TAB behaviour is odd in RTL mode

After typing any Arabic text, I need to press TAB twice to have it jump on screen, and with multiple tabs the text disappears altogether! Actually it's there somewhere but it seems it goes out of the window margin to the right behind the curtain . Maximizing the window size would show the hidden text.

A simple snippet that generates the problem goes like this:

{
QApplication app (argc, argv);
QTextEdit *text = new QTextEdit;
text->setPlainText(QObject::trUtf8("ض\t\t\t\tظ"));
text->show();
return app.exec();
}