QCompleter::setPopup() - refactor and cleanup

QCompleter::setPopup() sets window flags, focus policy, parent, focus
proxy, item delate and installs an event filter, before the popup
argument is assigned to d->popup.

In the QCompleter::eventFilter override, QObject::eventFilter is called
(under more) if d->popup is nullptr.

If a custom class is inherited from QCompleter and it overrides
QObject::eventFilter(), this causes an infinite loop.

This patch re-factors the method.
- early return is added if the new popup != d->popup
- remembering the existing widget's focus policy is constified and
  moved ahead of the delete secion.
- assignment of d->popup to popup argument is moved after the delete
  section.
- after assignment, the argument variable is no longer used.

The refactoring eliminates two issues:
- potential risk of double-installing event filter due to missing
  early return.
- inifite loop if inherited class installs another event filter.

The patch adds a test function to tst_QCompleter, which implements an
inherited class, installs an event filter on a popup and checks if a
ChildAdded event hass been recorded.

Fixes: QTBUG-111869
Pick-to: 6.5 6.2
Change-Id: I3f7a2434a11476077a5260e7686a912da9f6c60d
Reviewed-by: Richard Moe Gustavsen <richard.gustavsen@qt.io>

0 files changed, 0 insertions, 0 deletions