关于cups_page_header_t 结构体问题

struct cups_page_header_s {
    unsigned AdvanceDistance;
    cups_adv_t AdvanceMedia;
    cups_bool_t Collate;
    cups_cut_t CutMedia;
    cups_bool_t Duplex;
    unsigned HWResolution[2];
    unsigned ImagingBoundingBox[4];
    cups_bool_t InsertSheet;
    cups_jog_t Jog;
    cups_edge_t LeadingEdge;
    cups_bool_t ManualFeed;
    unsigned Margins[2];
    char MediaClass[64];
    char MediaColor[64];
    unsigned MediaPosition;
    char MediaType[64];
    unsigned MediaWeight;
    cups_bool_t MirrorPrint;
    cups_bool_t NegativePrint;
    unsigned NumCopies;
    cups_orient_t Orientation;
    cups_bool_t OutputFaceUp;
    char OutputType[64];
    unsigned PageSize[2];
    cups_bool_t Separations;
    cups_bool_t TraySwitch;
    cups_bool_t Tumble;
    unsigned cupsBitsPerColor;
    unsigned cupsBitsPerPixel;
    unsigned cupsBytesPerLine;
    cups_order_t cupsColorOrder;
    cups_cspace_t cupsColorSpace;
    unsigned cupsCompression;
    unsigned cupsHeight;
    unsigned cupsMediaType;
    unsigned cupsRowCount;
    unsigned cupsRowFeed;
    unsigned cupsRowStep;
    unsigned cupsWidth;
};

这么多的成员中，哪个是记录页码的呢？
打印中，怎么知道换页了呢？
请高手指点
等待中………………