Who is setting the Xresource Xft.dpi?

We recently received new laptops with a 2160p display. I received it with Ubuntu 16.04 installed with the Unity desktop. I've since installed and use Xfce 4, but kept the Unity greeter (because pretty). I fully expected to see font scaling issues with the high-DPI display, but something has set the Xresource Xft.dpi to 192, rather than the typical 96. This is picked up by nearly all applications, making the internal display mostly usable. 10 out of 10, right? Well, no, because I can't figure out where this is being set. Xfce's appearance panel claims the DPI is 96. dconf variables where they exist also show 96. xdpyinfo also says it's 96. Xorg.0.log has one message regarding DPI, and says it's 96. lightdm.conf (configuration file for the Unity greeter) shows no attempt to change it. And xrandr is reporting an identity transformation matrix (no scaling). My suspicion is that either GNOME or the Unity greeter are the culprit, since the greeter starts out rendered in Flyspeck 3, but then rescales itself after a moment. But I can't figure out where it was told to do this, or how it persists to the desktop session. My goal is to plug in an external 1080p display and tweak the DPI such that both displays are vaguely legible. But I can't effectively do that if I'm fighting with something else trying to do it behind my back. All clues welcome. ### System Info ### - Ubuntu 16.04.3 - unity 7.4.0+16.04.20160906-0ubuntu1 - xorg 1:7.7+13ubuntu3 - xfce 4.12.2