Configure the behavior of offsets passed to onDragStart.
If set to DragStartBehavior.start, the onDragStart callback will be called with the position of the pointer at the time this gesture recognizer won the arena. If DragStartBehavior.down, onDragStart will be called with the position of the first detected down event for the pointer. When there are no other gestures competing with this gesture in the arena, there's no difference in behavior between the two settings.
For more information about the gesture arena: https://flutter.dev/docs/development/ui/advanced/gestures#gesture-disambiguation
By default, the drag start behavior is DragStartBehavior.start.
- DragGestureRecognizer.dragStartBehavior, which includes more details and an example.