IconGrid: Defer and group animation cleanup
reactive property of icon actors was being restored 24 times over
the course of the spring animation, all at slightly different times as
each icon finished animating at different times.
The problem is that toggling
reactive on an
StWidget incurs a style
change of the
insensitive pseudo class, and style changes would quickly
queue relayouts incurring full stage reallocation. This occurred many times
during a spring animation hogging the CPU and limiting the frame rate.
The solution is defer and batch the cleanup for all icons until after the last icon has finished animating. This way the CPU impact of the style change and stage relayout isn't felt during the animation so the frame rate remains higher and smoother. The overall CPU usage of the animation is also reduced as the remaining relayouts are much more likely to be grouped into a single frame.
Icon spring animation performance on an i7-7700:
Before: 83% CPU and 47 FPS
After : 78% CPU and 54 FPS
which is about a 22% increase in performance per clock (FPS/CPU).