How about use CEGUI as cocos2dx's gui module?

CEGUI has a OpenGLRenderer rendering by OpenGL, and cocos2dx use OpenGL too. I guess it is possible to use CEGUI in cocos2dx games.
I write a CEGUILayer inherited from cocos2d::CCLayer, and override the draw function with CEGUI::System::getSingletonPtr()->renderGUI().
But the renderGUI function looks useless.

(CEGUI-0.7.9 and cocos2d-x-2.1.4)

I know little about OpenGL, although familiar with CEGUI.
Help me, please.
Thanks.