DOCUMENT:Q156067  06-MAY-2001  [visualc]
TITLE   :FIX: Setting Tooltip Text in OnToolHitTest Causes Assertion
PRODUCT :Microsoft C Compiler
PROD/VER:winnt:4.0,4.1,4.2
OPER/SYS:
KEYWORDS:kbMFC kbToolTip KbUIDesign kbVC400bug kbVC410bug kbVC420bug kbVC500fix kbGrpDSMFCATL kb

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The information in this article applies to:

 - The Microsoft Foundation Classes (MFC), used with:
    - Microsoft Visual C++, 32-bit Editions, versions 4.0, 4.1 
    - Microsoft Visual C++, 32-bit Enterprise Edition, version 4.2 
    - Microsoft Visual C++, 32-bit Professional Edition, version 4.2 
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SYMPTOMS
========

Attempting to set the text for a tooltip in the OnToolHitTest function of a CWnd
by assigning a resource ID to the TOOLINFO struct's lpszText member causes the
following assertion to occur:

   

   Debug assertion failed
   File: dbgheap.c
   Line: 1011

For example, setting the TOOLINFO struct as follows:

      pTI->lpszText= MAKEINTRESOURCE(SomeId);
      pTI->hinst=AfxGetInstanceHandle();

where pTI is a pointer to the TOOLINFO struct, will cause the problem. Setting
the TOOLINFO struct members in this manner allows the programmer to specify a
resource that the tooltip uses to get the text for the tooltip.

CAUSE
=====

The CWnd::FilterToolTipMessage() function contains the following code:

      if (tiHit.lpszText != LPSTR_TEXTCALLBACK)
          free(tiHit.lpszText);

Because lpszText is not set to LPSTR_TEXTCALLBACK, the free function is called.
However, a resource ID, rather than a string, was specified in the
OnToolHitTest() function, and therefore the assertion occurs.

RESOLUTION
==========

Instead of specifying a resource ID to load, load the resource and assign the
text to the TOOLINFO struct's lpszText member as follows:

      pTI->lpszText = (char *)malloc(200, sizeof(char));
      if (::LoadString(AfxGetInstanceHandle(),pTI->uId, pTI->lpszText,200)==0)
      {
         ASSERT(FALSE);   //String resource doesn't exist
      }

MFC frees the allocated buffer after it has added the tool (that is, after it has
sent the TTM_ADDTOOL message).

STATUS
======

Microsoft has confirmed this to be a bug in the Microsoft products listed at the
beginning of this article. This problem has been fixed in Visual C++ version
5.0.

Additional query words: kbVC400bug tool tip

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Keywords          : kbMFC kbToolTip KbUIDesign kbVC400bug kbVC410bug kbVC420bug kbVC500fix kbGrpDSMFCATL kbNoUpdate 
Technology        : kbAudDeveloper kbMFC
Version           : winnt:4.0,4.1,4.2
Issue type        : kbbug
Solution Type     : kbfix

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