Webgl Draw Line

<!--
  说明：线段渲染样式
  核心逻辑：Stroke 的 width / lineDash / lineDashOffset 配绘制交互，虚线偏移定时更新
  依赖：OpenLayers 10.3.1 · 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>线段渲染样式</title>
<link rel="stylesheet" href="https://cdn.jsdelivr.net/npm/ol@10.3.1/ol.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}
  .bar{flex:0 0 auto;padding:8px 12px;background:#f6f7f9;border-bottom:1px solid #e3e6ea;
       display:flex;gap:12px;align-items:center;font-size:12px;color:#58606e;flex-wrap:wrap}
  .bar input[type=range]{width:120px}
  .bar input[type=color]{width:36px;height:24px;padding:0;border:1px solid #c9d0da;background:#fff}
  #info{margin-left:auto}
  #map{flex:1 1 auto;min-height:0;background:#eef0f3}
</style>
</head>
<body>
<div class="bar">
  <label>颜色 <input type="color" id="color" value="#1f5fd0"></label>
  <label>线宽 <input type="range" id="width" min="1" max="12" step="1" value="4"></label>
  <span id="wv">4 px</span>
  <label><input type="checkbox" id="anim" checked> 虚线动画</label>
  <span id="info">在地图上拖拽绘制折线</span>
</div>
<div id="map"></div>
<script src="https://cdn.jsdelivr.net/npm/ol@10.3.1/dist/ol.js"></script>
<script>
(function () {
  'use strict';

  if (typeof ol === 'undefined') {
    document.getElementById('map').innerHTML =
      '<div style="padding:20px;color:#b42318">OpenLayers 加载失败，请检查能否访问 cdn.jsdelivr.net</div>';
    return;
  }

  var fromLonLat = ol.proj.fromLonLat;

  var source = new ol.source.Vector();
  var color = '#1f5fd0';
  var width = 4;
  var offset = 0;
  var animate = true;

  function styleFn() {
    return new ol.style.Style({
      stroke: new ol.style.Stroke({
        color: color,
        width: width,
        lineCap: 'round',
        lineJoin: 'round',
        lineDash: [14, 10],
        lineDashOffset: offset
      })
    });
  }

  var layer = new ol.layer.Vector({ source: source, style: styleFn });

  var map = new ol.Map({
    target: 'map',
    layers: [new ol.layer.Tile({ source: new ol.source.XYZ({url: 'https://server.arcgisonline.com/ArcGIS/rest/services/World_Street_Map/MapServer/tile/{z}/{y}/{x}', attributions: 'Tiles © Esri'}) }), layer],
    view: new ol.View({ center: fromLonLat([116.391, 39.907]), zoom: 12, minZoom: 2, maxZoom: 19 }),
    controls: ol.control.defaults.defaults({ attribution: false, rotate: false })
  });

  var draw = new ol.interaction.Draw({
    source: source,
    type: 'LineString',
    style: styleFn
  });
  map.addInteraction(draw);

  var info = document.getElementById('info');

  draw.on('drawend', function () {
    info.textContent = '线段 ' + source.getFeatures().length + ' 条';
  });

  document.getElementById('color').addEventListener('input', function () {
    color = this.value;
    layer.changed();
  });

  document.getElementById('width').addEventListener('input', function () {
    width = Number(this.value);
    document.getElementById('wv').textContent = width + ' px';
    layer.changed();
  });

  document.getElementById('anim').addEventListener('change', function () {
    animate = this.checked;
  });

  setInterval(function () {
    if (!animate) return;
    offset -= 1;
    if (offset < -48) offset = 0;
    layer.changed();
  }, 60);
})();
</script>
</body>
</html>