DOC: GetClientRect() May Assert in OLE Controls
Article ID: 138664
Article Last Modified on 11/21/2006
APPLIES TO
- Microsoft Foundation Class Library 4.2, when used with:
- Microsoft OLE Control Developer's Kit (CDK)
- Microsoft Visual C++ 4.0 Professional Edition
- Microsoft Visual C++ 4.1 Subscription
- Microsoft Visual C++ 4.2 Professional Edition
- Microsoft Visual C++ 4.2 Enterprise Edition
- Microsoft Visual C++ 5.0 Learning Edition
- Microsoft Visual C++ 5.0 Learning Edition
This article was previously published under Q138664
SUMMARY
In chapter 4 of the Ole Control Tutorial, the section labeled Setting the
CircleOffset Property Step 2, which describes how to implement the
InBounds() function, incorrectly calls GetClientRect() and should read as
follows instead:
- Add the function implementation at the end of your CIRCCTL.CPP file:
BOOL CCirc2Ctrl::InBounds(short nOffset)
{
int diameter;
int length;
int cx;
int cy;
// Note that GetControlSize() is called here instead of
// GetClientRect()
GetControlSize(&cx, &cy);
if (cx > cy)
{
length = cx;
diameter = cy;
}
else
{
length = cy;
diameter = cx;
}
if (nOffset < 0)
nOffset = (short) -nOffset;
return (diameter / 2 + nOffset) <= (length / 2);
}
This documentation error was corrected in Visual C++ version 5.0.
MORE INFORMATION
In some control containers (such as Visual Basic and Microsoft Access) in
design mode, the control has no window, and therefore no hwnd, so calling
GetClientRect(rc) will assert.
There are actually two solutions to this problem. The first solution is
documented in the "Summary" section of this article. The second solution is
to replace the call to GetClientRect() with a call to GetRectInContainer(),
which will obtain the coordinates of the control's rectangle relative to
the container. The size of the control can then be calculated from this
rectangle.
Keywords: kbbug kbfix kbdocfix kbctrlcreate kbvc500fix kbprb kbdocerr KB138664