#include <QtWidgets>

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

    QWidget w;
    QPushButton *minimize = new QPushButton("Minimize");
    QPushButton *restore = new QPushButton("Restore Down");
    QPushButton *maximize = new QPushButton("Maximize");
    QPushButton *fullScreen = new QPushButton("Fullscreen");
    QPushButton *close = new QPushButton("Close");
    QOpenGLWidget *glWidget = new QOpenGLWidget;
    glWidget->setMinimumSize(20, 20);

    QMenu *menu = new QMenu("Menu");
    menu->addAction("Item 1");
    menu->addAction("Item 2");
    menu->addAction("Item 3");
    QPushButton *menuButton = new QPushButton("Open menu...");
    menuButton->setMenu(menu);

    QObject::connect(minimize, SIGNAL(clicked()), &w, SLOT(showMinimized()));
    QObject::connect(restore, SIGNAL(clicked()), &w, SLOT(showNormal()));
    QObject::connect(maximize, SIGNAL(clicked()), &w, SLOT(showMaximized()));
    QObject::connect(fullScreen, SIGNAL(clicked()), &w, SLOT(showFullScreen()));
    QObject::connect(close, SIGNAL(clicked()), &w, SLOT(close()));

    QVBoxLayout *layout = new QVBoxLayout(&w);
    layout->addWidget(menuButton);
    layout->addWidget(minimize);
    layout->addWidget(restore);
    layout->addWidget(maximize);
    layout->addWidget(fullScreen);
    layout->addWidget(close);
    layout->addWidget(glWidget);

    // This causes the window to completely hide the task bar on Windows
    // when the auto-hide taskbar is turned on, you can't bring the menu
    // up anymore, even when maximized (not fullscreen).
//    w.setWindowFlags(Qt::Window | Qt::FramelessWindowHint);

    w.show();

    return a.exec();
}