I am not sure if this is a bug or works as intended, but found it odd that on a low-end embedded ARM hardware running on eglfs platform the CPU usage hikes up to 40% when running NumberAnimation at 60fps, even when nothing is animated or needs to be redrawn on the screen. From QML profiler you can see scene graph starts spewing out frames. The CPU usage drops to 1-2% if vsync is disabled by modifying QSurfaceFormat swap interval.

This also means that using FrameAnimation to play idle screen animations on lower refresh rate to limit CPU usage is not really possible (though yeah you can use Timer instead).