Hit Tolerance

<!--
  说明：命中容差
  核心逻辑：forEachFeatureAtPixel 的 hitTolerance 控制像素级命中范围，滑块实时调整
  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>命中容差</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:160px}
  #info{margin-left:auto}
  #map{flex:1 1 auto;min-height:0;background:#eef0f3}
</style>
</head>
<body>
<div class="bar">
  <label>容差 <input type="range" id="tol" min="0" max="24" step="1" value="0"></label>
  <span id="tv">0 px</span>
  <span id="info">点地图上的小圆点</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 tolerance = 0;

  var features = [];
  for (var i = 0; i < 8; i++) {
    var f = new ol.Feature({
      geometry: new ol.geom.Point(fromLonLat([116.36 + (i % 4) * 0.018, 39.90 - Math.floor(i / 4) * 0.014]))
    });
    f.set('name', '点位 ' + (i + 1));
    features.push(f);
  }

  var source = new ol.source.Vector({ features: features });

  var clickMark = new ol.Feature({ geometry: new ol.geom.Point(fromLonLat([0, 0])), hidden: true });

  var layer = new ol.layer.Vector({
    source: source,
    style: new ol.style.Style({
      image: new ol.style.Circle({
        radius: 4,
        fill: new ol.style.Fill({ color: '#1f5fd0' }),
        stroke: new ol.style.Stroke({ color: '#ffffff', width: 1.5 })
      })
    })
  });

  var markLayer = new ol.layer.Vector({
    source: new ol.source.Vector({ features: [clickMark] }),
    style: new ol.style.Style({
      image: new ol.style.Circle({
        radius: 3,
        fill: new ol.style.Fill({ color: '#e2483c' })
      })
    })
  });

  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, markLayer],
    view: new ol.View({ center: fromLonLat([116.39, 39.90]), zoom: 14, minZoom: 2, maxZoom: 19 }),
    controls: ol.control.defaults.defaults({ attribution: false, rotate: false })
  });

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

  map.on('singleclick', function (evt) {
    clickMark.getGeometry().setCoordinates(evt.coordinate);
    clickMark.setStyle(new ol.style.Style({
      image: new ol.style.Circle({
        radius: 3,
        fill: new ol.style.Fill({ color: '#e2483c' })
      })
    }));

    var hit = map.forEachFeatureAtPixel(evt.pixel, function (f) {
      return f === clickMark ? null : f;
    }, { hitTolerance: tolerance });

    info.textContent = hit ? '命中 ' + hit.get('name') + '（容差 ' + tolerance + ' px）'
      : '未命中（容差 ' + tolerance + ' px）';
  });

  document.getElementById('tol').addEventListener('input', function () {
    tolerance = Number(this.value);
    document.getElementById('tv').textContent = tolerance + ' px';
  });
})();
</script>
</body>
</html>