Article: Q150574
Product(s): Microsoft C Compiler
Version(s): winnt:2.0,2.1,2.2
Operating System(s):
Keyword(s): kbDocView kbMFC kbVC150bug kbVC151bug kbVC152bug kbVC200bug kbVC210bug kbVC220bug kbVC4
Last Modified: 03-AUG-2001
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The information in this article applies to:
- The Microsoft Foundation Classes (MFC), used with:
- Microsoft Visual C++ for Windows, 16-bit edition, versions 1.5, 1.51, 1.52
- Microsoft Visual C++, 32-bit Editions, versions 2.0, 2.1, 2.2
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SYMPTOMS
========
Scroll messages generated by scroll related controls in a CScrollView- derived
object fail to invoke the control's OnChildNotify function.
CAUSE
=====
CScrollView::OnVScroll and CScrollView::OnHScroll do not call
SendChildNotifyLastMsg, which is responsible for calling OnChildNotify.
RESOLUTION
==========
Override OnVScroll and/or OnHScroll for your CScrollView-derived class, and
implement this code:
void CMyView::OnVScroll(UINT nSBCode, UINT nPos, CScrollBar*
pScrollBar)
{
if (pScrollBar != NULL && pScrollBar->SendChildNotifyLastMsg())
return; // eat it
// ignore scroll bar msgs from other controls
if (pScrollBar != GetScrollBarCtrl(SB_VERT))
return;
OnScroll(MAKEWORD(-1, nSBCode), nPos);
}
void CMyView::OnHScroll(UINT nSBCode, UINT nPos, CScrollBar*
pScrollBar)
{
// same as above
...
}
STATUS
======
Microsoft has confirmed this to be a bug in the Microsoft products listed at the
beginning of this article. This problem is corrected in Microsoft Visual C++
version 4.0.
MORE INFORMATION
================
OnChildNotify is called by the control's parent window when the parent window
receives a notification message that applies to this control. Notification
messages include control notification messages such as WM_COMMAND sent by
controls, some specific Windows messages such as WM_HSCROLL, WM_VSCROLL, and
WM_CTLCOLOR, and a few others.
NOTE: For more information, see Tech note #21.
OnChildNotify allows a control an initial opportunity to view these messages
before the control reaches its parent.
The code reflects corrections for a bug reported in the following article in the
Microsoft Knowledge Base:
Q133034 BUG: CSpinButtonCtrl Causes Assertion in Viewscrl.cpp line 698
The need for CScrollView to pass scroll messages correctly to OnChildNotify
arises from implementing a CSpinButtonCtrl control, or an additional CScrollbar
control in the view.
REFERENCES
==========
For additional information, please see the following article in the Microsoft
Knowledge Base:
Q133034 BUG: CSpinButtonCtrl Causes Assertion in viewscrl.cpp line 698.
MFC Technical Note #21 - Command and Message Routine
Books Online - CWnd::OnChildNotify
Additional query words: 1.50 1.51 1.52 2.00 2.10 2.20
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Keywords : kbDocView kbMFC kbVC150bug kbVC151bug kbVC152bug kbVC200bug kbVC210bug kbVC220bug kbVC400fix kbGrpDSMFCATL kbNoUpdate kbbuglist kbfixlist
Technology : kbAudDeveloper kbMFC
Version : winnt:2.0,2.1,2.2
Issue type : kbbug
Solution Type : kbfix
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