Initially the function was used as a helper function for QWidget,
implemented in da55a1b041. But with
e0bb9e81ab we started overriding it
e.g. QDialog. This "worked" because QDialog itself would call the
private helper, but left a footgun when called via a plain QWidget
pointer, as we did in 5ba0982b28.
That specific instance of the problem was solved by the change in
fc4c6fb5f6bd6bd63b13f1f8b5b7a7289a5fd230, but the trap still exists.
To ensure we can use the function in a polymorphic context in the
future we make it virtual.
Task-number: QTBUG-127806
Change-Id: Ic0810c5439b1e696cfbf199e701f41217acc5742
Reviewed-by: Volker Hilsheimer <volker.hilsheimer@qt.io>
(cherry picked from commit 1a0f056f318417ba5e54c8110257b75cf5537acb)
Reviewed-by: Qt Cherry-pick Bot <cherrypick_bot@qt-project.org>
79be5fa986