如何制作一个可以缩放和绘制的画布QWidget？

#include <QApplication>
#include <QWidget>
#include <QPainter>
#include <QWheelEvent>

class Canvas : public QWidget {
public:
    Canvas(QWidget *parent = nullptr) : QWidget(parent), scale(1.0) {}

protected:
    void paintEvent(QPaintEvent *event) override {
        QPainter painter(this);
        painter.scale(scale, scale);
        // 在这里添加绘制代码
        painter.drawRect(10, 10, 100, 100);
    }

    void wheelEvent(QWheelEvent *event) override {
        int delta = event->angleDelta().y();
        if (delta > 0) {
            scale *= 1.1;
        } else {
            scale /= 1.1;
        }
        update();
    }

private:
    double scale;
};

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