#include <QtWidgets/QApplication>
#include <QtWidgets/QWidget>
#include <QtWidgets/QApplication>
#include <QtOpenGLWidgets/QtOpenGLWidgets>

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

    // tlw: red.
    QWidget tlw;
    tlw.resize(640, 480);
    tlw.setStyleSheet("QWidget { background-color: red; }");

    // alien widget: yellow.
    QWidget alien(&tlw);
    alien.setGeometry(0, 0, 640, 240);
    alien.setStyleSheet("QWidget { background-color: yellow; }");

    // native widget: blue.
    // the parent alien widget is still alien due to WA_DontCreateNativeAncestors flag.
    QWidget native(&alien);
    native.setAttribute(Qt::WA_DontCreateNativeAncestors);
    native.winId();
    native.setStyleSheet("QWidget { background-color: blue; }");

    // trigger window re-create by inserting a QOpenGLWidget.
    QOpenGLWidget* gl = new QOpenGLWidget(&native);
    gl->setGeometry(0, 0, 50, 50);

    tlw.show();
    return app.exec();
}