dll to caller main dialog - visual-studio

Question

I am desparately in search of MFC dll sample that updates an edit field on a dialog derived from CDialog with a string using only the callback function. I realize static functions are the ones that are used in the calback.

Answer 1

I guess you realise that the dll should have something (like a separate thread, or a certain third-party message handler for this model. So, this is out of scope for this question.
Back to the question:
In order to create a callback function you need to "typedef" its prototype and pass the address of this function from your calling app to the dll. In your dll "h" file specify this:
// This is the Mfcdll1.h header file
// You should have some code created by the wizard, similar to the following:
#ifdef MYDLL_EXPORTS
#define MYDLL_API __declspec(dllexport)
#else
#define MYDLL_API __declspec(dllimport)
#endif
// This is the typedef for your callback function type:
typedef void (CALLBACK* MY_DLL_CALLBACK)
(
LPVOID lpParam,
LPCTSTR lpszMessage
);
class CMyDllApp : public CWinApp
{
public:
CMyDllApp();
// etc.
void SetCallBack(MY_DLL_CALLBACK pCallback, LPVOID pCallbackParm){m_pCallback = pCallback; m_pCallbackParm = pCallbackParm;}
private:
MY_DLL_CALLBACK m_pCallback;
LPVOID m_pCallbackParm;
};
MYDLL_API void SetCallBack(MY_DLL_CALLBACK pCallback, LPVOID pCallbackParm);
In your dll's cpp file specify this:
CMyDllApp::CMyDllApp()
{
m_pCallback = NULL;
m_pCallbackParm = NULL;
}
MYDLL_API void SetCallBack(MY_DLL_CALLBACK pCallback, LPVOID pCallbackParm)
{
theApp.SetCallBack(pCallback, pCallbackParm);
}
Now, if your dll wants to call the callback function, all you need to do is:
CMyDllApp::SendCallbackToTheCaller(LPCTSTR lpszMessage)
{
if(m_pCallback) (*(m_pCallback))(m_pCallbackParm, lpszMessage);
}
At this stage you have done coding in the dll. Now, all you need to do is specify the static callback function in your dialog that will update you Edit control, similar to this:
In the h file:
// TestDlg.h - My Test dialog with the Edit Control
CTestDlg: public CDialog
{
public:
static void CALLBACK StatusCallback(LPVOID lpParam, LPCTSTR lpszMessage);
};
In the cpp file:
BOOL CTestDlg::OnInitDialog()
{
CDialog::OnInitDialog();
// Insert this line along your stuff
::SetCallback((MY_DLL_CALLBACK)StatusCallback, (LPVOID)this);
}
void CALLBACK CTestDlg::StatusCallback(LPVOID lpParam, LPCTSTR lpszMessage)
{
CTestDlg* pTestDlg = reinterpret_cast<CTestDlg*>(lpParam);
ASSERT(pTestDlg!=NULL);
pTestDlg->m_edStatus.SetWindowText(lpszMessage);
}