Fixed doxygen issue with old cmake version (issue #55)

resources/doxygen/CMakeLists.txt

@@ -7,6 +7,14 @@ find_package(Doxygen)
 # Add a target to generate API documentation with Doxygen
 if(DOXYGEN_FOUND)
 
+    if(${CMAKE_VERSION} VERSION_LESS "3.9.0")
+        # Use old commands if CMake does not support the command doxygen_add_docs
+        set(CMAKE_DOXYGEN_OUTPUT_DIR "${CMAKE_CURRENT_BINARY_DIR}/doc")
+        string(REGEX REPLACE ";" " " CMAKE_DOXYGEN_INPUT_LIST "${PROJECT_SOURCE_DIR}/src")
+        configure_file("${CMAKE_CURRENT_SOURCE_DIR}/resources/doxygen/Doxyfile.in" "${CMAKE_CURRENT_BINARY_DIR}/Doxyfile" @ONLY)
+        add_custom_target(doc ${DOXYGEN_EXECUTABLE} "${CMAKE_CURRENT_BINARY_DIR}/Doxyfile" DEPENDS "${CMAKE_CURRENT_BINARY_DIR}/Doxyfile" COMMENT "Generating API documentation with Doxygen" VERBATIM)
+    else()
+
         # We use the doxygen command of CMake instead of using the separate config file
         set(DOXYGEN_PROJECT_NAME "Storm")
         set(DOXYGEN_PROJECT_BRIEF "A Modern Probabilistic Model Checker")
@@ -27,10 +35,6 @@ if(DOXYGEN_FOUND)
             "${PROJECT_SOURCE_DIR}/src"
             COMMENT "Generating API documentation with Doxygen"
         )
+    endif()
 
-    # These commands can be used if the separate config files should be used
-    #set(CMAKE_DOXYGEN_OUTPUT_DIR "${CMAKE_CURRENT_BINARY_DIR}/doc")
-    #string(REGEX REPLACE ";" " " CMAKE_DOXYGEN_INPUT_LIST "${PROJECT_SOURCE_DIR}/src")
-    #configure_file("${CMAKE_CURRENT_SOURCE_DIR}/resources/doxygen/Doxyfile.in.new" "${CMAKE_CURRENT_BINARY_DIR}/Doxyfile" @ONLY)
-    #add_custom_target(doc ${DOXYGEN_EXECUTABLE} "${CMAKE_CURRENT_BINARY_DIR}/Doxyfile" DEPENDS "${CMAKE_CURRENT_BINARY_DIR}/Doxyfile" COMMENT "Generating API documentation with Doxygen" VERBATIM)
 endif(DOXYGEN_FOUND)