onColumnMove property
Contains a callback that will be called whenever the position of a column needs to change.
The null value here will result in move handle not appearing on the screen.
Internal logic assumes that the changes will get applied the next build-cycle. Failing to so will lead to unexpected behavior.
Can be changed at any time (except SchedulerPhase.persistentCallbacks).
Implementation
final ValueNotifier<ColumnMoveCallback?> onColumnMove;