drawArc in the rectangle issues

[Santosh Reddy]

I think this is what you want

class ArcWidget : public QWidget
{
protected:
    void paintEvent(QPaintEvent * event) override
    {
        QPainter painter(this);
 
        const double radius = qSqrt(qPow(width()/2.0, 2) + qPow(height()/2.0, 2));
        const int startAngle = qAtan((width()/2.0)/radius) * 180 / M_PI * 16;
        const int spanAngle = (90 - startAngle) * 2 * 16;
        const QRect rect = event->rect().adjusted(-(radius-width()/2.0), height()-radius, (radius-width()/2.0), radius);
 
        painter.drawArc(rect, startAngle, spanAngle);
    }
};
 
int main(int argc, char *argv[])
{
    QApplication app(argc, argv);
 
    ArcWidget widget;
    widget.show();
 
    return app.exec();
}

class ArcWidget : public QWidget
{
protected:
    void paintEvent(QPaintEvent * event) override
    {
        QPainter painter(this);

        const double radius = qSqrt(qPow(width()/2.0, 2) + qPow(height()/2.0, 2));
        const int startAngle = qAtan((width()/2.0)/radius) * 180 / M_PI * 16;
        const int spanAngle = (90 - startAngle) * 2 * 16;
        const QRect rect = event->rect().adjusted(-(radius-width()/2.0), height()-radius, (radius-width()/2.0), radius);

        painter.drawArc(rect, startAngle, spanAngle);
    }
};

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

    ArcWidget widget;
    widget.show();

    return app.exec();
}

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