Similar to MC-77633, when Minecraft is running and I switch to another desktop, its CPU usage leaps up. For example, with Minecraft running in the foreground it uses ~60% CPU. When I switch to another desktop, it jumps to 100% CPU, the CPU core temperature rises and the fans come on full blast.

I have Minecraft on what I believe are the default settings: max frame rate 120fps and vsync: on. If I reduce the max frame rate to 60fps, I don't see an increase in CPU usage when I switch to another desktop. I suspect that when Minecraft is on a non-foreground desktop, vsync no longer has any effect, so Minecraft suddenly starts using 100% CPU to try to render as fast as possible.

Ideally, Minecraft would not render at all while on a non-foreground desktop (perhaps not possible, since OSX can still show a realtime preview of other desktops), failing that it would render at a low framerate, and failing that when vsync is enabled it would not render above the vsync rate when on a non-foreground desktop.