Path: utzoo!utgpu!news-server.csri.toronto.edu!rutgers!cs.utexas.edu!evax!utacfd!merch!spudge!thorp
From: thorp@spudge.UUCP (Don Thorp)
Newsgroups: comp.windows.ms
Subject: Child Windows
Keywords: windows 3.0
Message-ID: <20995@spudge.UUCP>
Date: 7 Sep 90 20:58:11 GMT
Reply-To: thorp@spudge.UUCP (Don Thorp)
Distribution: usa
Organization: Friends of Guru Bob
Lines: 254

I'm having problems with the following code.  I was attempting to create a 
listbox as a child window to my main application window.  I originally tried
to create the listbox in the WM_CREATE section of the MainWindowProc.  This
always returns a NULL handle for the window.  The section of code that is
enabled by defining THIS_DOES_NOT_WORK was the original attempt.  I then
moved the same code into the InitApplication procedure and it worked just
fine.  I have been stumped for quite awhile on how this could be.  Any
suggestions would be greatly appreciated.

Don Thorp


==========================================================================

#include "windows.h"        /* required for all Windows applications */
#define NULL 0
#include "wmail.h"          /* specific to this program        */

HANDLE hInst;               /* current instance          */
HWND   hMainWindow;         /* Main window handle.                */
HWND   hMailList;

char szChildClass[] = "listbox";


int PASCAL WinMain(hInstance, hPrevInstance, lpCmdLine, nCmdShow)
HANDLE hInstance;			     /* current instance	     */
HANDLE hPrevInstance;			     /* previous instance	     */
LPSTR lpCmdLine;			     /* command line		     */
int nCmdShow;				     /* show-window type (open/icon) */
{
  MSG msg;             /* message          */

  if (!hPrevInstance) {

    if (!InitApplication(hInstance))  {

      return (FALSE);    /* Exits if unable to initialize     */
    }
  }

  if (!InitInstance(hInstance, nCmdShow)) {

    return (FALSE);
  }


  /* Acquire and dispatch messages until a WM_QUIT message is received. */

  while (GetMessage(&msg, NULL, NULL, NULL)) {

    TranslateMessage(&msg);  /* Translates virtual key codes       */
    DispatchMessage(&msg);   /* Dispatches message to window       */
  }

  return (msg.wParam);     /* Returns the value from PostQuitMessage */
}

BOOL InitApplication(hInstance)
HANDLE hInstance;			       /* current instance	     */
{
  WNDCLASS  wc;

  /* Fill in window class structure with parameters that describe the       */
  /* main window.                                                           */

  wc.style = NULL;                    /* Class style(s).                    */
  wc.lpfnWndProc = MainWndProc;       /* Function to retrieve messages for  */
                                      /* windows of this class.             */
  wc.cbClsExtra = 0;                  /* No per-class extra data.           */
  wc.cbWndExtra = 0;                  /* No per-window extra data.          */
  wc.hInstance = hInstance;           /* Application that owns the class.   */

  wc.hIcon = LoadIcon(NULL, IDI_APPLICATION);
  wc.hCursor = LoadCursor(NULL, IDC_ARROW);
  wc.hbrBackground = GetStockObject(WHITE_BRUSH);

  wc.lpszMenuName =  "WMailMenu";   /* Name of menu resource in .RC file. */
  wc.lpszClassName = "WMailWClass"; /* Name used in call to CreateWindow. */

  /* Register the window class and return success/failure code. */

  if(!RegisterClass(&wc)) {

    MessageBeep(880);
    return(FALSE);
  }

  return(TRUE);
}


BOOL InitInstance(hInstance, nCmdShow)
    HANDLE          hInstance;          /* Current instance identifier.       */
    int             nCmdShow;           /* Param for first ShowWindow() call. */
{
  HWND            hWnd;               /* Main window handle.                */

  /* Save the instance handle in static variable, which will be used in  */
  /* many subsequence calls from this application to Windows.            */

  hInst = hInstance;

  /* Create a main window for this application instance.  */

  hWnd = CreateWindow(
    "WMailWClass",                  /* See RegisterClass() call.          */
    "WMail",                        /* Text for window title bar.         */
    WS_OVERLAPPEDWINDOW ,
    CW_USEDEFAULT,                  /* Default horizontal position.       */
    CW_USEDEFAULT,                  /* Default vertical position.         */
    CW_USEDEFAULT,                  /* Default width.                     */
    CW_USEDEFAULT,                  /* Default height.                    */
    NULL,                           /* Overlapped windows have no parent. */
    NULL,                           /* Use the window class menu.         */
    hInstance,                      /* This instance owns this window.    */
    NULL                            /* Pointer not needed.                */
  );

  /* If window could not be created, return "failure" */

  if (!hWnd) {

    return (FALSE);
  }


  /* Make the window visible; update its client area; and return "success" */

  hMainWindow = hWnd;

  ShowWindow(hWnd, nCmdShow);  /* Show the window                        */
  UpdateWindow(hWnd);          /* Sends WM_PAINT message                 */

#if defined(THIS_WORKS)

  hMailList = CreateWindow(szChildClass,
                            NULL,
                            WS_CHILD | WS_VISIBLE | LBS_STANDARD,
                            10,10,
                            200,200,
                            hWnd,
                            IDC_LISTBOX,
                            hInst,
                            NULL);

  if(!hMailList) {

    return(FALSE);
  }

  {
    LONG rc;

    rc = SendMessage(hMailList,LB_ADDSTRING, NULL, (LONG) (LPSTR) "Hello");

    displayWordError("LB_ADDSTRING",(WORD) rc);

    SendMessage(hMailList,LB_ADDSTRING, NULL, (LONG) (LPSTR) "Hello");
    SendMessage(hMailList,LB_ADDSTRING, NULL, (LONG) (LPSTR) "Hello");
    SendMessage(hMailList,LB_ADDSTRING, NULL, (LONG) (LPSTR) "Hello");
  }


#endif

  return (TRUE);               /* Returns the value from PostQuitMessage */

}

LONG FAR PASCAL MainWndProc(hWnd, message, wParam, lParam)
HWND hWnd;				  /* window handle		     */
unsigned message;			  /* type of message		     */
WORD wParam;				  /* additional information	     */
LONG lParam;				  /* additional information	     */
{
  FARPROC lpProcAbout;      /* pointer to the "About" function */
  LONG rc;

  switch (message) {

#if defined(THIS_DOES_NOT_WORK)
    case WM_CREATE:


      hMailList = CreateWindow(szChildClass,
                                NULL,
                                WS_CHILD | WS_VISIBLE | LBS_STANDARD,
                                10,10,
                                200,200,
                                hWnd,
                                IDC_LISTBOX,
                                hInst,
                                NULL);

      if(!hMailList) {

        MessageBeep(440);
        break;
      }
      else {

        LONG rc;

        rc = SendMessage(hMailList,LB_ADDSTRING, NULL, (LONG) (LPSTR) "Hello");

        displayWordError("LB_ADDSTRING",(WORD) rc);

        SendMessage(hMailList,LB_ADDSTRING, NULL, (LONG) (LPSTR) "Hello");
        SendMessage(hMailList,LB_ADDSTRING, NULL, (LONG) (LPSTR) "Hello");
        SendMessage(hMailList,LB_ADDSTRING, NULL, (LONG) (LPSTR) "Hello");
      }

      break;
#endif

    case WM_COMMAND:     /* message: command from application menu */

      if (wParam == IDM_ABOUT) {

        lpProcAbout = MakeProcInstance(About, hInst);

        DialogBox(hInst, "ABOUT", hWnd, lpProcAbout);

        FreeProcInstance(lpProcAbout);

      }
      else {         /* Lets Windows process it       */

        return (DefWindowProc(hWnd, message, wParam, lParam));
      }

      break;

    case WM_DESTROY:      /* message: window being destroyed */

        PostQuitMessage(0);
        break;

    default:        /* Passes it on if unproccessed    */

        return (DefWindowProc(hWnd, message, wParam, lParam));
  }

  return (NULL);
}


==========================================================================
Don Thorp 

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