GetClassLong

This function retrieves the specified 32-bit (long) value from the WNDCLASS structure associated with the specified window.

DWORD GetClassLong( 
HWND hWnd, 
int nIndex); 

Parameters

• hWnd
  Handle to the window and, indirectly, the class to which the window belongs.
• nIndex
  Specifies the 32-bit value to retrieve. To retrieve a 32-bit value from the extra class memory, specify the positive, zero-based byte offset of the value to be retrieved. Valid values are in the range zero through the number of bytes of extra class memory, minus four; for example, if you specified 12 or more bytes of extra class memory, a value of 8 would be an index to the third 32-bit integer. To retrieve any other value from the WNDCLASS structure, specify one of the following values:

  Value	Description
  GCW_ATOM	Retrieves an ATOM value that uniquely identifies the window class. This is the same atom that the RegisterClass function returns.
  GCL_CBCLSEXTRA	Retrieves the size, in bytes, of the extra memory associated with the class.
  GCL_CBWNDEXTRA	Retrieves the size, in bytes, of the extra window memory associated with each window in the class. For information on how to access this memory, see GetWindowLong.
  GCL_HBRBACKGROUND	Retrieves a handle to the background brush associated with the class.
  GCL_HCURSOR	Retrieves a handle to the cursor associated with the class.
  GCL_HICON	Retrieves a handle to the icon associated with the class.
  GCL_HICONSM	Retrieves a handle to the small icon associated with the class.
  GCL_HMODULE	Retrieves a handle to the module that registered the class.
  GCL_MENUNAME	Retrieves the address of the menu name string. The string identifies the menu resource associated with the class.
  GCL_STYLE	Retrieves the window-class style bits.
  GCL_WNDPROC	Retrieves the address of the window procedure associated with the class.

Return Values

The requested 32-bit value indicates success. Zero indicates failure. To get extended error information, call GetLastError.

Remarks

The nIndex parameter is a byte offset but must be a multiple of 4 bytes. Windows CE does not support unaligned access.

The only values supported for the nIndex parameter are GCL_HICON and GCL_STYLE.

If you are using the Windows CE Iconcurs component, which supports mouse cursors on appropriate target platforms, you can also use the GCL_HCURSOR value in the nIndex parameter.

Windows CE versions that support mouse cursors include the Iconcurs and Mcursor components rather than the Icon and Cursor components.

Reserve extra class memory by specifying a nonzero value in the cbClsExtra member of the WNDCLASS structure used with the RegisterClass function.

Requirements

Note   This API is part of the complete Windows CE OS package as provided by Microsoft. The functionality of a particular platform is determined by the original equipment manufacturer (OEM) and some devices may not support this API.

See Also

GetLastError, GetWindowLong, RegisterClass, SetClassLong, WNDCLASS

 Last updated on Tuesday, July 13, 2004

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