From ef1727f21a1d63c6715a4168e31b318b7b0a1de7 Mon Sep 17 00:00:00 2001
From: Hans-Christian Ebke <ebke@cs.rwth-aachen.de>
Date: Fri, 9 Aug 2013 09:57:18 +0000
Subject: [PATCH] Added mesh cast for meshes with different but identical
 traits.

git-svn-id: http://www.openmesh.org/svnrepo/OpenMesh/trunk@920 fdac6126-5c0c-442c-9429-916003d36597
---
 src/OpenMesh/Core/Mesh/AttribKernelT.hh   |  2 +
 src/OpenMesh/Core/Mesh/FinalMeshItemsT.hh | 88 +++++++++++++++++++++++
 src/OpenMesh/Core/Mesh/PolyMeshT.hh       | 49 +++++++++++++
 3 files changed, 139 insertions(+)

diff --git a/src/OpenMesh/Core/Mesh/AttribKernelT.hh b/src/OpenMesh/Core/Mesh/AttribKernelT.hh
index 879deeee..639d170f 100644
--- a/src/OpenMesh/Core/Mesh/AttribKernelT.hh
+++ b/src/OpenMesh/Core/Mesh/AttribKernelT.hh
@@ -73,6 +73,8 @@ public:
 
   //---------------------------------------------------------------- item types
 
+  typedef MeshItems MeshItemsT;
+  typedef Connectivity ConnectivityT;
   typedef typename Connectivity::Vertex     Vertex;
   typedef typename Connectivity::Halfedge   Halfedge;
   typedef typename Connectivity::Edge       Edge;
diff --git a/src/OpenMesh/Core/Mesh/FinalMeshItemsT.hh b/src/OpenMesh/Core/Mesh/FinalMeshItemsT.hh
index 9c7986d1..506bdd41 100644
--- a/src/OpenMesh/Core/Mesh/FinalMeshItemsT.hh
+++ b/src/OpenMesh/Core/Mesh/FinalMeshItemsT.hh
@@ -124,6 +124,94 @@ struct FinalMeshItemsT
 };
 
 
+#ifndef DOXY_IGNORE_THIS
+namespace {
+namespace TM {
+template<typename Lhs, typename Rhs> struct TypeEquality;
+template<typename Lhs> struct TypeEquality<Lhs, Lhs> {};
+
+template<typename LhsTraits, typename RhsTraits> struct ItemsEquality {
+    TypeEquality<typename LhsTraits::Point, typename RhsTraits::Point> te1;
+    TypeEquality<typename LhsTraits::Scalar, typename RhsTraits::Scalar> te2;
+    TypeEquality<typename LhsTraits::Normal, typename RhsTraits::Normal> te3;
+    TypeEquality<typename LhsTraits::Color, typename RhsTraits::Color> te4;
+    TypeEquality<typename LhsTraits::TexCoord1D, typename RhsTraits::TexCoord1D> te5;
+    TypeEquality<typename LhsTraits::TexCoord2D, typename RhsTraits::TexCoord2D> te6;
+    TypeEquality<typename LhsTraits::TexCoord3D, typename RhsTraits::TexCoord3D> te7;
+    TypeEquality<typename LhsTraits::TextureIndex, typename RhsTraits::TextureIndex> te8;
+};
+
+} /* namespace TM */
+} /* anonymous namespace */
+#endif
+
+/**
+ * @brief Cast a mesh with different but identical traits into each other.
+ *
+ * Note that there exists a syntactically more convenient global method
+ * mesh_cast().
+ *
+ * Example:
+ * @code{.cpp}
+ * struct Traits1 : public OpenMesh::DefaultTraits {
+ *   typedef Vec3d Point;
+ * }
+ * struct Traits2 : public OpenMesh::DefaultTraits {
+ *   typedef Vec3d Point;
+ * }
+ * struct Traits3 : public OpenMesh::DefaultTraits {
+ *   typedef Vec3f Point;
+ * }
+ *
+ * TriMesh_ArrayKernelT<TriTraits1> a;
+ * TriMesh_ArrayKernelT<TriTraits2> &b = MeshCast<TriMesh_ArrayKernelT<TriTraits2>&, TriMesh_ArrayKernelT<TriTraits1>&>::cast(a); // OK
+ * TriMesh_ArrayKernelT<TriTraits3> &c = MeshCast<TriMesh_ArrayKernelT<TriTraits3>&, TriMesh_ArrayKernelT<TriTraits1>&>::cast(a); // ERROR
+ * @endcode
+ *
+ * @see mesh_cast()
+ *
+ * @param rhs
+ * @return
+ */
+template<typename LhsMeshT, typename RhsMeshT> struct MeshCast;
+
+template<typename LhsMeshT, typename RhsMeshT>
+struct MeshCast<LhsMeshT&, RhsMeshT&> {
+    static LhsMeshT &cast(RhsMeshT &rhs) {
+        (void)sizeof(TM::ItemsEquality<typename LhsMeshT::MeshItemsT, typename RhsMeshT::MeshItemsT>);
+        (void)sizeof(TM::TypeEquality<typename LhsMeshT::ConnectivityT, typename RhsMeshT::ConnectivityT>);
+        return reinterpret_cast<LhsMeshT&>(rhs);
+    }
+};
+
+template<typename LhsMeshT, typename RhsMeshT>
+struct MeshCast<const LhsMeshT&, const RhsMeshT&> {
+    static const LhsMeshT &cast(const RhsMeshT &rhs) {
+        (void)sizeof(TM::ItemsEquality<typename LhsMeshT::MeshItemsT, typename RhsMeshT::MeshItemsT>);
+        (void)sizeof(TM::TypeEquality<typename LhsMeshT::ConnectivityT, typename RhsMeshT::ConnectivityT>);
+        return reinterpret_cast<const LhsMeshT&>(rhs);
+    }
+};
+
+template<typename LhsMeshT, typename RhsMeshT>
+struct MeshCast<LhsMeshT*, RhsMeshT*> {
+    static LhsMeshT *cast(RhsMeshT *rhs) {
+        (void)sizeof(TM::ItemsEquality<typename LhsMeshT::MeshItemsT, typename RhsMeshT::MeshItemsT>);
+        (void)sizeof(TM::TypeEquality<typename LhsMeshT::ConnectivityT, typename RhsMeshT::ConnectivityT>);
+        return reinterpret_cast<LhsMeshT*>(rhs);
+    }
+};
+
+template<typename LhsMeshT, typename RhsMeshT>
+struct MeshCast<const LhsMeshT*, const RhsMeshT*> {
+    static const LhsMeshT *cast(const RhsMeshT *rhs) {
+        (void)sizeof(TM::ItemsEquality<typename LhsMeshT::MeshItemsT, typename RhsMeshT::MeshItemsT>);
+        (void)sizeof(TM::TypeEquality<typename LhsMeshT::ConnectivityT, typename RhsMeshT::ConnectivityT>);
+        return reinterpret_cast<const LhsMeshT*>(rhs);
+    }
+};
+
+
 //=============================================================================
 } // namespace OpenMesh
 //=============================================================================
diff --git a/src/OpenMesh/Core/Mesh/PolyMeshT.hh b/src/OpenMesh/Core/Mesh/PolyMeshT.hh
index 41ded5ca..c3f762a3 100644
--- a/src/OpenMesh/Core/Mesh/PolyMeshT.hh
+++ b/src/OpenMesh/Core/Mesh/PolyMeshT.hh
@@ -492,6 +492,55 @@ public:
   inline void split(EdgeHandle _eh, VertexHandle _vh)
   { Kernel::split_edge(_eh, _vh); }
   
+  /**
+   * @brief Cast a mesh with different but identical traits into each other.
+   *
+   * Example:
+   * @code{.cpp}
+   * struct Traits1 : public OpenMesh::DefaultTraits {
+   *   typedef Vec3d Point;
+   * }
+   * struct Traits2 : public OpenMesh::DefaultTraits {
+   *   typedef Vec3d Point;
+   * }
+   * struct Traits3 : public OpenMesh::DefaultTraits {
+   *   typedef Vec3f Point;
+   * }
+   *
+   * TriMesh_ArrayKernelT<TriTraits1> a;
+   * TriMesh_ArrayKernelT<TriTraits2> &b = mesh_cast<TriMesh_ArrayKernelT<TriTraits2>&>(a); // OK
+   * TriMesh_ArrayKernelT<TriTraits3> &c = mesh_cast<TriMesh_ArrayKernelT<TriTraits3>&>(a); // ERROR
+   * @endcode
+   *
+   * @see MeshCast
+   *
+   * @param rhs
+   * @return
+   */
+  template<typename LHS>
+  friend
+  LHS mesh_cast(PolyMeshT &rhs) {
+      return MeshCast<LHS, PolyMeshT&>::cast(rhs);
+  }
+
+  template<typename LHS>
+  friend
+  LHS mesh_cast(PolyMeshT *rhs) {
+      return MeshCast<LHS, PolyMeshT*>::cast(rhs);
+  }
+
+  template<typename LHS>
+  friend
+  const LHS mesh_cast(const PolyMeshT &rhs) {
+      return MeshCast<LHS, const PolyMeshT&>::cast(rhs);
+  }
+
+  template<typename LHS>
+  friend
+  const LHS mesh_cast(const PolyMeshT *rhs) {
+      return MeshCast<LHS, const PolyMeshT*>::cast(rhs);
+  }
+
 };