Edit

Hit tolerance priority

simple5 openstreetmap22

Shows bad behavior of hit detection with hit tolerance.

Hover over the map and observe how the small circles get a black outline as you hover over them. Is the expected feature getting highlighted?

main.js
import 'ol/ol.css';
import CircleStyle from 'ol/style/Circle';
import Feature from 'ol/Feature';
import Map from 'ol/Map';
import VectorLayer from 'ol/layer/Vector';
import VectorSource from 'ol/source/Vector';
import View from 'ol/View';
import {Fill, Stroke, Style} from 'ol/style';
import {Point} from 'ol/geom';

const map = new Map({
  target: 'map',
  view: new View({
    center: [0, 0],
    resolution: 1,
    resolutions: [1],
  }),
});

const vectorLayer = new VectorLayer({
  source: new VectorSource({
    features: [
      new Feature({
        geometry: new Point([0, 0]),
        color: 'white',
      }),
      new Feature({
        geometry: new Point([-10, 0]),
        color: 'fuchsia',
      }),
      new Feature({
        geometry: new Point([-10, -10]),
        color: 'orange',
      }),
      new Feature({
        geometry: new Point([-10, 10]),
        color: 'cyan',
      }),
    ],
  }),
  style: (feature) => {
    return new Style({
      image: new CircleStyle({
        radius: 5,
        fill: new Fill({
          color: feature.get('color'),
        }),
        stroke: new Stroke({
          color: 'gray',
          width: 1,
        }),
      }),
    });
  },
});
map.addLayer(vectorLayer);

const highlightFeature = new Feature(new Point([NaN, NaN]));
highlightFeature.setStyle(
  new Style({
    image: new CircleStyle({
      radius: 5,
      stroke: new Stroke({
        color: 'black',
        width: 2,
      }),
    }),
  })
);
vectorLayer.getSource().addFeature(highlightFeature);
map.on('pointermove', (e) => {
  const hit = map.forEachFeatureAtPixel(
    e.pixel,
    (feature) => {
      highlightFeature.setGeometry(feature.getGeometry().clone());
      return true;
    },
    {
      hitTolerance: 10,
    }
  );
  if (!hit) {
    highlightFeature.setGeometry(new Point([NaN, NaN]));
  }
});
index.html
<!DOCTYPE html>
<html lang="en">
  <head>
    <meta charset="UTF-8">
    <title>Hit tolerance priority</title>
    <!-- Pointer events polyfill for old browsers, see https://caniuse.com/#feat=pointer -->
    <script src="https://unpkg.com/elm-pep"></script>
    <!-- The line below is only needed for old environments like Internet Explorer and Android 4.x -->
    <script src="https://cdn.polyfill.io/v3/polyfill.min.js?features=fetch,requestAnimationFrame,Element.prototype.classList,URL,TextDecoder,Number.isInteger"></script>
    <style>
      .map {
        width: 100%;
        height:400px;
      }
    </style>
  </head>
  <body>
    <div id="map" class="map"></div>
    <script src="main.js"></script>
  </body>
</html>
package.json
{
  "name": "hit-tolerance-priority",
  "dependencies": {
    "ol": "6.6.1"
  },
  "devDependencies": {
    "parcel": "^2.0.0-beta.1"
  },
  "scripts": {
    "start": "parcel index.html",
    "build": "parcel build --public-url . index.html"
  }
}