DOCERR: Do Not Use MB_NOFOCUS Flag with MessageBox Function

The information in this article applies to:

• Microsoft Windows Software Development Kit (SDK) for Windows version 3.1

In the Microsoft Windows graphical environment, an application can use the MessageBox function to create, display, and operate a message box window. The fourth parameter of the MessageBox function is fuStyle, which has the UINT data type.

The fuStyle parameter specifies the message box style; it can be a combination of the MB_* values, including MB_OK, MB_ICONHAND, MB_SYSTEMMODAL, and so on. These values are defined in the WINDOWS.H header file provided with the Microsoft Windows Software Development Kit (SDK).

WINDOWS.H defines MB_NOFOCUS, which is not listed in the SDK documentation (printed or electronic). In the book "Programming Windows 3" by Charles Petzold (Microsoft Press), page 440 states that when the MB_NOFOCUS flag is specified, Windows creates the message box but does not give it the focus. This statement is incorrect.

MB_NOFOCUS is not one of the standard MB_* values and it cannot be used in the fuStyle parameter. Although MB_NOFOCUS is used internally by Windows, it is not passed to or accepted from an application.