How to properly scale i3 on HiDPI displays

So I nuked my laptop last week and re-installed Arch (no Windows in this house anymore). I need to post a lot of cool new things I learned, but here's another scaling tip for everyone.

The old way I was doing scaling was a little broken. I had a hodgepodge of scaling soltuons for each different app. This turned out to be a nightmare, surprising nobody.

My new way is a simple .Xdefaults file, containting one (1) line:

    Xft.dpi: 168

That's literally it. Now, all of my fonts are back to normal-ish values (Terminal font is now 12 instead of 30), Thunar no longer is impossible to see, Firefox scaling works as expected, and I expect that WINE applications and other apps with suboptimal application scaling (looking at you, FreeCAD) will be much easier to see.