onPanStart method
Implementation
onPanStart(DragStartDetails _) {
_buildSlotRectCaches();
var _pickUp = findItemByEventPosition(_.globalPosition);
if (_pickUp != null && _pickUp.item?.fixed == false) {
this.pickUp = _pickUp;
_dragOffset = getRect(_stackKey.currentContext!).topLeft;
_fromSlot = findSlotFromTile(_pickUp);
final offset = _pickUp.key.currentState!.rect.topLeft + _dragOffset;
_pickUp.key.currentState!
..dragging = true
..rect = Rect.fromLTWH(
offset.dx,
offset.dy,
_pickUp.rect.width,
_pickUp.rect.height,
);
_createOverlay();
setState(() {});
}
}