Question

A call to RegisterClassEx in my application is failing with error code 87, “The parameter is incorrect.”

memset( &m_wcx, 0, sizeof(WNDCLASSEX) );

m_wcx.cbSize = sizeof(WNDCLASSEX);  // size of structure
m_wcx.style = WS_ICONIC;            // initially minimized
m_wcx.lpfnWndProc = &WndProc;       // points to window procedure
m_wcx.cbClsExtra = 0;               // no extra class memory
m_wcx.cbWndExtra = 0;               // no extra window memory
m_wcx.hInstance = m_hInstance;      // handle to instance
m_wcx.hIcon = ::LoadIcon( NULL, IDI_APPLICATION ); // default app icon
m_wcx.hCursor = ::LoadCursor( NULL, IDC_ARROW ); // standard arrow cursor
m_wcx.hbrBackground = NULL;         // no background to paint
m_wcx.lpszMenuName = NULL;          // no menu resource
m_wcx.lpszClassName = _pwcWindowClass; // name of window class
m_wcx.hIconSm = NULL;               // search system resources for sm icon

m_atom = ::RegisterClassEx( &m_wcx );

if ( m_atom == 0 )
{
    TRACE(_T("CNotifyWindow::CNotifyWindow : Failed to register window class.\r\n\tError: %d\r\n\tFile: %s\r\n\tLine: %d\r\n"), ::GetLastError(), __WFILE__, __LINE__);
    THROW(::GetLastError());
}

Does anyone know what I’m doing wrong? Thanks.

Answer 1

The style member of the WNDCLASSEX structure accepts class styles, not window styles. In other words, you can’t make all windows of that class initially minimized that way.

You should pass WS_ICONIC in the dwStyle argument to CreateWindow() or CreateWindowEx() instead.