Add rendering test for decluttered multipolygons

rendering/cases/layer-vector-multigeometry-decluttering/main.js

@@ -0,0 +1,55 @@
+import Map from '../../../src/ol/Map.js';
+import View from '../../../src/ol/View.js';
+import GeoJSON from '../../../src/ol/format/GeoJSON.js';
+import VectorLayer from '../../../src/ol/layer/Vector.js';
+import VectorSource from '../../../src/ol/source/Vector.js';
+import {Fill, Stroke, Style, Text} from '../../../src/ol/style.js';
+
+const map = new Map({
+  target: 'map',
+  view: new View({
+    center: [-17465028, 2331736],
+    zoom: 5
+  })
+});
+
+const labelStyle = new Style({
+  text: new Text({
+    font: '16px Ubuntu',
+    overflow: true,
+    fill: new Fill({
+      color: '#000'
+    }),
+    stroke: new Stroke({
+      color: '#fff',
+      width: 3
+    })
+  })
+});
+const countryStyle = new Style({
+  fill: new Fill({
+    color: 'rgba(255, 255, 255, 0.6)'
+  }),
+  stroke: new Stroke({
+    color: '#319FD3',
+    width: 1
+  })
+});
+const style = [countryStyle, labelStyle];
+
+const vectorLayer = new VectorLayer({
+  source: new VectorSource({
+    url: '/data/countries.json',
+    format: new GeoJSON()
+  }),
+  style: function(feature) {
+    labelStyle.getText().setText(feature.get('name'));
+    return style;
+  },
+  declutter: true
+});
+
+map.addLayer(vectorLayer);
+
+
+render({tolerance: 0.007});