Örnek: Windows Message Event Handling

#DEFINE WM_THEMECHANGED    0x031A

#DEFINE GWL_WNDPROC    (-4)

PUBLIC oHandler

oHandler=CREATEOBJECT("AppState")

BINDEVENT(_SCREEN.hWnd, WM_THEMECHANGED, oHandler, "HandleEvent")

MESSAGEBOX("Test by changing Themes.")

DEFINE CLASS AppState AS Custom

nOldProc=0

PROCEDURE Destroy

    UNBINDEVENT(_SCREEN.hWnd, WM_THEMECHANGED)

ENDPROC

PROCEDURE Init

    DECLARE integer GetWindowLong IN WIN32API ;

        integer hWnd, ;

        integer nIndex

    DECLARE integer CallWindowProc IN WIN32API ;

        integer lpPrevWndFunc, ;

        integer hWnd,integer Msg,;

        integer wParam,;

        integer lParam

    THIS.nOldProc=GetWindowLong(_VFP.HWnd,GWL_WNDPROC)

ENDPROC

PROCEDURE HandleEvent(hWnd as Integer, Msg as Integer, ;

    wParam as Integer, lParam as Integer)

    lResult=0

    IF msg=WM_THEMECHANGED

        MESSAGEBOX("Theme changed...")

    ENDIF

    lResult=CallWindowProc(this.nOldProc,hWnd,msg,wParam,lParam)

    RETURN lResult

ENDPROC

ENDDEFINE