function showProgress(p) {
      range.value = Math.round(p * 100);
      output.value = range.value + '%';
    }
    
    if (!window.gsap || !window.ScrollTrigger) {
      document.querySelector('.error').hidden = false;
      return;
    }
    gsap.registerPlugin(ScrollTrigger);
    const tween = gsap.timeline({ paused: true });
    tween.fromTo('.strip', { xPercent: 0 }, { xPercent: -200 / 3, ease: 'none' });
    let trigger;
    function render(p) {
      tween.progress(p);
      showProgress(p);
    }
    function connectScroll() {
      trigger = ScrollTrigger.create({
        trigger: track,
        start: 'top top',
        end: () => '+=' + (track.offsetHeight - sticky.offsetHeight),
        animation: tween,
        scrub: true,
        onUpdate: self => showProgress(self.progress),
        onRefresh: self => showProgress(self.progress),
      });
      showProgress(trigger.progress);
    }
    function disconnectScroll() {
      trigger?.kill(false, true);
      tween.pause();
    }
  
    function setScroll(active) {
      track.classList.toggle('scroll-mode', active);
      toggle.setAttribute('aria-pressed', active);
      range.disabled = active;

      if (active) connectScroll();
      else {
        disconnectScroll();
        render(manual);
      }
    }
    function syncMotion() {
      document.querySelector('.range-row').hidden = motion.matches;
      document.querySelector('.steps').hidden = !motion.matches;
      toggle.hidden = motion.matches;
      if (motion.matches) {
        manual = manual < 0.5 ? 0 : 1;
        setScroll(false);
      }
    }

    toggle.addEventListener('click', () => setScroll(!track.classList.contains('scroll-mode')));
    track.addEventListener('formtempo:guide-reset', () => setScroll(false));
    range.addEventListener('input', () => {
      manual = Number(range.value) / 100;
      render(manual);
    });
    document.querySelectorAll('[data-progress]').forEach(button => {
      button.addEventListener('click', () => {
        manual = Number(button.dataset.progress);
        render(manual);
      });
    });
    motion.addEventListener('change', syncMotion);
    render(manual);
    syncMotion();
    document.querySelector('.controls').hidden = false;
  })();
</script>
<script>
(() => {
/** @param {number} duration @param {AbortSignal} signal @param {(progress: number) => void} [render] */
function guideBeat(duration, signal, render) {
  if (signal.aborted) return Promise.resolve();
  if (duration === 0) {
    render?.(1);
    return Promise.resolve();
  }

  return new Promise((resolve) => {
    let timer = 0;
    let frame = 0;
    const done = () => {
      clearTimeout(timer);
      cancelAnimationFrame(frame);
      signal.removeEventListener('abort', done);
      resolve(undefined);
    };
    signal.addEventListener('abort', done, { once: true });
    if (!render) {
      timer = window.setTimeout(done, duration);
      return;
    }

    const start = performance.now();
    const tick = (now) => {
      const progress = Math.min(1, (now - start) / duration);
      render(progress);
      if (progress === 1) done();
      else if (!signal.aborted) frame = requestAnimationFrame(tick);
    };
    frame = requestAnimationFrame(tick);
  });
}

/** @param {HTMLElement} root @param {import('./demo-guide-cases').DemoGuide} guide */
function bindDemoGuide(root, guide) {
  const view = root.querySelector(guide.view);
  if (!view || root.dataset.guideState || guide.steps.some(({ target }) => !root.querySelector(target))) return;

  const dock = guide.dock ? root.querySelector(guide.dock) : null;
  const bar = document.createElement('div');
  bar.className = 'demo-guide';
  bar.innerHTML = '<p data-guide-caption></p><button type="button" data-guide-replay>重播导览</button>';
  const caption = bar.querySelector('[data-guide-caption]');
  const replay = bar.querySelector('button');
  const heading = root === document.body ? root.querySelector('h1') : null;
  if (dock) dock.prepend(bar);
  else if (heading) heading.after(bar);
  else root.prepend(bar);

  const cursor = document.createElement('div');
  cursor.className = 'demo-guide-cursor';
  cursor.setAttribute('aria-hidden', 'true');
  cursor.hidden = true;
  cursor.innerHTML = '<svg viewBox="0 0 20 24" focusable="false"><path d="M2 2v17l4.8-4.5L10 21l3.2-1.6-3.2-6.2 6.6-.7L2 2Z" fill="#222c36" stroke="#fff" stroke-width="1.5" stroke-linejoin="round"/></svg>';
  document.body.append(cursor);

  const reduced = matchMedia('(prefers-reduced-motion: reduce)');
  const threshold = .5;
  const idleCaption = '导览在画面进入视口后播放一次。';
  const reducedCaption = '可重播关键状态,或直接操作。';
  const reset = guide.reset ? (root.matches(guide.reset) ? root : root.querySelector(guide.reset)) : null;
  const releaseTarget = guide.release ? root.querySelector(guide.release) : null;
  let autoPending = !reduced.matches;
  let inView = false;
  let playbackScroll = window.scrollY;
  /** @type {AbortController | undefined} */
  let run;
  /** @type {[number, number] | undefined} */
  let cursorPosition;

  root.dataset.guideState = 'idle';
  caption.textContent = reduced.matches ? reducedCaption : idleCaption;

  function hideCursor() {
    cursor.hidden = true;
    delete cursor.dataset.press;
    cursorPosition = undefined;
  }

  /** @param {PointerEvent} [pointer] */
  function stop(pointer) {
    autoPending = false;
    if (!run) return;
    run.abort();
    run = undefined;
    hideCursor();
    if (releaseTarget) {
      // A real pointer inside the target keeps its hover when the guide yields.
      if (pointer) sendPointer(releaseTarget, 'pointerenter', [pointer.clientX, pointer.clientY]);
      else sendPointer(releaseTarget, 'pointerleave', [0, 0]);
    }
    reset?.dispatchEvent(new Event('formtempo:guide-cancel'));
    root.dataset.guideState = 'interrupted';
    caption.textContent = '导览已停止,可以继续手动操作。';
  }

  /** @param {[number, number]} position */
  function moveCursor(position) {
    cursor.hidden = false;
    cursor.style.transform = `translate3d(${position[0]}px, ${position[1]}px, 0)`;
    cursorPosition = position;
  }

  /** @param {Element} target @param {readonly [number, number]} point */
  function location(target, [x, y]) {
    const rect = target.getBoundingClientRect();
    return /** @type {[number, number]} */ ([rect.left + rect.width * x, rect.top + rect.height * y]);
  }

  /** @param {Element} target @param {string} type @param {readonly [number, number]} position */
  function sendPointer(target, type, [clientX, clientY]) {
    target.dispatchEvent(new PointerEvent(type, { pointerType: 'mouse', clientX, clientY }));
  }

  /** @param {HTMLInputElement} slider @param {number} value */
  function setProgress(slider, value) {
    const next = Math.round(value);
    if (slider.valueAsNumber === next) return;
    slider.value = String(next);
    slider.dispatchEvent(new Event('input', { bubbles: true }));
  }

  /** @param {number} value */
  function showReducedProgress(value) {
    const options = Array.from(root.querySelectorAll('button[data-driven-step], button[data-scale-step], button[data-progress-step], button[data-progress]'));
    const percent = (button) => button.hasAttribute('data-progress')
      ? Number(button.getAttribute('data-progress')) * 100
      : Number(button.getAttribute('data-driven-step') ?? button.getAttribute('data-scale-step') ?? button.getAttribute('data-progress-step'));
    options.sort((a, b) => Math.abs(percent(a) - value) - Math.abs(percent(b) - value));
    if (options[0] instanceof HTMLButtonElement) options[0].click();
  }

  /** @param {import('./demo-guide-cases').DemoGuide['steps'][number]} step @param {AbortSignal} signal */
  async function playStep(step, signal) {
    const target = root.querySelector(step.target);
    if (!target) return;
    caption.textContent = step.text;
    const { action, value = 0, point = [.5, .5] } = step;

    if (action === 'progress' && target instanceof HTMLInputElement) {
      if (reduced.matches) {
        showReducedProgress(value);
      } else {
        const from = target.valueAsNumber;
        await guideBeat(step.duration ?? 0, signal, (progress) => {
          const current = from + (value - from) * progress;
          setProgress(target, current);
          moveCursor(location(target, [.04 + .92 * current / 100, .65]));
        });
      }
    } else {
      if (!reduced.matches) {
        const to = location(target, point);
        const [x, y] = point;
        const entry = x < .25 ? [-.08, y] : x > .75 ? [1.08, y] : [x, y < .5 ? -.08 : 1.08];
        const from = action === 'enter' ? location(target, /** @type {[number, number]} */ (entry))
          : cursorPosition ?? [to[0] + 26, to[1] + 19];
        const duration = action === 'leave' ? 200 : 340;
        await guideBeat(duration, signal, (progress) => {
          const t = 1 - (1 - progress) ** 3;
          const end = location(target, point);
          const position = /** @type {[number, number]} */ ([
            from[0] + (end[0] - from[0]) * t,
            from[1] + (end[1] - from[1]) * t,
          ]);
          moveCursor(position);
          if (action === 'move') sendPointer(target, 'pointermove', position);
        });
      }
      if (signal.aborted) return;

      if (action === 'click' && target instanceof HTMLElement) {
        if (!reduced.matches) {
          cursor.dataset.press = '';
          await guideBeat(125, signal);
          if (signal.aborted) return;
        }
        target.click();
        delete cursor.dataset.press;
      } else if (action === 'enter' || action === 'leave') {
        sendPointer(target, `pointer${action}`, location(target, point));
      }
    }

    await guideBeat(reduced.matches ? 600 : step.hold ?? 500, signal);
  }

  function bringViewIntoFrame() {
    const rect = view.getBoundingClientRect();
    const visibleHeight = Math.min(rect.bottom, window.innerHeight) - Math.max(rect.top, 0);
    if (visibleHeight < rect.height * threshold) view.scrollIntoView({ block: 'center', behavior: 'instant' });
  }

  async function start(replaying = false) {
    stop();
    const controller = new AbortController();
    const { signal } = controller;
    run = controller;
    root.dataset.guideState = 'playing';

    if (guide.ready) {
      caption.textContent = '正在等待视频就绪…';
      const deadline = performance.now() + 4000;
      while (!signal.aborted && !root.querySelector(guide.ready) && performance.now() < deadline &&
        !root.querySelector('[data-video-state="error"]')) {
        await guideBeat(90, signal);
      }
      if (signal.aborted) return;
      if (!root.querySelector(guide.ready)) {
        run = undefined;
        root.dataset.guideState = 'unavailable';
        caption.textContent = '视频暂未就绪,可以查看关键帧或重播。';
        return;
      }
    }

    reset?.dispatchEvent(new Event('formtempo:guide-reset'));
    if (replaying) bringViewIntoFrame();
    playbackScroll = window.scrollY;
    const steps = (reduced.matches && guide.reducedSteps) || guide.steps;
    for (const step of steps) {
      if (signal.aborted) return;
      await playStep(step, signal);
    }
    if (signal.aborted) return;

    run = undefined;
    hideCursor();
    root.dataset.guideState = 'complete';
    caption.textContent = '导览结束,可以继续手动操作。';
  }

  function tryAutoplay() {
    if (autoPending && inView && !document.hidden) void start();
  }

  if (typeof IntersectionObserver === 'function') {
    const observer = new IntersectionObserver(([entry]) => {
      inView = entry.intersectionRatio >= threshold;
      if (!entry.isIntersecting && run) stop();
      tryAutoplay();
    }, { threshold: [0, threshold] });
    observer.observe(view);
  }

  replay.addEventListener('click', () => {
    bringViewIntoFrame();
    void start(true);
  });

  const takeOver = (event) => {
    if (!event.isTrusted || replay.contains(event.target)) return;
    if (!run) {
      if (event.type === 'wheel' || !(event.target instanceof Element)) return;
      if (!event.target.closest('button, input') && !view.contains(event.target)) return;
    }
    const pointer = event instanceof PointerEvent && event.pointerType === 'mouse' && releaseTarget?.contains(event.target)
      ? event : undefined;
    stop(pointer);
  };
  for (const event of ['pointerdown', 'keydown', 'focusin', 'input', 'click', 'wheel']) {
    root.addEventListener(event, takeOver, { capture: true, passive: true });
  }
  if (guide.steps.some(({ action }) => action === 'enter' || action === 'move')) {
    view.addEventListener('pointermove', takeOver, { capture: true, passive: true });
  }
  if (guide.pageScrollInput) {
    window.addEventListener('scroll', () => {
      if (run && window.scrollY !== playbackScroll) stop();
    }, { passive: true });
  }
  document.addEventListener('visibilitychange', () => {
    if (document.hidden && run) stop();
    else tryAutoplay();
  });
  reduced.addEventListener('change', () => {
    if (!reduced.matches) return;
    const wasIdle = root.dataset.guideState === 'idle';
    stop();
    if (wasIdle) caption.textContent = reducedCaption;
  });
}

bindDemoGuide(document.body, {"view":".driven-stage, .track .stage","dock":".driven-sticky, .track .sticky","reset":"[data-driven], .track","steps":[{"text":"从首幅作品开始。","target":"input[type=\"range\"]","action":"progress","value":0,"duration":0,"hold":360},{"text":"进度向前,画廊横向移动到中间作品。","target":"input[type=\"range\"]","action":"progress","value":50,"duration":600,"hold":600},{"text":"进度到达终点,看到最后一幅。","target":"input[type=\"range\"]","action":"progress","value":100,"duration":600,"hold":360},{"text":"反向操作,回到中间作品。","target":"input[type=\"range\"]","action":"progress","value":50,"duration":600,"hold":360}],"reducedSteps":[{"text":"从首幅作品开始。","target":"input[type=\"range\"]","action":"progress","value":0,"duration":0,"hold":360},{"text":"进度到达终点,看到最后一幅。","target":"input[type=\"range\"]","action":"progress","value":100,"duration":600,"hold":360}]});
})();
</script>
</body>
</html>