禁用“关闭”按钮，直到模式视图PDF向下滚动

<div id="pdf-container">
  <!-- PDF内容 -->
</div>
<button id="close-button" disabled>关闭</button>

#pdf-container {
  height: 300px; /* 设置一个固定高度 */
  overflow-y: auto; /* 允许垂直滚动 */
}

#close-button {
  margin-top: 10px;
}

document.addEventListener('DOMContentLoaded', function() {
  const pdfContainer = document.getElementById('pdf-container');
  const closeButton = document.getElementById('close-button');

  pdfContainer.addEventListener('scroll', function() {
    if (pdfContainer.scrollTop > 0) {
      closeButton.disabled = false;
    } else {
      closeButton.disabled = true;
    }
  });
});