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Q200099: PRB: Owner-Drawn List Control in 68K App Crashes Macintosh

Article: Q200099
Product(s): Microsoft C Compiler
Version(s): MACINTOSH:4.0b
Operating System(s): 
Keyword(s): kbHWMAC kbVC kbDSupportkbbuglist
Last Modified: 06-FEB-2000

-------------------------------------------------------------------------------
The information in this article applies to:

- Microsoft Visual C++, Macintosh Cross-Development Addon, version 4.0b 
-------------------------------------------------------------------------------

SYMPTOMS
========

When displaying an owner-drawn ListView control in report view on a 68K
Macintosh, the Macintosh system crashes displaying the following message:

  Sorry, a system error occurred.
  "application name"
  divide by zero

If the program is executed under the debugger, Developer Studio displays the
following message:

  Exception in xxx.exe: 0x00000004: Divide by Zero

CAUSE
=====

A bug with the height initialization of the ListView item for the control causes
the internal call to ShowWindow to perform a divide-by-zero operation.

RESOLUTION
==========

Set the height of the ListView control item to an appropriate value in the
parent window's WM_MEASUREITEM handler for the ListView control. This can be
done through the itemHeight field of the LPMEASUREITEMSTRUCT structure pointer
provided.

STATUS
======

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

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

The workaround involves setting the itemHeight data member of the
LPMEASUREITEMSTRUCT structure pointer before the control is displayed. This can
be done only in the parent window's WM_MEASUREITEM handler. It is not necessary
to initially create the control without the WS_VISIBLE flag.

The code below shows an example for an owner-drawn ListView control in a form
view. The default height of a ListView control item on the Macintosh is 14
pixels.

  BEGIN_MESSAGE_MAP(CMyView, CFormView)
      ON_WM_MEASUREITEM()
      ...
  END_MESSAGE_MAP()

  // WM_MEASUREITEM is sent to parent of list control
  void CMyView::OnMeasureItem(int nIDCtl,
      LPMEASUREITEMSTRUCT lpMeasureItemStruct)
  {
      if (nIDCtl == IDC_LIST1) {

          // Calculate appropriate font height.
          int newHeight = 0;
          CFont* pFont = (CFont*)GetFont();
          if (pFont) {
              LOGFONT lf;
              pFont->GetLogFont(&lf);
              newHeight = (lf.lfHeight > 0) ? lf.lfHeight : -lf.lfHeight;
          }

          // Set new itemHeight, use 14 as default height.
          lpMeasureItemStruct->itemHeight = newHeight ? newHeight : 14;
      }
      CFormView::OnMeasureItem(nIDCtl, lpMeasureItemStruct);
  }

IDC_LIST1 is the ID of the owner-drawn ListView control.

NOTE: This problem does NOT appear on Visual C++ for the Macintosh version 4.0.

REFERENCES
==========

(c) Microsoft Corporation 1999, All Rights Reserved. Contributions by Adam Kim,
Microsoft Corporation.


Additional query words: ownerdrawn ownerdraw CListCtrl list view WLM 4.0 4.1 4.2 owner-draw

======================================================================
Keywords          : kbHWMAC kbVC kbDSupport kbbuglist
Technology        : kbVCsearch kbHWMAC kbOSMAC kbAudDeveloper kbVCXDev400bMac
Version           : MACINTOSH:4.0b
Issue type        : kbprb

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

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