Specify an actual extent when loading features in the Webgl points renderer

This means any specified loading strategy will be taken into account.

Also added some tests to make sure the interaction with the source is
correct.

src/ol/renderer/webgl/PointsLayer.js

@@ -7,7 +7,7 @@ import {AttributeType, DefaultUniform} from '../../webgl/Helper.js';
 import GeometryType from '../../geom/GeometryType.js';
 import WebGLLayerRenderer, {colorDecodeId, colorEncodeId, WebGLWorkerMessageType} from './Layer.js';
 import ViewHint from '../../ViewHint.js';
-import {createEmpty, equals} from '../../extent.js';
+import {buffer, createEmpty, equals} from '../../extent.js';
 import {
   apply as applyTransform,
   create as createTransform,
@@ -18,6 +18,7 @@ import {create as createWebGLWorker} from '../../worker/webgl.js';
 import {getUid} from '../../util.js';
 import WebGLRenderTarget from '../../webgl/RenderTarget.js';
 import {assert} from '../../asserts.js';
+import BaseVector from '../../layer/BaseVector.js';
 
 /**
  * @typedef {Object} CustomAttribute A description of a custom attribute to be passed on to the GPU, with a value different
@@ -296,20 +297,22 @@ class WebGLPointsLayerRenderer extends WebGLLayerRenderer {
     const layer = this.getLayer();
     const vectorSource = layer.getSource();
     const viewState = frameState.viewState;
-
-    // the source has changed: clear the feature cache & reload features
-    const sourceChanged = this.sourceRevision_ < vectorSource.getRevision();
-    if (sourceChanged) {
-      this.sourceRevision_ = vectorSource.getRevision();
-
-      const projection = viewState.projection;
-      const resolution = viewState.resolution;
-      vectorSource.loadFeatures([-Infinity, -Infinity, Infinity, Infinity], resolution, projection);
-    }
-
     const viewNotMoving = !frameState.viewHints[ViewHint.ANIMATING] && !frameState.viewHints[ViewHint.INTERACTING];
     const extentChanged = !equals(this.previousExtent_, frameState.extent);
-    if ((sourceChanged || extentChanged) && viewNotMoving) {
+    const sourceChanged = this.sourceRevision_ < vectorSource.getRevision();
+
+    if (sourceChanged) {
+      this.sourceRevision_ = vectorSource.getRevision();
+    }
+
+    if (viewNotMoving && (extentChanged || sourceChanged)) {
+      const projection = viewState.projection;
+      const resolution = viewState.resolution;
+
+      const renderBuffer = layer instanceof BaseVector ? layer.getRenderBuffer() : 0;
+      const extent = buffer(frameState.extent, renderBuffer * resolution);
+      vectorSource.loadFeatures(extent, resolution, projection);
+
       this.rebuildBuffers_(frameState);
       this.previousExtent_ = frameState.extent.slice();
     }

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

@@ -104,7 +104,8 @@ describe('ol.renderer.webgl.PointsLayer', function() {
 
     beforeEach(function() {
       layer = new VectorLayer({
-        source: new VectorSource()
+        source: new VectorSource(),
+        renderBuffer: 10
       });
       renderer = new WebGLPointsLayerRenderer(layer, {
         vertexShader: simpleVertexShader,
@@ -233,6 +234,35 @@ describe('ol.renderer.webgl.PointsLayer', function() {
       renderer.prepareFrame(frameState);
       expect(spy.callCount).to.be(2);
     });
+
+    it('triggers source loading when the extent changes', function() {
+      const spy = sinon.spy(layer.getSource(), 'loadFeatures');
+
+      renderer.prepareFrame(frameState);
+      expect(spy.callCount).to.be(1);
+
+      renderer.prepareFrame(frameState);
+      expect(spy.callCount).to.be(1);
+
+      frameState.extent = [10, 20, 30, 40];
+      renderer.prepareFrame(frameState);
+      expect(spy.callCount).to.be(2);
+      expect(spy.getCall(1).args[0]).to.eql([0, 10, 40, 50]); // renderBuffer is 10
+    });
+
+    it('triggers source loading when the source revision changes', function() {
+      const spy = sinon.spy(layer.getSource(), 'loadFeatures');
+
+      renderer.prepareFrame(frameState);
+      expect(spy.callCount).to.be(1);
+
+      renderer.prepareFrame(frameState);
+      expect(spy.callCount).to.be(1);
+
+      layer.getSource().changed();
+      renderer.prepareFrame(frameState);
+      expect(spy.callCount).to.be(2);
+    });
   });
 
   describe('#forEachFeatureAtCoordinate', function() {