Article ID: 122219
Article Last Modified on 11/21/2006
APPLIES TO
- Microsoft Foundation Class Library 4.2, when used with:
- Microsoft Visual C++ 2.0 Professional Edition
- Microsoft Visual C++ 5.0 Enterprise Edition
- Microsoft Visual C++ 5.0 Professional Edition
This article was previously published under Q122219
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".
Keywords: kbbug kbdocerr kbdocfix kbuidesign KB122219
