QPinchGesture::scaleFactor is relative to the previous zoom factor,
so either we need to multiply the total zoom by scaleFactor,
or set it based on totalScaleFactor, which is simpler. Pinch-zoom is
now working in this example.
There's also no reason to use getProperty() when the accessors are
directly accessible in QPinchGesture.
Task-number: QTBUG-6010
Change-Id: I150dc0b18b4b871a08ec55c0f77463509ab26afe
Reviewed-by: Friedemann Kleint <Friedemann.Kleint@theqtcompany.com>