#include <QApplication>
#include <QLabel>
#include <QMainWindow>
#include <QDockWidget>
#include <QOpenGLWidget>
#include <QOpenGLFunctions>

class MyGLWidget : public QOpenGLWidget, protected QOpenGLFunctions
{
protected:
    void initializeGL()
    {
        initializeOpenGLFunctions();
        glClearColor(1.0f, 0.0f, 0.0f, 1.0f);
    }

    void paintGL()
    {
        glClear(GL_COLOR_BUFFER_BIT);
    }
};

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

    QApplication app(argc, argv);
    app.setObjectName("Main app");
    QMainWindow mw;
    mw.setObjectName("Main window");
    mw.setDockOptions(mw.dockOptions() | QMainWindow::GroupedDragging);

    QLabel central("I'm the central widget");
    central.setObjectName("Central label");
    mw.setCentralWidget(&central);

    QDockWidget dw1("Dock Widget 1", &mw);
    dw1.setObjectName("Dock widget 1");
    QLabel dl1("Dock label 1");
    dl1.setObjectName("Dock label 1");
    dw1.setAllowedAreas(Qt::AllDockWidgetAreas);
    dw1.setWidget(&dl1);
    mw.addDockWidget(Qt::LeftDockWidgetArea, &dw1);

    QDockWidget dw2("Dock Widget 2", &mw);
    dw2.setObjectName("Dock widget 2");
    MyGLWidget glw;
    glw.setObjectName("MyGLWidget");
    dw2.setAllowedAreas(Qt::AllDockWidgetAreas);
    dw2.setWidget(&glw);
    mw.addDockWidget(Qt::LeftDockWidgetArea, &dw2);

    // Force the dock widget to become a native widget
    dw1.winId();

    dw2.setFloating(true);

    mw.adjustSize();
    mw.show();
    return app.exec();
}