Changes after Andreas' review

BGL/include/CGAL/boost/graph/Connected_components_graph.h

@@ -65,31 +65,32 @@ struct Connected_components_graph
 
     /*!
      * \brief Creates a Connected_components_graph of the connected components of `graph` that are listed in `pids`.
+    typedef unspecified_type Indices;
+
      * \param graph the graph containing the wanted patches.
-     * \param fccmap the property_map that assigns a patch to each face, with
+     * \param fccmap the property_map that assigns a connected component to each face, with
         `boost::graph_traits<Graph>::%face_descriptor` as key type and
         `graph_traits<Graph>::faces_size_type` as value type.
-     * \param pids the indices of the patches of interest.
+     * \param ir the indices of the connected components of interest.
      */
+  template <typename IndexRange>
     Connected_components_graph(const Graph& graph,
-                     FaceComponentMap fccmap,
+                               FaceComponentMap fccmap,
-                     const boost::unordered_set<typename boost::property_traits<FaceComponentMap>::value_type>& pids)
+                               const IndexRange& ir)
-        : _graph(graph), _property_map(fccmap), _patch_indices(pids)
+      : _graph(graph), _property_map(fccmap), _patch_indices(ir.begin(),ir.end())
-    {
+    {}
-    }
 
     /*!
-     * \brief Creates a Connected_components_graph of the connected component `pid` of `graph`.
+     * \brief Creates a Connected_components_graph of the connected component `id` of `graph`.
      * \param graph the graph containing the wanted patch.
      * \param fccmap the property_map that assigns a patch to each face
-     * \param pid the index of the patch of interest.
+     * \param id the index of the connected component of interest.
      */
     Connected_components_graph(const Graph& graph,
-                     FaceComponentMap fccmap,
+                               FaceComponentMap fccmap,
-                     typename boost::property_traits<FaceComponentMap>::value_type pid)
+                               typename boost::property_traits<FaceComponentMap>::value_type pid)
         : _graph(graph), _property_map(fccmap)
     {
-        _patch_indices = boost::unordered_set<typename boost::property_traits<FaceComponentMap>::value_type>();
         _patch_indices.insert(pid);
     }
     ///returns the graph of the Connected_components_graph.
@@ -98,9 +99,21 @@ struct Connected_components_graph
     ///returns the property map of the Connected_components_graph.
     FaceComponentMap property_map()const{ return _property_map; }
     ///returns the unordered set of patch ids of the Connected_components_graph.
-    boost::unordered_set<typename boost::property_traits<FaceComponentMap>::value_type> patch_indices()const{ return _patch_indices; }
+#ifndef DOXYGEN_RUNNING
+    const boost::unordered_set<typename boost::property_traits<FaceComponentMap>::value_type>& 
+#else
+    Index_range
+#endif
+    indices()const{ return _patch_indices; }
+
     /// Replaces the current unordered set of patches by `pids`
-    void change_patch_id(boost::unordered_set<typename boost::property_traits<FaceComponentMap>::value_type> pids) { _patch_indices = pids;}
+    template <typename IndexRange>
+    void set_connected_components(const IndexRange& ir) { _patch_indices = boost::unordered_set<typename boost::property_traits<FaceComponentMap>::value_type>(ir.begin(), ir.end());}
+
+    void set_connected_component(typename boost::property_traits<FaceComponentMap>::value_type pid) {
+      _patch_indices.clear();
+      _patch_indices.insert(pid);
+    }
   
     struct Is_simplex_valid
     {
@@ -194,7 +207,7 @@ bool
 in_CC(const typename boost::graph_traits< Connected_components_graph<Graph, FaceComponentMap> >::face_descriptor f,
          const Connected_components_graph<Graph, FaceComponentMap> & w)
 {
-    return  w.patch_indices().find(boost::get(w.property_map(), f)) != w.patch_indices().end();
+    return  w.indices().find(boost::get(w.property_map(), f)) != w.indices().end();
 }
 
 template <class Graph, typename FaceComponentMap >
@@ -546,8 +559,7 @@ halfedge(typename boost::graph_traits< Connected_components_graph<Graph, FaceCom
 
 
 template <class Graph, typename FaceComponentMap >
-std::pair<typename boost::graph_traits<Connected_components_graph<Graph, FaceComponentMap> >::face_iterator,
+Iterator_range<typename boost::graph_traits<Connected_components_graph<Graph, FaceComponentMap> >::face_iterator>
-typename boost::graph_traits<Connected_components_graph<Graph, FaceComponentMap> >::face_iterator>
 faces(const Connected_components_graph<Graph, FaceComponentMap> & w)
 {
     typedef typename boost::graph_traits<Connected_components_graph<Graph, FaceComponentMap> >::face_iterator face_iterator;

Polygon_mesh_processing/doc/Polygon_mesh_processing/Polygon_mesh_processing.txt

@@ -598,7 +598,7 @@ should be discarded in favour of major connected components.
 
 \subsection CCExample Connected Components Example
 
-The following example shows how to record the connected
+The first example shows how to record the connected
 components of a polygon mesh.
 In particular, we provide an example for the optional parameter \c EdgeConstraintMap,
 a property map that returns information about an edge being a \e constraint or not.
@@ -607,6 +607,12 @@ the propagation of a connected component index to cross it.
 
 \cgalExample{Polygon_mesh_processing/connected_components_example.cpp}
 
+The second example shows how to use the class template `Connected_components_graph`
+which enables to treat one or several connected components as a face graph.
+
+\cgalExample{Polygon_mesh_processing/connected_components_graph_example.cpp}
+
+
 \section PMPDistance Approximate Hausdorff Distance
 
 This package provides methods to compute (approximate) distances between meshes and point sets.

Polygon_mesh_processing/doc/Polygon_mesh_processing/examples.txt

@@ -7,6 +7,7 @@
 \example Polygon_mesh_processing/point_inside_example.cpp
 \example Polygon_mesh_processing/triangulate_faces_example.cpp
 \example Polygon_mesh_processing/connected_components_example.cpp
+\example Polygon_mesh_processing/connected_components_graph_example.cpp
 \example Polygon_mesh_processing/polygon_soup_example.cpp
 \example Polygon_mesh_processing/triangulate_polyline_example.cpp
 \example Polygon_mesh_processing/refine_fair_example.cpp

Polygon_mesh_processing/examples/Polygon_mesh_processing/CMakeLists.txt

@@ -90,6 +90,7 @@ create_single_source_cgal_program( "compute_normals_example.cpp" CXX_FEATURES cx
 create_single_source_cgal_program( "point_inside_example.cpp")
 create_single_source_cgal_program( "triangulate_faces_example.cpp")
 create_single_source_cgal_program( "connected_components_example.cpp")
+create_single_source_cgal_program( "connected_components_graph_example.cpp")
 create_single_source_cgal_program( "polygon_soup_example.cpp")
 create_single_source_cgal_program( "triangulate_polyline_example.cpp")
 create_single_source_cgal_program( "mesh_slicer_example.cpp")

Polygon_mesh_processing/examples/Polygon_mesh_processing/connected_components_graph_example.cpp

@@ -0,0 +1,63 @@
+#include <CGAL/Exact_predicates_inexact_constructions_kernel.h>
+#include <CGAL/Surface_mesh.h>
+
+#include <CGAL/Polygon_mesh_processing/connected_components.h>
+#include <CGAL/boost/graph/Connected_components_graph.h>
+
+#include <boost/property_map/property_map.hpp>
+#include <boost/foreach.hpp>
+#include <iostream>
+#include <fstream>
+#include <map>
+
+typedef CGAL::Exact_predicates_inexact_constructions_kernel Kernel;
+typedef Kernel::Point_3                                     Point;
+
+typedef CGAL::Surface_mesh<Point>                           Mesh;
+typedef boost::graph_traits<Mesh>::face_descriptor          face_descriptor;
+typedef boost::graph_traits<Mesh>::faces_size_type          faces_size_type;
+
+typedef Mesh::Property_map<face_descriptor, faces_size_type> FCCmap;
+  typedef CGAL::Connected_components_graph<Mesh,FCCmap> CCG;
+
+namespace PMP = CGAL::Polygon_mesh_processing;
+
+
+int main(int argc, char* argv[])
+{
+  std::ifstream input((argc > 1) ? argv[1] : "data/blobby_3cc.off");
+
+  Mesh mesh;
+  if (!input || !(input >> mesh) || mesh.is_empty()) {
+    std::cerr << "Not a valid off file." << std::endl;
+    return 1;
+  }
+
+  FCCmap fccmap = mesh.add_property_map<face_descriptor, faces_size_type>("f:CC").first;
+
+  faces_size_type num = PMP::connected_components(mesh,fccmap);
+
+  std::cerr << "- The graph has " << num << " connected components (face connectivity)" << std::endl;
+ 
+  CCG ccg(mesh, fccmap, faces_size_type(0));
+
+  std::cout << "The faces in component 0 are:" << std::endl;
+  BOOST_FOREACH(boost::graph_traits<CCG>::face_descriptor f, faces(ccg)){
+    std::cout  << f << std::endl;
+  }
+
+  if(num>1){
+    std::vector<faces_size_type> components;
+    components.push_back(0);
+    components.push_back(1);
+
+    ccg.set_connected_components(components);
+    
+    std::cout << "The faces in components 0 and 1 are:" << std::endl;
+    BOOST_FOREACH(CCG::face_descriptor f, faces(ccg)){
+    std::cout  << f << std::endl;
+    }
+  }
+  return 0;
+}
+