DragUpdateDetails({Offset delta: Offset.zero, double primaryDelta, Point globalPosition })

Creates details for a DragUpdateDetails.

The delta argument must not be null.

If primaryDelta is non-null, then its value must match one of the coordinates of delta and the other coordinate must be zero.

Source 

DragUpdateDetails({
  this.delta: Offset.zero,
  this.primaryDelta,
  this.globalPosition
}) {
  assert(primaryDelta == null
      || (primaryDelta == delta.dx && delta.dy == 0.0)
      || (primaryDelta == delta.dy && delta.dx == 0.0));
}