Select by drawn polygon

by Vladimir Vershinin

HTML

<script src="https://unpkg.com/vue@latest/dist/vue.min.js"></script>
<script src="https://cdn.jsdelivr.net/gh/openlayers/openlayers.github.io/en/v5.3.0/build/ol.js"></script>
<script src="https://unpkg.com/[email protected]/turf.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">
  <div>
    Current selection: {{ selectedFeatures }}
  </div>
  <div v-if="drawnFeatures.length === 0">
      Draw polygon to select features first
  </div>
  <div v-else>
      <button @click="selectInDrawnPolygon">Select intersected features</button>
  </div>
  <vl-map ref="map" @created="mapCreated">
    <vl-view ref="mapView" :zoom.sync="zoom" :center.sync="center"></vl-view>
    
    <vl-layer-tile>
      <vl-source-osm />
    </vl-layer-tile>
    
    <vl-layer-vector ref="vectorLayer" id="my-features">
      <vl-source-vector ref="vectorSource">
        <vl-feature v-for="feature in geojsonObject.features" :key="feature.id"
                    :id="feature.id" :properties="feature.properties">
          <vl-geom-polygon :coordinates="feature.geometry.coordinates" />
        </vl-feature>
      </vl-source-vector>
    </vl-layer-vector>
    
    <vl-interaction-select ref="selectInteraction" :features.sync="selectedFeatures" :filter="selectFilter">
    </vl-interaction-select>

    <!-- draw components -->
    <vl-layer-vector id="draw-pane">
      <vl-source-vector ref="drawSource" ident="draw-target" :features.sync="drawnFeatures"></vl-source-vector>
    </vl-layer-vector>
    <vl-interaction-draw source="draw-target" type="Polygon"></vl-interaction-draw>
    <vl-interaction-modify source="draw-target"></vl-interaction-modify>
  </vl-map>  
</div>

CSS

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

JavaScript

let geojsonObject = {
  'type': 'FeatureCollection',
  'crs': {
    'type': 'name',
    'properties': {
      'name': 'EPSG:3857'
    }
  },
  'features': [{
  	'id': 1,
    'type': 'Feature',
    'geometry': {
      'type': 'Polygon',
      'coordinates': [[[-5e6, 6e6], [-5e6, 8e6], [-3e6, 8e6],
                       [-3e6, 6e6], [-5e6, 6e6]]]
    }
  }, {
  	'id': 2,
    'type': 'Feature',
    'geometry': {
      'type': 'Polygon',
      'coordinates': [[[-2e6, 6e6], [-2e6, 8e6], [0, 8e6],
                       [0, 6e6], [-2e6, 6e6]]]
    }
  }, {
  	'id': 3,
    'type': 'Feature',
    'geometry': {
      'type': 'Polygon',
      'coordinates': [[[1e6, 6e6], [1e6, 8e6], [3e6, 8e6],
                       [3e6, 6e6], [1e6, 6e6]]]
    }
  }, {
  	'id': 4,
    'type': 'Feature',
    'geometry': {
      'type': 'Polygon',
      'coordinates': [[[-2e6, -1e6], [-1e6, 1e6],
                       [0, -1e6], [-2e6, -1e6]]]
    }
  }]
};

new Vue({
	el: '#app',
  data () {
  	return {
    	zoom: 5,
      center: [0, 3000000],
      geojsonObject: geojsonObject,
      selectedFeatures: [],
      drawnFeatures: [],
    }
  },
  mounted () {
  	setTimeout(() => {    
    	this.$refs.mapView.$view.fit(this.$refs.vectorSource.$source.getExtent(), {
      	size: this.$refs.map.$map.getSize(),
      	duration: 1000,
      })
    }, 1000)
  },
  methods: {
    /**
     * @param {Vue} map - vl-map instance
     */
    mapCreated (map) {
      // a DragBox interaction used to select features by drawing boxes
      const dragBox = new ol.interaction.DragBox({
        condition: ol.events.condition.platformModifierKeyOnly
      })

      map.$map.addInteraction(dragBox)
      
      dragBox.on('boxend', () => {
        // features that intersect the box are added to the collection of
        // selected features
        const extent = dragBox.getGeometry().getExtent()
        /** @var {ol.source.Vector} source */
        const source = this.$refs.vectorSource.$source
        
   ...