Radeon Open Source Drivers

[GlacialTurtle]

I could be wrong here, but it could be related to SDL 2. SDL 2 seems like it avoids messing with the actual monitor settings in general on Linux. so e.g. it doesn't actually change your desktop resolution when in games fullscreen, it just creates a fullscreen window and limits the internal rendering resolution (I think). I've noticed other SDL 2 games with broken gamma/brightness controls, so it might be related to that - SDL 2 avoiding changing anything about the monitor settings in Linux (outside of NVIDIA it would seem here).

Maybe look into xrandr? http://www.x.org/wiki/Projects/XRandR/

Also of note that fullscreen borderless doesn't appear on top of the desktop (with Catalyst), unity/compiz still appear on top. Will test it in GNOME under Arch and see if it's any different.