Qt的DIY滚动条有关问题

#include <QWindowsStyle>class newStyle : public QWindowsStyle{    Q_OBJECTpublic:    newStyle();    virtual int pixelMetric(PixelMetric pm, const QStyleOption * opt=0, const QWidget * widget=0) const; //重载函数    virtual void drawComplexControl(ComplexControl cc, const QStyleOptionComplex *opt, QPainter *p, const QWidget *widget=0) const; //重载函数private:    void diyScrollBar(const QStyleOptionComplex *opt, QPainter *p) const; //重画滚动条private:    QPixmap *m_pBkPixmap;    QPixmap *m_pHndPixmap;};