QApplicationPrivate::focus_widget became a dangling pointer
in the following scenario:
A widget first gets focus and later on gets a focus proxy.
QApplicationPrivate::focus_widget was still pointing to the initial widget.
Upon destruction, QWidget::hasFocus() [which follows to the focus proxy
and then compares with focus_widget] was therefore false for both
widgets. So QWidget::clearFocus() didn't call
QApplicationPrivate::setFocusWidget(0) for either of them. As a
result, focus_widget remained set, and became dangling.
In real life, this happened with a QWebEngineView, which the application
gave focus to upon creation. At that time it doesn't have a focus proxy
yet. That happens later, in QWebEngineViewPrivate::widgetChanged.
https://bugs.kde.org/show_bug.cgi?id=381793
Change-Id: Ifee610bb76a2d4d2797b98ece9bffe5fffe3c6a6
Reviewed-by: Volker Hilsheimer <volker.hilsheimer@qt.io>
3e7463411e