폼 위에 마우스를 드래그하면 마우스를 따라서 처음 클릭한 곳으로부터 직선을 그어지게 하려 하는데요...

다음고 같이 코딩을 했는데 의도대로 되질 않는군요....ㅡㅡ;

//---------------------------------------------------------------------------
void __fastcall TForm1::FormMouseDown(TObject *Sender, TMouseButton Button,
      TShiftState Shift, int X, int Y)
{
  if (Button == mbLeft)
  {
    m_ptOne.x = X;
    m_ptOne.y = Y;

    m_ptTwo = m_ptOne;
  }
}
//---------------------------------------------------------------------------
void __fastcall TForm1::FormMouseMove(TObject *Sender, TShiftState Shift,
      int X, int Y)
{
  if (Shift == (TShiftState() << ssLeft))
  {
    TPenMode pmMode = Canvas->Pen->Mode;
    Canvas->Pen->Mode = pmXor;

    Canvas->MoveTo(m_ptOne.x, m_ptOne.y);
    Canvas->LineTo(m_ptTwo.x, m_ptTwo.y);

    m_ptTwo.x = X;
    m_ptTwo.y = Y;
    Canvas->MoveTo(m_ptOne.x, m_ptOne.y);
    Canvas->LineTo(m_ptTwo.x, m_ptTwo.y);

    Canvas->Pen->Mode = pmMode;
  }
}
//---------------------------------------------------------------------------

조언 부탁드립니다.