Close Widget Window if mouse clicked outside of it

I used:

setWindowFlags(Qt::FramelessWindowHint | Qt::Popup);

This seems to work well on OSX and Windows. My window appears correctly, does not steal the focus from my main window's caption, and the focus loss event is called correctly as soon as I click outside of it.

If your widget could have focus, and 'steal' the caption focus of some of your other widgets, it would have been easier. Something like this could work:

class ToolBarWidget : public QWidget
{
    Q_OBJECT

public:
    explicit ToolBarWidget(QWidget * parent = 0)
    {
        setFocusPolicy(Qt::ClickFocus);
    }

protected:
    void focusOutEvent(QFocusEvent * event)
    {
        close();
    }
}

And when you create any of your widgets you'd do:

ToolBarWidget * pWidget = new ToolBarWidget(this);
pWidget->show();
pWidget->setFocus();

Done! Well, I guess not quiet. first, you don't want the ToolBarWidget to get any focus in the first place. And second, you want for the user to be able to click anywhere and the ToolBarWidget to be hidden. So, you may keep track of every ToolBarWidget that you create. For example, in a 'QList ttWidgets' member variable. Then, whenever you create a new ToolBarWidget, you'd do this:

ToolBarWidget * pWidget = new ToolBarWidget(this);
pWidget->installEventFilter(this);
pWidget->show();

and in your main widget class, implement the eventFilter() function. Something like:

bool MainWidget::eventFilter(QObject *obj, QEvent *event)
{
    if (event->type() == QEvent::FocusOut ||
        event->type() == QEvent::KeyPress ||
        event->type() == QEvent::MouseButtonPress)
    {
        while (!ttWidgets.isEmpty()) {
            ToolBarWidget * p = ttWidgets->takeFirst();
            p->close();
            p->deleteLater();
        }
    }
    return MainWidget::eventFilter(obj, event);
}

And that will work. Because this way, even though your ToolTabWidgets aren't getting focus, some other widget in your main widget has focus. And once that changes (whether the user clicked out of your window, or on another control inside it, or in this case, a key or mouse button is pressed, the control will reach that eventFilter() function and close all your tab widgets.

BTW, in order to capture the MouseButtonPress, KeyPress etc. from the other widgets, you would either need to installEventFilter on them too, or just reimplement the QWidget::event(QEvent * event) function in your main widget, and look for those events there.

you can do this by using QDesktopWidget.h like this

void MainWindow::on_actionAbout_triggered()
{
    AboutDialog aboutDialog;
    //Set location of player in center of display
    aboutDialog.move(QApplication::desktop()->screen()->rect().center() -aboutDialog.rect().center());
    // Adding popup flags so that dialog closes when it losses focus
    aboutDialog.setWindowFlags(Qt::Popup);
    //finally opening dialog
    aboutDialog.exec();

}