The axis movement from a smooth scroll device, such as a touchpad.
When applicable, the size of the motion delta should be equivalent to the motion vector of a pointer motion done using the same advice.
May only be called on a remote desktop session with `XDP_DEVICE_POINTER` access.
| this |
a [class@Session] |
| finish |
whether this is the last in a series of related events |
| dx |
relative axis movement on the X axis |
| dy |
relative axis movement on the Y axis |