Arch Linux (up-to-date)
Card: GeForce GTX 970M
Not sure if this is the right place to post Linux Driver bugs.
If I configure my displays to have a border (aka underscan), the screen size obtained via xcb_randr_monitor_info_* calls (RandR 1.5) are wrong. They appear to report the entire screen rather than the part that is being used. This does not affect the old CRTC info structs, which report only the region used.
See this GitHub issue for complete back story: https://github.com/i3/i3/issues/3708