Allow to set background FPS like we had with beta's MainLoop

vvvv gamma feature
7

@bjoern
Thanks for the snippet!

But how to “ensure” a framerate without a perf drop even when vvvv is in the background?
It seems your patch is typically to cool framerate down when vvvv doesn’t have focus (can be useful too), but what if I want a steady framerate without drop when I lose focus?

UE has a “Use Less CPU when in Background” setting to uncheck for this, I’m basically trying to hack something similar in Gamma.