Put multiple monitors together virtually to create one big screen on wayland

Hello guys,

I recently just got two projectors (1200x800) of the exact same model and i’d love to combine them to create one big ultrawide (2400x800) screen in software using KDE (wayland) on linux. There are two ways i’ve considered two different options.

  1. Somehow create a way to add a ‘monitor group’ with both projectors in them. Present this to applications as a single screen.
  2. Create a virtual screen at 2400x800 and overlay the screen on top of both of the projectors in system settings. For this, I’d love to know how the kde portal creates virtual screens so i can define a custom resolution.

Could someone point me on how to do this? Or relevant documentation.

I think that option (2) is the only one that makes sense. In X11 days, you could create a manually configured Xinerama configuration that defined a screen as two physical devices - but I believe this configuration has already become obsolete from before Wayland became a thing.

On Wayland, the KDE “virtual screen” that you get when screen casting applications ask for remote desktop sharing from the KDE portal, is implemented - AFAIK - using the non-standard zkde_screencast_unstable_v1 protocol and specifically its stream_virtual_output call.

I don’t think there’s a way to trigger that manually using a GUI or CLI tool - you need to write something that talks the Wayland protocol on the Wayland socket (which, at its simplest, requires C++ and libkf5waylandclient5), and possibly be privileged for that to work.

Theoretically (I haven’t tried) you can start a screen casting application (Google Meet with yourself, OBS, whatever) and have that request a virtual output, then use the Display Configuration KCM to arrange the virtual output where you want it - and then tell application to use that as the screen.