Enable GmshReader for multiple domains

dune/grid/multidomaingrid/factory.hh

+#ifndef DUNE_MULTIDOMAINGRID_FACTORY_HH
+#define DUNE_MULTIDOMAINGRID_FACTORY_HH
+
+namespace Dune {
+
+namespace mdgrid {
+
+// forward declaration
+template<typename HostGrid,typename MDGridTraits>
+class MultiDomainGrid;
+
+} // namespace mdgrid
+
+// forward declaration
+
+template <class GridType>
+class GridFactoryInterface;
+
+template<class HostGrid, class MDGTraits>
+class GridFactory<Dune::mdgrid::MultiDomainGrid<HostGrid, MDGTraits>> : public GridFactoryInterface<Dune::mdgrid::MultiDomainGrid<HostGrid, MDGTraits>> {
+
+  using Grid = Dune::mdgrid::MultiDomainGrid<HostGrid, MDGTraits>;
+  using Base = GridFactoryInterface<Grid>;
+public:
+
+  GridFactory()
+    : _host_grid_factory{}
+  {}
+
+  // use default implementation from base class
+  using Base::insertBoundarySegment;
+
+  void insertVertex(const FieldVector<typename Grid::ctype, Grid::dimensionworld>& pos) override {
+    _host_grid_factory.insertVertex(pos);
+  }
+
+  void insertElement(const GeometryType& type, const std::vector<unsigned int>& vertices) override {
+    _host_grid_factory.insertElement(type, vertices);
+  }
+
+  void insertBoundarySegment(const std::vector<unsigned int>& vertices) override {
+    _host_grid_factory.insertBoundarySegment(vertices);
+  }
+
+  std::unique_ptr<Grid> createGrid() override  {
+    if (not _grid_ptr)
+      makeGrid();
+    assert(_grid_ptr);
+    return std::exchange(_grid_ptr, nullptr);
+  }
+
+  void makeGrid(int max_subdomains = 1) {
+    assert(not _grid_ptr);
+
+    std::unique_ptr<MDGTraits> traits;
+    if constexpr (std::is_default_constructible_v<MDGTraits>)
+      traits = std::make_unique<MDGTraits>();
+    else
+      traits = std::make_unique<MDGTraits>(max_subdomains);
+
+    if (traits->maxSubDomainIndex() < max_subdomains)
+      DUNE_THROW(IOError, "Maximum number of sub-domains is bigger than what grid traits allows");
+
+    _grid_ptr = std::make_unique<Grid>(_host_grid_factory.createGrid(), *traits);
+  }
+
+  Grid& grid() {
+    assert(_grid_ptr);
+    return *_grid_ptr;
+  }
+
+  HostGrid& hostGrid() {
+    assert(_host_grid_ptr);
+    return *_host_grid_ptr;
+  }
+
+  const std::shared_ptr<HostGrid>& hostGridPtr() {
+    return _host_grid_ptr;
+  }
+
+
+  Dune::GridFactory<HostGrid>& hostGridFactory() {
+    return _host_grid_factory;
+  }
+
+private:
+  Dune::GridFactory<HostGrid> _host_grid_factory;
+  std::shared_ptr<HostGrid> _host_grid_ptr;
+  std::unique_ptr<Grid> _grid_ptr;
+};
+
+} // namespace Dune
+
+#endif // DUNE_MULTIDOMAINGRID_FACTORY_HH