Assertion failed when creating CPaneDialog In MFC

Question

I have a simple .exe MFC project and a DLL project with MFC statically linked. It exports the following function for creating a CPaneDialog:

extern "C" __declspec(dllexport) void init_toolbox_gui(HWND ptr) {

AFX_MANAGE_STATE(AfxGetStaticModuleState());

CPaneDialog *_gui = new CPaneDialog;
CWnd *p = CWnd::FromHandle(ptr);

_gui->Create(_T("DialogBar"), p, TRUE, (IDD_DIALOG1),
    WS_CHILD | WS_VISIBLE | WS_CLIPSIBLINGS | WS_CLIPCHILDREN | CBRS_LEFT | CBRS_FLOAT_MULTI,
    0);

}

I call this from my main .exe app class (derived from CWinAppEx) as follows:

// dll is a handle to the DLL lib
ToolboxInitFunc func = (ToolboxInitFunc)GetProcAddress(dll, "init_toolbox_gui"); 

func(m_pMainWnd->GetSafeHwnd());

This fails in the following debug assertion, in void CMFCDragFrameImpl::Init(CWnd* pDraggedWnd):

m_pDockManager = afxGlobalUtils.GetDockingManager(pDockSite);
ENSURE(m_pDockManager != NULL);

I can give the full code of that function but it is from standard MFC libraries.

This is the call stack:

toolbox-3d.dll!CMFCDragFrameImpl::Init(CWnd * pDraggedWnd) Line 106 C++
toolbox-3d.dll!CPane::CreateEx(unsigned long dwStyleEx, const wchar_t * lpszClassName, unsigned long dwStyle, const tagRECT & rect, CWnd * pParentWnd, unsigned int nID, unsigned long dwControlBarStyle, CCreateContext * pContext) Line 177   C++
toolbox-3d.dll!CDockablePane::CreateEx(unsigned long dwStyleEx, const wchar_t * lpszCaption, CWnd * pParentWnd, const tagRECT & rect, int bHasGripper, unsigned int nID, unsigned long dwStyle, unsigned long dwTabbedStyle, unsigned long dwControlBarStyle, CCreateContext * pContext) Line 175   C++
toolbox-3d.dll!CDockablePane::Create(const wchar_t * lpszWindowName, CWnd * pParentWnd, CSize sizeDefault, int bHasGripper, unsigned int nID, unsigned long dwStyle, unsigned long dwTabbedStyle, unsigned long dwControlBarStyle) Line 148 C++
toolbox-3d.dll!CPaneDialog::Create(const wchar_t * lpszWindowName, CWnd * pParentWnd, int bHasGripper, const wchar_t * lpszTemplateName, unsigned int nStyle, unsigned int nID, unsigned long dwTabbedStyle, unsigned long dwControlBarStyle) Line 48   C++
toolbox-3d.dll!CPaneDialog::Create(const wchar_t * lpszWindowName, CWnd * pParentWnd, int bHasGripper, unsigned int nIDTemplate, unsigned int nStyle, unsigned int nID) Line 42 C++
toolbox-3d.dll!init_toolbox_gui(HWND__ * ptr) Line 45   C++

What could be wrong?

xMRi xMRi · Accepted Answer · 2015-04-22T13:22:53

You can't use the docking features "stand alone".

This docking stuff needs a specially prepared CFrameWndEx class. If the MFC project uses such a class you are forced to use the MFC dynamically linked, when you want to use a DLL.

The ASSERT you get is just an indicator that the current module (your DLL), has neither a frame nor a dock manager to support such dockable panes.

The reason is simple. The statically linked EXE and the DLL will just use there own representation of a CObject, so all IsKindOf calls internally used in the MFC will only work inside the module.

Assertion failed when creating CPaneDialog In MFC

1 Answers