#DEFINE SAMPLE_WIN_PROPERTY "MyWinProperty"
DO declare
 
LOCAL hWindow, hProperty, cBuffer, nBufsize
hWindow = _screen.HWnd
 
IF VARTYPE(oProperty) <> "O"
* this variable must not be released until
* the window property is not required anymore
    PUBLIC oProperty As PChar
 
    oProperty = CREATEOBJECT("PChar",;
        TRANSFORM(DATETIME()))
 
    * creating and assigning window property
    IF SetProp(hWindow, SAMPLE_WIN_PROPERTY,;
        oProperty.GetAddr()) = 0
        ? "SetProp failed with error code:", GetLastError()
        RETURN
    ENDIF
ENDIF
 
* reading window property
hProperty = GetProp(hWindow, SAMPLE_WIN_PROPERTY)
IF hProperty = 0
    ? "GetProp failed with error code:", GetLastError()
    RETURN
ENDIF
 
nBufsize = GlobalSize(hProperty)
cBuffer = REPLICATE(CHR(0), nBufsize)
= MemToStr(@cBuffer, hProperty, nBufsize)
? "Property read:", cBuffer
* end of main
 
PROCEDURE declare
    DECLARE INTEGER GetLastError IN kernel32
    DECLARE INTEGER GlobalSize IN kernel32 INTEGER hMem
 
    DECLARE RtlMoveMemory IN kernel32 As MemToStr;
        STRING @, INTEGER, INTEGER
 
    DECLARE INTEGER SetProp IN user32;
        INTEGER hWindow, STRING lpString,;
        INTEGER hData
 
    DECLARE INTEGER GetProp IN user32;
        INTEGER hWindow, STRING lpString
 
DEFINE CLASS PChar As Session
PROTECTED hMem
 
PROCEDURE Init(lcString)
    THIS.hMem = 0
    THIS.setValue(lcString)
 
PROCEDURE Destroy
    THIS.ReleaseString
 
FUNCTION GetAddr
RETURN THIS.hMem
 
FUNCTION GetValue
    LOCAL lnSize, lcBuffer
    lnSize = THIS.GetAllocSize()
    lcBuffer = SPACE(lnSize)
 
    IF THIS.hMem <> 0
        DECLARE RtlMoveMemory IN kernel32 As MemToStr;
            STRING @, INTEGER, INTEGER
        = MemToStr(@lcBuffer, THIS.hMem, lnSize)
    ENDIF
RETURN lcBuffer
 
FUNCTION GetAllocSize
    DECLARE INTEGER GlobalSize IN kernel32 INTEGER hMem
RETURN Iif(THIS.hMem=0, 0, GlobalSize(THIS.hMem))
 
PROCEDURE SetValue(lcString)
#DEFINE GMEM_FIXED 0 
    THIS.ReleaseString
 
    DECLARE INTEGER GlobalAlloc IN kernel32 INTEGER, INTEGER
    DECLARE RtlMoveMemory IN kernel32 As StrToMem;
        INTEGER, STRING @, INTEGER
 
    LOCAL lnSize
    lcString = lcString + Chr(0)
    lnSize = Len(lcString)
    THIS.hMem = GlobalAlloc(GMEM_FIXED, lnSize)
    IF THIS.hMem <> 0
        = StrToMem(THIS.hMem, @lcString, lnSize)
    ENDIF
 
PROCEDURE ReleaseString
    IF THIS.hMem <> 0
        DECLARE INTEGER GlobalFree IN kernel32 INTEGER
        = GlobalFree (THIS.hMem)
        THIS.hMem = 0
    ENDIF
ENDDEFINE