Function eventFilter

kdevplatform/util/shellutils.cpp:51–73

    }

    bool eventFilter(QObject* watched, QEvent* event) override
    {
        // Saving geometry on a nonspontaneous hide event is the only choice that is both reliable and safe:
        // * the close event is received only when a dialog is dismissed via
        //   its standard window close button and not when it is accepted or rejected;
        // * the QDialog::finished() signal is unavailable for non-dialog widgets (less general) and is not emitted
        //   if the dialog is explicitly hidden or destroyed while visible rather than finished normally;
        // * Qt documentation does not directly promise to emit the QObject::destroyed() signal from ~QWidget()
        //   as opposed to the too-late ~QObject(). Also Qt developers do not guarantee that the state
        //   of the widget being destroyed can be safely accessed in a slot connected to this signal.
        //   Some parts of the widget, e.g. its layout, are destroyed before the destroyed() signal is emitted.
        // A downside of handling the hide event is that when a widget is hidden, then shown again, its geometry
        // is saved multiple times redundantly. Fortunately, a dialog is unlikely to be shown again
        // after being hidden. If the redundant saving becomes a bottleneck for some widget, the visibility
        // of which changes often, a custom saving of geometry can be implemented in that widget's destructor.
        // See also the discussion of when to save geometry at https://codereview.qt-project.org/c/qt/qtbase/+/498797
        if (event->type() == QEvent::Hide && !event->spontaneous()) {
            const auto& widget = this->widget();
            Q_ASSERT(watched == &widget);
            configGroup().writeEntry(entryName(), widget.saveGeometry());
        }
        return false; // do not filter any events out
    }

private:
    static QString entryName()