I recently switched to a laptop with a 16:10 QHD display (popularized as Retina by a certain shoddy company), and I faced a problem that I had been fearing for a while – scaling on X11/Openbox. Specifically, I really didn’t want to switch to anything Wayland, GNOME and/or KDE related – not because I have anything against them, but because I’m too old and don’t want to. I have been using Openbox (and some version of the same configuration files) for 10+ years, longer than my current Linux distribution, so you can say that there is some attachment involved.
Searching online does not yield any helpful guides or tips, and while there is a detailed article on HiDPI displays on the Arch Wiki, it doesn’t go into any detail on the less popular window managers out there. There is, in fact, a singular grain of gold, but it is well hidden under a section cryptically titled “X Resources”:
If you are not using a desktop environment such as KDE, Xfce, or other that manipulates the X settings for you, you can set the desired DPI setting manually via the Xft.dpi variable in Xresources:
After about half an hour of messing around with fonts for individual applications, it turned out that this was the only setting that had to be changed. Of course, there will always be that app that does not care about your system-wide configuration (looking at you, tint2), but 95% of the work was handled by that change.