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WNDCLASSEXA structure (winuser.h)

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Contains window class information. It is used with the RegisterClassEx and GetClassInfoEx  functions.

The WNDCLASSEX structure is similar to the WNDCLASS structure. There are two differences. WNDCLASSEX includes the cbSize member, which specifies the size of the structure, and the hIconSm member, which contains a handle to a small icon associated with the window class.

Syntax

typedef struct tagWNDCLASSEXA {
  UINT      cbSize;
  UINT      style;
  WNDPROC   lpfnWndProc;
  int       cbClsExtra;
  int       cbWndExtra;
  HINSTANCE hInstance;
  HICON     hIcon;
  HCURSOR   hCursor;
  HBRUSH    hbrBackground;
  LPCSTR    lpszMenuName;
  LPCSTR    lpszClassName;
  HICON     hIconSm;
} WNDCLASSEXA, *PWNDCLASSEXA, *NPWNDCLASSEXA, *LPWNDCLASSEXA;

Members

cbSize

Type: UINT

The size, in bytes, of this structure. Set this member to sizeof(WNDCLASSEX). Be sure to set this member before calling the GetClassInfoEx function.

style

Type: UINT

The class style(s). This member can be any combination of the Class Styles.

lpfnWndProc

Type: WNDPROC

A pointer to the window procedure. You must use the CallWindowProc function to call the window procedure. For more information, see WindowProc.

cbClsExtra

Type: int

The number of extra bytes to allocate following the window-class structure. The system initializes the bytes to zero.

cbWndExtra

Type: int

The number of extra bytes to allocate following the window instance. The system initializes the bytes to zero. If an application uses WNDCLASSEX to register a dialog box created by using the CLASS directive in the resource file, it must set this member to DLGWINDOWEXTRA.

hInstance

Type: HINSTANCE

A handle to the instance that contains the window procedure for the class.

hIcon

Type: HICON

A handle to the class icon. This member must be a handle to an icon resource. If this member is NULL, the system provides a default icon.

hCursor

Type: HCURSOR

A handle to the class cursor. This member must be a handle to a cursor resource. If this member is NULL, an application must explicitly set the cursor shape whenever the mouse moves into the application's window.

hbrBackground

Type: HBRUSH

A handle to the class background brush. This member can be a handle to the brush to be used for painting the background, or it can be a color value. A color value must be one of the following standard system colors (the value 1 must be added to the chosen color). If a color value is given, you must convert it to one of the following HBRUSH types:

  • COLOR_ACTIVEBORDER
  • COLOR_ACTIVECAPTION
  • COLOR_APPWORKSPACE
  • COLOR_BACKGROUND
  • COLOR_BTNFACE
  • COLOR_BTNSHADOW
  • COLOR_BTNTEXT
  • COLOR_CAPTIONTEXT
  • COLOR_GRAYTEXT
  • COLOR_HIGHLIGHT
  • COLOR_HIGHLIGHTTEXT
  • COLOR_INACTIVEBORDER
  • COLOR_INACTIVECAPTION
  • COLOR_MENU
  • COLOR_MENUTEXT
  • COLOR_SCROLLBAR
  • COLOR_WINDOW
  • COLOR_WINDOWFRAME
  • COLOR_WINDOWTEXT
The system automatically deletes class background brushes when the class is unregistered by using UnregisterClass. An application should not delete these brushes.

When this member is NULL, an application must paint its own background whenever it is requested to paint in its client area. To determine whether the background must be painted, an application can either process the WM_ERASEBKGND message or test the fErase member of the PAINTSTRUCT structure filled by the BeginPaint function.

lpszMenuName

Type: LPCTSTR

A pointer to a null-terminated character string that specifies the resource name of the class menu, as the name appears in the resource file. If you use an integer to identify the menu, use the MAKEINTRESOURCE macro. If this member is NULL, windows belonging to this class have no default menu.

lpszClassName

Type: LPCTSTR

A pointer to a null-terminated string or is an atom. If this parameter is an atom, it must be a class atom created by a previous call to the RegisterClass or RegisterClassEx function. The atom must be in the low-order word of lpszClassName; the high-order word must be zero.

If lpszClassName is a string, it specifies the window class name. The class name can be any name registered with RegisterClass or RegisterClassEx, or any of the predefined control-class names.

The maximum length for lpszClassName is 256. If lpszClassName is greater than the maximum length, the RegisterClassEx function will fail.

hIconSm

Type: HICON

A handle to a small icon that is associated with the window class. If this member is NULL, the system searches the icon resource specified by the hIcon member for an icon of the appropriate size to use as the small icon.

Remarks

Note

The winuser.h header defines WNDCLASSEX as an alias that automatically selects the ANSI or Unicode version of this function based on the definition of the UNICODE preprocessor constant. Mixing usage of the encoding-neutral alias with code that is not encoding-neutral can lead to mismatches that result in compilation or runtime errors. For more information, see Conventions for Function Prototypes.

Requirements

Requirement Value
Minimum supported client Windows 2000 Professional [desktop apps only]
Minimum supported server Windows 2000 Server [desktop apps only]
Header winuser.h (include Windows.h)

See also

Conceptual

GetClassInfoEx

Reference

RegisterClassEx

UnregisterClass

Window Classes