This drag and drop operation, ok.
As I understand it, you want to drag a rectangle out across the screen and upon releasing the key, you want every 3d object
inside the rectangle, to be selected???
The way the selection buffer works, you define a viewport onto which you are drawing,but it is positioned at the mouse coordinates, and is only a few pixels wide.
You draw your objects, and any named object which is draw into this very small viewport,
is added to a list, for your perusal later.
ok, why not use the dragged rectangle to define your viewport size?
The opengl Superbible has an example of this.
That’s what I used and it worked great!