The title is pretty straight forward to the question, how can one activate retina display when using JSB and cocos2d-x?
I figured it out.
You have to read this:
http://www.cocos2d-x.org/projects/cocos2d-x/wiki/Multi_resolution_support
This will enable retina display for the iphone5 for example:
(in applicationDidFinishLauching)
@
EGLView* pEGLView = EGLView::getInstance();
pEGLView~~>setDesignResolutionSize;
director~~>setContentScaleFactor(2);
@