当逻辑坐标很小且为分数时，如何设置QPainter窗口？

MyWindow::MyWindow(QWidget *parent) : QMainWindow(parent)
{
    setFixedSize(800, 600); // 设置窗口大小为800x600
    setWindowTitle("My Window"); // 设置窗口标题为"My Window"
}

void MyWindow::paintEvent(QPaintEvent *event)
{
    QPainter painter(this);
    
    // 设置逻辑坐标系
    painter.setRenderHint(QPainter::Antialiasing); // 抗锯齿
    painter.setWindow(0, 0, 1, 1); // 设置逻辑坐标系的范围为[0, 1]x[0, 1]
    
    // 绘制图形
    painter.drawLine(QPointF(0.2, 0.2), QPointF(0.8, 0.8));
    painter.drawRect(QRectF(0.3, 0.3, 0.4, 0.4));
    painter.drawText(QPointF(0.5, 0.5), "Hello, World!");
}

int main(int argc, char *argv[])
{
    QApplication app(argc, argv);
    
    MyWindow window;
    window.show();
    
    return app.exec();
}