The distance fraction in the vertical direction.
A value of -1.0 corresponds to the topmost edge. A value of 1.0 corresponds to the bottommost edge. Values are not limited to that range; values less than -1.0 represent positions above the top, and values greater than 1.0 represent positions below the bottom.
This value is passed through to Alignment.y unmodified by the resolve method.
final double y;