Paints IOGraphs to a GDI+ Graphics object.
 /// <summary>
 /// Constructs with the provided graph painter and layout manager.
 /// </summary>
 public IOGraphViewportPainter(IOGraphPainter graphPainter, ILayoutManager layoutManager)
 {
     _graph         = null;
     _layoutManager = layoutManager;
     _graphPainter  = graphPainter;
 }
 /// <summary>
 /// Constructs with the provided graph painter and layout manager.
 /// </summary>
 public IOGraphViewportPainter(IOGraphPainter graphPainter, ILayoutManager layoutManager)
 {
     _graph = null;
     _layoutManager = layoutManager;
     _graphPainter = graphPainter;
 }
 /// <summary>
 /// Constructs with the provided graph painter and a default layout manager.
 /// </summary>
 public IOGraphViewportPainter(IOGraphPainter graphPainter)
 {
     _graph         = null;
     _layoutManager = new DepthLayoutManager();
     _graphPainter  = graphPainter;
 }
 /// <summary>
 /// Constructs with the provided graph painter and a default layout manager.
 /// </summary>
 public IOGraphViewportPainter(IOGraphPainter graphPainter)
 {
     _graph = null;
     _layoutManager = new DepthLayoutManager();
     _graphPainter = graphPainter;
 }