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 RegisterClass

The RegisterClass function registers a window class for subsequent use in calls to the CreateWindow or CreateWindowEx function.

The RegisterClass function has been superseded by the RegisterClassEx function. You can still use RegisterClass, however, if you do not need to set the class small icon.

Syntax

    ATOM RegisterClass(
        CONST WNDCLASS *lpWndClass
    );

Parameters

• lpWndClass
  [in] Pointer to a WNDCLASS structure. You must fill the structure with the appropriate class attributes before passing it to the function.

Return Value

If the function succeeds, the return value is a class atom that uniquely identifies the class being registered. This atom can only be used by the CreateWindow, CreateWindowEx, GetClassInfo, GetClassInfoEx, FindWindow, FindWindowEx, and UnregisterClass functions and the IActiveIMMap::FilterClientWindows method.

If the function fails, the return value is zero. To get extended error information, call GetLastError.

Remarks

If you register the window class by using RegisterClassA, the application tells the system that the windows of the created class expect messages with text or character parameters to use the ANSI character set; if you register it by using RegisterClassW, the application requests that the system pass text parameters of messages as Unicode. The IsWindowUnicode function enables applications to query the nature of each window. For more information on ANSI and Unicode functions, see Conventions for Function Prototypes.

All window classes that an application registers are unregistered when it terminates.

Windows 95/98/Me: All window classes registered by a DLL are unregistered when the DLL is unloaded.

Windows NT/2000/XP: No window classes registered by a DLL are unregistered when the DLL is unloaded. A DLL must explicitly unregister its classes when it is unloaded.

Windows 95/98/Me: RegisterClass fails if the cbWndExtra or cbClsExtra member of the WNDCLASS structure contains more than 40 bytes.

Windows 95/98/Me: RegisterClassW is supported by the Microsoft Layer for Unicode (MSLU). To use this version, you must add certain files to your application, as outlined in Microsoft Layer for Unicode on Windows 95/98/Me Systems .

Function Information

• Minimum DLL Version user32.dll
• Header Declared in Winuser.h, include Windows.h
• Import library User32.lib
• Minimum operating systems Windows 95, Windows NT 3.1
• Unicode Implemented as ANSI and Unicode versions.

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Notebook exported on Monday, 7 July 2008, 18:56:50 PM Eastern Daylight Time