Yes, all of the coordinates returned by gluUnProject were negative in my test. Doubleclicking is also affected.
The strange thing is that the very same code works fine in YACReaderLibrary.
My answers are not necessarily official YACReader statements but mostly represent my own opinion in technical matters.
It really doesn't work fine in YACReaderLibrary. The x,y origin is displaced to the right, you have to click on the very right side for getting the desired action.
I think that the real problem is in glReadPixels, the z-buffer is not working properly...
YACReader
