problem with layout direction and QFileDialog

Hi All,
I have developed an application witch use QMainWIndow, QWizard and other graphical elements.

I determine layout direction of my application in the main method:

Code:

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QApplication app(argc, argv);
app.setLayoutDirection(Qt::RightToLeft);
MainWindow *mainWin = new MainWindow;
mainWin->show();
return app.exec();

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when I run application, at first all things is correct and layout direction of all dialogs and wizards is correct.
When I open a QDialogFile in my application, all layout directions change to "left to right"!
I dont know why layout direction change?
I open a file chooser with static methods of QFileDialog class:

Code:

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QFileDialog::getExistingDirectory(this, tr("Select Directory"), QDir::home().path());

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Any solution to this.

Thanks in advance.

My Qt version: 4.7
My OS: OpenSUSE 11.4