code: public void addGeometry(Geometry geometry) throws GeometryMergeException {
  		if (!busy) {
  			throw new GeometryMergeException("Can't add a geometry if no merging process is active.");
  		}
  		geometries.add(geometry);
  		eventBus.fireEvent(new GeometryMergeAddedEvent(geometry));
  	}
docs: Add a geometry to the list for merging. When <code>stop</code> is called, it is this list that is merged.
  
  @param geometry The geometry to add.
  @throws GeometryMergeException In case the merging process has not been started.