[lmikle]

Из моего проекта.

Код:

procedure TPLOrderForm.ListBox1DragOver(Sender, Source: TObject; X,
  Y: Integer; State: TDragState; var Accept: Boolean);

  procedure DrawLn(FromX, ToX, Y : Integer);
  begin
    ListBox1.Canvas.MoveTo(FromX,Y);
    ListBox1.Canvas.LineTo(ToX,Y);
  end;

var
  P : TPoint;
  R : TRect;
  Idx : Integer;
begin
  P.x := X;
  P.y := Y;
  Idx := ListBox1.ItemAtPos(P,False);
  If Idx = DrwIdx Then Exit;
  If DrwIdx > -1 Then
    Begin
      R := ListBox1.ItemRect(DrwIdx);
      ListBox1.Canvas.Pen.Color := ListBox1.Color;
      If DrwIdx < ListBox1.ItemIndex
        Then DrawLn(R.Left,R.Right,R.Top)
        Else DrawLn(R.Left,R.Right,R.Bottom);
    End;
  R := ListBox1.ItemRect(Idx);
  ListBox1.Canvas.Pen.Color := clHighlight;
  If Idx < ListBox1.ItemIndex
    Then DrawLn(R.Left,R.Right,R.Top)
    Else DrawLn(R.Left,R.Right,R.Bottom);
  DrwIdx := Idx;
  Accept := Source Is TListBox;
end;

procedure TPLOrderForm.ListBox1DragDrop(Sender, Source: TObject; X,
  Y: Integer);
var
  P : TPoint;
  Idx : Integer;
begin
  P.x := X;
  P.y := Y;
  Idx := ListBox1.ItemAtPos(P,False);
  If Idx >= ListBox1.Items.Count-1 Then
    Idx := ListBox1.Items.Count-1;
  ListBox1.Items.BeginUpdate;
  SwapPics(stTo, Idx);
  ListBox1.Items.EndUpdate;
  UpdateButtons;
end;