QPainter创建路径

路径的交叉并补可以通过函数或者操作符进行操作，如下：

//函数
QPainterPath subtracted(const QPainterPath &p) const;   //差集
QPainterPath united(const QPainterPath &p) const;       //并集
QPainterPath intersected(const QPainterPath &p) const;//交集
//操作符
QPainterPath operator&(const QPainterPath &other) const;
QPainterPath &operator&=(const QPainterPath &other);
QPainterPath operator+(const QPainterPath &other) const;
QPainterPath &operator+=(const QPainterPath &other);
QPainterPath operator-(const QPainterPath &other) const;
QPainterPath &operator-=(const QPainterPath &other);

示例代码：

void QwIFNTProgressBar::Pate_Test3(QPainter& painter)
{
    painter.save();
    painter.setWindow(0, 0, 400, 400);
    painter.translate(200,0);
    painter.scale(0.8, 0.8);

    painter.setRenderHint(QPainter::Antialiasing);
    QPainterPath path;
    path.lineTo(100, 0);
    path.cubicTo(200, 0, 100, 50, 200, 100);
    path.closeSubpath();
    path.addRect(50, 50, 50, 50);

    QPainterPath path2;
    path2.addEllipse(80, 30, 50, 50);
    path = path.subtracted(path2);

    QPoint offsetPoint(20, 20);
    painter.translate(offsetPoint);
    painter.setBrush(Qt::lightGray);
    painter.drawPath(path);
    painter.setBrush(Qt::NoBrush);
    painter.drawRect(path.boundingRect());

    QPen pen;
    pen.setWidth(5);
    pen.setColor(Qt::red);
    painter.setPen(pen);
    painter.drawPoint(QPoint(100, 0) );
    painter.drawPoint(QPoint(200, 0) );
    painter.drawPoint(QPoint(100, 50) );
    painter.drawPoint(QPoint(200, 100) );

    painter.restore();
}