MFC, invisible dialog app with timer

[BertAndErnie]

Hello

I'm making a MFC program that needs to start invisible, with a timer running. Then on timer expiry, if certain conditions are met, a dialog is supposed to display. I am trying a Dialog based application because that seems the most straightforward. I have been able to get roughly what I want with the standard modal dialog code generated by Visual Studio, by putting ShowWindow(SW_HIDE) in the dialog's OnPaint method. That approach causes a flicker of the dialog when the program is starting and I think there is a more correct way.

I have also tried:

BOOL CMyApp::InitInstance()
{
    InitCommonControls();
    CWinApp::InitInstance();
    m_pMainWnd = new CMyDlg;
    UINT_PTR uTimerId = SetTimer(NULL, 0, 2000, &TimerCallback);
    return (m_pMainWnd != NULL);
}

But this causes an assertion failure in CDialog at

BOOL CDialog::PreTranslateMessage(MSG* pMsg)
{
	// for modeless processing (or modal)
	ASSERT(m_hWnd != NULL);
}

It makes sense that m_hWnd is NULL because I haven't called the dailog's DoModal method but I don't know what to do about it.

What is the correct technique for this kind of application?

Thanks.

[GCDEF]

Call the Dialog's Create method, followed by ShowWindow(SW_HIDE).

[Arjay]

Another approach is to handle the OnWindowPosChanging message in the dialog.

First, just use the standard InitInstance:

BOOL CTestApp::InitInstance()
{
    // std initialization removed for demo

 
  CTestDlg dlg;
  m_pMainWnd = &dlg;
 
  INT_PTR nResponse = dlg.DoModal();
 
  return[SIZE=2] FALSE;
}

Add a timer variable and a variable to keep track of visibility state. Add to the class decl and init in the ctor

CTestDlg::CTestDlg(CWnd* pParent /*=NULL*/[SIZE=2])
  : CDialog(CTestDlg::IDD, pParent)
  , m_uTimerId( NULL )
  , m_bVisible( FALSE )
{
  m_hIcon = AfxGetApp()->LoadIcon(IDR_MAINFRAME);
}

Start the timer in OnInitDialog.

BOOL CTestDlg::OnInitDialog()
{
  CDialog::OnInitDialog();
 
  // std initialization removed for demo
 
  // Start the timer
  m_uTimerId = SetTimer( 1, 4000, NULL );

 
  return TRUE;
}

Handle the timer message. Set the visible variable to true, show
the dialog, and kill the timer:

void CTestDlg::OnTimer(UINT_PTR nIDEvent)
{
  m_bVisible = TRUE;
 
  ShowWindow( SW_SHOW );
 
  KillTimer( m_uTimerId );
 
  CDialog::OnTimer(nIDEvent);
}

Handle the OnWindowPosChanging message. If the m_bVisible variable is false, remove the show window style

void CTestDlg::OnWindowPosChanging(WINDOWPOS* lpwndpos)
{
  if( !m_bVisible )
  {
    lpwndpos->flags &= ~SWP_SHOWWINDOW;
  }
  
  CDialog::OnWindowPosChanging(lpwndpos);
}

[Msm]

use

RunModalLoop()

[VictorN]

use [CODE RunModalLoop()[/CODE]

Where an hat for?
RunModalLoop is used internally within CDialog:oModal

Use Arjay's approach: it will work good!