Merge pull request #10960 from SDaron/clipping-layer

Improve Vector Clipping Layer example with a background layer and intersect

examples/layer-clipping-vector.js

@@ -1,13 +1,20 @@
 import GeoJSON from '../src/ol/format/GeoJSON.js';
 import Map from '../src/ol/Map.js';
-import OSM from '../src/ol/source/OSM.js';
-import VectorSource from '../src/ol/source/Vector.js';
 import View from '../src/ol/View.js';
 import {Fill, Style} from '../src/ol/style.js';
+import {OSM, Stamen, Vector as VectorSource} from '../src/ol/source.js';
 import {Tile as TileLayer, Vector as VectorLayer} from '../src/ol/layer.js';
 import {fromLonLat} from '../src/ol/proj.js';
 import {getVectorContext} from '../src/ol/render.js';
 
+//A distinct className is required to use another canvas for the background
+const background = new TileLayer({
+  className: 'stamen',
+  source: new Stamen({
+    layer: 'toner',
+  }),
+});
+
 const base = new TileLayer({
   source: new OSM(),
 });
@@ -20,6 +27,11 @@ const clipLayer = new VectorLayer({
   }),
 });
 
+//Giving the clipped layer an extent is necessary to avoid rendering when the feature is outside the viewport
+clipLayer.getSource().on('addfeature', function () {
+  base.setExtent(clipLayer.getSource().getExtent());
+});
+
 const style = new Style({
   fill: new Fill({
     color: 'black',
@@ -27,8 +39,8 @@ const style = new Style({
 });
 
 base.on('postrender', function (e) {
-  e.context.globalCompositeOperation = 'destination-in';
   const vectorContext = getVectorContext(e);
+  e.context.globalCompositeOperation = 'destination-in';
   clipLayer.getSource().forEachFeature(function (feature) {
     vectorContext.drawFeature(feature, style);
   });
@@ -36,7 +48,7 @@ base.on('postrender', function (e) {
 });
 
 const map = new Map({
-  layers: [base, clipLayer],
+  layers: [background, base, clipLayer],
   target: 'map',
   view: new View({
     center: fromLonLat([8.23, 46.86]),