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Vector Label Decluttering

Label decluttering with a custom renderer.

Decluttering is used to avoid overlapping labels. The overflow: true setting on the text style makes it so labels that do not fit within the bounds of a polygon are also included.

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index.html<!DOCTYPE html>
<html lang="en">
  <head>
    <title>Vector Label Decluttering</title>
    <!-- The line below is only needed for old environments like Internet Explorer and Android 4.x -->
    <script src="https://cdn.polyfill.io/v2/polyfill.min.js?features=requestAnimationFrame,Element.prototype.classList,URL"></script>
    <script src="https://cdn.polyfill.io/v2/polyfill.min.js?features=Set""></script>
    <style>
      .map {
        width: 100%;
        height:400px;
      }
    </style>
  </head>
  <body>
    <div id="map" class="map"></div>
    <script src="index.js"></script>
  </body>
</html>
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index.jsimport 'ol/ol.css';
import Map from 'ol/Map';
import View from 'ol/View';
import GeoJSON from 'ol/format/GeoJSON';
import VectorLayer from 'ol/layer/Vector';
import VectorSource from 'ol/source/Vector';
import {Fill, Stroke, Style, Text} from 'ol/style';

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

var labelStyle = new Style({
  text: new Text({
    font: '12px Calibri,sans-serif',
    overflow: true,
    fill: new Fill({
      color: '#000'
    }),
    stroke: new Stroke({
      color: '#fff',
      width: 3
    })
  })
});
var countryStyle = new Style({
  fill: new Fill({
    color: 'rgba(255, 255, 255, 0.6)'
  }),
  stroke: new Stroke({
    color: '#319FD3',
    width: 1
  })
});
var style = [countryStyle, labelStyle];

var vectorLayer = new VectorLayer({
  source: new VectorSource({
    url: 'data/geojson/countries.geojson',
    format: new GeoJSON()
  }),
  style: function(feature) {
    labelStyle.getText().setText(feature.get('name'));
    return style;
  },
  declutter: true
});

map.addLayer(vectorLayer);
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package.json{
  "name": "vector-label-decluttering",
  "dependencies": {
    "ol": "6.1.1"
  },
  "devDependencies": {
    "parcel": "1.11.0"
  },
  "scripts": {
    "start": "parcel index.html",
    "build": "parcel build --experimental-scope-hoisting --public-url . index.html"
  }
}