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I am running i3 window manager on Arch Linux, and am trying to use xrandr to use both my laptop screen and desktop monitor together. I intend the screens to have separate workspaces but to be able to move workspaces between monitors as needed. The laptop screen is 4K (3840x2160) but the monitor is only 1920x1080. From research on i3 with multiple monitors, and people with my same situation, I put together the following xrandr command:

$ xrandr --output eDP-1 --mode 3840x2160 --pos 0x0 --auto \\
--output HDMI-1-0 --mode 1920x1080 --pos 3840x0 --auto \\
--panning 3840x2610+3840+0 --scale 2.0x2.0 --fb 7680x2160

Upon running this command, the laptop monitor works as normal (running at 4k with full coverage) but the desktop monitor only display my background image (through feh) and i3 windows on the top left portion (which appears to be a 1920x1080 chunk of the scaled screen). The other three quarters of the display are black. However, I am able to move my cursor between the two displays without issue. The cursor transitions seamlessly between screens and even displays over the black portion of the desktop monitor (on which i3 windows do not show).

Is my xrandr command not doing what I intend, or is there some kind of external factor (maybe I have conflicting DPI settings) which is causing this?

Edit:

In case it is relevant, the laptop is running a newer NVIDIA graphics card (RTX 2070) along with Intel integrated graphics. I have the packages nvidia and nvidia-utils installed as graphical drivers and OpenGL support respectively.

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  • 2
    Does this answer your question? Multiple monitors HiDPI scaling
    – prosoitos
    Dec 11, 2020 at 16:36
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    See my answer for this exact situation.
    – prosoitos
    Dec 11, 2020 at 17:04
  • @prosoitos Thank you for your solution. I don't have access to my monitor at the moment to try it out, but I'll tell you if it works when I do.
    – Max Christman
    Jun 20, 2021 at 19:03

2 Answers 2

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On latest installations you might fix this problem by using Wayland instead of X11 (it has support embedded for changing scaling per monitor).

On X11 you might be able to pull it off with xrandr scaling magic.

xrandr --output eDP-1 --auto --output DP-1 --auto --scale 2x2 --right-of eDP-1

or for multiple display monitors

xrandr --output eDP1 --scale 0.5x0.5 --output DP2 --right-of eDP1 --output HDMI1 --right-of DP2

(ref https://wiki.archlinux.org/title/HiDPI#Multiple_displays ).

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  • Please add the details from the link, in the probable case of link rot.
    – Greenonline
    Sep 9, 2021 at 16:14
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I've put in an article here with the visual explaination and hopefully a helpful bash script that you can parameterize:

https://ptgamr.notion.site/xrand-4k-mixed-monitors-7a026e5345994267aebfa01a32044a2f

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