Store QGraphicsItems that are either not added to a scene or
removed from it again and that are also not children of other
items - iow: those that were leaked, even on successful runs
of the tests, in either a QScopedPointer, or, where that'd
cause too much churn due to adding of .data() calls, back the
pointer by a stack-allocated object.
This fixes the remaining leaks reported by GCC 6.2.1's ASan on
successful runs of tests/auto/widgets/graphicsview/qgraphicsitem.
Change-Id: I61c3a1cd39b9e96e83c5d7b8cf392e0b26ecbaf0
Reviewed-by: Edward Welbourne <edward.welbourne@qt.io>
Reviewed-by: Sérgio Martins <sergio.martins@kdab.com>