#include <QtGui>

class MyCentralWidget : public QTextEdit
{
public:
   MyCentralWidget() : QTextEdit() {
      setSizePolicy(QSizePolicy(QSizePolicy::Expanding, QSizePolicy::Expanding));
   }
};

class MyTabWidget : public QTabWidget
{
public:
   MyTabWidget() : QTabWidget() {}
   virtual QSize sizeHint() const { return QSize( 100, 512); }
};

class MyTextEdit : public QTextEdit
{
public:
   MyTextEdit() : QTextEdit() {}
   virtual QSize sizeHint() const { return QSize( 256, 512); }
};

class MyMainWindow : public QMainWindow
{
   Q_OBJECT
public:
   MyMainWindow(QWidget* parent = 0) : QMainWindow(parent)
   {
      QTabWidget* tw = new MyTabWidget;
      tw->addTab(new QLineEdit, "One");
      tw->addTab(new QLineEdit, "Two");
      tw->addTab(new QLineEdit, "Three");
      tw->addTab(new QLineEdit, "Four");
      tw->addTab(new QLineEdit, "Five");
      QDockWidget* dw = new QDockWidget;
      dw->setWidget(tw);
      addDockWidget(Qt::LeftDockWidgetArea, dw, Qt::Horizontal);
      resize( 800, 600);
      QTimer::singleShot(5000, this, SLOT(addOtherWidgets()));
   }
   public slots:
      void addOtherWidgets()
      {
		 setCentralWidget(new MyTextEdit);
      }
};

#include "main.moc"

int main(int argc, char **argv)
{
    QApplication a(argc, argv);
    MyMainWindow mw;
    mw.show();
    return a.exec();
}