It's 2020, we can make rockets land on self-driven barges, and somehow we're still forced to use xrandr manually...? This is the sort of thing that keeps me from going back to the Linux desktop.

You don't have to. Ubuntu 20.04 and Gnome desktop provide a fine hidpi experience. There are a few warts, but it all generally works. If you start dabbling with other desktop environments like xmonad or i3, it gets tricky.

I can never get it to work properly with multiple displays. I have a 4k monitor and two 1080p monitors. Using 192dpi with 2x scale (param passing to xrandr), all kind of display errors popup (wrong color, weird fonts etc).

Yeah, I wanted to configure hidpi on linux recently, when I had to work on FHD 14" screen without external monitor for a while. I found no config options in UI, and guides involving xrandr and fifteen different steps on the internet. I thought hell no and abandoned that idea altogether, cranked font size in the terminal and worked like that. And I actually "can" work in Linux and configure easier stuff. As far as I'm concerned at least some distros/DEs have non-existent hidpi support right now.

My configuration panel only has 2 options for scaling: 100% or 200%. Needless to say neither option is very helpful.

If in Gnome, fractional scaling is possible but not enabled by default. I use 125% and it has been fine. I did it via Gnome-tweak, or you can manually enable it [1].

[1] https://www.linuxuprising.com/2019/04/how-to-enable-hidpi-fr...

There should be a slightly hidden custom option if you're using windows. (Not in the drop-down)

You'll have to relog for the scaling to take effect with custom numbers for some reason

You can only do integer scales though this way, can’t you?

As for me: I haven't figured it out yet, sometimes a fractional scale works, sometimes you get vague errors. In any case what I have noticed is that quality drops significantly if you use fractionals.

For my set-up at home (1080 - 4k - 1080) I have a simple script, that really was more of a `write once - use always`-experience. E.g.

    xrandr --output HDMI1 --auto --scale 2x2 --pos 0x0+0+0
    xrandr --output eDP1 --auto --scale 2x2 --pos 7680x0+0+0
    xrandr --output DP1 --auto --mode 3840x2160 --scale 1x1 --pos 3840x0+0+0 --primary

So basically what I do is, I virtually up-scale my other screens up to 4k, such that system-wide zoom settings are (more or less) consistent and enjoyable.

No, with `xrandr` you can scale to any fractional amount. For example, I had 2 24" external monitors (full-hd, not 4k), and a 13" thinkpad (chromebook, booted into linux). Obviously, the respective DPI's were way off.

Just a quick calculation in a repl, then called xrandr with the right scaling number, and presto, I had them exactly the same.

Then, with precise lining up of the displays, it was basically one seamless "sheet of paper". If I had a long web page or pdf spanning the displays (the laptop was directly under the monitors), then scrolling through it was quite "trippy".

I think because this was now a unified display where the bottom 1/3 was tilted differently to the top 2/3'rds (think of a curved ultrawide, but in portrait mode)

Honestly, it really was that simple.

If you want fractional scaling I’d suggest you look into wayland.

How do you use xrandr in Wayland?

You don't want to. Wayland-based GTK and Qt should to do per device DPI. XRandR cannot.