Q280447: BUG: Text from a Rich Edit Control Is Truncated During DDX

Article: Q280447
Product(s): Microsoft C Compiler
Version(s): 6.0
Operating System(s): 
Keyword(s): kbCmnCtrls kbMFC kbRichEdit kbClassWizard
Last Modified: 07-MAY-2002

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The information in this article applies to:

- Microsoft Visual C++, 32-bit Editions, version 6.0 
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SYMPTOMS
========

The text in a rich edit control may be truncated under the following
circumstances:

- You associate a CString variable with the rich edit control on a dialog box
  template.

- The rich edit control exceeds 64 kilobytes (KB).

CAUSE
=====

This problem occurs because the WM_GETTEXT message is not programmed to work
with rich edit controls that are larger than 64 KB. The Class Wizard generates
code that uses the DDX_Text function to exchange data between the rich edit
control and the CString variable. The DDX_Text function uses the GetWindowText
function, which sends the WM_GETTEXT message to the control to retrieve the text
in the control. The WM_GETTEXT message does not accept text that is larger than
64 KB.

RESOLUTION
==========

To work around this problem, use the DDX_RichText function as demonstrated in
the "More Information" section of this article.

STATUS
======

Microsoft has confirmed this to be a bug in the Microsoft products listed at the
beginning of this article.

MORE INFORMATION
================

To work around this problem, add the following two functions to your project:

      DWORD CALLBACK ES2MemCallBack(DWORD_PTR dwCookie,
                                    LPBYTE pbBuff, LONG cb, LONG *pcb)
      {
          LPTSTR& lpszStrFill = *(LPTSTR*)dwCookie;
          memcpy(lpszStrFill, pbBuff, *pcb = cb);
          lpszStrFill += cb;
          *lpszStrFill = TCHAR('\0');

          return 0;
      }

      void AFXAPI DDX_RichText(CDataExchange* pDX, int nIDC, CString& value)
      {
          extern void AFXAPI AfxSetWindowText(HWND hWndCtrl, LPCTSTR lpszNew);
          HWND hWndCtrl = pDX->PrepareEditCtrl(nIDC);
          if (pDX->m_bSaveAndValidate)
          {
              int nLen = ::GetWindowTextLength(hWndCtrl);

              LPTSTR lpszStrFill = value.GetBufferSetLength(nLen);
              EDITSTREAM es = { (DWORD_PTR) &lpszStrFill, 0, ES2MemCallBack };
              ::SendMessage(hWndCtrl, EM_STREAMOUT, SF_TEXT, (LPARAM) &es);
              value.ReleaseBuffer();
          }
          else
          {
              AfxSetWindowText(hWndCtrl, value);
          }
      }

To add Class Wizard support for the new data exchange function, add the following
lines to the .clw file or to the Ddx.clw file of your project:

See the "References" section of this article for more information about DDX and
DDV Routines.

      ExtraDDXCount=1
      ExtraDDX1=7;;TextOver64KB;CString;;RichText;Retrieves text in excess of 64KB from RichEdit controls

Alternatively, if the ExtraDDXCount line already exists, you can increment the
value of ExtraDDXCount by one.

NOTE: Seven is the numeric constant that indicates a rich edit control.

If you do not use the preceding step, you must manually replace all calls to
DDX_Text with DDX_RichText. Then, you must move these calls outside the
wizard-controlled code. Wizard-controlled code is the code that is bracketed by
//{{AFX_DATA_INIT(...) and //}}AFX_DATA_INIT, and //{{AFX_DATA_MAP(...)
//}}AFX_DATA_MAP.

For more information about DDX and dialog data validation (DDV) routines, see the
"References" section.

REFERENCES
==========

For more information, see the following MSDN Web sites:

TN026: DDX and DDV Routines:
http://msdn.microsoft.com/library/devprods/vs6/visualc/vcmfc/_mfcnotes_tn026.htm

Windows User Interface WM_GETTEXT:
http://msdn.microsoft.com/library/default.asp?url=/library/en-us/winui/windows_34ok.asp

Additional query words: CRichEdit truncate

======================================================================
Keywords          : kbCmnCtrls kbMFC kbRichEdit kbClassWizard 
Technology        : kbVCsearch kbAudDeveloper kbVC600 kbVC32bitSearch
Version           : :6.0
Issue type        : kbbug
Solution Type     : kbpending

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