Different font sizes for different windows

A disclaimer, I am a new Atom user, but a long time Emacs user trying to migrate. One thing I haven’t figured out how to do is set a different font size for each window. I am running on Linux, and certain X drivers (notably the nVidia one) don’t properly handle different screens with different DPIs. It doesn’t even set the DPI hint properly. The way I have worked around this is just by scaling up the font size on a window on the high DPI screen.
This is easy on Emacs, because I can set per-frame or per-buffer properties. But the CSS in Atom seems to be global. Even when I hit ctrl-+, it scales up all of my windows.
Is there something I’m missing on how to do this?