Wl_pointer.Axis_sourceAxis source types.
Describes the source types for axis events. This indicates to the client how an axis event was physically generated; a client may adjust the user interface accordingly. For example, scroll events from a "finger" source may be in a smooth coordinate space with kinetic scrolling whereas a "wheel" source may be in discrete steps of a number of lines.
The "continuous" axis source is a device generating events in a continuous coordinate space, but using something other than a finger. One example for this source is button-based scrolling where the vertical motion of a device is converted to scroll events while a button is held down.
The "wheel tilt" axis source indicates that the actual device is a wheel but the scroll event is not caused by a rotation but a (usually sideways) tilt of the wheel.