GetClassLong
The GetClassLong
function retrieves the specified 32-bit (long) value from the WNDCLASS structure associated with
the specified window.
DWORD GetClassLong(
|
HWND hWnd, |
// handle of window |
|
int nIndex |
// offset of value
to retrieve |
|
); |
|
Parameters
hWnd
Identifies
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 |
Action |
|
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 and GetWindowWord . |
|
GCL_HBRBACKGROUND |
Retrieves
the handle of the background brush associated with the class. |
|
GCL_HCURSOR |
Retrieves
the handle of the cursor associated with the class. |
|
GCL_HICON |
Retrieves
the handle of the icon associated with the class. |
|
GCL_HICONSM |
Retrieves
the handle of the small icon associated with the class. |
|
GCL_HMODULE |
Retrieves
the handle of 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
If the
function succeeds, the return value is the requested 32-bit value.
If the
function fails, the return value is zero. To get extended error information,
call GetLastError.
Remarks
Reserve extra
class memory by specifying a nonzero value in the cbClsExtra member of
the WNDCLASS structure used with the RegisterClass function.
See Also