Compositing is done by the OS though (WindowServer in case of mac). Ever since OSX stopped allowing direct framebuffer access I think the only way to read (e.g.

Compositing is done by the OS though (WindowServer in case of mac). Ever since OSX stopped allowing direct framebuffer access I think the only way to read (e.g. for screenshots) windows of other processes' is by asking WindowServer to do it for you, so I'm guessing that's how this protection is implemented. WindowServer ultimately still needs to get access to the framebuffer somehow though, so there must be some private API somewhere to bridge kernel and userspace part. I suspect if you could bypass SIP or just write a kext to access video memory directly then it'd be possible to defeat this protection.