listener for changing background data overlay added

frontend-js/src/main/js/map/CustomMap.js

@@ -37,6 +37,7 @@ function CustomMap(options) {
   this.registerListenerType("onBioEntityClick");
   this.registerListenerType("onShowOverlay");
   this.registerListenerType("onHideOverlay");
+  this.registerListenerType("onBackgroundOverlayChange");
 
   this._selectedOverlays = [];
 
@@ -230,14 +231,18 @@ CustomMap.prototype.openDataOverlay = function (param) {
           });
         }
       } else {
-        self.getGoogleMap().setMapTypeId(identifier.toString());
+        if (identifier.toString() === self.getGoogleMap().getMapTypeId()) {
+          return Promise.resolve();
+        } else {
+          self.getGoogleMap().setMapTypeId(identifier.toString());
 
-        var submaps = self.getSubmaps();
-        for (var i = 0; i < submaps.length; i++) {
-          var submap = submaps[i];
-          submap.openDataOverlay(identifier);
+          var submaps = self.getSubmaps();
+          for (var i = 0; i < submaps.length; i++) {
+            var submap = submaps[i];
+            submap.openDataOverlay(identifier);
+          }
+          return self.callListeners("onBackgroundOverlayChange", identifier);
         }
-        return Promise.resolve();
       }
     }).then(function () {
       return self.callListeners("onShowOverlay", overlayToOpen);

frontend-js/src/test/js/map/CustomMap-test.js

@@ -132,6 +132,35 @@ describe('CustomMap', function () {
       });
     });
 
+    it("check backgroundChangeListener", function () {
+      var map = helper.createCustomMap();
+      var overlay = helper.createOverlay();
+      overlay.setInitialized(true);
+      overlay.setInputDataAvailable(true);
+      map.getProject().addDataOverlay(overlay);
+      var overlay2 = helper.createOverlay();
+      overlay2.setInitialized(true);
+      overlay2.setInputDataAvailable(true);
+      map.getProject().addDataOverlay(overlay2);
+
+      var emptyBackground = helper.createOverlay();
+      emptyBackground.setInputDataAvailable(false);
+      emptyBackground.setName("Empty");
+      map.getProject().addDataOverlay(emptyBackground);
+
+      var counter = 0;
+      map.addListener("onBackgroundOverlayChange", function () {
+        counter++;
+      });
+
+      return map.openDataOverlay(overlay.getId()).then(function () {
+        assert.equal(1, counter, "listener wasn't fired");
+        return map.openDataOverlay(overlay2.getId());
+      }).then(function () {
+        assert.equal(1, counter, "listener shouldn't be fired again because nothing changed");
+      });
+    });
+
     it("simple", function () {
       var map = helper.createCustomMap();
       var alias = helper.createAlias(map);