Question

In my application the function CreateWindow is failing for some reason. GetLastError indicates error 1407, which, according to the MSDN documentation is “Cannot find window class.” The following code shows how CreateWindow is being called and the respective variables names at time of call:

m_hInstance = ::GetModuleHandle( NULL );

if ( m_hInstance == NULL )
{
    TRACE(_T("CNotifyWindow::CNotifyWindow : Failed to retrieve the module handle.\r\n\tError: %d\r\n\tFile: %s\r\n\tLine: %d\r\n"), ::GetLastError(), __WFILE__, __LINE__);
    THROW(::GetLastError());
}

m_hWnd = ::CreateWindow(
    _pwcWindowClass,    // L"USBEventNotificationWindowClass"
    _pwcWindowName,     // L"USBEventNotificationWindow"
    WS_ICONIC,
    0,
    0,
    CW_USEDEFAULT,
    0,
    NULL,
    NULL,
    m_hInstance,        // 0x00400000
    NULL
    );

if ( m_hWnd == NULL )   // m_hWnd is returned as NULL and exception is thrown.
{
    TRACE(_T("CNotifyWindow::CNotifyWindow : Failed to create window.\r\n\tError: %d\r\n\tFile: %s\r\n\tLine: %d\r\n"), ::GetLastError(), __WFILE__, __LINE__);
    THROW(::GetLastError());
}

::ShowWindow( m_hWnd, SW_HIDE );

What am I doing wrong?

Answer 1

You have to call RegisterClassEx before you can use the window class on CreateWindow.

Example code here.

Each process must register its own
window classes. To register an
application local class, use the
RegisterClassEx function. You must
define the window procedure, fill the
members of the WNDCLASSEX structure,
and then pass a pointer to the
structure to the RegisterClassEx
function.