The scale factor relative to the points of the two touches in screen coordinates.
- iOS 3.2+
- Mac Catalyst 13.0+
You may set the scale factor, but doing so resets the velocity.
The scale value is an absolute value that varies over time. It is not the delta value from the last time that the scale was reported. Apply the scale value to the state of the view when the gesture is first recognized—do not concatenate the value each time the handler is called.