QWidgetPrivate::focusObject() always returns nullptr. That has lead to
mismatches between QGuiApplication::focusObject() and
QApplication::focusWidget(), when a widget got focus by the window
system (e.g. mouse click).
This patch implements QWidgetPrivate::focusObject.
It returns the current widget, if it doesn't have a focus proxy.
If it has a focus proxy, it resolves the proxy chain and returns the
deepest focus proxy.
(Note: It does not return QWidget::focusWidget(), because the focus
widget might not yet have been set, when the method is called).
Fixes: QTBUG-92464
Fixes: QTBUG-108522
Pick-to: 6.6 6.5 6.2
Done-With: Liang Qi <liang.qi@qt.io>
Change-Id: Icf01e8ac4fc5f722fbf8e0ca5a562617ae9ae8f2
Reviewed-by: Volker Hilsheimer <volker.hilsheimer@qt.io>
Reviewed-by: Tor Arne Vestbø <tor.arne.vestbo@qt.io>
Reviewed-by: Liang Qi <liang.qi@qt.io>
f83ea89622