ENH: vtk::vtmWriter for generating vtkMultiBlockDataSet (.vtm) (issue #926)

- Provides a means of accumulating file entries for generating vtm
  by accumulate blocks, datasets and writing them later.

  Only a single block depth is currently supported and the methods
  are kept fairly simple.

applications/test/vtmWriter/Make/files

@@ -0,0 +1,3 @@
+Test-vtmWriter.C
+
+EXE = $(FOAM_APPBIN)/Test-vtmWriter

applications/test/vtmWriter/Make/options

@@ -0,0 +1,5 @@
+EXE_INC = \
+    -I$(LIB_SRC)/fileFormats/lnInclude
+
+EXE_LIBS = \
+    -lfileFormats

applications/test/vtmWriter/Test-vtmWriter.C

@@ -0,0 +1,159 @@
+/*---------------------------------------------------------------------------*\
+  =========                 |
+  \\      /  F ield         | OpenFOAM: The Open Source CFD Toolbox
+   \\    /   O peration     |
+    \\  /    A nd           | Copyright (C) 2018 OpenCFD Ltd.
+     \\/     M anipulation  |
+-------------------------------------------------------------------------------
+License
+    This file is part of OpenFOAM.
+
+    OpenFOAM is free software: you can redistribute it and/or modify it
+    under the terms of the GNU General Public License as published by
+    the Free Software Foundation, either version 3 of the License, or
+    (at your option) any later version.
+
+    OpenFOAM is distributed in the hope that it will be useful, but WITHOUT
+    ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
+    FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License
+    for more details.
+
+    You should have received a copy of the GNU General Public License
+    along with OpenFOAM.  If not, see <http://www.gnu.org/licenses/>.
+
+Application
+    Test-vtmWriter
+
+Description
+    Basic functionality tests for vtk::vtmWriter
+
+\*---------------------------------------------------------------------------*/
+
+#include "foamVtmWriter.H"
+
+using namespace Foam;
+
+// * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * //
+
+int main(int argc, char *argv[])
+{
+    vtk::vtmWriter writer1;
+    {
+        fileName base = "region1_0001";
+
+        writer1.beginBlock("internal");
+        writer1.append_vtu
+        (
+            base/"internal"
+        );
+        writer1.endBlock("internal");
+
+        {
+            writer1.beginBlock("boundary");
+            writer1.append_vtp
+            (
+                base/"patch0"
+            );
+            writer1.append("");  // bad entry
+            writer1.append_vtp
+            (
+                base/"patch1"
+            );
+            writer1.append_vtp
+            (
+                base/"patch2"
+            );
+        }
+
+        writer1.endBlock("boundary");
+
+        {
+            writer1.beginBlock("empty");
+            writer1.endBlock("empty");
+        }
+        {
+            writer1.beginBlock("dangling1");
+            writer1.beginBlock("dangling2");
+        }
+    }
+
+    Info<< nl << "vtm information" << nl;
+    writer1.dump(Info),
+    Info<< nl;
+
+//    writer1.repair();
+//
+//   Info<< nl << "vtm information - after repair" << nl;
+//    writer1.dump(Info),
+//    Info<< nl;
+
+    writer1.repair(true);
+
+//    Info<< nl << "vtm information - after repair(collapse)" << nl;
+//    writer1.dump(Info),
+//    Info<< nl;
+//
+//    Info<< nl << "vtm information - after repair(collapse)" << nl;
+//    writer1.dump(Info),
+//    Info<< nl;
+
+    Info<< nl << "Write to file" << nl;
+    writer1.write("vtmWriter1.vtm");
+
+
+    vtk::vtmWriter writer2;
+    {
+        fileName base = "region2_0001";
+
+        writer2.beginBlock("internal");
+        writer2.append_vtu
+        (
+            base/"internal"
+        );
+        writer2.endBlock("internal");
+
+        {
+            writer2.beginBlock("boundary");
+            writer2.append_vtp
+            (
+                base/"patch0"
+            );
+            writer2.append("");  // bad entry
+            writer2.append_vtp
+            (
+                base/"patch1"
+            );
+            writer2.append_vtp
+            (
+                base/"patch2"
+            );
+        }
+
+        writer2.endBlock("boundary");
+
+        // These should be automatically skiped
+        writer2.endBlock();
+        writer2.endBlock();
+        writer2.endBlock();
+        writer2.endBlock();
+    }
+
+    Info<< nl << "vtm information" << nl;
+    writer2.dump(Info);
+
+    writer2.repair(true);
+
+
+    vtk::vtmWriter writer3;
+
+    writer3.add("some-region1", writer1);
+    writer3.add("some-region2", writer2);
+
+    Info<< nl << "Combined:" << nl;
+    writer3.dump(Info);
+
+    return 0;
+}
+
+
+// ************************************************************************* //