P2715Q, desktop reset when switching input

I just got issued a P2715Q at work. I am connecting it to both an iMac 5K via DisplayPort and a Windows 10 PC via mini DisplayPort. Whenever I switch the input on the monitor from one to the other, the computer that's switched away has its desktop reset to single display and all the windows and desktop icons get rearranged. It's beyond annoying. How can I keep this from happening? The Lenovo 24 inch monitor it replaced didn't have this issue.