GetClassInfoA function (winuser.h)

Article
02/09/2023

Retrieves information about a window class.

Note The GetClassInfo function has been superseded by the GetClassInfoEx function. You can still use GetClassInfo, however, if you do not need information about the class small icon.

Syntax

BOOL GetClassInfoA(
  [in, optional] HINSTANCE   hInstance,
  [in]           LPCSTR      lpClassName,
  [out]          LPWNDCLASSA lpWndClass
);

Parameters

[in, optional] hInstance

Type: HINSTANCE

A handle to the instance of the application that created the class. To retrieve information about classes defined by the system (such as buttons or list boxes), set this parameter to NULL.

[in] lpClassName

Type: LPCTSTR

The class name. The name must be that of a preregistered class or a class registered by a previous call to the RegisterClass or RegisterClassEx function.

Alternatively, this parameter can be an atom. If so, it must be a class atom created by a previous call to RegisterClass or RegisterClassEx. The atom must be in the low-order word of lpClassName; the high-order word must be zero.

[out] lpWndClass

Type: LPWNDCLASS

A pointer to a WNDCLASS structure that receives the information about the class.

Return value

Type: BOOL

If the function finds a matching class and successfully copies the data, the return value is nonzero.

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

Remarks

Note

The winuser.h header defines GetClassInfo as an alias which 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 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]
Target Platform	Windows
Header	winuser.h (include Windows.h)
Library	User32.lib
DLL	User32.dll
API set	ext-ms-win-ntuser-windowclass-l1-1-0 (introduced in Windows 8)