DO decl
 
LOCAL hWnd, lcClassName, hInstance, lcWndClass,;
    lcClassNameRet, lcMenuNameRet
 
STORE SPACE(250) TO lcClassNameRet, lcMenuNameRet
 
hWnd = GetActiveWindow()
lcClassName = GetClsName (hWnd)
hInstance = GetModuleHandle(0)
 
? "*** Input parameters"
? "Class name retrieved through the GetClassName:", lcClassName
? "Module handle:", hInstance
?
 
*| typedef struct _WNDCLASS {
*|     UINT       style;           0:4
*|     WNDPROC    lpfnWndProc;     4:4
*|     int        cbClsExtra;      8:4
*|     int        cbWndExtra;     12:4
*|     HINSTANCE  hInstance;      16:4
*|     HICON      hIcon;          20:4
*|     HCURSOR    hCursor;        24:4
*|     HBRUSH     hbrBackground;  28:4
*|     LPCTSTR    lpszMenuName;   32:4
*|     LPCTSTR    lpszClassName;  36:4
*| } WNDCLASS, *PWNDCLASS; total bytes: 40
#DEFINE WNDCLASS_SIZE  40
 
lcWndClass = Repli(Chr(0), WNDCLASS_SIZE)
= GetClassInfo (hInstance, lcClassName, @lcWndClass)
 
* While tested under VFP6+WinMe:
* Have fun: there is no guarantee for you to get the Class and Menu names back;
* despite of the GetClassInfo returns the proper pointers to 
* corresponding memory blocks -- lpszMenuName and lpszClassName
 
* quite often the VFP has its time and inspiration to fill these memory blocks
* with some other stuff within a jiffy before or after the GetClassInfo 
* finishes and returns control to the program; at least it looks like it does;
 
* switch between Try A and Try B -- you could find them returning different
* results, despite their identity; sometimes even Try A returns a garbage
 
* Try A:
= FillBuffer (@lcClassNameRet, buf2dword(SUBSTR(lcWndClass, 37,4)))
= FillBuffer (@lcMenuNameRet, buf2dword(SUBSTR(lcWndClass, 33,4)))
 
? "*** Output from the GetClassInfo"
? "Style:        ", buf2dword(SUBSTR(lcWndClass,  1,4))
? "lpfnWndProc:  ", buf2dword(SUBSTR(lcWndClass,  5,4))
? "cbClsExtra:   ", buf2dword(SUBSTR(lcWndClass,  9,4))
? "cbWndExtra:   ", buf2dword(SUBSTR(lcWndClass, 13,4))
? "hInstance:    ", buf2dword(SUBSTR(lcWndClass, 17,4))
? "hIcon:        ", buf2dword(SUBSTR(lcWndClass, 21,4))
? "hCursor:      ", buf2dword(SUBSTR(lcWndClass, 25,4))
? "hbrBackground:", buf2dword(SUBSTR(lcWndClass, 29,4))
? "lpszMenuName: ", buf2dword(SUBSTR(lcWndClass, 33,4))
? "lpszClassName:", buf2dword(SUBSTR(lcWndClass, 37,4))
?
 
* Try B:
*= FillBuffer (@lcClassNameRet, buf2dword(SUBSTR(lcWndClass, 37,4)))
*= FillBuffer (@lcMenuNameRet, buf2dword(SUBSTR(lcWndClass, 33,4)))
 
? "Class name:   ", lcClassNameRet
? "Menu name:    ", lcMenuNameRet
 
PROCEDURE  FillBuffer (lcBuffer, lnPtr)
    IF lnPtr = 0
        lcBuffer = ""
    ELSE
        = Heap2String (@lcBuffer, lnPtr, Len(lcBuffer))
        lcBuffer = SUBSTR(lcBuffer, 1, AT(Chr(0), lcBuffer)-1)
    ENDIF
 
FUNCTION  GetClsName (lnHwnd)
    LOCAL lnBufsize, lcClassName
    lnBufsize = 250
    lcClassName = SPACE(lnBufsize)
    lnBufsize = GetClassName (lnHwnd, @lcClassName, lnBufsize)
RETURN  SUBSTR(lcClassName, 1, lnBufsize)
 
FUNCTION  buf2dword (lcBuffer)
RETURN Asc(SUBSTR(lcBuffer, 1,1)) + ;
    Asc(SUBSTR(lcBuffer, 2,1)) * 256 +;
    Asc(SUBSTR(lcBuffer, 3,1)) * 65536 +;
    Asc(SUBSTR(lcBuffer, 4,1)) * 16777216
 
PROCEDURE  decl
    DECLARE INTEGER GetActiveWindow IN user32
    DECLARE INTEGER GetModuleHandle IN kernel32 STRING lpModuleName
 
    DECLARE RtlMoveMemory IN kernel32 As Heap2String;
        STRING @Dest, INTEGER Src, INTEGER nLength
 
    DECLARE INTEGER GetClassName IN user32;
        INTEGER hWnd, STRING lpClassName, INTEGER nMaxCount
 
    DECLARE INTEGER GetClassInfo IN user32;
        INTEGER hInstance, STRING lpClassName, STRING @lpWndClass