Multihead HiDPI

lumeno · 2017-10-03 14:57:52

I'm having a hard time finding a solution for a set-up that I would think is very common, and I'm surprised there isn't a simple solution out there already.

I'm running Arch Linux with i3 on my laptop. It has a 1366x768 screen.

Sometimes I bring it to work and dock it at desk and connect a 4k monitor to it. It has a resolution of 3840x2160.

Ideally, I'd like to use both screens. By default, xrandr will set things up so that the dpi is the same and things on the 4k screen look too small.

Most of the proposed solutions out there are application-specific. For example, if I set --dpi in xrandr globally, it only helps with the i3 panel. Chromium and terminator still appear with small text and icons.

Is there a way to set the dpi individually on each screen in such a way that all applications respect it? Gnome 3 seems to do it out of the box. But I don't want to switch from i3 to Gnome just for this.

Last edited by lumeno (2017-10-03 14:58:23)

V1del · 2017-10-03 16:16:24

Afaik you can't set individual dpi, this is one of the things Wayland fixes. I'd be interested if someone knows more here.

seth · 2017-10-03 17:05:59

X11/Xorg supports only one logical DPI.
Regardless of that, clients can oc. make use of xrandr to calculate the physical DPI of each output (and offer precedence to the logical one and whatnot)
The major limitation of X11 compared to wayland is actually not the DPI but input redirection.
A compositor *could* in theory scale windows according to the positional physical DPI, but that has no impact on the dimensions of the actual window - which receives input directly.
IOW, eg. gnome on xorg could *look* just like gnome on wayland, but you'd always misclick things because they're not where they appear to be.

seiichiro0185 · 2017-10-04 10:56:09

Did you try to use the --scale option in xrandr? It should be able change the "zoom-factor" for a specific output/screen and work with all applications. I have used it to downscale an external screen so a HiDPI Laptop setup wouldn't look overly big on the external FullHD screen. It should also work the other way round to my understanding.

seth · 2017-10-04 12:21:25

If possible, it's actually better to use one of the announced lower resolutions of the output (eg. 1920x1080), but either way will kill the 4k aspect of the monitor...

Arch Linux

#1 2017-10-03 14:57:52

Multihead HiDPI

#2 2017-10-03 16:16:24

Re: Multihead HiDPI

#3 2017-10-03 17:05:59

Re: Multihead HiDPI

#4 2017-10-04 10:56:09

Re: Multihead HiDPI

#5 2017-10-04 12:21:25

Re: Multihead HiDPI

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