CreateWindow

[confalonieri]

Hi, In my application I need to create an empty window just to receive messages and treat them. I wrote the following code: HINSTANCE hApi = (HINSTANCE) GetModuleHandle(NULL); if (! hApi) ...// manage error CHAR * WindowClassName = "MyWindowClass"; WNDCLASS WindowClassInfo; if (! GetClassInfo(hApi, WindowClassName, &WindowClassInfo)) { WindowClassInfo.hCursor = NULL; WindowClassInfo.hIcon = NULL; WindowClassInfo.lpszMenuName = NULL; WindowClassInfo.lpszClassName = WindowClassName; WindowClassInfo.hbrBackground = NULL; WindowClassInfo.hInstance = hApi; WindowClassInfo.style = CS_OWNDC | CS_VREDRAW | S_HREDRAW; WindowClassInfo.lpfnWndProc = (WNDPROC) MyProc; WindowClassInfo.cbClsExtra = 0; WindowClassInfo.cbWndExtra = 0; if (! RegisterClass(&WindowClassInfo)) ...//manage error } HWND hWnd = CreateWindow(WindowClassName, "MyWindow", WS_OVERLAPPEDWINDOW, 0, 0, CW_USEDEFAULT, CW_USEDEFAULT, NULL, NULL, hApi, NULL); if (! hWnd) ...//manage error But, unfortunately, CreateWindow return NULL and GetLastError return 0 !!! Did anybody could help me ? Thanks in advance. Robin.

[Joaquin M Lopez Munoz]

Everything seems OK. The only possible problem I can think of is that MyProc is not properly declared as a WINDPROC should. Could you show us this function? Joaquín M López Muñoz Telefónica, Investigación y Desarrollo

[Ernest Laurentin]

Try this, if it work, check your WindowProc function like Joaquim suggested:

LPCTSTR szWindowClassName = \_T("MyWindowClass");

WNDCLASS WindowClassInfo;

if (!GetClassInfo(hApi,szWindowClassName, &WindowClassInfo))
{
	WindowClassInfo.hCursor = NULL;
	WindowClassInfo.hIcon = NULL;
	WindowClassInfo.lpszMenuName = NULL;
	WindowClassInfo.lpszClassName = szWindowClassName;
	WindowClassInfo.hbrBackground = NULL;
	WindowClassInfo.hInstance = hApi;
	WindowClassInfo.style = CS\_OWNDC | CS\_VREDRAW | CS\_HREDRAW;
	WindowClassInfo.lpfnWndProc = (WNDPROC) ::DefWindowProc;
	WindowClassInfo.cbClsExtra = 0;
	WindowClassInfo.cbWndExtra = 0;

	if (!RegisterClass(&WindowClassInfo))
	{
		TRACE( " ERROR \\n");
	}
}

HWND hWnd = CreateWindow(szWindowClassName,
			"MyWindow",
			WS\_OVERLAPPEDWINDOW,
			0,
			0,
			CW\_USEDEFAULT,
			CW\_USEDEFAULT,
			NULL,
			NULL,
			hApi,
			NULL);
ASSERT( hWnd != NULL );

[confalonieri]

MyProc is declared in a header as following: LRESULT CALLBACK fidLinkEventProc(HWND _hWnd, UINT _iMsg, WPARAM _wParam, LPARAM _lParam); and MyProc is defined in a .c file: LRESULT CALLBACK MyProc(HWND _hWnd, UINT _iMsg, WPARAM _wParam, LPARAM _lParam) { switch (_iMsg) { ... } return 0; }

[confalonieri]

Thank for your help. I solved my problem: MyProc was always returning 0 whatever the message was, whereas it has to treat Windows messages such as "WM_CREATE", ... (traditional messages to create a window). Now, I use "return DefWindowProc(_hWnd,_iMsg,_wParam,_lParam)" when I receive a Windows message different from my messages.