Merge pull request #456 from jpanetta/master

Work-around for GLFW+GLEW+NANOGUI CMake conflict

Former-commit-id: f7bd7852525adf73c4a1282886c8c7ec80d2648a

shared/cmake/CMakeLists.txt

@@ -343,7 +343,12 @@ if(LIBIGL_WITH_OPENGL)
       list(APPEND GLFW_INCLUDE_DIRS "${NANOGUI_DIR}/ext/glew/include")
     endif()
 
-    add_subdirectory("${NANOGUI_DIR}/ext/glfw" "glfw")
+    # Note: if add_subdirectory("${NANOGUI_DIR}" "nanogui") runs below it will
+    # add GLFW as a side-effect; in this case, CMake will complain about
+    # duplicates if we add them here.
+    if (NOT (LIBIGL_WITH_VIEWER AND LIBIGL_WITH_NANOGUI))
+        add_subdirectory("${NANOGUI_DIR}/ext/glfw" "glfw")
+    endif()
     set(LIBIGL_OPENGL_GLFW_EXTRA_LIBRARIES "glfw" ${GLFW_LIBRARIES})
     if(LIBIGL_USE_STATIC_LIBRARY)
       CompileIGL_Module("opengl/glfw" "")