Re: ActiveX event and DoModal

RAN <>
Tue, 8 Dec 2009 13:11:18 -0800 (PST)
On 8 dec, 21:32, Joseph M. Newcomer <> wrote:

See below...

On Tue, 8 Dec 2009 09:36:13 -0800 (PST), RAN <> wrote:


I use VS2008Pro.
I have created an ActiveX control dat shows a chessboard etc,
I have created an ActiveX event called OnPromotion();
I created a standard CDialog project and inserted the chess activex
I added the activex event OnPromotion() and want to show a second
CDailog using DoModal() inside of this OnPromotion() event.
The second (promotion dialog) is shown, but when i click it i get a
debug assertion failed message. Can i not call a DoModal() inside an
activex event in my dialog?

I am absolutely certain you do not get "a" debug assertion message. I =

have a great

confidence that you get a VERY SPECIFIC assertion failure, that specifies=

 a file, and

line, and you can supply a backtrace from that location to your code. =

Be sure to tell us

what version of VS you are using so we know how to correlate the file/lin=

e with actual

source code.

CXPTESTDlg::OnPromotion, VTS_NONE)

void CXPTESTDlg::OnPromotion()
   // TODO: Add your message handler code here

   // This call causes a debug assertion failed

   ::PostMessage (this->m_hWnd ,_UDM_TEST,0,0);

Why such a clumsy method? Would't it be easier to write

void CXPTESTDlg::OnBnClickedButton1()

One of the VERY FIRST things you should do when you add a control is chan=

ge the ID from

the useless IDC_BUTTON1 to something that makes sense.

   // TODO: Add your control notification handler code here
   o_PromotionDlg.DoModal ();

   o_PromotionDlg.DoModal ();
   return 0;

There isn't enough information here. Lacking any description of the as=

sertion failure,

there's nothing to try but psychic vibrations, and they don't work too we=



If i use PostMessage instead to call the DoModal() it works fine.
I dont know why this happens.
Could someone help please?

First, give us complete information.

Second, where is o_PromotionDlg declared? It should be a local variabl=

e in the function,

since there is no reason for it to exist outside the scope of the functio=

n that does the

DoModal. If you are inventing new notational conventions, such as a pr=

efix "o_", it is

important that you explain what it means.


Joseph M. Newcomer [MVP]
MVP Tips: Tekst uit oorspronkelijk b=

ericht niet weergeven -

- Tekst uit oorspronkelijk bericht weergeven -

1) I use Microsoft Visual Studio 2008, version 9.0.21022.8 RTM
2) i use the notational convention prefix _o for anything that is a
class or object.
3) the declaration of o_PromotionDlg is in class CXPTESTDlg:

// XP TESTDlg.h : header file

#pragma once
#include "chessactivectrl1.h"
#include "PromotionDlg.h"

#define _UDM_TEST WM_USER + 100

// CXPTESTDlg dialog
class CXPTESTDlg : public CDialog
// Construction
    CXPTESTDlg(CWnd* pParent = NULL); // standard constructor

// Dialog Data
    enum { IDD = IDD_XPTEST_DIALOG };

    virtual void DoDataExchange(CDataExchange* pDX); // DDX/DDV support

// Implementation
    HICON m_hIcon;

    // Generated message map functions
    virtual BOOL OnInitDialog();
    afx_msg void OnSysCommand(UINT nID, LPARAM lParam);
    afx_msg void OnPaint();
    afx_msg HCURSOR OnQueryDragIcon();
    CChessactivectrl1 o_ChessActive;
    void OnPromotion();
    CPromotionDlg o_PromotionDlg;
    afx_msg void OnBnClickedButton1();
    LRESULT OnTest(WPARAM wParam, LPARAM lParam);

4) if i click the break button after the debug assertion failed box it
jumps to file:
f:\dd\vctools\vc7libs\ship\atlmfc\src\mfc\dlgcore.cpp (line 492)

HWND CDialog::PreModal()
    // cannot call DoModal on a dialog already constructed as modeless
    ASSERT(m_hWnd == NULL);

    // allow OLE servers to disable themselves
    CWinApp* pApp = AfxGetApp();
    if (pApp != NULL)

    // find parent HWND
    HWND hWnd = CWnd::GetSafeOwner_(m_pParentWnd->GetSafeHwnd(),

    // hook for creation of dialog

    // return window to use as parent for dialog
    return hWnd;

the first ASSERT() failes.

5) i also tried :

void CXPTESTDlg::OnPromotion()
    // TODO: Add your message handler code here

    CDialog o_Test;

    o_Test.Create (IDD_PROMOTION);

    // This call causes a debug assertion failed

I get the same error.

I hope i have send you some information you can use.

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