DialogBoxParam returning error

I am getting an error 1400 which is an "Invalid window handle". I have checked and the handle is correct. I just do not know where else to look. It is being called in the MainWndProc. The code below is an outtake from my project. Any help would be greatly appreciated. Thanks in advance.

John Saxon

int WINAPI MainWndProc(HWND hWnd, unsigned message, WPARAM wParam, LPARAM lParam)
{
  DLGPROC lpProcAbout;                  // pointer to the "About" function
  DLGPROC lpDialProc;                           // Pointer to Dial Selections
  DLGPROC lpNavSetup;                       // Pointer to Navigator dialog
  DLGPROC lpCommDlg;                // pointer to the "Network hostname" dialog
  RECT rc;
  GLOBALHANDLE hgMem;
  LPSTR lpData;
  int i,j,sr,er,sc,ec, trow, tcol;    //VT
  DWORD dw ;
  CHAR szBuf[80];
  static HCURSOR hCursor;
  static BOOL bMouseMove;
  POINT ptTemp;

  BOOL bRet;                                            //VT

  switch (message)
  {  
           case EMU_LOGIN:             /* Display login dialog box */
                lpProcAbout = MakeProcInstance(LoginDlg, hInst);
                    //hWnd = 0x081604FA;
                    DialogBoxParam(hInst, MAKEINTRESOURCE(LOGINBOX), hWnd, (DLGPROC)lpProcAbout, (LPARAM)0L);
                    dw = GetLastError();
                    sprintf(szBuf, " failed: GetLastError returned %u\n",dw);
                    MessageBox(NULL, szBuf, "Error", MB_OK);
                    //ExitProcess(dw);
                    FreeProcInstance(lpProcAbout);  
                break;

  }
  return (DefWindowProc(hWnd,message,wParam,lParam));
}
LVL 3
jsaxon2Asked:
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jkrCommented:
OK, let's see then:

Is 'LOGINBOX' a valid resource ID? Where do you get 'hInst' from? Does it work with


DialogBoxParam(hInst, MAKEINTRESOURCE(LOGINBOX), hWnd, (DLGPROC)LoginDlg, (LPARAM)0L);

(The MakeProcInstance function is obsolete)?

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jkrCommented:
>>I am getting an error 1400 which is an "Invalid window handle".

Why do you know the 'DialogBoxParam()' call failed? You are not checking the return value. 'GetLastError()' will return some arbitrary value if there was no error before. But, if you want to use it, make sure to call 'SetLastError()' first, e.g.


SetLastError ( 0);
DialogBoxParam(hInst, MAKEINTRESOURCE(LOGINBOX), hWnd, (DLGPROC)lpProcAbout, (LPARAM)0L);
dw = GetLastError();

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jsaxon2Author Commented:
I know it fails because the dialog never displays. I did try your suggestion and am still getting the same error.
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jsaxon2Author Commented:
Also, I did check the return value prior to using GetLast Error and it also was 1400.
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DanRollinsCommented:
DialogBox and DialogBoxParam fail whenever there is a child window that can't be created.  This most often occurs when an ActiveX control is involved, but it could be a rich edit control, etc..  

To test to see if this is the problem, create a new dialog that contains only an OK button and try to bring it up instead.  If that works, look at each of the controls in the dialog box that is failing.

-- Dan
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jsaxon2Author Commented:
It turns out tht the program was using some Borland specific controls that were not valid. That is why the dialogs were not diaplaying.

This is a program was written some years ago by a person that is no longer with the company. Unfortunately there are not many comments in the code. Thanks for your time.
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DanRollinsCommented:
>>using some Borland specific controls that were not valid.
So the solutuoin was apparently unrelated to any child windows that could not be created...

-- Dan
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jkrCommented:
Yes, indeed, technically speaking, Dan should have received the points, as he was closest to the solution...
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jsaxon2Author Commented:
I appologize, but I corrected the problem before I saw Dans post. I am posting points for Dan. Thanks for your help.
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DanRollinsCommented:
Proof at last!  The crying baby DOES get the milk!  -- Dan
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