QT中，关闭窗口时的有关问题

QT中，关闭窗口时的问题
本人在制作一个文本编辑器，想模仿gedit关闭时的功能，即在文本修改后，点窗口的关闭按钮，会弹出要求用户保存的信息。
具体如图：


我在QT里写了一个
connect(qApp,SIGNAL(aboutToQuit()),this,SLOT(MyProgramClose()));
来捕获关闭信号，在MyProgramClose函数中，加入一个保存的对话框。如果选择取消时，应该是不关闭主程序窗口，但是我发现，保存对话框是出来了，主程序窗口也没有了。
MyProgramClose函数如下：

C/C++ code

        QMessageBox msgBox;
        msgBox.setText("The document has been modified.");
        msgBox.setInformativeText("Do you want to save your changes?");
        msgBox.setStandardButtons(QMessageBox::SaveAll | QMessageBox::Discard | QMessageBox::Cancel);
        msgBox.setDefaultButton(QMessageBox::SaveAll);
        int ret = msgBox.exec();
        switch (ret) {
           case QMessageBox::SaveAll:
               break;
           case QMessageBox::Discard:
               break;
           case QMessageBox::Cancel:
               return;
               break;
           default:
               break;
         }

不知道是我获取关闭信号获取错了，还是我在Cancel里的操作不正确？希望各位高人们指点指点！！

------解决方案--------------------
建议override editor的closeEvent事件函数

------解决方案--------------------
connect(qApp,SIGNAL(aboutToQuit()),this,SLOT(MyProgramClose()));
这样达不到你想要的效果；


help doc：

void QCoreApplication::aboutToQuit () [signal]
This signal is emitted when the application is about to quit the main event loop, e.g. when the event loop level drops to zero. This may happen either after a call to quit() from inside the application or when the users shuts down the entire desktop session.

The signal is particularly useful if your application has to do some last-second cleanup. Note that no user interaction is possible in this state