QPushButton in QStackedWidget in QDialog

Question

I'm using Qt 5.2 and I have detect a special problematic behaviour by using QPushButtons inside a QStackedWidget which is child of a QDialog.

Here's a simplified sample code (TestMainWindow is a QMainWindow and TestWidget a QWidget):

void TestMainWindow::onPushbutton()
{
  QDialog d;
  QVBoxLayout* mainLayout = new QVBoxLayout(&d);

  this->stackedWidget = new QStackedWidget;
  this->stackedWidget->addWidget( new TestWidget("Widget 1") );
  this->stackedWidget->addWidget( new TestWidget("Widget 2") );

  QPushButton* switcher = new QPushButton("switch Widget");

  mainLayout->addWidget( this->stackedWidget );
  mainLayout->addWidget( switcher );

  connect( switcher, SIGNAL(clicked()), this, SLOT(switchWidget()) );    

  d.exec();
}

void TestMainWindow::switchWidget()
{
  if( this->stackedWidget )
  {
    this->stackedWidget->setCurrentIndex( this->stackedWidget->currentIndex() == 0 ? 1 : 0 );
  }
}

TestWidget::TestWidget(const QString &labelText, QWidget *parent)
: QWidget( parent )
{
  QHBoxLayout* mainLayout = new QHBoxLayout( this );
  mainLayout->addWidget( new QLabel(labelText) );
  mainLayout->addWidget( new QPushButton("test") );
}

On Windows 7 you know the animation/effect, when you hover a button. This will happen in an endless loop (hover/not-hover) to the Button in the first Widget ("Widget 1") by starting the Dialog d.

In my real application I noticed also that other events for this widget (e.g. focusing a line-edit) will only proceed when the QDialog is moved. So it also seems to me, that the first widget with a button in a QStackedWidget runs in another event loop. I captured this behaviour to the QPushButton. When I don't have a QPushButton in the widget, the focusing of the other widgets (e.g. line-edits) works fine as it should be. Only if there's a QPushButton, the events are blocked until the parent Dialog is moved.

Have anybody ideas where this can came from and how to fix it?