2026-css-anchor-positioning/anchor-size-intro.html at main · codegrid/2026-css-anchor-positioning · GitHub

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<!DOCTYPE html>
<html lang="ja">
<head>
  <meta charset="UTF-8">
  <meta name="viewport" content="width=device-width, initial-scale=1.0">
  <link rel="stylesheet" href="style.css">
  <title>anchor-size()の概要</title>
  <style>
    *, *::before, *::after {
      box-sizing: border-box;
    }

    body {
      display: grid;
      place-items: center;
      margin: 0;
      font-family: sans-serif;
      min-height: 100dvh;
      background-color: #f5f5f5;
    }

    .controls {
      position: fixed;
      bottom: 0;
      left: 0;
      right: 0;
      padding: 12px 16px;
      background-color: #fff;
      border-top: 1px solid #e0e0e0;
      display: flex;
      align-items: center;
      justify-content: center;
      gap: 24px;
      font-size: 14px;
    }

    .control-item {
      display: flex;
      align-items: center;
      gap: 8px;
    }

    .anchor {
      anchor-name: --my-anchor;
      width: var(--anchor-width, 120px);
      height: var(--anchor-height, 40px);
      background-color: #1a73e8;
      border-radius: 4px;
      display: grid;
      place-items: center;
      color: #fff;
      font-size: 0.875rem;
    }

    .tooltip {
      position: absolute;
      position-anchor: --my-anchor;
      position-area: center right;
      width: anchor-size(width);
      height: anchor-size(height);
      margin-left: 16px;
      background-color: #333;
      color: #fff;
      border-radius: 4px;
      font-size: 0.875rem;
      display: grid;
      place-items: center;
      text-align: center;
      padding: 4px;
      overflow: hidden;
    }

    .tooltip::before {
      content: "";
      position: absolute;
      left: -6px;
      top: 50%;
      translate: 0 -50%;
      border: 6px solid transparent;
      border-left: none;
      border-right-color: #333;
    }
  </style>
</head>
<body>
  <div class="controls">
    <div class="control-item">
      <label for="width-range">アンカーの幅：</label>
      <input id="width-range" type="range" min="80" max="200" value="120" step="10">
      <output id="width-output">120px</output>
    </div>
    <div class="control-item">
      <label for="height-range">アンカーの高さ：</label>
      <input id="height-range" type="range" min="40" max="120" value="40" step="10">
      <output id="height-output">40px</output>
    </div>
  </div>
  <div class="anchor">アンカー要素</div>
  <div class="tooltip">紐づいた要素</div>
  <script>
    const widthRange = document.getElementById('width-range');
    const widthOutput = document.getElementById('width-output');
    const heightRange = document.getElementById('height-range');
    const heightOutput = document.getElementById('height-output');

    widthRange.addEventListener('input', () => {
      document.documentElement.style.setProperty('--anchor-width', `${widthRange.value}px`);
      widthOutput.textContent = `${widthRange.value}px`;
    });

    heightRange.addEventListener('input', () => {
      document.documentElement.style.setProperty('--anchor-height', `${heightRange.value}px`);
      heightOutput.textContent = `${heightRange.value}px`;
    });
  </script>
</body>
</html>