#include <QtGui>
#include <QtWidgets>

class TMdiSubWindow : public QMdiSubWindow
{
public:
	TMdiSubWindow(QWidget* parent)
		:
		QMdiSubWindow(parent)
		{
			showMaximized();
		}

	void mousePressEvent(QMouseEvent* e)
	{
		qDebug(isMaximized() ? "maximized" : "NOT maximized");
		QMdiSubWindow::mousePressEvent(e);
	}
	void resizeEvent(QResizeEvent* e)
	{
		qDebug(isMaximized() ? "maximized" : "NOT maximized");
		QMdiSubWindow::resizeEvent(e);
	}
};

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

    QMdiArea *mdiArea = new QMdiArea;
    QMainWindow *mainWindow = new QMainWindow;
    mainWindow->setCentralWidget(mdiArea);

    mdiArea->addSubWindow(new TMdiSubWindow(mdiArea));

    mainWindow->show();
	app.exec();
	return 0;
}