Determines the way that drag start behavior is handled.
If set to DragStartBehavior.start, the drag behavior used for opening and closing a drawer will begin at the position where the drag gesture won the arena. If set to DragStartBehavior.down it will begin at the position where a down event is first detected.
By default, the drag start behavior is DragStartBehavior.start.
- DragGestureRecognizer.dragStartBehavior, which gives an example for the different behaviors.
final DragStartBehavior drawerDragStartBehavior;