scroll-jank-profiler/demo/optimised.html at main · css-scroll-driven/scroll-jank-profiler · GitHub

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<!doctype html>
<html lang="en">
<head>
<meta charset="utf-8">
<meta name="viewport" content="width=device-width, initial-scale=1">
<title>Optimised scroll animations — scroll-jank-profiler demo</title>
<style>
  /*
    The same four effects as janky.html, rebuilt so every animated property is
    one the compositor can handle on its own thread.
  */
  * { box-sizing: border-box; }
  body { margin: 0; font: 16px/1.6 system-ui, sans-serif; background: #101216; color: #e8eaed; }
  header { padding: 4rem 2rem; text-align: center; }
  h1 { margin: 0 0 .5rem; font-size: clamp(1.6rem, 4vw, 2.6rem); }
  p.lede { color: #9aa2ad; max-width: 40rem; margin: 0 auto; }
  section { min-height: 100vh; padding: 4rem 2rem; border-top: 1px solid #23262d; }
  .grid { display: grid; grid-template-columns: repeat(auto-fill, minmax(160px, 1fr)); gap: 1rem; }

  /* scale() instead of width/height/margin. */
  @keyframes grow-transform {
    from { transform: scale(1) translateX(0); }
    to   { transform: scale(2.6) translateX(46px); }
  }
  .grower {
    width: 120px; height: 120px;
    transform-origin: top left;
    background: linear-gradient(135deg, #4cc38a, #7aa2f7);
    border-radius: 18px;
    animation: grow-transform linear both;
    animation-timeline: view();
    animation-range: entry 0% cover 60%;
  }

  /* The shadow is carried by a pseudo-element and cross-faded with opacity. */
  .grower::after {
    content: "";
    position: absolute;
    inset: 0;
    border-radius: 18px;
    box-shadow: 0 40px 90px rgba(0, 0, 0, .7);
    opacity: 0;
    animation: fade-in linear both;
    animation-timeline: view();
    animation-range: entry 0% cover 60%;
  }
  @keyframes fade-in { from { opacity: 0; } to { opacity: 1; } }

  /* translate() instead of top/left. */
  @keyframes slide-transform {
    from { transform: translate3d(0, 0, 0); }
    to   { transform: translate3d(60px, 240px, 0); }
  }
  .slider {
    width: 140px; height: 140px;
    background: #7aa2f7;
    border-radius: 12px;
    animation: slide-transform linear both;
    animation-timeline: scroll(root block);
  }

  /* An oversized child is translated instead of moving background-position. */
  .panner { height: 300px; overflow: hidden; }
  .panner > .strip {
    height: 1500px;
    background-image: repeating-linear-gradient(45deg, #2a2e35 0 20px, #1a1d22 20px 40px);
    animation: pan-transform linear both;
    animation-timeline: view();
  }
  @keyframes pan-transform {
    from { transform: translate3d(0, 0, 0); }
    to   { transform: translate3d(0, -1200px, 0); }
  }

  /*
    No blanket will-change. Only the handful of elements that actually animate
    are promoted, and they are promoted by the animation itself.
  */
  .tile { height: 120px; border-radius: 10px; background: #1c1f25; }
</style>
</head>
<body>
<header>
  <h1>Optimised scroll animations</h1>
  <p class="lede">The same effects as the janky demo, expressed entirely with <code>transform</code>
    and <code>opacity</code>, with no scroll listener and no blanket layer promotion.</p>
</header>

<section>
  <h2>Growing box (transform: scale)</h2>
  <div class="grower"></div>
</section>

<section>
  <h2>Sliding box (transform: translate3d)</h2>
  <div class="slider"></div>
</section>

<section>
  <h2>Panning strip (transform on an oversized child)</h2>
  <div class="panner"><div class="strip"></div></div>
</section>

<section>
  <h2>Plain tiles</h2>
  <div class="grid" id="tiles"></div>
</section>

<section>
  <h2>End of the page</h2>
  <p>Compare against <a href="janky.html">janky.html</a>.</p>
</section>

<script>
  const tiles = document.getElementById('tiles');
  const fragment = document.createDocumentFragment();
  for (let i = 0; i < 120; i += 1) {
    const tile = document.createElement('div');
    tile.className = 'tile';
    fragment.append(tile);
  }
  tiles.append(fragment);
</script>
</body>
</html>