Improvement: Update the helper methods using the new export function

tutorials/mesh_handle/t8_mesh_step5_element_data.cxx

@@ -43,6 +43,7 @@
 #include "t8_mesh_tutorials_common.hxx" /** Adaption function definition used for this tutorial. */
 #include <memory>
 #include <span>
+#include <vector>
 
 /** The data that we want to store for each element.
  * In this example we want to store the element's level and volume. */
@@ -119,27 +120,19 @@ template <t8_mesh_handle::T8MeshType TMeshClass>
 static void
 output_data_to_vtu (const TMeshClass &mesh, const char *prefix)
 {
-  t8_locidx_t num_elements = mesh.get_num_local_elements ();
-  /* We need to allocate a new array to store the volumes on their own.
-   * This array has one entry per local element. */
-  double *element_volumes = T8_ALLOC (double, num_elements);
-  /* The number of user-defined data fields to write. */
-  int num_data = 1;
-  /* For each user-defined data field we need one t8_vtk_data_field_t variable */
-  t8_vtk_data_field_t vtk_data;
-  /* Set the type of this variable. Since we have one value per element, we pick T8_VTK_SCALAR. */
-  vtk_data.type = T8_VTK_SCALAR;
-  /* The name of the field as should be written to the file. */
-  strcpy (vtk_data.description, "Element volume");
-  vtk_data.data = element_volumes;
-  /* Copy the element's volumes from our data array to the output array. */
-  for (t8_locidx_t ielem = 0; ielem < num_elements; ++ielem) {
-    element_volumes[ielem] = mesh[ielem].get_element_data ().volume;
+  /* We collect the volumes with one entry per local element. */
+  std::vector<double> element_volumes;
+  element_volumes.reserve (mesh.get_num_local_elements ());
+  /* Copy the element's volumes from the element data. */
+  for (const auto &elem : mesh) {
+    element_volumes.push_back (elem.get_element_data ().volume);
   }
-  /* To write user-defined data, we need the extended output function write_mesh_to_vtk_ext.
-   * Despite writing user data, it also offers more control over which properties to write. */
-  t8_mesh_handle::write_mesh_to_vtk_ext (mesh, prefix, num_data, &vtk_data);
-  T8_FREE (element_volumes);
+  /* To write user-defined data, we use the output function write_mesh_to_vtk_ext_data.
+   * Each data field consists of its name, as it should be written to the file, and its values.
+   * Scalar fields are passed in the first list, vector fields in the optional second list.
+   * Further arguments offer more control over which properties to write, as in write_mesh_to_vtk_ext.
+   */
+  t8_mesh_handle::write_mesh_to_vtk_ext_data (mesh, prefix, { { "Element volume", element_volumes } });
 }
 
 /** Entry point of the program. */

tutorials/mesh_handle/t8_mesh_stepA_competences.cxx

@@ -49,7 +49,7 @@
 #include <mesh_handle/mesh_io.hxx>              /** Used to export mesh to vtk files. */
 #include <mesh_handle/concepts.hxx> /** Include this to use c++ concepts related to the mesh handle. This can be used to constrain the template parameters to only allow mesh handle classes. */
 #include <t8_vector/t8_vec.hxx>     /** t8code vector dataclass. */
-#include <cstring>
+#include <vector>
 
 using namespace t8_mesh_handle; /** Using the namespace to avoid the t8_mesh_handle:: prefix everywhere and shorten the code. */
 
@@ -217,24 +217,18 @@ main (int argc, char** argv)
     demonstrate_custom_competence (*custom_mesh);
 
     /* Collect the squared volume of each local element (computed by our custom competence) for the vtk output. */
-    double* squared_volumes = T8_ALLOC (double, custom_mesh->get_num_local_elements ());
-    int ielem = 0;
+    std::vector<double> squared_volumes;
+    squared_volumes.reserve (custom_mesh->get_num_local_elements ());
     for (const auto& elem : *custom_mesh) {
-      squared_volumes[ielem++] = elem.get_squared_volume ();
+      squared_volumes.push_back (elem.get_squared_volume ());
     }
 
-    /* Wrap the data in a vtk data field, one scalar value per element. */
-    t8_vtk_data_field_t vtk_data;
-    vtk_data.type = T8_VTK_SCALAR;
-    strcpy (vtk_data.description, "Squared volume");
-    vtk_data.data = squared_volumes;
-
-    /* Output the custom competence data to vtu. */
-    write_mesh_to_vtk_ext (*custom_mesh, prefix_mesh_with_data, 1, &vtk_data);
+    /* Output the custom competence data to vtu.
+     * The data field is given by its name and its values, one scalar value per element. */
+    t8_mesh_handle::write_mesh_to_vtk_ext_data (*custom_mesh, prefix_mesh_with_data,
+                                                { { "Squared volume", squared_volumes } });
     t8_global_productionf (" [mesh_stepA] Wrote mesh and squared volume data to %s*.\n", prefix_mesh_with_data);
 
-    /* Free the memory. */
-    T8_FREE (squared_volumes);
   } /* End of mesh scope. */
   /* Finalizing. */
   sc_finalize ();