Qt: How to find why QTextEdit is being closed?

I write a simple MDI text editor using Qt 4. When a text window (MyDoc derived from QTextEdit) is being closed, I want to know whether it is being closed by pressi开发者_如何转开发ng [X] on that child window or by closing the whole application. Then I will use this info some way (say, I want to issue a message box with an additional question in case of using [X]). How can I achieve this? I don't know a way of distinguishing that in redefined closeEvent(), which could be the best solution...

Thanks!

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Install an event filter on the global instance of QApplication and watch for Close event. It should arrive before the closeEvent() is called on your widget.