Allow nanoflann and alglib to be external packages

CMakeLists.txt

@@ -23,9 +23,11 @@ include(FeatureSummary)
 dune_project()
 
 option(ENABLE_NANOFLANN "Use KDTree search tree from nanoflann." ON)
+option(DOWNLOAD_NANOFLANN "Download and build nanoflann library." OFF)
 add_feature_info(ENABLE_NANOFLANN ENABLE_NANOFLANN "Use KDTree search tree from nanoflann.")
 
 option(ENABLE_ALGLIB "Use ALGLIB to implement the LM constrained least-squares solver." ON)
+option(DOWNLOAD_ALGLIB "Download and build ALGLIB library." OFF)
 add_feature_info(ENABLE_ALGLIB ENABLE_ALGLIB "Use ALGLIB to implement the LM constrained least-squares solver.")
 
 # provide external packages
@@ -59,5 +61,8 @@ add_subdirectory(src)
 add_subdirectory(dune)
 add_subdirectory(doc)
 
+# write contents into DUNE_CUSTOM_PKG_CONFIG_SECTION
+string(JOIN "\n" DUNE_CUSTOM_PKG_CONFIG_SECTION ${DUNE_MESHDIST_PACKAGE_DEPENDENCIES})
+
 # finalize the dune project, e.g. generating config.h etc.
 finalize_dune_project()

libs/CMakeLists.txt

 include(FetchContent)
 
+set(_find_dependencies)
 if(ENABLE_NANOFLANN)
-  if(NOT nanoflann_SOURCE_DIR)
+  if(DOWNLOAD_NANOFLANN)
     set(NANOFLANN_BUILD_EXAMPLES OFF CACHE BOOL "Do not build examples for nanoflann" FORCE)
     set(NANOFLANN_BUILD_TESTS OFF CACHE BOOL "Do not build tests for nanoflann" FORCE)
     FetchContent_Declare(nanoflann                                # name of the content
@@ -12,22 +13,25 @@ if(ENABLE_NANOFLANN)
     if(NOT nanoflann_POPULATED)
       FetchContent_Populate(nanoflann)
     endif()
-  endif()
 
-  file(GLOB NANOFLANN_HEADERS CONFIGURE_DEPENDS "${nanoflann_SOURCE_DIR}/include/*.hpp")
+    file(GLOB NANOFLANN_HEADERS CONFIGURE_DEPENDS "${nanoflann_SOURCE_DIR}/include/*.hpp")
 
-  # Create a library from the source files
-  dune_add_library(nanoflann INTERFACE
-    EXPORT_NAME nanoflann NAMESPACE nanoflann::)
-  target_include_directories(nanoflann INTERFACE
-    $<BUILD_INTERFACE:${nanoflann_SOURCE_DIR}/include>
-    $<INSTALL_INTERFACE:${CMAKE_INSTALL_INCLUDEDIR}/nanoflann>)
-  install(FILES ${NANOFLANN_HEADERS}
-    DESTINATION "${CMAKE_INSTALL_INCLUDEDIR}/nanoflann" )
+    # Create a library from the source files
+    dune_add_library(nanoflann INTERFACE
+      EXPORT_NAME nanoflann NAMESPACE nanoflann::)
+    target_include_directories(nanoflann INTERFACE
+      $<BUILD_INTERFACE:${nanoflann_SOURCE_DIR}/include>
+      $<INSTALL_INTERFACE:${CMAKE_INSTALL_INCLUDEDIR}/nanoflann>)
+    install(FILES ${NANOFLANN_HEADERS}
+      DESTINATION "${CMAKE_INSTALL_INCLUDEDIR}/nanoflann" )
+    else()
+      find_package(nanoflann 1.6 REQUIRED)
+      list(APPEND _find_dependencies "find_dependency(nanoflann 1.6)")
+    endif()
 endif()
 
 if(ENABLE_ALGLIB)
-  if(NOT alglib_SOURCE_DIR)
+  if(DOWNLOAD_ALGLIB)
     FetchContent_Declare(alglib
       URL https://www.alglib.net/translator/re/alglib-4.03.0.cpp.gpl.tgz
       DOWNLOAD_EXTRACT_TIMESTAMP TRUE
@@ -35,17 +39,23 @@ if(ENABLE_ALGLIB)
         ${CMAKE_COMMAND} -E create_symlink <SOURCE_DIR>/src <SOURCE_DIR>/alglib
     )
     FetchContent_MakeAvailable(alglib)
+
+    file(GLOB ALGLIB_HEADERS CONFIGURE_DEPENDS "${alglib_SOURCE_DIR}/src/*.hpp")
+    file(GLOB ALGLIB_SOURCES CONFIGURE_DEPENDS "${alglib_SOURCE_DIR}/src/*.cpp")
+
+    # Create a library from the source files
+    dune_add_library(alglib SOURCES ${ALGLIB_SOURCES}
+      EXPORT_NAME alglib NAMESPACE alglib::)
+    target_include_directories(alglib PUBLIC
+      $<BUILD_INTERFACE:${alglib_SOURCE_DIR}>
+      $<INSTALL_INTERFACE:${CMAKE_INSTALL_INCLUDEDIR}>)
+    install(FILES ${ALGLIB_HEADERS}
+      DESTINATION "${CMAKE_INSTALL_INCLUDEDIR}/alglib" )
+  else()
+    find_package(alglib 4.0 REQUIRED)
+    list(APPEND _find_dependencies "find_dependency(alglib 4.0)")
   endif()
+endif()
+
 
-  file(GLOB ALGLIB_HEADERS CONFIGURE_DEPENDS "${alglib_SOURCE_DIR}/src/*.hpp")
-  file(GLOB ALGLIB_SOURCES CONFIGURE_DEPENDS "${alglib_SOURCE_DIR}/src/*.cpp")
-
-  # Create a library from the source files
-  dune_add_library(alglib SOURCES ${ALGLIB_SOURCES}
-    EXPORT_NAME alglib NAMESPACE alglib::)
-  target_include_directories(alglib PUBLIC
-    $<BUILD_INTERFACE:${alglib_SOURCE_DIR}>
-    $<INSTALL_INTERFACE:${CMAKE_INSTALL_INCLUDEDIR}>)
-  install(FILES ${ALGLIB_HEADERS}
-    DESTINATION "${CMAKE_INSTALL_INCLUDEDIR}/alglib" )
-endif()
\ No newline at end of file
+set(DUNE_MESHDIST_PACKAGE_DEPENDENCIES "${_find_dependencies}" PARENT_SCOPE)
\ No newline at end of file