Adding a view to MDI program

=?Utf-8?B?RkhEQg==?= <>
Mon, 10 Aug 2009 22:22:01 -0700
VS2008 Pro, XP

I am having trouble adding a view to a MDI program.

I followed the instructions in

However, instead of implementing a switcher function, I want both views
active and displayed simultaneously in separate windows. For the added view,
I chose CScrollView,

A specific problem with the code in the above guide is that the given method
for obtaining the current document: CDocument* pCurrentDoc =
returns NULL. Googling, I encountered someone who encountered this, and
solved it by getting the current document from the original child window of
the original view:
 CDocument* pCurrentDoc = ((CFrameWnd*)pChild)->GetActiveDocument();

The Create statement below fails when the first argument is
_T("CMDIChildWnd"). It does not fail when the first argument is NULL, though
I get a warning about creating a view without a document. So my naive guess
is that there is something wrong with pCurrentDoc obtained via the above
statement, but I don't know what.

When Create is called with _T("CMDIChildWnd"), the trace seems to show some
complaints when this statement:
 m_pFloatView->Create( _T("CMDIChildWnd"), _T("FloatViewWindow"),
   WS_CHILD | WS_VISIBLE | WS_VSCROLL, rect, m_pMainWnd, viewID, &newContext);
fails with
 "Debug Assertion Failed!..."afxwin2.inl...Line: 42."
 Warning: Window creation failed: GetLastError returns 0x0000057F
""Debug Assertion Failed!..." is not always present, but the 2nd message
always is.

When Create is called with first argument NULL, it does not fail. But the
result is a window that has no function.

In either case, the program continues to create the original view/window.

The commented statements at the bottom of the InitInstance function are part
of my experiments.

BOOL CdualApp::InitInstance()
 InitCtrls.dwSize = sizeof(InitCtrls);
 InitCtrls.dwICC = ICC_WIN95_CLASSES;

 SetRegistryKey(_T("Local AppWizard-Generated Applications"));
 LoadStdProfileSettings(4); // Load standard INI file options (including MRU)

 CMultiDocTemplate* pDocTemplate;
 pDocTemplate = new CMultiDocTemplate(IDR_dualTYPE,
 RUNTIME_CLASS(CChildFrame), // custom MDI child frame
 if (!pDocTemplate)
 return FALSE;

 // create main MDI Frame window
 CMainFrame* pMainFrame = new CMainFrame;
 if (!pMainFrame || !pMainFrame->LoadFrame(IDR_MAINFRAME))
 delete pMainFrame;
 return FALSE;
 m_pMainWnd = pMainFrame;
 // Enable DDE Execute open
 // Parse command line for standard shell commands, DDE, file open
 CCommandLineInfo cmdInfo;

 if (!ProcessShellCommand(cmdInfo))
 return FALSE;
 CMDIChildWnd * pChild =
 CDocument* pCurrentDoc = ((CFrameWnd*)pChild)->GetActiveDocument();

 CView* pActiveView = ((CFrameWnd*) m_pMainWnd)->GetActiveView();
 m_pdualView = pActiveView;
// The new view is called FloatView.
 m_pFloatView = (CView*) new FloatView;
 if (NULL == m_pFloatView)
 return FALSE;
// Initialize a CCreateContext to point to the active document.
// With this context, the new view is added to the document
// when the view is created in CView::OnCreate().
 CCreateContext newContext;
 newContext.m_pNewViewClass = NULL;
 newContext.m_pNewDocTemplate = NULL;
 newContext.m_pLastView = NULL;
 newContext.m_pCurrentFrame = NULL;
 newContext.m_pCurrentDoc = pCurrentDoc;

 CRect rect(200, 200, 600, 600); // Gets resized later.
 m_pFloatView->Create( _T("CMDIChildWnd"), _T("FloatViewWindow"),
   WS_CHILD | WS_VISIBLE | WS_VSCROLL, rect, m_pMainWnd, viewID, &newContext);

// When a document template creates a view, the WM_INITIALUPDATE
// message is sent automatically. However, this code must
// explicitly send the message, as follows.
    m_pFloatView->SendMessage(WM_INITIALUPDATE, 0, 0);

 // The main window has been initialized, so show and update it
// m_pFloatView->ShowWindow(SW_SHOW );

 return TRUE;

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