2026-css-anchor-positioning/anchor-size-omit.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()の第二引数を省略する</title>
  <style>
    *, *::before, *::after {
      box-sizing: border-box;
    }

    body {
      margin: 0;
      font-family: sans-serif;
      min-height: 100vh;
      display: flex;
      align-items: center;
      justify-content: center;
      background-color: #f5f5f5;
    }

    .anchor {
      anchor-name: --my-anchor;
      width: 200px;
      height: 80px;
      padding: 8px 16px;
      background-color: #1a73e8;
      color: #fff;
      border-radius: 4px;
      border: none;
      font-size: 1rem;
      cursor: pointer;
    }

    .tooltip {
      position: absolute;
      position-anchor: --my-anchor;
      position-area: center right;
      /* anchor-size(width)、anchor-size(height) を省略した書き方 */
      width: anchor-size();
      height: anchor-size();
      margin-left: 16px;
      padding: 8px 16px;
      background-color: #333;
      color: #fff;
      border-radius: 4px;
      display: flex;
      align-items: center;
      justify-content: center;
    }

    .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="anchor">アンカー要素</div>
  <div class="tooltip">アンカーと同じサイズ</div>
</body>
</html>