Display connected via DisplayPort disconnects, reconnects when resuming, resizing windows on display
This appears to be an issue with OSX &amp; Windows. HDMI devices are able to be queried by the connected computer to check display resolutions even when powered off, so this is a non-issue. DisplayPort devices seem to not have this feature. When Windows &amp; OSX wakes up from a sleep state, it checks to see if the monitor is still connected but finds the DP monitor to be in powersaving mode and cannot determine if your 2560 x 1080 desktop is still there and so resizes everything down.

Windows users appear to have a bassackwards solution:


Connect monitor via DisplayPort and HDMI/DVI
Configure Windows to mirror desktop on the 2 displays.