Using std::optional for Property_container::get<T> (CGAL#8035)

## Summary of Changes
Switching from `std::pair<Property_map<T>, bool>` to `std::optional` in
`Property_container::get<T>`

Introducing `Pair_optional_adaptor` for backward compatibility which
extends `std::optional<T>` to interface of `std::pair`

using `Pair_optional_adaptor` for `Surface_mesh` and `Point_set_3`

## Release Management

* Affected package(s): Point_set_3, Surface_mesh, STL_Extension

BGL/test/BGL/test_Collapse_edge_with_constraints.cpp

@@ -11,9 +11,8 @@ typedef Mesh::Property_map<Mesh::Edge_index, bool> ECM;
 
 bool test_one_side(Mesh::Halfedge_index h, Mesh m)
 {
-  std::pair<ECM, bool> ecm_and_bool = m.property_map<Mesh::Edge_index, bool>("ecm");
   Mesh::Vertex_index vkept=target(h, m);
-  CGAL::Euler::collapse_edge(edge(h, m), m, ecm_and_bool.first);
+  CGAL::Euler::collapse_edge(edge(h, m), m, m.property_map<Mesh::Edge_index, bool>("ecm").value());
   return (!m.is_removed(vkept) && CGAL::is_valid_polygon_mesh(m));
 }
 

Basic_viewer/examples/Basic_viewer/draw_surface_mesh_small_faces.cpp

@@ -27,22 +27,23 @@ struct Graphics_scene_options_small_faces:
 
   Graphics_scene_options_small_faces(const SM& sm): Base(), m_sm(sm)
   {
-    typename SM::template Property_map<face_descriptor, FT> faces_size;
-    boost::tie(faces_size, m_with_size)=sm.template property_map<face_descriptor, FT>("f:size");
+    std::optional<typename SM::template Property_map<face_descriptor, FT>> faces_size
+      = sm.template property_map<face_descriptor, FT>("f:size");
+    m_with_size = faces_size.has_value();
     if(!m_with_size)
     { return; }
 
-    m_min_size=faces_size[*(sm.faces().begin())];
+    m_min_size=faces_size.value()[*(sm.faces().begin())];
     m_max_size=m_min_size;
     FT cur_size;
     for (typename SM::Face_range::iterator f=sm.faces().begin(); f!=sm.faces().end(); ++f)
     {
-      cur_size=faces_size[*f];
+      cur_size=faces_size.value()[*f];
       if (cur_size<m_min_size) m_min_size=cur_size;
       if (cur_size>m_max_size) m_max_size=cur_size;
     }
 
-    this->face_color=[=](const SM& sm,
+    this->face_color=[this](const SM& sm,
                          typename boost::graph_traits<SM>::face_descriptor fh) -> CGAL::IO::Color
     { return this->get_face_color(sm, fh); };
 
@@ -59,13 +60,12 @@ struct Graphics_scene_options_small_faces:
     if(!m_with_size) { return c; }
 
     // Compare the size of the face with the % m_threshold
-    bool exist;
-    typename SM::template Property_map<face_descriptor, FT> faces_size;
-    boost::tie(faces_size, exist)=sm.template property_map<face_descriptor, FT>("f:size");
-    assert(exist);
+    std::optional<typename SM::template Property_map<face_descriptor, FT>> faces_size
+      = sm.template property_map<face_descriptor, FT>("f:size");
+    assert(faces_size.has_value());
 
     // If the face is small, color it in red.
-    if (get(faces_size, fh)<m_min_size+((m_max_size-m_min_size)/(100-m_threshold)))
+    if (get(faces_size.value(), fh)<m_min_size + ((m_max_size - m_min_size) / (100 - m_threshold)))
     { return CGAL::IO::Color(255,20,20); }
 
     return c; // Default color

Classification/examples/Classification/example_ethz_random_forest.cpp

@@ -47,10 +47,8 @@ int main (int argc, char** argv)
   std::cerr << "Reading input" << std::endl;
   in >> pts;
 
-  Imap label_map;
-  bool lm_found = false;
-  std::tie (label_map, lm_found) = pts.property_map<int> ("label");
-  if (!lm_found)
+  std::optional<Imap> label_map = pts.property_map<int> ("label");
+  if (!label_map.has_value())
   {
     std::cerr << "Error: \"label\" property not found in input file." << std::endl;
     return EXIT_FAILURE;
@@ -78,7 +76,7 @@ int main (int argc, char** argv)
   Label_handle roof = labels.add ("roof");
 
   // Check if ground truth is valid for this label set
-  if (!labels.is_valid_ground_truth (pts.range(label_map), true))
+  if (!labels.is_valid_ground_truth (pts.range(label_map.value()), true))
     return EXIT_FAILURE;
 
   std::vector<int> label_indices(pts.size(), -1);
@@ -89,7 +87,7 @@ int main (int argc, char** argv)
   std::cerr << "Training" << std::endl;
   t.reset();
   t.start();
-  classifier.train (pts.range(label_map));
+  classifier.train (pts.range(label_map.value()));
   t.stop();
   std::cerr << "Done in " << t.time() << " second(s)" << std::endl;
 
@@ -104,7 +102,7 @@ int main (int argc, char** argv)
   std::cerr << "Classification with graphcut done in " << t.time() << " second(s)" << std::endl;
 
   std::cerr << "Precision, recall, F1 scores and IoU:" << std::endl;
-  Classification::Evaluation evaluation (labels, pts.range(label_map), label_indices);
+  Classification::Evaluation evaluation (labels, pts.range(label_map.value()), label_indices);
 
   for (Label_handle l : labels)
   {
@@ -126,7 +124,7 @@ int main (int argc, char** argv)
 
   for (std::size_t i = 0; i < label_indices.size(); ++ i)
   {
-    label_map[i] = label_indices[i]; // update label map with computed classification
+    label_map.value()[i] = label_indices[i]; // update label map with computed classification
 
     Label_handle label = labels[label_indices[i]];
     const CGAL::IO::Color& color = label->color();

Classification/examples/Classification/example_generation_and_training.cpp

@@ -44,10 +44,8 @@ int main (int argc, char** argv)
   std::cerr << "Reading input" << std::endl;
   in >> pts;
 
-  Imap label_map;
-  bool lm_found = false;
-  std::tie (label_map, lm_found) = pts.property_map<int> ("label");
-  if (!lm_found)
+  std::optional<Imap> label_map = pts.property_map<int> ("label");
+  if (!label_map.has_value())
   {
     std::cerr << "Error: \"label\" property not found in input file." << std::endl;
     return EXIT_FAILURE;
@@ -82,7 +80,7 @@ int main (int argc, char** argv)
   std::cerr << "Training" << std::endl;
   t.reset();
   t.start();
-  classifier.train<CGAL::Parallel_if_available_tag> (pts.range(label_map), 800);
+  classifier.train<CGAL::Parallel_if_available_tag> (pts.range(label_map.value()), 800);
   t.stop();
   std::cerr << "Done in " << t.time() << " second(s)" << std::endl;
 
@@ -97,7 +95,7 @@ int main (int argc, char** argv)
   std::cerr << "Classification with graphcut done in " << t.time() << " second(s)" << std::endl;
 
   std::cerr << "Precision, recall, F1 scores and IoU:" << std::endl;
-  Classification::Evaluation evaluation (labels, pts.range(label_map), label_indices);
+  Classification::Evaluation evaluation (labels, pts.range(label_map.value()), label_indices);
 
   for (Label_handle l : labels)
   {

Classification/examples/Classification/example_opencv_random_forest.cpp

@@ -43,10 +43,8 @@ int main (int argc, char** argv)
   Point_set pts;
   in >> pts;
 
-  Imap label_map;
-  bool lm_found = false;
-  std::tie (label_map, lm_found) = pts.property_map<int> ("label");
-  if (!lm_found)
+  std::optional<Imap> label_map = pts.property_map<int> ("label");
+  if (!label_map.has_value())
   {
     std::cerr << "Error: \"label\" property not found in input file." << std::endl;
     return EXIT_FAILURE;
@@ -81,7 +79,7 @@ int main (int argc, char** argv)
   std::cerr << "Training" << std::endl;
   t.reset();
   t.start();
-  classifier.train (pts.range(label_map));
+  classifier.train (pts.range(label_map.value()));
   t.stop();
   std::cerr << "Done in " << t.time() << " second(s)" << std::endl;
 
@@ -96,7 +94,7 @@ int main (int argc, char** argv)
   std::cerr << "Classification with graphcut done in " << t.time() << " second(s)" << std::endl;
 
   std::cerr << "Precision, recall, F1 scores and IoU:" << std::endl;
-  Classification::Evaluation evaluation (labels, pts.range(label_map), label_indices);
+  Classification::Evaluation evaluation (labels, pts.range(label_map.value()), label_indices);
 
   for (Label_handle l : labels)
   {
@@ -118,7 +116,7 @@ int main (int argc, char** argv)
 
   for (std::size_t i = 0; i < label_indices.size(); ++ i)
   {
-    label_map[i] = label_indices[i]; // update label map with computed classification
+    label_map.value()[i] = label_indices[i]; // update label map with computed classification
 
     Label_handle label = labels[label_indices[i]];
     const CGAL::IO::Color& color = label->color();

Classification/examples/Classification/gis_tutorial_example.cpp

@@ -691,11 +691,9 @@ int main (int argc, char** argv)
   //! [Classification]
 
   // Get training from input
-  Point_set::Property_map<int> training_map;
-  bool training_found;
-  std::tie (training_map, training_found) = points.property_map<int>("training");
+  std::optional<Point_set::Property_map<int>> training_map = points.property_map<int>("training");
 
-  if (training_found)
+  if (training_map.has_value())
   {
     std::cerr << "Classifying ground/vegetation/building" << std::endl;
 
@@ -718,7 +716,7 @@ int main (int argc, char** argv)
 
     // Train a random forest classifier
     Classification::ETHZ::Random_forest_classifier classifier (labels, features);
-    classifier.train (points.range(training_map));
+    classifier.train (points.range(training_map.value()));
 
     // Classify with graphcut regularization
     Point_set::Property_map<int> label_map = points.add_property_map<int>("labels").first;
@@ -732,7 +730,7 @@ int main (int argc, char** argv)
     // Evaluate
     std::cerr << "Mean IoU on training data = "
               << Classification::Evaluation(labels,
-                                            points.range(training_map),
+                                            points.range(training_map.value()),
                                             points.range(label_map)).mean_intersection_over_union() << std::endl;
 
     // Save the classified point set

Installation/CHANGES.md

@@ -116,6 +116,12 @@ Release date: June 2024
     `CGAL::Simplicial_mesh_cell_base_3`
     have been modified to enable passing a geometric traits and a custom cell base class.
 
+### [Surface Mesh](https://doc.cgal.org/6.0/Manual/packages.html#PkgSurfaceMesh)
+-   **Breaking change**: The return type of `CGAL::Surface_mesh::property_map()` has been changed to `std::optional`.
+
+### [3D Point Set](https://doc.cgal.org/6.0/Manual/packages.html#PkgPointSet3)
+-   **Breaking change**: The return type of `CGAL::Point_set_3::property_map()` has been changed to `std::optional`.
+
 ### [Surface Mesh Parameterization](https://doc.cgal.org/6.0/Manual/packages.html#PkgSurfaceMeshParameterization)
 - **Breaking change**: LSCM_parameterizer_3 needs Eigen
 

Lab/demo/Lab/Plugins/Classification/Cluster_classification.cpp

@@ -30,13 +30,13 @@ Cluster_classification::Cluster_classification(Scene_points_with_normal_item* po
 
   backup_existing_colors_and_add_new();
 
-  bool cluster_found = false;
-  boost::tie (m_cluster_id, cluster_found) = m_points->point_set()->property_map<int>("shape");
-  if (!cluster_found)
+  std::optional<Point_set::Property_map<int>> cluster_id = m_points->point_set()->property_map<int>("shape");
+  if (!cluster_id.has_value())
   {
     std::cerr << "Error! Cluster not found!" << std::endl;
     abort();
   }
+  m_cluster_id = cluster_id.value();
 
   CGAL::Classification::create_clusters_from_indices (*(m_points->point_set()),
                                                       m_points->point_set()->point_map(),
@@ -57,20 +57,20 @@ Cluster_classification::Cluster_classification(Scene_points_with_normal_item* po
 
   if (!classif_found)
   {
-    Point_set::Property_map<unsigned char> las_classif;
-    boost::tie (las_classif, las_found) = m_points->point_set()->property_map<unsigned char>("classification");
+    std::optional<Point_set::Property_map<unsigned char>> las_classif = m_points->point_set()->property_map<unsigned char>("classification");
+    las_found = las_classif.has_value();
     if (las_found)
     {
       m_input_is_las = true;
       for (Point_set::const_iterator it = m_points->point_set()->begin();
            it != m_points->point_set()->first_selected(); ++ it)
       {
-        unsigned char uc = las_classif[*it];
+        unsigned char uc = las_classif.value()[*it];
         m_classif[*it] = int(uc);
         if (!training_found)
           m_training[*it] = int(uc);
       }
-      m_points->point_set()->remove_property_map (las_classif);
+      m_points->point_set()->remove_property_map (las_classif.value());
       classif_found = true;
       training_found = true;
     }
@@ -606,7 +606,7 @@ int Cluster_classification::real_index_color() const
 void Cluster_classification::reset_indices ()
 {
   Point_set::Property_map<Point_set::Index> indices
-    = m_points->point_set()->property_map<Point_set::Index>("index").first;
+    = m_points->point_set()->property_map<Point_set::Index>("index").value();
 
   m_points->point_set()->unselect_all();
   Point_set::Index idx;
@@ -636,11 +636,9 @@ void Cluster_classification::compute_features (std::size_t nb_scales, float voxe
 
   bool colors = (m_color != Point_set::Property_map<CGAL::IO::Color>());
 
-  Point_set::Property_map<std::uint8_t> echo_map;
-  bool echo;
-  boost::tie (echo_map, echo) = m_points->point_set()->template property_map<std::uint8_t>("echo");
-  if (!echo)
-    boost::tie (echo_map, echo) = m_points->point_set()->template property_map<std::uint8_t>("number_of_returns");
+  std::optional<Point_set::Property_map<std::uint8_t>> echo_map = m_points->point_set()->template property_map<std::uint8_t>("echo");
+  if (!echo_map.has_value())
+    echo_map = m_points->point_set()->template property_map<std::uint8_t>("number_of_returns");
 
   Feature_set pointwise_features;
 
@@ -658,8 +656,8 @@ void Cluster_classification::compute_features (std::size_t nb_scales, float voxe
     generator.generate_normal_based_features (pointwise_features, normal_map);
   if (colors)
     generator.generate_color_based_features (pointwise_features, m_color);
-  if (echo)
-    generator.generate_echo_based_features (pointwise_features, echo_map);
+  if (echo_map.has_value())
+    generator.generate_echo_based_features (pointwise_features, echo_map.value());
 
 #ifdef CGAL_LINKED_WITH_TBB
   pointwise_features.end_parallel_additions();

Lab/demo/Lab/Plugins/Classification/Cluster_classification.h

@@ -124,14 +124,13 @@ class Cluster_classification : public Item_classification_base
   bool try_adding_simple_feature (Feature_set& feature_set, const std::string& name)
   {
     typedef typename Point_set::template Property_map<Type> Pmap;
-    bool okay = false;
-    Pmap pmap;
-    boost::tie (pmap, okay) = m_points->point_set()->template property_map<Type>(name.c_str());
-    if (okay)
+
+    std::optional<Pmap> pmap = m_points->point_set()->template property_map<Type>(name.c_str());
+    if (pmap.has_value())
       feature_set.template add<CGAL::Classification::Feature::Simple_feature <Point_set, Pmap> >
-        (*(m_points->point_set()), pmap, name.c_str());
+        (*(m_points->point_set()), pmap.value(), name.c_str());
 
-    return okay;
+    return pmap.has_value();
   }
 
   void add_selection_to_training_set (std::size_t label)

Lab/demo/Lab/Plugins/Classification/Point_set_item_classification.cpp

@@ -24,15 +24,13 @@ Point_set_item_classification::Point_set_item_classification(Scene_points_with_n
 
   reset_indices();
 
-  Point_set::Property_map<int> cluster_id;
-  bool cluster_found = false;
-  boost::tie (cluster_id, cluster_found) = m_points->point_set()->property_map<int>("shape");
-  if (cluster_found)
+  std::optional<Point_set::Property_map<int>> cluster_id = m_points->point_set()->property_map<int>("shape");
+  if (cluster_id.has_value())
   {
     for (Point_set::const_iterator it = m_points->point_set()->begin();
          it != m_points->point_set()->first_selected(); ++ it)
     {
-      int c = cluster_id[*it];
+      int c = cluster_id.value()[*it];
       if (c == -1)
         continue;
       if (std::size_t(c) >= m_clusters.size())
@@ -54,20 +52,20 @@ Point_set_item_classification::Point_set_item_classification(Scene_points_with_n
 
   if (!classif_found)
   {
-    Point_set::Property_map<unsigned char> las_classif;
-    boost::tie (las_classif, las_found) = m_points->point_set()->property_map<unsigned char>("classification");
+    std::optional<Point_set::Property_map<unsigned char>> las_classif = m_points->point_set()->property_map<unsigned char>("classification");
+    las_found = las_classif.has_value();
     if (las_found)
     {
       m_input_is_las = true;
       for (Point_set::const_iterator it = m_points->point_set()->begin();
            it != m_points->point_set()->first_selected(); ++ it)
       {
-        unsigned char uc = las_classif[*it];
+        unsigned char uc = las_classif.value()[*it];
         m_classif[*it] = int(uc);
         if (!training_found)
           m_training[*it] = int(uc);
       }
-      m_points->point_set()->remove_property_map (las_classif);
+      m_points->point_set()->remove_property_map (las_classif.value());
       classif_found = true;
       training_found = true;
     }
@@ -498,7 +496,7 @@ int Point_set_item_classification::real_index_color() const
 void Point_set_item_classification::reset_indices ()
 {
   Point_set::Property_map<Point_set::Index> indices
-    = m_points->point_set()->property_map<Point_set::Index>("index").first;
+    = m_points->point_set()->property_map<Point_set::Index>("index").value();
 
   m_points->point_set()->unselect_all();
   Point_set::Index idx;
@@ -531,11 +529,9 @@ void Point_set_item_classification::compute_features (std::size_t nb_scales, flo
 
   bool colors = (m_color != Point_set::Property_map<CGAL::IO::Color>());
 
-  Point_set::Property_map<std::uint8_t> echo_map;
-  bool echo;
-  boost::tie (echo_map, echo) = m_points->point_set()->template property_map<std::uint8_t>("echo");
-  if (!echo)
-    boost::tie (echo_map, echo) = m_points->point_set()->template property_map<std::uint8_t>("number_of_returns");
+  std::optional<Point_set::Property_map<std::uint8_t>> echo_map = m_points->point_set()->template property_map<std::uint8_t>("echo");
+  if (!echo_map.has_value())
+    echo_map = m_points->point_set()->template property_map<std::uint8_t>("number_of_returns");
 
   m_generator = new Generator (*(m_points->point_set()), m_points->point_set()->point_map(), nb_scales, voxel_size);
 
@@ -551,8 +547,8 @@ void Point_set_item_classification::compute_features (std::size_t nb_scales, flo
     m_generator->generate_normal_based_features (m_features, normal_map);
   if (colors)
     m_generator->generate_color_based_features (m_features, m_color);
-  if (echo)
-    m_generator->generate_echo_based_features (m_features, echo_map);
+  if (echo_map.has_value())
+    m_generator->generate_echo_based_features (m_features, echo_map.value());
 
 #ifdef CGAL_LINKED_WITH_TBB
   m_features.end_parallel_additions();