Q138664: DOC: GetClientRect() May Assert in OLE Controls

Article: Q138664
Product(s): Microsoft C Compiler
Version(s): winnt:
Operating System(s): 
Keyword(s): kbdocfix kbdocerr kbActiveX kbCOMt kbCtrlCreate kbVC400bug kbVC410bug kbVC420bug kbVC50
Last Modified: 06-MAY-2001

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The information in this article applies to:

- The Microsoft Foundation Classes (MFC), used with:
   - Microsoft OLE Control Developer's Kit (CDK) 
   - Microsoft Visual C++ 32-bit Edition, versions 4.0, 4.1, 4.2 
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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:

1. 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.

Additional query words:

======================================================================
Keywords          : kbdocfix kbdocerr kbActiveX kbCOMt kbCtrlCreate kbVC400bug kbVC410bug kbVC420bug kbVC500fix kbGrpDSMFCATL 
Technology        : kbAudDeveloper kbMFC
Version           : winnt:
Issue type        : kbprb
Solution Type     : kbfix

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