When does IsIconic() work?

void CAboutDlg::OnPaint(){ // This code, normally emitted by the Application Wizard for a dialog- // based project for the dialog's WM_PAINT handler, runs only if the // window is iconic. The window erases the icon's area, then // paints the icon referenced by m_hIcon. if (IsIconic()) { CPaintDC dc(this); // device context for painting SendMessage(WM_ICONERASEBKGND, (WPARAM)dc.GetSafeHdc(), 0); // Center icon in client rectangle int cxIcon = GetSystemMetrics(SM_CXICON); int cyIcon = GetSystemMetrics(SM_CYICON); CRect rect; GetClientRect(&rect); int x = (rect.Width() - cxIcon + 1) / 2; int y = (rect.Height() - cyIcon + 1) / 2; // Draw the icon dc.DrawIcon(x, y, m_hIcon); } else { CDialog::OnPaint(); }}