Изменение позиций элементов ListBox с помощью Drag and Drop 2

unit Draglb;

interface

uses
  SysUtils, WinTypes, WinProcs, Messages, Classes, Graphics, Controls,
  Forms, Dialogs, StdCtrls;

type
  TDragListBox = class(TListBox)
  private
    { Private declarations }
  protected
    { Protected declarations }
  public
    { Public declarations }
    procedure DragOver(Sender, Source: TObject; X, Y: Integer; State:
      TDragState; var Accept: Boolean);
    procedure DragDrop(Sender, Source: TObject; X, Y: Integer);
    constructor Create(AOwner: TComponent); override;
    { Published declarations }
  end;

procedure Register;

implementation

procedure Register;
begin
  RegisterComponents('Custom', [TDragListBox]);
end;

constructor TDragListBox.Create(AOwner: TComponent);
begin
  inherited Create(AOwner);
  DragMode := dmAutomatic;
  OnDragDrop := DragDrop;
  OnDragOver := DragOver;
end;

procedure TDragListBox.DragOver(Sender, Source: TObject; X, Y: Integer;
  State: TDragState; var Accept: Boolean);
begin
  Accept := Source = Self;
end;

procedure TDragListBox.DragDrop(Sender, Source: TObject; X, Y: Integer);
var
  Value: Integer;
begin
  if Sender = Self then
  begin
    Value := Self.ItemAtPos(Point(x, y), True);

    if Value = -1 then
    begin
      Self.Items.Add(Self.Items[Self.ItemIndex]);
      Self.Items.Delete(Self.ItemIndex);
    end
    else
    begin
      Self.Items.Insert(Value {+ 1}, Self.Items[Self.ItemIndex]);
      Self.Items.Delete(Self.ItemIndex);
    end;
  end;
end;

end.