what is the usage of these funcitons ?Code:void CTransparentDialogDlg::OnLButtonDown(UINT nFlags, CPoint point) { CDialog::OnLButtonDown(nFlags, point); //<<<< this } void CTransparentDialogDlg::OnSize(UINT nType, int cx, int cy) { CDialog::OnSize(nType, cx, cy); //<< and this }