When you use the arrow keys to change between controls in a Visual C++ 4.0
generated container, the DISPID_AMBIENT_DISPLAYASDEFAULT ambient property
of the control site is not updated, and any control that relies on this
property doesn't function correctly.
For example, a subclassed button control that is programmed to update its
border according to the DISPID_AMBIENT_DISPLAYASDEFAULT ambient property
will exhibit this behavior. In a Visual C++ generated container, the
control won't update its border.
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In Occdlg.cpp, the following line 542 shouldn't be called:
bCheckDef = FALSE;
This line keeps CheckDefPushButton from being called and the ambient
property from being updated.
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The best solution is to upgrade to Visual C++ 4.1. If this is not a
possibility, the MFC DLL can be rebuilt without bCheckDef = FALSE; however,
Microsoft recommends against this because you need to rebuild the DLL with
a different name (see tech note 33).
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Microsoft has confirmed this to be a bug in the Microsoft products listed
at the beginning of this article. This problem was corrected in Microsoft
Visual C++ version 4.1.
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Sample Code
The following code can be added to the Button Control sample shipped
with Visual C++ to demonstrate this problem.
///////////////////////////////////////////////////////////////////////////
/
// Display the button with a thick border if appropriate
void CButtonCtrl::OnAmbientPropertyChange(DISPID dispid)
{
TRACE("OnAmbientPropertyChange called\n");
BOOL bDisplayAsDefault = FALSE;
if(DISPID_AMBIENT_DISPLAYASDEFAULT != dispid)
return;
// Check the control site to see if you should add or remove the border
if (!GetAmbientProperty(DISPID_AMBIENT_DISPLAYASDEFAULT, VT_BOOL,
&bDisplayAsDefault))
ASSERT(FALSE);
if(bDisplayAsDefault)
SendMessage(BM_SETSTYLE, BS_DEFPUSHBUTTON, 0);
else
SendMessage(BM_SETSTYLE, BS_PUSHBUTTON, 0);
InvalidateControl();
}
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This article was written about products for which Microsoft no longer offers support. Therefore, this article is offered "as is" and will no longer be updated.
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