This follows up on commits 3e7463411e and
947883141d.
The changing of the pointer of QApplicationPrivate does not transfer
focus properly. It updates the pointer, but it doesn't deliver events
or update the widget hierarchy's focus chain. The result is that
multiple line edits might show a blinking cursor.
Instead, use QWidget::setFocus when the focus proxy has changed while
it had focus, and pass OtherFocusReason rather than NoFocusReason.
Add a basic test for QWidget::focusProxy, which exercises this code
path and verifies that pointers are consistent when focus changes as
a side effect of modifying the focusProxy.
Change-Id: I15a4d868bab2b590cfe4a1daa6a3c8cebc9c9ca2
Fixes: QTBUG-83720
Fixes: QTBUG-79707
Pick-to: 5.15
Reviewed-by: David Faure <david.faure@kdab.com>
23b998fa45