Polygon Dashed

<!--
  示例：虚线描边多边形
  核心逻辑：PathStyleExtension 打开 dash，PolygonLayer 的描边就按 getLineDashArray 断开
  数据：页面内构造的五个规划片区多边形
  依赖：deck.gl 9.0 · jsDelivr CDN
-->
<!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>虚线描边多边形</title>
<style>
  html,body{height:100%;margin:0;background:#0d1117}
  body{display:flex;flex-direction:column;overflow:hidden;
       font:13px/1.6 -apple-system,"Segoe UI","PingFang SC",sans-serif;color:#e6e8ec}
  .bar{position:relative;z-index:5;flex:0 0 auto;padding:8px 12px;background:#161b22;border-bottom:1px solid #252c36;
       display:flex;gap:14px;align-items:center;font-size:12px;color:#8b93a1;flex-wrap:wrap}
  .bar b{color:#58a6ff;font-weight:600}
  .bar input[type=range]{width:120px}
  #cv{flex:1 1 auto;min-height:0;width:100%}
</style>
</head>
<body>
<div class="bar">
  <span>片区 <b>5</b></span>
  <label>虚线节拍 <input id="d" type="range" min="1" max="12" step="1" value="6"> <b id="dv">6</b></label>
  <span>虚线与实心填充互不影响</span>
</div>
<canvas id="cv"></canvas>
<script src="https://cdn.jsdelivr.net/npm/deck.gl@9.0.35/dist.min.js"></script>
<script>
(function () {
  'use strict';

  if (typeof deck === 'undefined') {
    document.body.innerHTML =
      '<div style="padding:24px;color:#ff8c74">deck.gl 加载失败，请检查能否访问 cdn.jsdelivr.net</div>';
    return;
  }

  /* 以中心点生成一个不规则的环，模拟行政边界 */
  function ring(lng, lat, r, seed) {
    var pts = [];
    for (var i = 0; i <= 32; i++) {
      var a = i / 32 * Math.PI * 2;
      var wobble = 1 + 0.18 * Math.sin(a * 3 + seed) + 0.1 * Math.cos(a * 5 - seed);
      pts.push([
        lng + Math.cos(a) * r * wobble,
        lat + Math.sin(a) * r * 0.7 * wobble
      ]);
    }
    return pts;
  }

  var areas = [
    { name: '北部片区', center: [116.39, 39.90], r: 1.6, seed: 0.4, c: [88, 166, 255] },
    { name: '东部片区', center: [121.47, 31.23], r: 1.2, seed: 1.6, c: [255, 166, 87] },
    { name: '南部片区', center: [113.26, 23.12], r: 1.4, seed: 2.7, c: [126, 231, 135] },
    { name: '西部片区', center: [104.06, 30.57], r: 1.7, seed: 3.9, c: [214, 137, 255] },
    { name: '西北片区', center: [108.94, 34.34], r: 1.1, seed: 5.1, c: [255, 121, 198] }
  ].map(function (a) {
    return {
      name: a.name,
      color: a.c,
      polygon: [ring(a.center[0], a.center[1], a.r, a.seed)]
    };
  });

  function build(dash) {
    return new deck.PolygonLayer({
      id: 'areas-' + dash,
      data: areas,
      getPolygon: function (d) { return d.polygon; },
      filled: true,
      getFillColor: function (d) { return [d.color[0], d.color[1], d.color[2], 55]; },
      stroked: true,
      getLineColor: function (d) { return d.color.concat([255]); },
      getLineWidth: 2.5,
      lineWidthUnits: 'pixels',
      getLineDashArray: [dash, Math.max(2, Math.round(dash / 2))],
      /* 虚线段在拐角处对半分，闭合环看起来更均匀 */
      dashJustified: true,
      extensions: [new deck.PathStyleExtension({ dash: true })],
      pickable: true
    });
  }

  var current = build(6);

  var deckgl = new deck.Deck({
    canvas: document.getElementById('cv'),
    width: '100%',
    height: '100%',
    initialViewState: {
      longitude: 110,
      latitude: 33,
      zoom: 3.6,
      pitch: 30,
      bearing: 0,
      maxPitch: 65
    },
    controller: true,
    layers: [current],
    getTooltip: function (info) {
      return info.object ? info.object.name : null;
    }
  });

  document.getElementById('d').addEventListener('input', function () {
    var v = parseInt(this.value, 10);
    document.getElementById('dv').textContent = v;
    current = build(v);
    deckgl.setProps({ layers: [current] });
  });

  window.__deck = deckgl;
})();
</script>
</body>
</html>