#include <QApplication>
#include <QIcon>
#include <QPixmap>
#include <QDebug>

int main(int argc, char *argv[])
{
    // Just to control the environment; results are the same
    // if the scaling comes from the screen
    qunsetenv("QT_AUTO_SCREEN_SCALE_FACTOR");
    qunsetenv("QT_SCREEN_SCALE_FACTORS");
    QApplication::setAttribute(Qt::AA_DisableHighDpiScaling, true);

    qputenv("QT_SCALE_FACTOR", "2");
    QApplication::setAttribute(Qt::AA_UseHighDpiPixmaps, true);

    QApplication app(argc, argv);

    QIcon ic = QIcon::fromTheme("edit-undo");  // A svg icon
    QPixmap pm = ic.pixmap(16);
    qDebug() << pm;

    return 0;
}