-add_subdirectory(TerraSync)
-add_subdirectory(fgviewer)
-add_subdirectory(GPSsmooth)
-
-if (FLTK_FOUND)
+if(ENABLE_FGADMIN)
add_subdirectory(fgadmin)
-endif (FLTK_FOUND)
+endif()
+
+# win32 is just excluded because of not having argument parsing there ...
+if(RTI_FOUND AND NOT WIN32)
+ add_subdirectory(fgai)
+endif()
+
+if(ENABLE_FGELEV)
+ add_subdirectory(fgelev)
+endif()
+
+if(WITH_FGPANEL)
+ add_subdirectory(fgpanel)
+endif()
+
+if(ENABLE_FGVIEWER)
+ add_subdirectory(fgviewer)
+endif()
+
+if(ENABLE_GPSSMOOTH)
+ add_subdirectory(GPSsmooth)
+endif()
+
+if(ENABLE_TERRASYNC)
+ add_subdirectory(TerraSync)
+endif()
+
+if(ENABLE_FGCOM)
+ add_subdirectory(fgcom)
+endif()
+
+if(ENABLE_STGMERGE)
+ add_subdirectory(stgmerge)
+endif()