Clusters defer

by Vladimir Vershinin

HTML

<script src="https://unpkg.com/[email protected]/lodash.js"></script>
<script src="https://unpkg.com/[email protected]/dist/vue.js"></script>
<script src="https://cdn.jsdelivr.net/gh/openlayers/openlayers.github.io@master/en/v5.3.0/build/ol.js"></script>
<script src="https://unpkg.com/[email protected]/lib/index.umd.js"></script>
<link rel="stylesheet" href="https://unpkg.com/[email protected]/lib/style.css">
<div id="app">
  <vl-map ref="map" data-projection="EPSG:4326">
    <vl-view ref="mapView" :zoom.sync="zoom" :center.sync="center"></vl-view>
    
    <vl-layer-tile>
      <vl-source-osm />
    </vl-layer-tile>
    
    <vl-layer-vector id="features" render-mode="image">
      <vl-source-cluster :distance="50">
        <vl-source-vector ref="featuresSource" @mounted="getFeatures"></vl-source-vector>
      </vl-source-cluster>
      
      <vl-style-func :factory="makeClusterStyleFunc"></vl-style-func>
    </vl-layer-vector>
  </vl-map>  
</div>

CSS

html, body, #app {
  width: 100%;
  height: 100%;
  margin: 0;
  padding: 0;
}

JavaScript

new Vue({
	el: '#app',
  data () {
  	return {
    	zoom: 2,
      center: [0, 0],
      places: _.range(0, 1000).map(i => {
      	let geom = [
        	_.random(-50, 50),
          _.random(-50, 50),
        ]
        return {
          id: 'random-' + i,
          geom,
        }
      }),
    }
  },
  methods: {
    getFeatures() {
      const sourceVm = this.$refs.featuresSource
      sourceVm.$source.clear()
      
      console.log(sourceVm, sourceVm.id, Object.prototype.hasOwnProperty(sourceVm, 'id'), 'id' in sourceVm)
      
      const features = this.places.map(place => {
        const geometry = new ol.geom.Point(place.geom)
        geometry.transform('EPSG:4326', 'EPSG:3857')
        
        let feature = new ol.Feature({ geometry })
        feature.setProperties(place)
        feature.setId(place.id)
        
        return feature
      })
      
      sourceVm.$source.addFeatures(features)
    },
  	makeClusterStyleFunc () {
    	const cache = {}
      
      return function __clusterStyleFunc (feature) {
        const size = feature.get('features').length
        let style = cache[size]
        
        if (!style) {
          style = VueLayers.olExt.createStyle({
            imageRadius: 10,
            strokeColor: '#fff',
            fillColor: '#3399cc',
            text: size.toString(),
            textFillColor: '#fff',
          })
          
          cache[size] = style
        }
        
        return [style]
      }
    },
  },
})