Context

Scrolling on Flutter Desktop prior to version 3.3.0 used PointerScrollEvent
messages to represent discrete scroll deltas. This system worked well for mouse
scroll wheels, but wasn’t a good fit for trackpad scrolling. Trackpad scrolling
is expected to cause momentum, which depends not only on the scroll deltas, but
also the timing of when fingers are released from the trackpad. In addition, trackpad
pinching-to-zoom could not be represented.

This means both that code designed only for touch interactions might trigger upon
trackpad interaction, and that code designed to handle all desktop scrolling
might now only trigger upon mouse scrolling, and not trackpad scrolling.

Description of change

The Flutter engine has been updated on all possible platforms to recognize
trackpad gestures and send them to the framework as PointerPanZoom events
instead of as PointerScrollSignal events. PointerScrollSignal events will
still be used to represent scrolling on a mouse wheel.