typedef void __fastcall (__closure *TDockOverEvent)(System::TObject* Sender, TDragDockObject* Source, int X, int Y, System::Uitypes::TDragState State, bool &Accept);
TDockOverEvent is the type of the OnDockOver event handler.
Sender is the object over which another object is being dragged.
Source is information about the object that is being dragged.
X and Y are the coordinates of the mouse pointer.
DragState is the current drag state.
Accept returns whether or not the control accepts the dragged object for docking.