Splitting Ultrawide monitor to two virtual displays.

odror · 2025-05-10 19:46:59

Hi

I have an ultrawide monitor 32x9 and a regular 16x9 monitor. I would like to Split the Ultrawide monitor to 2 virtual monitors recognized by X11 as 2 separade monitors for two reasons.

1. When expanding an app in gnome to a "fullscreen" on the Ultrawide monitor I would like it to be only on half the monitor not on the entire monitor.
2. I have a background slide show. I like it to split in to two and not magnify on the ultrawide monitor.

Apparently this can be done with the xrandr --setmode, but not when there are more than 1 physical monitor as in my situation.

My temporary solution is to supply 2 outputs to the ultrawide monitor. By doing that I am loosing most of the monitor setting, for example the HDR and other display settings.

seth · 2025-05-10 21:10:01

https://www.baeldung.com/linux/xrandr-s … ual-screen
But brace yourself: https://www.reddit.com/r/xfce/comments/ … s_created/
Not all clients support randr 1.5 - but if cinnamon/muffin does, there's actually a good chance gnome/mutter does, too.

odror · 2025-05-10 21:47:52

I have done the following:

xrandr --setmonitor  HD-2 3840/770x2160/385+7680+0 none
xrandr --setmonitor  HD-1 3840/770x2160/385+3840+0 HDMI-0
xrandr --fb 11540x2160

Checking that it was done

> xrandr --listactivemonitors
Monitors: 3
 0: HD-2 3840/770x2160/385+7680+0 
 1: HD-1 3840/770x2160/385+3840+0  HDMI-0
 2: +HDMI-1 3840/697x2160/392+0+0  HDMI-1

The screen flushed after the xrandr --fb 11540x2160 command but there was not split. arandr did not show any split and when trying auto-expansion of an app to a full screen, it fills the entire monitor.

seth · 2025-05-10 21:56:59

https://gitlab.gnome.org/GNOME/mutter/-/issues/1406
https://gitlab.gnome.org/GNOME/mutter/-/issues/1507

Seems mutter doesn't support randr 1.5

zukote1991 · 2025-05-12 11:56:36

I've run into a similar setup with a 49" ultrawide and a secondary 16:9 display. One approach that worked reasonably well for me was using xrandr in combination with a dummy display configuration via xorg.conf to simulate two virtual outputs on the same physical monitor. It's definitely tricky when more than one physical monitor is involved though — GNOME doesn’t always play nice with it. You might also want to look into using i3 or another tiling WM temporarily just to see if it gives you the split behavior you're looking for, without the need to spoof displays.

seth · 2025-05-12 13:16:25

GNOME doesn’t always play nice with it.

Mind to elaborate? Afaiu gnome's randr 1.5 support is non-existent, ie. logical (sub) monitors are completely ignored?

Arch Linux

#1 2025-05-10 19:46:59

Splitting Ultrawide monitor to two virtual displays.

#2 2025-05-10 21:10:01

Re: Splitting Ultrawide monitor to two virtual displays.

#3 2025-05-10 21:47:52

Re: Splitting Ultrawide monitor to two virtual displays.

#4 2025-05-10 21:56:59

Re: Splitting Ultrawide monitor to two virtual displays.

#5 2025-05-12 11:56:36

Re: Splitting Ultrawide monitor to two virtual displays.

#6 2025-05-12 13:16:25

Re: Splitting Ultrawide monitor to two virtual displays.

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