Find system jsoncpp via pkg-config, add system include

extern/CMakeProject-json.cmake

@@ -1,8 +1,6 @@
 if(WITH_SYSTEM_JSONCPP)
-  find_library(JSONCPP_LIBRARY jsoncpp)
-  if(JSONCPP_LIBRARY MATCHES "JSONCPP_LIBRARY-NOTFOUND")
-    message(FATAL_ERROR "Need jsoncpp.")
-  endif()
+  find_package(PkgConfig REQUIRED)
+  pkg_check_modules(JSONCPP REQUIRED jsoncpp)
 else()
   list(APPEND JSON_SRC
               "jsoncpp/src/lib_json/json_reader.cpp"

src/CMakeLists.txt

@@ -449,7 +449,7 @@ else()
 endif()
 
 if(WITH_SYSTEM_JSONCPP)
-  list(APPEND SMDATA_LINK_LIB ${JSONCPP_LIBRARY})
+  list(APPEND SMDATA_LINK_LIB ${JSONCPP_LIBRARIES})
 else()
   list(APPEND SMDATA_LINK_LIB "jsoncpp")
 endif()
@@ -617,7 +617,9 @@ if(NOT APPLE)
                 "${SM_EXTERN_DIR}/glew-1.5.8/include")
   endif()
 
-  if(NOT WITH_SYSTEM_JSONCPP)
+  if(WITH_SYSTEM_JSONCPP)
+    list(APPEND SM_INCLUDE_DIRS ${JSONCPP_INCLUDE_DIRS})
+  else()
     list(APPEND SM_INCLUDE_DIRS
                 "${SM_EXTERN_DIR}/jsoncpp/include")
   endif()