Add `surfaceSelectedEvent`

src/Surfaces/SurfaceManager.cpp

@@ -84,6 +84,7 @@ BaseSurface * SurfaceManager::selectSurface(BaseSurface * surface){
 		if(_surfaces[i] == surface){
 			selectedSurface = surface;
 			ofSendMessage("surfaceSelected");
+			ofNotifyEvent(surfaceSelectedEvent, i, this);
 			return selectedSurface;
 		}
 	}

src/Surfaces/SurfaceManager.h

@@ -45,6 +45,7 @@ class SurfaceManager {
 	
 		ofEvent <ofVec3f> vertexChangedEvent;
 		ofEvent <vector<ofVec3f>> verticesChangedEvent;
+		ofEvent <int> surfaceSelectedEvent;
 	
 		void onVertexChanged(ofVec3f & vertex);
 		void onVerticesChanged(vector<ofVec3f> & vertices);