Regression: QGLWidget : Slow response with QSplitter

    #include <QApplication>
    #include <QGLWidget>
    #include <QMainWindow>
    #include <QSplitter>
    #include <QTextEdit>
     
    class GLWidget : public QGLWidget
    {
    public:
    GLWidget(QWidget *parent = 0) : QGLWidget(parent) {}
    GLWidget(const QGLFormat &format, QWidget *parent = 0, const QGLWidget *shareWidget = 0, Qt::WindowFlags f = 0) :
    QGLWidget(format, parent, shareWidget, f){}
     
    protected:
    virtual void paintGL();
    virtual void resizeGL(int, int) { }
    };
     
    void GLWidget :: paintGL()
    {
     
    glClear(GL_COLOR_BUFFER_BIT | GL_DEPTH_BUFFER_BIT);
    glLoadIdentity();
     
    glTranslatef(0.5f,0.5f,0.0f);
     
    glBegin(GL_QUADS);
    glVertex3f(-1.0f, 1.0f, 0.0f);
    glVertex3f( 1.0f, 1.0f, 0.0f);
    glVertex3f( 1.0f,-1.0f, 0.0f);
    glVertex3f(-1.0f,-1.0f, 0.0f);
    glEnd();
    }
     
    int main(int argc, char **argv)
    {
    QApplication app(argc, argv);
     
    QMainWindow mainwindow;
     
    mainwindow.setFixedSize(1000,600);
     
    QSplitter *splitter = new QSplitter(Qt::Horizontal);
    splitter->addWidget(new QTextEdit());
    splitter->addWidget(new GLWidget());
     
    mainwindow.setCentralWidget(splitter);
     
    mainwindow.show();
     
    return app.exec();
    }