C / C++ / MFC

HWND hMain = AfxGetMainWnd()->m_hWnd;
::PostMessage(hMain, MYMESSAGE, 0, 0);

CWinThread* pThread = ::AfxBeginThread( MyWorkerThreadProc, this );

UINT MyWorkerThreadProc( void* pParam )
{
    //
    // ... other worker code
    //
   
    // EVERYTIME using Doc in this thread proc,
    // ensure doc object is still around. (Think MDI app)
    // Some Synch-primitive *necessary* but not shown here.
    if( doc is no longer around )
    {
        // doc ptr is not valid. 
        // Worker thread should terminate immediately.
        return -1;   // returning will destroy this thread automatically
    }
    else
    {
        // Feel free to call any member function of the doc.
        CMyDocument* pDoc = (CMyDocument*) pParam;
        pDoc->CallAnyMemberFunction();
    }
    //
    // ... other worker code
    //

    // Worker task through successfully
    return 1;
}

m_pThread->m_pCreatingDoc = this; // this means doc

m_pThread->PostThreadMessage( UWM_PROGRESSDELETE, 0, (LPARAM) pData );

// global #define user message
#define MYMESSAGE (WM_USER+7)

// Prototype 
static UINT MyThreadProc( void* pParam ); 

// Function implementation
UINT MyThreadProc( void* pParam )
{
	HWND hWnd = (HWND) pParam;
	int nIters = 10;
	for( int i = 0; i < nIters; i++ )
	{
		// Simulate worker doing a part of real work
		::Sleep( 500 );	

		CString* pS = new CString; // Handler will delete
		pS->Format( "Done %d of %d", i, nIters );

		// Make sure we can post
		// Unfortuantely, the C-commented portion, (checking window
		// handle without event support, leads to memory leaks 
		// due to undeleted pS.
		/* 
		if( ! ::IsWindow( hWnd ) )
		{
			delete pS;
			pS = 0;
			return -2;
		}
		*/
		::PostMessage( pH->m_hWnd, MYMESSAGE, (WPARAM)i, (LPARAM) pS );
	}
	return 0;
}

// This is the menu handler I added in Doc
// for actually starting the ball roll...
void CMyDoc::OnLaunchWorkerThread() 
{
	CWnd* pWnd = ::AfxGetMainWnd();
	HWND hWnd = pWnd->GetSafeHwnd();
	::AfxBeginThread( MyThreadProc, (void*) hWnd );	
}

// Generated message map functions
protected:
	//{{AFX_MSG(CMainFrame)
	afx_msg int OnCreate(LPCREATESTRUCT lpCreateStruct);
	afx_msg void OnMyMessage(WPARAM wParam, LPARAM lParam); // Typed manually
	//}}AFX_MSG
	DECLARE_MESSAGE_MAP()

BEGIN_MESSAGE_MAP(CMainFrame, CMDIFrameWnd)
	//{{AFX_MSG_MAP(CMainFrame)
	ON_WM_CREATE()
	ON_THREAD_MESSAGE(MYMESSAGE, OnMyMessage) // Typed manually.
	//}}AFX_MSG_MAP
END_MESSAGE_MAP()


void CMainFrame::OnMyMessage(WPARAM wParam, LPARAM lParam)
{
	CString* pS = (CString*) lParam;
	TRACE( "Got (%d) %s\n", (int)wParam, *pS );
	delete pS;
	pS = 0;
}