Webgl / add utils for pushing geojson geometries in webgl buffers

For now only point geometries are handled.

test/spec/ol/renderer/webgl/layer.test.js

@@ -1,6 +1,6 @@
-import VectorLayer from '../../../../../src/ol/layer/Vector.js';
-import VectorSource from '../../../../../src/ol/source/Vector.js';
-import WebGLLayerRenderer, {getBlankTexture} from '../../../../../src/ol/renderer/webgl/Layer';
+import WebGLLayerRenderer, {getBlankTexture, pushFeatureInBuffer} from '../../../../../src/ol/renderer/webgl/Layer';
+import WebGLArrayBuffer from '../../../../../src/ol/webgl/Buffer';
+import Layer from '../../../../../src/ol/layer/Layer';
 
 
 describe('ol.renderer.webgl.Layer', function() {
@@ -21,15 +21,94 @@ describe('ol.renderer.webgl.Layer', function() {
     });
 
     it('creates a new instance', function () {
-      const layer = new VectorLayer({
-        source: new VectorSource()
-      });
+      const layer = new Layer({});
       const renderer = new WebGLLayerRenderer(layer);
       expect(renderer).to.be.a(WebGLLayerRenderer);
     });
 
   });
 
+  describe('pushFeatureInBuffer', function() {
+    let vertexBuffer, indexBuffer;
+
+    beforeEach(function () {
+      vertexBuffer = new WebGLArrayBuffer();
+      indexBuffer = new WebGLArrayBuffer();
+    });
+
+    it('does nothing if the feature has no geometry', function() {
+      const feature = {
+        type: "Feature",
+        id: "AFG",
+        properties: {
+          color:[0.5, 1, 0.2, 0.7],
+          size: 3
+        },
+        geometry: null
+      };
+      pushFeatureInBuffer(vertexBuffer, indexBuffer, feature);
+      expect(vertexBuffer.getArray().length).to.eql(0);
+      expect(indexBuffer.getArray().length).to.eql(0);
+    });
+
+    it('adds two triangles with the correct attributes for a point geometry', function() {
+      const feature = {
+        type: "Feature",
+        id: "AFG",
+        properties: {
+          color:[0.5, 1, 0.2, 0.7],
+          size: 3
+        },
+        geometry: {
+          type: "Point",
+          coordinates: [ -75, 47 ]
+        }
+      };
+      const attributePerVertex = 12;
+      pushFeatureInBuffer(vertexBuffer, indexBuffer, feature);
+      expect(vertexBuffer.getArray().length).to.eql(attributePerVertex * 4);
+      expect(indexBuffer.getArray().length).to.eql(6);
+    });
+
+    it('correctly sets indices & coordinates for several features', function() {
+      const feature = {
+        type: "Feature",
+        id: "AFG",
+        properties: {
+          color:[0.5, 1, 0.2, 0.7],
+          size: 3
+        },
+        geometry: {
+          type: "Point",
+          coordinates: [ -75, 47 ]
+        }
+      };
+      const attributePerVertex = 12;
+      pushFeatureInBuffer(vertexBuffer, indexBuffer, feature);
+      pushFeatureInBuffer(vertexBuffer, indexBuffer, feature);
+      expect(vertexBuffer.getArray()[0]).to.eql(-75);
+      expect(vertexBuffer.getArray()[1]).to.eql(47);
+      expect(vertexBuffer.getArray()[0 + attributePerVertex]).to.eql(-75);
+      expect(vertexBuffer.getArray()[1 + attributePerVertex]).to.eql(47);
+
+      // first point
+      expect(indexBuffer.getArray()[0]).to.eql(0);
+      expect(indexBuffer.getArray()[1]).to.eql(1);
+      expect(indexBuffer.getArray()[2]).to.eql(3);
+      expect(indexBuffer.getArray()[3]).to.eql(1);
+      expect(indexBuffer.getArray()[4]).to.eql(2);
+      expect(indexBuffer.getArray()[5]).to.eql(3);
+
+      // second point
+      expect(indexBuffer.getArray()[6]).to.eql(4);
+      expect(indexBuffer.getArray()[7]).to.eql(5);
+      expect(indexBuffer.getArray()[8]).to.eql(7);
+      expect(indexBuffer.getArray()[9]).to.eql(5);
+      expect(indexBuffer.getArray()[10]).to.eql(6);
+      expect(indexBuffer.getArray()[11]).to.eql(7);
+    });
+  });
+
   describe('getBlankTexture', function() {
     it('creates a 1x1 white texture', function() {
       const texture = getBlankTexture();