Fix crash in QMacPanGestureRecognizer

The reason it crashed was this:
1. Button was pressed => _panTimer started with the graphics view as
   destination.
2. Button was released => the graphicsview is destroyed
3. 300 ms later: Qt tries to deliver TimerEvent from _panTimer to the
   graphics view. Unfortunately, the graphics view is deleted, but Qt
   doesn't know that... (*crash*)

We therefore chose to start the timer with a destination we are controlling the
lifetime of: the QMacPanGestureRecognizer. Inside the timerEvent of that we can
check if the actual target is already destroyed.

Task-number: QTBUG-60404
Change-Id: Iff8f5b7217de42c4c5cf551ca507f0cff1c99a78
Reviewed-by: Frederik Gladhorn <frederik.gladhorn@qt.io>

0 files changed, 0 insertions, 0 deletions