ENH: prune cloud fields by names only once

- can remove directly from the temporary objectRegistry prior to
  converting by field type. Cannot, however, do the same for volFields
  or areaFields since these reside on their respective mesh objects.

src/catalyst/cloud/foamVtkCloudAdaptor.C

@@ -98,7 +98,7 @@ Foam::vtk::cloudAdaptor::getCloudImpl
 
     auto output = vtkSmartPointer<vtkMultiPieceDataSet>::New();
 
-    auto objPtr = mesh.lookupObjectPtr<cloud>(cloudName);
+    const auto* objPtr = mesh.lookupObjectPtr<cloud>(cloudName);
     if (!objPtr)
     {
         return output;
@@ -126,12 +126,27 @@ Foam::vtk::cloudAdaptor::getCloudImpl
     {
         vtkmesh = startLagrangian(*pointsPtr);
 
-        convertLagrangianFields<label>(vtkmesh, obrTmp, matcher);
-        convertLagrangianFields<scalar>(vtkmesh, obrTmp, matcher);
-        convertLagrangianFields<vector>(vtkmesh, obrTmp, matcher);
+        // Prevent any possible conversion of positions as a field
+        obrTmp.filterKeys
+        (
+            [](const word& k)
+            {
+                return k.startsWith("position")
+                    || k.startsWith("coordinate");
+            },
+            true  // prune
+        );
+
+        // Restrict to specified fields
+        obrTmp.filterKeys(matcher);
+
+        convertLagrangianFields<label>(vtkmesh, obrTmp);
+        convertLagrangianFields<scalar>(vtkmesh, obrTmp);
+        convertLagrangianFields<vector>(vtkmesh, obrTmp);
     }
     else
     {
+        // This should never occur
         vtkmesh = vtkSmartPointer<vtkPolyData>::New();
     }
 

src/catalyst/cloud/foamVtkCloudAdaptor.H

@@ -77,12 +77,11 @@ class cloudAdaptor
         );
 
         //- Lagrangian fields from objectRegistry
-        template<class Type, class UnaryPredicate>
+        template<class Type>
         static label convertLagrangianFields
         (
             vtkPolyData* vtkmesh,
-            const objectRegistry& obr,
-            const UnaryPredicate& pred
+            const objectRegistry& obr
         );
 
         //- Get cloud with point/cell data

src/catalyst/cloud/foamVtkCloudAdaptorTemplates.C

@@ -30,32 +30,14 @@ License
 
 // * * * * * * * * * * * * * Private Member Functions  * * * * * * * * * * * //
 
-template<class Type, class UnaryMatchPredicate>
+template<class Type>
 Foam::label Foam::vtk::cloudAdaptor::convertLagrangianFields
 (
     vtkPolyData* vtkmesh,
-    const objectRegistry& obr,
-    const UnaryMatchPredicate& pred
+    const objectRegistry& obr
 )
 {
-    label nFields = 0;
-
-    wordHashSet names(obr.names<IOField<Type>>());
-
-    // Restrict to specified names
-    names.filterKeys(pred);
-
-    // Avoid converting particle positions as a field too.
-    names.filterKeys
-    (
-        [](const word& k)
-        {
-            return k.startsWith("position") || k.startsWith("coordinate");
-        },
-        true  // prune
-    );
-
-    const wordList fieldNames(names.sortedToc());
+    const wordList fieldNames(obr.sortedNames<IOField<Type>>());
 
     for (const word& fieldName : fieldNames)
     {
@@ -71,11 +53,9 @@ Foam::label Foam::vtk::cloudAdaptor::convertLagrangianFields
         // Provide identical data as cell and as point data
         vtkmesh->GetCellData()->AddArray(data);
         vtkmesh->GetPointData()->AddArray(data);
-
-        ++nFields;
     }
 
-    return nFields;
+    return fieldNames.size();
 }