【qt】视口和窗口坐标

void Widget::paintEvent(QPaintEvent *event)
{
    QPainter painter(this);
    QRect rect(200,0,200,200);
    painter.drawRect(rect);
    //设置视口的范围,相当于一个窗口
    painter.setViewport(rect);
    //设置窗口坐标,这是逻辑大小,可以自己任意设计
    //左上角的坐标为(-50,-50),长为100,宽为100,这是逻辑大小
    //原本我们的设置的视口范围为长200,宽200
    painter.setWindow(-50,-50,100,100);
    QPen pen;
    pen.setColor(Qt::blue);//换个颜色区分
    painter.setPen(pen);
    painter.drawRect(QRect(0,0,50,50));
}

void Widget::paintEvent(QPaintEvent *event)
{
    QPainter painter(this);
    int minSide=qMin(this->width(),this->height());//取最小的窗口边
    QRect rect((this->width()-minSide)/2,(this->height()-minSide)/2,minSide,minSide);
    painter.drawRect(rect);
    painter.drawEllipse(QPoint(200,200),50,50);//圆心,水平半径,垂直半径
}

void Widget::paintEvent(QPaintEvent *event)
{
    QPainter painter(this);
    int minSide=qMin(this->width(),this->height());//取最小的窗口边
    QRect rect((this->width()-minSide)/2,(this->height()-minSide)/2,minSide,minSide);
    painter.drawRect(rect);
    painter.drawEllipse(QPoint(200,200),50,50);
    painter.setViewport(rect);
    painter.setWindow(-100,-100,200,200);
    QPen pen;
    pen.setColor(Qt::red);
    painter.setPen(pen);
    int count=10;
    for(int i=0;i<count;i++)
    {
        painter.drawEllipse(QPoint(50,0),50,50);
        painter.rotate(360/count);//坐标旋转
    }
}