DOCUMENT:Q199538  11-MAR-2000  [visualc]
TITLE   :BUG: Scroll Bars May Be Re-Enabled or Crash App When Clicked
PRODUCT :Microsoft C Compiler
PROD/VER:MACINTOSH:4.0,4.0b
OPER/SYS:
KEYWORDS:kbDocView kbHWMAC kbMFC KbUIDesign kbVC400bug kbDSupport kbGrpDSMFCATLkbbuglist

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The information in this article applies to:

 - Microsoft Visual C++, Macintosh Cross-Development Addon, versions 4.0, 4.0b 
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SYMPTOMS
========

When clicking a disabled scroll bar of a window, the scroll bar becomes enabled.
If the mouse click occurs where the scroll thumb would be, the application
crashes.

CAUSE
=====

There is a bug in the Windows Portability Layer.

RESOLUTION
==========

Set the scroll range to 0, 0 (zero, zero) using SetScrollSizes() or
SetScrollInfo().

STATUS
======

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

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

When a window has its scroll bar enabled, and is disabled using the following
code

      // hWnd is a handle to window
      EnableScrollBar(hWnd, SB_BOTH, ESB_DISABLE_BOTH);

then the scroll bars are enabled if the user generates a mousedown in the
disabled scroll bar. If the mousedown occurs where the scroll thumb would be,
the application crashes with the following error message:

   Sorry, a system error occurred.
   "myapplication"
   Bus error

This problem appears for the scroll bar of a combo box but does not appear for
the scroll-bar control. This fails with both PowerPC and 68KB platforms.

The workaround is to set the scroll range to 0, 0, as demonstrated below:

      SCROLLINFO si;
      si.cbSize = sizeof(SCROLLINFO);
      si.fMask = SIF_RANGE;
      si.nMin = si.nMax = 0;
      SetScrollInfo(hWnd, SB_HORZ, &si, TRUE);
      SetScrollInfo(hWnd, SB_VERT, &si, TRUE);

REFERENCES
==========

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


Additional query words: CScrollView CComboBox CScrollBar bus error scrollbar

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Keywords          : kbDocView kbHWMAC kbMFC KbUIDesign kbVC400bug kbDSupport kbGrpDSMFCATL kbbuglist
Technology        : kbVCsearch kbHWMAC kbOSMAC kbAudDeveloper kbVCXDev400Mac kbVCXDev400bMac
Version           : MACINTOSH:4.0,4.0b
Issue type        : kbbug
Solution Type     : kbnofix

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