helper EventGadget
{
    typedef UINT (CALLBACK * EventHandler)(void * pvData, EventMsg * pmsg);
};


helper Visual
{
    struct VisualCI : public DUser::Gadget::ConstructInfo
    {
        Visual *    pgvParent;
    };

    inline HRESULT IsVisible(BOOL * pfVisible, UINT nFlags)
    {
        return IsParentChainStyle(GS_VISIBLE, pfVisible, nFlags); 
    }

    inline HRESULT IsEnabled(BOOL * pfEnabled, UINT nFlags)
    {
        return IsParentChainStyle(GS_ENABLED, pfEnabled, nFlags); 
    }
};


helper Flow
{
    enum ETime
    {
        tBegin      = 0,
        tEnd
    };

    struct FlowCI : public DUser::Gadget::ConstructInfo
    {
        DWORD       cbSize;
        Visual *    pgvSubject;
    };
};


helper AlphaVertexFlow
{
    static PRID GetPRID()
    {
        return DUserGetAlphaVertexPRID();
    }

    struct AlphaKeyFrame : DUser::KeyFrame
    {
        BYTE        bAlpha;
    };
};


helper RectFlow
{
    static PRID GetPRID()
    {
        return DUserGetRectPRID();
    }

    struct RectKeyFrame : DUser::KeyFrame
    {
        UINT        nChangeFlags;
        RECT        rcPxl;
    };
};


helper RotateFlow
{
    enum EDirection
    {
        dMin        = 0,
        dShort      = 0,                // Shortest arc
        dLong       = 1,                // Longer arc
        dCW         = 2,                // Clock-wise
        dCCW        = 3,                // Counter clock-wise
        dMax        = 3,
    };

    static PRID GetPRID()
    {
        return DUserGetRotatePRID();
    }

    struct RotateKeyFrame : DUser::KeyFrame
    {
        float       flRotation;
        EDirection  nDir;
    };
};


helper ScaleFlow
{
    static PRID GetPRID()
    {
        return DUserGetScalePRID();
    }

    struct ScaleKeyFrame : DUser::KeyFrame
    {
        UINT        nChangeFlags;
        float       flScale;
    };
};

helper LightFlow
{
    static PRID GetPRID()
    {
        return DUserGetLightPRID();
    }

    struct LightKeyFrame : DUser::KeyFrame
    {
        UINT id;
        float x;
        float y;
        float z;
        float xDirection;
        float yDirection;
        float zDirection;
        float outerCone;
        float innerCone;
        float attenuationA0;
        float attenuationA1;
        float attenuationA2;
        int flags;
    };
};

helper Sequence
{
    struct AnimationInfo
    {
        DWORD       cbSize;
    };

    BEGIN_STRUCT(CompleteEvent, EventMsg)
        BOOL        fNormal;      // Sequenced finished normally
    END_STRUCT(CompleteEvent)

    DEFINE_EVENT(evComplete, "E90A6ABB-E4CF-4988-87EA-6D1EEDCD0097");
};