Add 'rendercomplete' event

src/ol/source/Image.js

@@ -201,16 +201,19 @@ class ImageSource extends Source {
     const image = /** @type {module:ol/Image} */ (event.target);
     switch (image.getState()) {
       case ImageState.LOADING:
+        this.loading = true;
         this.dispatchEvent(
           new ImageSourceEvent(ImageSourceEventType.IMAGELOADSTART,
             image));
         break;
       case ImageState.LOADED:
+        this.loading = false;
         this.dispatchEvent(
           new ImageSourceEvent(ImageSourceEventType.IMAGELOADEND,
             image));
         break;
       case ImageState.ERROR:
+        this.loading = false;
         this.dispatchEvent(
           new ImageSourceEvent(ImageSourceEventType.IMAGELOADERROR,
             image));

src/ol/source/Source.js

@@ -66,6 +66,13 @@ class Source extends BaseObject {
     */
     this.attributions_ = this.adaptAttributions_(options.attributions);
 
+    /**
+     * This source is currently loading data. Sources that defer loading to the
+     * map's tile queue never set this to `true`.
+     * @type {boolean}
+     */
+    this.loading = false;
+
     /**
     * @private
     * @type {module:ol/source/State}

src/ol/source/Vector.js

@@ -871,6 +871,7 @@ class VectorSource extends Source {
   loadFeatures(extent, resolution, projection) {
     const loadedExtentsRtree = this.loadedExtentsRtree_;
     const extentsToLoad = this.strategy_(extent, resolution);
+    this.loading = false;
     for (let i = 0, ii = extentsToLoad.length; i < ii; ++i) {
       const extentToLoad = extentsToLoad[i];
       const alreadyLoaded = loadedExtentsRtree.forEachInExtent(extentToLoad,
@@ -884,6 +885,7 @@ class VectorSource extends Source {
       if (!alreadyLoaded) {
         this.loader_.call(this, extentToLoad, resolution, projection);
         loadedExtentsRtree.insert(extentToLoad, {extent: extentToLoad.slice()});
+        this.loading = true;
       }
     }
   }