Active element that displays nothing but lets you control two parameters at the same time: one for the horizontal movements (x), one for the vertical movements (y). The values of the parameters depend on the position of the mouse on the pad.
This particular control supports the common widget attributes. It also has the attributes common to all param control widgets and param widgets, but with a 'x_' or 'y_' prefix for each dimension. Note that only one dimension is mandatory (you do not need to connect all parameters, you can use for example the x control only).