163303e7_54_3__Event_types__Description
[Type] 38 [Name] MouseWheel [Description] 
The user moved the mouse wheel up or down. At present, this binding works on Windows and MacOS, but not under Linux. For Windows and MacOS, see the discussion of the .delta field of the Event instance in Section 54.6, “Writing your handler: The Event class”. For Linux, see the note above under Button.
54.3. Event types
Description