Add example for polygon vertices styling

examples/polygon-styles.js

@@ -0,0 +1,101 @@
+goog.require('ol.Map');
+goog.require('ol.View');
+goog.require('ol.geom.MultiPoint');
+goog.require('ol.layer.Vector');
+goog.require('ol.source.GeoJSON');
+goog.require('ol.style.Circle');
+goog.require('ol.style.Fill');
+goog.require('ol.style.Stroke');
+goog.require('ol.style.Style');
+
+var styles = [
+  /* 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: 'blue',
+      width: 3
+    }),
+    fill: new ol.style.Fill({
+      color: 'rgba(0, 0, 255, 0.1)'
+    })
+  }),
+  new ol.style.Style({
+    image: new ol.style.Circle({
+      radius: 5,
+      fill: new ol.style.Fill({
+        color: 'orange'
+      })
+    }),
+    geometry: function(feature) {
+      // return the coordinates of the first ring of the polygon
+      var coordinates = feature.getGeometry().getCoordinates()[0];
+      return new ol.geom.MultiPoint(coordinates);
+    }
+  })
+];
+
+var source = new ol.source.GeoJSON(/** @type {olx.source.GeoJSONOptions} */ ({
+  object: {
+    'type': 'FeatureCollection',
+    'crs': {
+      'type': 'name',
+      'properties': {
+        'name': 'EPSG:3857'
+      }
+    },
+    'features': [
+      {
+        'type': 'Feature',
+        'geometry': {
+          'type': 'Polygon',
+          'coordinates': [[[-5e6, 6e6], [-5e6, 8e6], [-3e6, 8e6],
+              [-3e6, 6e6], [-5e6, 6e6]]]
+        }
+      },
+      {
+        'type': 'Feature',
+        'geometry': {
+          'type': 'Polygon',
+          'coordinates': [[[-2e6, 6e6], [-2e6, 8e6], [0, 8e6],
+              [0, 6e6], [-2e6, 6e6]]]
+        }
+      },
+      {
+        'type': 'Feature',
+        'geometry': {
+          'type': 'Polygon',
+          'coordinates': [[[1e6, 6e6], [1e6, 8e6], [3e6, 8e6],
+              [3e6, 6e6], [1e6, 6e6]]]
+        }
+      },
+      {
+        'type': 'Feature',
+        'geometry': {
+          'type': 'Polygon',
+          'coordinates': [[[-2e6, -1e6], [-1e6, 1e6],
+              [0, -1e6], [-2e6, -1e6]]]
+        }
+      }
+    ]
+  }
+}));
+
+var layer = new ol.layer.Vector({
+  source: source,
+  style: styles
+});
+
+var map = new ol.Map({
+  layers: [layer],
+  target: 'map',
+  view: new ol.View({
+    center: [0, 1000000],
+    zoom: 2
+  })
+});