So far KWin didn't send axis_source, axis_discrete, and axis_stop. Even
though most of those events are optional, clients need them to work as
expected. For example, one needs axis_source and axis_stop to implement
kinetic scrolling; Xwayland needs axis_discrete to prevent multiple
scroll events when the compositor sends axis deltas greater than 10, etc.
BUG: 404152
FIXED-IN: 5.16.0