给我写一个QT的圆形进度条程序，并展示下效果

抱歉，我是AI语言模型，无法展示效果。以下是一个基于QT的圆形进度条程序，供您参考：

#include <QApplication>
#include <QWidget>
#include <QProgressBar>
#include <QHBoxLayout>
#include <QTimer>
#include <QPainter>

class CircleProgressBar : public QWidget
{
public:
    CircleProgressBar(QWidget *parent = nullptr) : QWidget(parent)
    {
        m_percent = 0;
        m_timer = new QTimer(this);
        connect(m_timer, SIGNAL(timeout()), this, SLOT(updatePercent()));
        m_timer->start(50);
    }

    void setPercent(int percent)
    {
        m_percent = percent;
        update();
    }

protected:
    void paintEvent(QPaintEvent *event)
    {
        QPainter painter(this);
        painter.setRenderHint(QPainter::Antialiasing, true);
        painter.setPen(Qt::NoPen);
        painter.setBrush(QColor(255, 255, 255));
        painter.drawRect(0, 0, width(), height());

        painter.setBrush(QColor(200, 200, 200));
        painter.drawEllipse(0, 0, width(), height());

        painter.setBrush(QColor(0, 255, 0));
        painter.drawPie(0, 0, width(), height(), 90 * 16, -m_percent * 16);
    }

private slots:
    void updatePercent()
    {
        m_percent++;
        if (m_percent > 100) {
            m_percent = 0;
        }
        update();
    }

private:
    int m_percent;
    QTimer *m_timer;
};

int main(int argc, char *argv[])
{
    QApplication app(argc, argv);

    QWidget *widget = new QWidget();
    QHBoxLayout *layout = new QHBoxLayout(widget);

    CircleProgressBar *progressbar = new CircleProgressBar();
    layout->addWidget(progressbar);

    widget->setFixedSize(200, 200);
    widget->show();

    return app.exec();
}