Max Bounds

<!--
  示例：边界限制
  核心逻辑：maxBounds 限制可拖动范围，setMaxBounds(null) 解除限制，对比夹取后的中心
  依赖：MapLibre GL JS 4 · jsDelivr CDN · demotiles 样式
-->
<!DOCTYPE html>
<html lang="zh-CN">
<head>
<meta name="robots" content="noindex,follow">
<meta charset="utf-8">
<meta name="viewport" content="width=device-width, initial-scale=1">
<title>边界限制</title>
<link rel="stylesheet" href="https://cdn.jsdelivr.net/npm/maplibre-gl@4/dist/maplibre-gl.css">
<style>
  html,body{height:100%;margin:0}
  body{display:flex;flex-direction:column;overflow:hidden;
       font:13px/1.6 -apple-system,"Segoe UI","PingFang SC",sans-serif;color:#16181d}
  .bar{flex:0 0 auto;display:flex;gap:10px;align-items:center;padding:8px 12px;
       background:#f6f7f9;border-bottom:1px solid #e3e6ea;font-size:12px;color:#58606e;flex-wrap:wrap}
  .bar b{color:#16181d;font-weight:600}
  .btn{border:1px solid #cdd3db;background:#fff;border-radius:4px;padding:3px 9px;
       font:12px/1.5 inherit;color:#16181d;cursor:pointer}
  .btn[disabled]{opacity:.5;cursor:default}
  .bar label{display:flex;gap:5px;align-items:center;cursor:pointer}
  #map{flex:1 1 auto;min-height:0}
</style>
</head>
<body>
<div class="bar">
  <label><input id="lock" type="checkbox" checked> 启用 maxBounds</label>
  <button class="btn" id="outside">跳到范围外</button>
  <span>中心 <b id="c">—</b></span>
  <span>缩放 <b id="z">—</b></span>
</div>
<div id="map"></div>
<script src="https://cdn.jsdelivr.net/npm/maplibre-gl@4/dist/maplibre-gl.js"></script>
<script>
(function () {
  'use strict';

  if (typeof maplibregl === 'undefined') {
    document.body.innerHTML =
      '<div style="padding:24px;color:#b42318">MapLibre 加载失败，请检查能否访问 cdn.jsdelivr.net</div>';
    return;
  }

  var BOUNDS = [[73.0, 3.0], [136.0, 54.0]];

  var map = new maplibregl.Map({
    container: 'map',
    style: 'https://demotiles.maplibre.org/style.json',
    center: [104.2, 35.5],
    zoom: 3.2,
    minZoom: 2,
    maxBounds: BOUNDS,
    attributionControl: { compact: true, customAttribution: 'MapLibre demo tiles' }
  });

  map.addControl(new maplibregl.NavigationControl(), 'top-right');

  function report() {
    var c = map.getCenter();
    document.getElementById('c').textContent =
      c.lng.toFixed(2) + ', ' + c.lat.toFixed(2);
    document.getElementById('z').textContent = map.getZoom().toFixed(2);
  }

  map.on('move', report);
  map.on('load', report);

  document.getElementById('lock').addEventListener('change', function () {
    map.setMaxBounds(this.checked ? BOUNDS : null);
    document.getElementById('outside').disabled = !this.checked;
    if (this.checked) map.fitBounds(BOUNDS, { padding: 10, duration: 500 });
  });

  document.getElementById('outside').addEventListener('click', function () {
    /* 目标落在范围外，地图会把中心夹回边界内 */
    map.easeTo({ center: [40.0, 10.0], zoom: 4.5, duration: 700 });
  });

  map.on('error', function (e) {
    if (e.error) console.warn('地图错误：' + e.error.message);
  });
})();
</script>
</body>
</html>