Subclassing Question

[LuckyLuke]

Hi,

I'm trying to make a dll for Visual Basic with ATL with my own control in it. I try to subclass the control created with CreateWindowEx by using SetWindowLong. However the compiler gives an type cast error when calling SetWindowLong. I was wondering if it's even possible to have a WindowProc inside a class and if so, how do you use it. If not or if there is a better way, please tell me how (I haven't got much experience with ATL or MFC). I think I can't use the built in message map macro's from ATL, since I've created my own window class with RegisterClass. Everything goes fine, until I want to subclass the windows I create with my dll. The code I use to subclass is this:

(Simplified test version)
[tt]
ToolWindow.h
class ATL_NO_VTABLE CToolWindow :
public CComObjectRootEx<CComSingleThreadModel>,
public CComCoClass<CToolWindow, &CLSID_ToolWindow>,
public IDispatchImpl<IToolWindow, &IID_IToolWindow, &LIBID_CTOOLWINDOWLib>
{
public:
CToolWindow()
{
}

DECLARE_REGISTRY_RESOURCEID(IDR_TOOLWINDOW)

DECLARE_PROTECT_FINAL_CONSTRUCT()

BEGIN_COM_MAP(CToolWindow)
COM_INTERFACE_ENTRY(IToolWindow)
COM_INTERFACE_ENTRY(IDispatch)
END_COM_MAP()

// IToolWindow
public:
LRESULT CALLBACK WindowProc(HWND hWnd, UINT uMsg, WPARAM wParam, LPARAM lParam);
STDMETHOD(Create)(/*[in]*/ long hWndParent, /*[in]*/ long hInstance, /*[out,retval]*/ long *lpRetVal);
private:
WNDPROC m_wpProcAddress;
};

#endif //__TOOLWINDOW_H_

ToolWindow.cpp
STDMETHODIMP CToolWindow::Create(long hWndParent, long hInstance, long *lpRetVal)
{
// TODO: Add your implementation code here
HWND hWnd = CreateWindowEx(0, _T(&quot;Button&quot, _T(&quot;Test&quot, WS_VISIBLE | WS_CHILD, 10, 10, 100, 100, (HWND) hWndParent, 0, (HINSTANCE) hInstance, NULL);

if (hWnd != 0)
m_wpProcAddress = (WNDPROC) SetWindowLong(hWnd, GWL_WNDPROC, (WNDPROC) WindowProc); //This is line 16

*lpRetVal = (long) hWnd;

return S_OK;
}

LRESULT CALLBACK CToolWindow::WindowProc(HWND hWnd, UINT uMsg, WPARAM wParam, LPARAM lParam)
{
return CallWindowProc(m_wpProcAddress, hWnd, uMsg, wParam, lParam);
}
[/tt]

The type cast error is:

[tt]
C:\Documents and Settings\Administrator\Desktop\Programmeren\CToolWindow\C\CToolWindow\ToolWindow.cpp(16) : error C2440: 'type cast' : cannot convert from '' to 'long (__stdcall *)(struct HWND__ *,unsigned int,unsigned int,long)'
None of the functions with this name in scope match the target type
[/tt]

Thanks in advance

 

[LuckyLuke]

Oh I spotted a mistake in my code (however it doesn't resolve the error):

line 16 should be:

[tt]
m_wpProcAddress = (WNDPROC) SetWindowLong(hWnd, GWL_WNDPROC, (LONG) WindowProc);
[\tt]

The error I get now is:
[tt]
C:\Documents and Settings\Administrator\Desktop\Programmeren\CToolWindow\C\CToolWindow\ToolWindow.cpp(16) : error C2440: 'type cast' : cannot convert from 'long (__stdcall CToolWindow::*)(struct HWND__ *,unsigned int,unsigned int,long)' to 'long'
Conversion is a valid standard conversion, which can be performed implicitly or by use of static_cast, C-style cast or function-style cast[/tt]

 

[LuckyLuke]

I have found a workaround. Thanks if you tried to help anyway

[tt]
LRESULT CALLBACK WindowProc(HWND hWnd, UINT uMsg, WPARAM wParam, LPARAM lParam);
WNDPROC wpProcAddress;

STDMETHODIMP CToolWindow::Create(long hWndParent, long hInstance, long *lpRetVal) {

m_hWnd = CreateWindowEx(0, _T(&quot;Button&quot, _T(&quot;Hiep Hoi&quot, WS_VISIBLE | WS_CHILD, 10, 10, 100, 100, (HWND) hWndParent, 0, (HINSTANCE) hInstance, NULL);

if (m_hWnd != 0) {
SetProp(m_hWnd, _T(&quot;PROP_WNDPROC&quot, (HANDLE) (this));
wpProcAddress = (WNDPROC) SetWindowLong(m_hWnd, GWL_WNDPROC, (LONG) WindowProc);
}

*lpRetVal = (long) m_hWnd;

return S_OK;

}

LRESULT CALLBACK CToolWindow::ToolwindowProc(UINT uMsg, WPARAM wParam, LPARAM lParam) {

if (uMsg == WM_LBUTTONDOWN)
MessageBeep(MB_ICONASTERISK);

return CallWindowProc(wpProcAddress, m_hWnd, uMsg, wParam, lParam);

}

LRESULT CALLBACK WindowProc(HWND hWnd, UINT uMsg, WPARAM wParam, LPARAM lParam) {

CToolWindow * ToolWindow = (CToolWindow *) GetProp(hWnd, _T(&quot;PROP_WNDPROC&quot);

if (ToolWindow != (CToolWindow *) 0)
return ToolWindow->ToolwindowProc(uMsg, wParam, lParam);

return CallWindowProc(wpProcAddress, hWnd, uMsg, wParam, lParam);

}
[/tt]