Creating multiple dialogs in an MFC app with no main Window, they become children of each other

(title updated) Following on from this question, now I have a clearer picture what's going on...

I have a MFC application with no main window, which exposes an API to create dialogs. When I call some of these methods repeatedly, the dialogs created are parented to each other instead of all being parented to the desktop... I have no idea why.

But anyway even after creation, I am unable to change the parent back to NULL or CWnd::GetDesktopWindow()... if I call SetParent followed by GetParent, nothing has changed.

So apart from the really weird question of why Windows is magically parenting each dialog to the last one created, is there anything I'm missing to be able to set these windows as children of the desktop?

UPDATED: I have found the reason for all this, but not the solution. From my dialog constructor, we end up in:

BOOL CDialog::CreateIndirect(LPCDLGTEMPLATE lpDialogTemplate, CWnd* pParentWnd,
    void* lpDialogInit, HINSTANCE hInst)
{
    ASSERT(lpDialogTemplate != NULL);

    if (pParentWnd == NULL)
        pParentWnd = AfxGetMainWnd();
    m_lpDialogInit = lpDialogInit;

    return CreateDlgIndirect(lpDialogTemplate, pParentWnd, hInst);
}

Note: if (pParentWnd == NULL)pParentWnd = AfxGetMainWnd();

The call-stack from my dialog constructor looks like this:

• mfc80d.dll!CDialog::CreateIndirect(const DLGTEMPLATE * lpDialogTemplate=0x005931a8, CWnd * pParentWnd=0x00000000, void * lpDialogInit=0x00000000, HINSTANCE__ * hInst=0x00400000)
• mfc80d.dll!CDialog::CreateIndirect(void * hDialogTemplate=0x005931a8, CWnd * pParentWnd=0x00000000, HINSTANCE__ * hInst=0x00400000)
• mfc80d.dll!CDialog::Create(const char * lpszTemplateName=0x0000009d, CWnd * pParentWnd=0x00000000)
• mfc80d.dll!CDialog::Create(unsigned int nIDTemplate=157, CWnd * pParentWnd=0x00000000)
• MyApp.exe!CMyDlg::CMyDlg(CWnd * pParent=0x00000000)

Running in the debugger, if I manually change pParentWnd back to 0 in CDialog::CreateIndirect, everything works fine... but how do I stop it happening in the first place?

Some thoughts:

First, you are passing NULL for the parent window the whole way through the chain. Its becomming non NULL when MFC tries to find your applications main window.

As I see it you have two mitigations:

1. Create a CWnd from the desktop window. CWnd::GetDesktopWindow will give you a non NULL window to use as a parent window that will inhibit the AfxGetMainWnd call.
2. Or trace into AfxGetMainWnd, find out where it is reading the main window from, and see if there is some setting to prevent it finding your dialog window.

On a final note. The MFC terminology is unfortunate :- On Windows, only child windows have parent windows. Popup or desktop windows have owner windows. CreateWindow takes a single parameter that accepts the owner, or parent of the window being created. The distinction is important because while a parent window can be changed, an owner cannot. SetParent will NOT change the owner window for a popup or overlapped window.