Invalid windowhandle

[Da-Nuka]

Hi.
I have done errorchekcing all and that, but at SOME points in my program, MoveWindow() returns error 1400, which is invalid windowhandle. Sometimes, later in the program, it works, even i havent done anything new to the handle!

I post some relevant code, and the full code included
The function which creates the window and return a handle

HWND CreateInputWindow(const char* AppName) {
     HWND returnHWND;
     WNDCLASS wndclass;
     wndclass.style         = CS_HREDRAW | CS_VREDRAW;
     wndclass.cbClsExtra    = 0 ;
     wndclass.cbWndExtra    = 0 ;
     wndclass.lpfnWndProc   = InputProc;
     wndclass.hIcon         = NULL;
     wndclass.hCursor       = LoadCursor (NULL, IDC_ARROW) ;
     wndclass.lpszMenuName  = NULL;
     wndclass.lpszClassName = AppName;
     wndclass.hInstance     = g_hInstance ;
     wndclass.hbrBackground = (HBRUSH)CreateSolidBrush(RGB(255,255,255));

            if (!RegisterClass (&wndclass)) {
            MessageBox (NULL, TEXT ("Could not register windows class. Shutting down.."), AppName, MB_ICONERROR) ;
            return (HWND)NULL ; // Error, exit and return
     }

     returnHWND=CreateWindow(AppName,AppName,WS_CHILD|WS_VISIBLE,0,0,0,0,output_W,(HMENU) ID_INPUT_W,g_hInstance,NULL);
     
                     



            if(returnHWND==NULL) {
            MessageBox(NULL,"Call to CreateWindow() failed", "Error", MB_OK);
            return (HWND) NULL; // Error, exit and return
     }

return returnHWND;
}

In the WinMain() function:

     input_W=CreateInputWindow(wndClassInput);
     ShowWindow (input_W, g_CmdShow) ;
     UpdateWindow (input_W) ;

In the MessageProcedure:

case WM_SIZE:
  if(MoveWindow(input_W,0,0,200,200,true)==0) {
     ReportError(GetLastError(),"MoveWindow()"); //This returns 1400...
     }

return 0;

[Ken Fitlike]

Sometimes WM_SIZE messages are issued before WM_CREATE or during system processing of CreateWindowEx, hence the invalid handle error.

I wouldn't worry about it; if MoveWindow fails in the context you're using it then it's not a problem but, if perfectionism is your thing, then just check for a non-NULL window handle prior to issuing the MoveWindow call.

edit: Alternatively, set the value of HWND variable, input_W within your WM_CREATE handler; as this message is sent during system processing of CreateWindowEx there's a good chance that handle will be valid for the first WM_SIZE - or just use the window handle delivered to your window procedure as it will be valid.