Programming full "holonomic" for mecanums

[iv1777]

Hello all.
I need some help programming full holonomic control for a 4 wheeled mecanum drive robot, wheels being in X formation...
We have had sideways, forwards, and twist movements for a long time now, and just recently I figured out how to get diagonal motion (shame to not have it last year)
Anyways, we are using Java, how can we program a full holonomic control to one joystick?
I'd like to point out we basically got diagonals at a 45 degree or so angle at GOOD speed, faster than going sideways but not quite as fast as forward or back, sudden changes in movement speed if you go from forward to diagonal to sideways isn't a problem or anything... Just getting a full 360 control is difficult.

As it is we tried to just get 8 direction on one joystick, and we could only get the forward/back/left/right, the diagonals wouldn't work...
But that won't matter if you help us get a 360 control
Thanks in advance...