[macOS] Retina display, fullscreen for desktop and amd fidelityfx

[galad87]

On macOS and a Retina display, if fullscreen mode is set to fullscreen for desktop, it's not possible to enable amd fidelityfx because the maximum selectable resolution is 1920 x 1080 on a 4k screen. I can't use the exclusive fullscreen because it changes the resolution to 4k non retina, and by doing so it changes the mouse speed.