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Q122219: INFO: CWnd::OnCommand() Parameters Documented Incorrectly

Article: Q122219
Product(s): Microsoft C Compiler
Version(s): winnt:
Operating System(s): 
Keyword(s): kbdocfix kbdocerr kbMFC KbUIDesign kbVC500bug kbGrpDSMFCATL
Last Modified: 07-MAY-2001

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The information in this article applies to:

- The Microsoft Foundation Classes (MFC), used with:
   - Microsoft Visual C++ 32-bit Edition, version 2.0 
   - Microsoft Visual C++, 32-bit Enterprise Edition, version 5.0 
   - Microsoft Visual C++, 32-bit Professional Edition, version 5.0 
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SUMMARY
=======

The online help and the "Class Library Reference" incorrectly describe the
CWnd::OnCommand() wParam and lParam as follows:

In Visual C++ 2.0
-----------------

wParam Identifies the command ID of the menu item or control.

lParam The low-order word of lParam identifies the control that sends the message
if the message is from a control. Otherwise the low-order word is 0. The
high-order word of lParam specifies the notification message if the message is
from a control. If the message is from an accelerator, the high-order word is 1.
If the message is from a menu, the high-order word is 0.

In Visual C++ 5.0
-----------------

wParam The low-order word of wParam identifies the command ID of the menu item or
control. The high-order word of wParam specifies the notification message if the
message is from a control. If the message is from an accelerator, the high-order
word is 1. If the message is from a menu, the high-order word is 0.

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

The description above is valid for Windows-based Applications, but it is invalid
for Win32-based Applications. The Win32 API widens the WPARAM type to 32 bits
and changes the packing of many of the messages. The parameters for
CWnd::OnCommand() should be documented as follows:

  wParam The low-order word of wParam specifies the identifier of the menu
  item, control, or accelerator. The high-order word specifies the notification
  code if the message is from a control. If the message is from an accelerator,
  the high-order word is 1. If the message is from a menu, the high-order word
  is 0.

  lParam Handle (HWND) of the control sending the message if the message is from
  a control. Otherwise, this parameter is NULL.

REFERENCES
==========

For additional information concerning this issue, please consult the following
topics in the Online Help: "WM_COMMAND" and "MFC: Porting Tips".

Additional query words:

======================================================================
Keywords          : kbdocfix kbdocerr kbMFC KbUIDesign kbVC500bug kbGrpDSMFCATL 
Technology        : kbAudDeveloper kbMFC
Version           : winnt:

=============================================================================

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