Style function update

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]/lib/index.umd.js"></script>
<link rel="stylesheet" href="https://unpkg.com/[email protected]/lib/style.css">
<div id="app">
  <div>Stroke color {{ strokeColor }}</div>
  <vl-map ref="map">
    <vl-view :zoom.sync="zoom" :center.sync="center"></vl-view>
    
    <vl-layer-vector>
      <vl-source-vector :features.sync="geojsonObject.features" />
      <vl-style-func :factory="styleFuncProp" />
    </vl-layer-vector>
  </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: 2,
      center: [0, 3000000],
      geojsonObject: geojsonObject,
      strokeColor: 'blue',
    }
  },
  computed: {
  	styleFuncProp () {  
    	// bind to the strokeColor changes
    	if (!this.strokeColor) {
      	return
      }
    
    	return () => {
      	return feature => {
          return [
            /* We are using two different styles for the polygons:
             *  - The first style is for the polygons themselves.
             *  - The second style is to draw the vertices of the polygons.
             *    In a custom `geometry` function the vertices of a polygon are
             *    returned as `MultiPoint` geometry, which will be used to render
             *    the style.
             */
            new ol.style.Style({
              stroke: new ol.style.Stroke({
                color: this.strokeColor,
                width: 3
              }),
              fill: new ol.style.Fill({
                color: 'rgba(0, 0, 255, 0.1)'
              })
     ...