Get bounding box of string with old TextRenderer

Hi :)
I'm trying to create vertices bounding a string I draw in 3D mode with com.jogamp.opengl.util.awt.TextRenderer but I don't understand well the getBounds() method. Anyone could explain me how width and height are returned ? Are they in pixels ? If so, could anyone help me to get vertices coordinates in OGL system wich could bound the string ? Do you think I need to unproject matrix to get them ?

Thanks a lot in advance.