private IEnumerable <TRenderObject> drawPoints(IEnumerable <IPoint> points,
                                                       Symbol2D symbol, Symbol2D highlightSymbol, Symbol2D selectSymbol,
                                                       RenderState renderState)
        {
            // If we have a null symbol, use the default
            if (symbol == null)
            {
                symbol = DefaultSymbol;
            }
            if (highlightSymbol == null)
            {
                highlightSymbol = symbol;
            }
            if (selectSymbol == null)
            {
                selectSymbol = symbol;
            }

            return(VectorRenderer.RenderSymbols(
                       convertPoints(points),
                       symbol,
                       highlightSymbol,
                       selectSymbol,
                       renderState));
        }