Comment 2 for bug 1337904

I've enabled a setting for Qt's renderer which appears to improve animations like this scrolling (I enabled support for buffer queuing, which means Qt can assume that each frame is displayed a fixed time after the previous - something Mir pretty much guarantees - so it can use fixed animation steps, and has less calculations to perform).

I had this accidentally turned off. The old unity8 arch was enabling the same optimization with QSG_FIXED_ANIMATION_STEP=1), so we know it works.

It hasn't landed in the silo yet. I'll update this bug when it has