Added Polygon mesh topology

- added Polygon to Topologies
- added mapping of Topologies::Polygon to EntityShape::Polygon in VTKTraits
- added a missing reference to a variable in MeshBuilder::validate

src/TNL/Meshes/MeshBuilder.h

@@ -92,7 +92,7 @@ private:
       assignedPoints.setValue( false );
 
       for( GlobalIndexType i = 0; i < getCellsCount(); i++ ) {
-         const auto cornerIds = this->cellSeeds[ i ].getCornerIds();
+         const auto& cornerIds = this->cellSeeds[ i ].getCornerIds();
          for( LocalIndexType j = 0; j < cornerIds.getSize(); j++ ) {
             assignedPoints[ cornerIds[ j ] ] = true;
             if( cornerIds[ j ] < 0 || getPointsCount() <= cornerIds[ j ] ) {

src/TNL/Meshes/Topologies/Polygon.h

+#pragma once
+
+#include <TNL/Meshes/Topologies/Edge.h>
+
+namespace TNL {
+namespace Meshes {
+namespace Topologies {
+
+struct Polygon
+{
+   static constexpr int dimension = 2;
+};
+
+template<>
+struct Subtopology< Polygon, 0 >
+{
+   typedef Vertex Topology;
+};
+
+template<>
+struct Subtopology< Polygon, 1 >
+{
+   typedef Edge Topology;
+};
+
+} // namespace Topologies
+} // namespace Meshes
+} // namespace TNL
\ No newline at end of file

src/TNL/Meshes/VTKTraits.h

@@ -19,6 +19,7 @@
 #include <TNL/Meshes/Topologies/Quadrangle.h>
 #include <TNL/Meshes/Topologies/Tetrahedron.h>
 #include <TNL/Meshes/Topologies/Hexahedron.h>
+#include <TNL/Meshes/Topologies/Polygon.h>
 
 namespace TNL {
 namespace Meshes {
@@ -122,12 +123,13 @@ inline int getEntityDimension( EntityShape shape )
 
 // static mapping of TNL entity topologies to EntityShape
 template< typename Topology > struct TopologyToEntityShape {};
-template<> struct TopologyToEntityShape< Topologies::Vertex >         { static constexpr EntityShape shape = EntityShape::Vertex; };
-template<> struct TopologyToEntityShape< Topologies::Edge >           { static constexpr EntityShape shape = EntityShape::Line; };
-template<> struct TopologyToEntityShape< Topologies::Triangle >       { static constexpr EntityShape shape = EntityShape::Triangle; };
+template<> struct TopologyToEntityShape< Topologies::Vertex >      { static constexpr EntityShape shape = EntityShape::Vertex; };
+template<> struct TopologyToEntityShape< Topologies::Edge >        { static constexpr EntityShape shape = EntityShape::Line; };
+template<> struct TopologyToEntityShape< Topologies::Triangle >    { static constexpr EntityShape shape = EntityShape::Triangle; };
 template<> struct TopologyToEntityShape< Topologies::Quadrangle >  { static constexpr EntityShape shape = EntityShape::Quad; };
-template<> struct TopologyToEntityShape< Topologies::Tetrahedron >    { static constexpr EntityShape shape = EntityShape::Tetra; };
-template<> struct TopologyToEntityShape< Topologies::Hexahedron >     { static constexpr EntityShape shape = EntityShape::Hexahedron; };
+template<> struct TopologyToEntityShape< Topologies::Tetrahedron > { static constexpr EntityShape shape = EntityShape::Tetra; };
+template<> struct TopologyToEntityShape< Topologies::Hexahedron >  { static constexpr EntityShape shape = EntityShape::Hexahedron; };
+template<> struct TopologyToEntityShape< Topologies::Polygon >     { static constexpr EntityShape shape = EntityShape::Polygon; };
 
 // mapping used in VTKWriter
 template< typename GridEntity >