HiDPI problem with Gnome or Xwayland

[Zan Lynx]

I have a 4K display machine running Fedora 22. When I run a Wayland
session it seems to me that applications which use X in some way get
confused about the pixel size. The window manager (gnome-shell) will
halve the size of the window whenever the window becomes active.
Alt-tabbing can get pretty amusing.

I'm not entirely sure whose software is doing it. If you're working on
Wayland and read this, and have a 4K display maybe you'll try it out and
see if it works for you.

Gnome Terminal is one of the apps that does it.