This reverts commit bf2ec0183c.
That patch changed the way the linear index works in QGraphicsScene
in order to speed up item removal. That patch occasionally rebuilt
the index by recursively exploring all items in the scene, starting
with the top level. Further testing revealved that in some
circumstances, rebuilding the index in this way can be slow, thereby
significantly slowing down the index compared to the unpatched
version.
The original patch only exists in the qt 5.4 branch and has not been
released.
Change-Id: I081dbcdcc86196ef382466c3e800a33eab9a5b79
Reviewed-by: Andreas Aardal Hanssen <andreas@hanssen.name>
ed418f91d5