Axis constant: Pressure axis of a motion event.

• For a touch screen or touch pad, reports the approximate pressure applied to the surface by a finger or other tool. The value is normalized to a range from 0 (no pressure at all) to 1 (normal pressure), although values higher than 1 may be generated depending on the calibration of the input device.
• For a trackball, the value is set to 1 if the trackball button is pressed or 0 otherwise.
• For a mouse, the value is set to 1 if the primary mouse button is pressed or 0 otherwise.