PlanarFigure::PolyLineElement is currently implemented as struct consisting of an index and a point. I guess it was once implemented this way to make handling of PolyLines easier which is a list of PolyLineElements.
However, handling PolyLines as lists is very inconvenient especially when accessing neighboring points. Hence, I will change PolyLine to a vector of PolyLineElements.
As a result we do not need to keep index information for each PolyLineElement which reduces a PolyLineElement to a Point2D. I will declare the Point and Index members as well as the current constructor of PolyLineElement as deprecated for release 2014-06 and provide Point2D conversion operators. This allows a smooth transition to finally replace the PolyLineElement struct by a Point2D typedef in release 2014-09.