Trouble Closing Message-Only Window - C++ - c++

Question

My application has a message-only window that is launched from a newly created thread. The thread function creates the message-only window and runs the message pump. The problem I am having is that the message pump never seems to get the WM_CLOSE message. I've removed error-handling to simplify the posted code. Does anyone know what I'm doing wrong?
Constructor:
this->m_hInstance = ::GetModuleHandle( NULL );
this->m_wcx.cbSize = sizeof(WNDCLASSEX); // size of structure
this->m_wcx.style = CS_HREDRAW | CS_VREDRAW; // initially minimized
this->m_wcx.lpfnWndProc = &WndProc; // points to window procedure
this->m_wcx.cbClsExtra = 0; // no extra class memory
this->m_wcx.cbWndExtra = 0; // no extra window memory
this->m_wcx.hInstance = m_hInstance; // handle to instance
this->m_wcx.hIcon = ::LoadIcon( NULL, IDI_APPLICATION ); // default app icon
this->m_wcx.hCursor = ::LoadCursor( NULL, IDC_ARROW ); // standard arrow cursor
this->m_wcx.hbrBackground = NULL; // no background to paint
this->m_wcx.lpszMenuName = NULL; // no menu resource
this->m_wcx.lpszClassName = s_pwcWindowClass; // name of window class
this->m_wcx.hIconSm = NULL; // search system resources for sm icon
this->m_atom = ::RegisterClassEx( &m_wcx );
this->m_hNotifyWindowThread = ::CreateThread(
NULL, // no security attributes
0, // use default initial stack size
reinterpret_cast<LPTHREAD_START_ROUTINE>(NotifyWindowThreadFn), // function to execute in new thread
NULL, // thread parameters
0, // use default creation settings
NULL // thread ID is not needed
);
Destructor:
::DestroyWindow( this->m_hWnd );
::WaitForSingleObject( this->m_hNotifyWindowThread, NW_DEFAULT_TIMEOUT ); // <-- Seems to get stuck here.
::UnregisterClass( s_pwcWindowClass, this->m_hInstance );
Thread function:
s_ptInterface->pobjNotifyWindow->m_hWnd = ::CreateWindow(
s_pwcWindowClass, // window class name
s_pwcWindowName, // window name
WS_ICONIC, // window style is minimized
0, // initial horizontal position
0, // initial vertical position
CW_USEDEFAULT, // window width
0, // window height
NULL, // no parent window
NULL, // no menu
s_ptInterface->pobjNotifyWindow->GetInstanceHandle(), // associated instance
NULL // no additional info for WM_CREATE
);
::ShowWindow( s_ptInterface->pobjNotifyWindow->GetWindowHandle(), SW_HIDE );
::UpdateWindow( s_ptInterface->pobjNotifyWindow->GetWindowHandle();
dbt.dbcc_size = sizeof(DEV_BROADCAST_DEVICEINTERFACE);
dbt.dbcc_devicetype = DBT_DEVTYP_DEVICEINTERFACE;
dbt.dbcc_classguid = s_guidForCP210xDevices;
m_hNotify = RegisterDeviceNotification( m_hWnd, &dbt, DEVICE_NOTIFY_WINDOW_HANDLE );
while ( (blRetVal = ::GetMessage(
&msg, // message structure
NULL, // retrieve messages for all windows on this thread
0, // lowest message value to retrieve
0 // highest message value to retrieve
)) != 0 )
{
if ( blRetVal == -1 )
{
return ::GetLastError();
}
else
{
::TranslateMessage( &msg );
::DispatchMessage( &msg );
}
}
Window procedure:
switch ( uMsg )
{
case WM_CLOSE:
if ( m_hNotify != NULL )
{
::UnregisterDeviceNotification( m_hNotify );
m_hNotify = NULL;
}
::DestroyWindow( hWnd );
break;
case WM_DESTROY:
::PostQuitMessage( 0 );
break;
case WM_DEVICECHANGE:
if ( pHeader != NULL )
{
if ( pHeader->dbch_devicetype == DBT_DEVTYP_PORT )
{
switch ( wParam)
{
case DBT_DEVICEREMOVECOMPLETE: // Device is gone
::EnterCriticalSection( &(s_ptInterface->csSerialPort) );
s_ptInterface->pobjSerialPort->Close();
::LeaveCriticalSection( &(s_ptInterface->csSerialPort) );
break;
case DBT_DEVICEARRIVAL: // System detected device
::EnterCriticalSection( &(s_ptInterface->csSerialPort) );
s_ptInterface->pobjSerialPort->Open();
::LeaveCriticalSection( &(s_ptInterface->csSerialPort) );
break;
default:
// Do nothing.
break;
}
}
}
break;
default:
// Do nothing.
break;
}
return ::DefWindowProc( hWnd, uMsg, wParam, lParam );

Answer 1

WM_CLOSE is sent when Windows asks your app to close the window. When the user clicks the upper right Close button or presses Alt+F4 for example. None of that is going to happen, you called DestroyWindow(). You need to use WM_DESTROY instead. Which is fine, no need to veto the close request.