Feature: Automatically create VTK header file containing T8_ENABLE_VTK and version macros.

src/CMakeLists.txt

@@ -84,6 +84,11 @@ if ( T8CODE_ENABLE_MPI )
 endif()
 
 if( T8CODE_ENABLE_VTK )
+    # Set link macro to 1 (will be used in t8_vtk_linkage.hxx)
+    set ( T8_ENABLE_VTK 1 )
+    # Define T8CODE_VTK_MAJOR/MINOR_VERSION to true, such that get defined in t8code_vtk_linkage.hxx
+    set ( T8_VTK_MAJOR_VERSION 1 )
+    set ( T8_VTK_MINOR_VERSION 1 )
     target_compile_definitions( T8 PUBLIC T8_VTK_VERSION_USED="${VTK_MAJOR_VERSION}.${VTK_MINOR_VERSION}" )
     target_compile_definitions( T8 PUBLIC T8_ENABLE_VTK=1 )
     target_include_directories( T8 PUBLIC ${VTK_INCLUDE_DIR} )
@@ -100,8 +105,26 @@ if( T8CODE_ENABLE_VTK )
       t8_vtk/t8_with_vtk/t8_vtk_unstructured.hxx
       t8_vtk/t8_with_vtk/t8_vtk_reader.hxx
     DESTINATION include)
+
+else ()
+  # Set link macro to 0 (will be used in t8_vtk_linkage.hxx)
+  set ( T8_ENABLE_VTK 0 )
+  # Ensure that these macros are not set if T8CODE_ENABLE_VTK is not set.
+  unset ( T8_VTK_MAJOR_VERSION )
+  unset ( T8_VTK_MINOR_VERSION )
 endif()
 
+#
+# Setup the file t8_vtk_linkage.hxx and write macros for the VTK version
+#
+configure_file (t8_vtk/t8_vtk_linkage.hxx.in t8_vtk/t8_vtk_linkage.hxx @ONLY)
+
+# install the automatically created t8_vtk_linkage.hxx into the include/t8_vtk folder
+install (FILES 
+    ${CMAKE_CURRENT_BINARY_DIR}/t8_vtk/t8_vtk_linkage.hxx
+    DESTINATION include/t8_vtk
+)
+
 if( T8CODE_ENABLE_OCC )
     target_compile_definitions( T8 PUBLIC T8_ENABLE_OCC=1 )
     target_include_directories( T8 SYSTEM PUBLIC ${OpenCASCADE_INCLUDE_DIR} )
@@ -248,6 +271,7 @@ install( FILES
     TYPE INCLUDE
 )
 
+
 # Note: Some of the created install directories will be empty, for example t8_cmesh/t8_cmesh_internal
 # since none of the files in them should be installed.
 # However, CMake still creates the folder. It would be better if it did not do so.

src/t8_vtk/t8_vtk_linkage.hxx.in

@@ -0,0 +1,39 @@
+/*
+  This file is part of t8code.
+  Copyright (C) 2025 the developers
+
+  t8code 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.
+
+  t8code 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 t8code; if not, write to the Free Software Foundation, Inc.,
+  51 Franklin Street, Fifth Floor, Boston, MA 02110-1301, USA.
+*/
+
+/** 
+ * \file t8_vtk_linkage.hxx
+ * Automatically generated from t8_vtk_linkage.hxx.in
+ * This file defines the macros
+ * \ref T8CODE_ENABLE_VTK - either 0 or 1 specifying if t8code links against VTK or not.
+ * \ref T8CODE_VTK_MAJOR_VERSION - If T8CODE_ENABLE_VTK The VTK major version number.
+ * \ref T8CODE_VTK_MINOR_VERSION - If T8CODE_ENABLE_VTK The VTK minor version number.
+ */
+
+#ifndef T8CODE_VTK_LINKAGE_HXX
+#define T8CODE_VTK_LINKAGE_HXX
+
+/** Macro that is 1 if we link against VTK on 0 if we don't. */
+#cmakedefine01 T8_ENABLE_VTK
+/** VTK major version number - Only defined if T8_ENABLE_VTK is 1 */
+#cmakedefine T8_VTK_MAJOR_VERSION @VTK_MAJOR_VERSION@
+/** VTK minor version number - Only defined if T8_ENABLE_VTK is 1 */
+#cmakedefine T8_VTK_MINOR_VERSION @VTK_MINOR_VERSION@
+
+#endif // T8CODE_VTK_LINKAGE_HXX

test/t8_gtest_vtk_linkage.cxx

@@ -30,20 +30,50 @@
  */
 #include <gtest/gtest.h>
 #include <t8.h>
+#include <t8_vtk/t8_vtk_linkage.hxx>
 #if T8_ENABLE_VTK
 #include <vtkUnstructuredGrid.h>
 #include <vtkVersionMacros.h>
 #include <vtkNew.h>
 #endif
 
 /* Test correct macro dependencies.
- * Will throw a compile time error if T8_VTK_VERSION_USED
- * is defined but T8_ENABLE_VTK is not. */
-#ifndef T8_ENABLE_VTK
-#ifdef T8_VTK_VERSION_USED
+ * Will throw a compile time error if T8_ENABLE_VTK is O
+ * but T8CODE_VTK_VERSION_USED or T8_VTK_MAJOR_VERSION or T8_VTK_MINOR_VERSION is defined. */
+#if not T8_ENABLE_VTK
+#ifdef T8CODE_VTK_VERSION_USED
 #error Configuration error: T8_VTK_VERSION_USED is defined despite \
  T8_ENABLE_VTK not being defined.
 #endif
+
+#ifdef T8_VTK_MAJOR_VERSION
+#error Configuration error: T8_VTK_MAJOR_VERSION is defined despite \
+ T8_ENABLE_VTK not being defined.
+#endif
+
+#ifdef T8_VTK_MINOR_VERSION
+#error Configuration error: T8_VTK_MINOR_VERSION is defined despite \
+ T8_ENABLE_VTK not being defined.
+#endif
+#endif
+
+/* Test correct macro dependencies.
+ * Will throw a compile time error if T8_ENABLE_VTK is 1
+ * but one of T8CODE_VTK_VERSION_USED, T8_VTK_MAJOR_VERSION, T8_VTK_MINOR_VERSION is not defined.
+ */
+#if T8_ENABLE_VTK
+#ifndef T8_VTK_VERSION_USED
+#error Configuration error: T8_ENABLE_VTK is defined despite \
+ T8CODE_VTK_VERSION_USED not being defined.
+#endif
+#ifndef T8_VTK_MAJOR_VERSION
+#error Configuration error: T8_ENABLE_VTK is defined despite \
+ T8_VTK_MAJOR_VERSION not being defined.
+#endif
+#ifndef T8_VTK_MINOR_VERSION
+#error Configuration error: T8_ENABLE_VTK is defined despite \
+ T8_VTK_MINOR_VERSION not being defined.
+#endif
 #endif
 
 /* Check whether T8_VTK_VERSION_USED equals VTK_MAJOR_VERSION.VTK_MINOR_VERSION */
@@ -52,11 +82,17 @@ TEST (t8_gtest_vtk_linkage, t8_test_vtk_version_number)
 #if T8_ENABLE_VTK
   char vtk_version[BUFSIZ];
   snprintf (vtk_version, BUFSIZ, "%i.%i", VTK_MAJOR_VERSION, VTK_MINOR_VERSION);
-  ASSERT_FALSE (strcmp (T8_VTK_VERSION_USED, vtk_version))
+  EXPECT_FALSE (strcmp (T8_VTK_VERSION_USED, vtk_version))
     << "linked vtk version (" << vtk_version << ") does not equal the version t8code was configured with ("
     << T8_VTK_VERSION_USED << ").\n";
+  // Check our internal version macros to match VTK version
+  EXPECT_EQ (T8_VTK_MAJOR_VERSION, VTK_MAJOR_VERSION);
+  EXPECT_EQ (T8_VTK_MINOR_VERSION, VTK_MINOR_VERSION);
+
   if (!strcmp (T8_VTK_VERSION_USED, vtk_version)) {
     t8_debugf ("Using vtk version %s.\n", vtk_version);
+    t8_debugf ("VTK Major version: %i\n", T8_VTK_MAJOR_VERSION);
+    t8_debugf ("VTK Minor version: %i\n", T8_VTK_MINOR_VERSION);
   }
 #endif
 }