gsettings get com.deepin.xsettings scale-factor

或者使用 dbus 获取

busctl --user call com.deepin.daemon.Appearance /com/deepin/daemon/Appearance com.deepin.daemon.Appearance GetScaleFactor

QPixmap Utils::renderSVG(const QString &path, const QSize &size)
{
    QImageReader reader;
    QPixmap pixmap;
    reader.setFileName(path);
    if (reader.canRead()) {
        const qreal ratio = qApp->devicePixelRatio();
        reader.setScaledSize(size * ratio);
        pixmap = QPixmap::fromImage(reader.read());
        pixmap.setDevicePixelRatio(ratio);
    }
    else {
        pixmap.load(path);
    }
    return pixmap;
}

大多数代码里都是这么处理缩放的，绘制图片的时候对 devicePixelRatio 进行处理。