Layer Z-Index


Example of ordering layers using Z-index.

There are are two managed layers (square and triangle) and one unmanaged layer (star).
The Z-index determines the rendering order; with {square: 1, triangle: 0, star: unmanaged} indices, the rendering order is triangle, square and star on top.

<!DOCTYPE html>
<html>
  <head>
    <title>Layer Z-Index</title>
    <link rel="stylesheet" href="https://openlayers.org/en/v5.3.0/css/ol.css" type="text/css">
    <!-- The line below is only needed for old environments like Internet Explorer and Android 4.x -->
    <script src="https://cdn.polyfill.io/v2/polyfill.min.js?features=requestAnimationFrame,Element.prototype.classList,URL"></script>

  </head>
  <body>
    <div id="map" class="map"></div>
    <div>
      <label for="idx1">
        <input type="number" id="idx1"></input>
        Square layer Z-index
      </label></br>

      <label for="idx2">
        <input type="number" id="idx2"></input>
        Triangle layer Z-index
      </label>
    </div>
    <script>
      import Feature from 'ol/Feature.js';
      import Map from 'ol/Map.js';
      import View from 'ol/View.js';
      import Point from 'ol/geom/Point.js';
      import VectorLayer from 'ol/layer/Vector.js';
      import VectorSource from 'ol/source/Vector.js';
      import {Fill, RegularShape, Stroke, Style} from 'ol/style.js';


      var stroke = new Stroke({color: 'black', width: 1});

      var styles = {
        'square': new Style({
          image: new RegularShape({
            fill: new Fill({color: 'blue'}),
            stroke: stroke,
            points: 4,
            radius: 80,
            angle: Math.PI / 4
          })
        }),
        'triangle': new Style({
          image: new RegularShape({
            fill: new Fill({color: 'red'}),
            stroke: stroke,
            points: 3,
            radius: 80,
            rotation: Math.PI / 4,
            angle: 0
          })
        }),
        'star': new Style({
          image: new RegularShape({
            fill: new Fill({color: 'green'}),
            stroke: stroke,
            points: 5,
            radius: 80,
            radius2: 4,
            angle: 0
          })
        })
      };


      function createLayer(coordinates, style, zIndex) {
        var feature = new Feature(new Point(coordinates));
        feature.setStyle(style);

        var source = new VectorSource({
          features: [feature]
        });

        var vectorLayer = new VectorLayer({
          source: source
        });
        vectorLayer.setZIndex(zIndex);

        return vectorLayer;
      }

      var layer0 = createLayer([40, 40], styles['star'], 0);
      var layer1 = createLayer([0, 0], styles['square'], 1);
      var layer2 = createLayer([0, 40], styles['triangle'], 0);

      var layers = [];
      layers.push(layer1);
      layers.push(layer2);

      var map = new Map({
        layers: layers,
        target: 'map',
        view: new View({
          center: [0, 0],
          zoom: 18
        })
      });

      layer0.setMap(map);


      function bindInputs(id, layer) {
        var idxInput = document.getElementById('idx' + id);
        idxInput.onchange = function() {
          layer.setZIndex(parseInt(this.value, 10) || 0);
        };
        idxInput.value = String(layer.getZIndex());
      }
      bindInputs(1, layer1);
      bindInputs(2, layer2);
    </script>
  </body>
</html>