Modal QDialog inside QMdiArea

Hi

I am trying to use modal (Qt::WindowModal) QDialog inside QMdiArea and it doesn't work.
Here is example code:

Code:

#include <QApplication>
#include <QtGui>
 
int main(int argc, char *argv[])
{
	QApplication app(argc, argv);
	QMainWindow mainWin;
 
	QMdiArea* area = new QMdiArea();
	mainWin.setCentralWidget(area);
 
	//window 1
	QWidget* w = new QWidget();
	w->setWindowTitle("w");
 
	QVBoxLayout* layout = new QVBoxLayout();
	layout->addWidget(new QLineEdit());
	layout->addWidget(new QTextEdit());
	layout->addWidget(new QPushButton("B1"));
	w->setLayout(layout);
 
	area->addSubWindow(w);
 
	//window 2
	QWidget* w2 = new QWidget();
	w2->setWindowTitle("w2");
 
	QVBoxLayout* layout2 = new QVBoxLayout();
	layout2->addWidget(new QLineEdit());
	layout2->addWidget(new QTextEdit());
	layout2->addWidget(new QPushButton("B2"));
	w2->setLayout(layout2);
 
	QMdiSubWindow* sw2 = area->addSubWindow(w2);
 
	mainWin.show();
 
	//dialog
	QDialog d(sw2);// block window 2
	d.setWindowTitle("d");
	d.setWindowModality(Qt::WindowModal);
 
	QVBoxLayout* layout3 = new QVBoxLayout();
	layout3->addWidget(new QLineEdit());
	layout3->addWidget(new QLineEdit());
	layout3->addWidget(new QPushButton("B3"));
	d.setLayout(layout3);
 
	area->addSubWindow(&d);
	d.exec();
 
	return app.exec();
}

Dialog should block window 2, but it deasn't block anything. It looks like ordinary window.

What is the correct way to do this?

Thank you.