On macOS 12.1 the NSEventPhaseCancelled phase can in some situations
report deltas, which causes the scroll to "jump". This happens for
example when initiating a momentum-scroll, and then putting two
fingers on the trackpad to cancel the momentum phase, which starts
a new NSEventPhaseMayBegin phase. When then lifting the two fingers
again, we get an NSEventPhaseCancelled event with deltas, but the
deltas seem like uninitialized data (has a x-value, after doing
a purely vertical scroll e.g.).
Task-number: QTBUG-97841
Pick-to: 6.3 6.2 5.15
Change-Id: I14e765b6111e53e7d3d0da219d4ac7fefe5243d0
Reviewed-by: Volker Hilsheimer <volker.hilsheimer@qt.io>
2c3198ab5f