XPost: comp.os.linux.misc   
   From: nospam@needed.invalid   
      
   On Sat, 12/20/2025 4:23 AM, Mike Scott wrote:   
   >   
   > I've been trying to set my 3 1920x1080 monitors up to look like a 1920- plus   
   a 3840-wide screen.   
   >   
   > The recipe seems to be something like:   
   >   
   > xrandr --setmonitor xyzzy 3840/1086x1080/302+1920+0 HDMI-0,HDMI-1-2   
   >   
   > xrandr --fb 5761; xrandr --fb 5760      # see https://chi   
   senkbeil.com/notes/linux-virtual-monitors-with-xrandr/   
   >   
   > and this seems successful:   
   >   
   > xrandr --listmonitors   
   > Monitors: 2   
   >  0: xyzzy 3840/1086x1080/302+1920+0  HDMI-0 HDMI-1-2   
   >  1: +DP-1 1920/543x1080/302+0+0  DP-1   
   >   
   >   
   > However, when I run either of LO Impress or OBS Studio, neither recognizes   
   the extended monitor. Each lists two monitors (rather than three), but treats   
   both as 1920 wide. So my presentation display is scaled down. Not what I need.   
   >   
   > Can anyone advise how to do this please?   
   >   
   > Thanks.   
      
   First I'd give you a little hardware background.   
      
   This is AMD Eyefinity, as rolled out on a custom gamer desk AMD used for a   
   P.R. win.   
   (Apparently the NVidia equivalent is called NVidia Surround.)   
      
             +-----------+-----------+-----------+   
             | 1920x1080 | 1920x1080 | 1920x1080 | ---- head0 --- Crossbar   
   counter uses 5760x1080   
             +-----------+-----------+-----------+   
             +-----------+-----------+-----------+   
             | 1920x1080 | 1920x1080 | 1920x1080 | ---- head1 --- Crossbar   
   counter uses 5760x1080   
             +-----------+-----------+-----------+   
      
   This appears as two monitors where the crossbar claims a virtual monitor   
   exists which is 5760 pixels wide. One reason this works, is the three   
   monitors across are identical, and that makes configuring the thing at   
   hardware level, a lot easier to do. The crossbar count is hinted to be   
   up to 16384 counts, so you might run three identical 5K monitors as a virtual   
   panoramic monitor.   
      
   The second row of monitors could be a different set of dimensions   
   (three 2560x1600 if you wanted), but then the gamer desk would look   
   a little silly if done that way. It looks better if the 2D matrix of monitors   
   is all done with the same model of monitor (thin bezels).   
      
   The crossbar could be programmed for fewer monitors, such as   
   combining your two monitors. You could do a 2x2 monitor set, as   
   two virtual monitors. And the crossbar counter is 3840 wide if using   
   the same monitors as in the picture.   
      
   With that little intro behind us, then the question is   
      
      "Does the desktop have the ability to properly manage Eyefinity mode ?"   
      
   I don't know the answer to that. The thread here, hints that it is   
   (unnecessarily) complicated.   
      
      https://bbs.archlinux.org/viewtopic.php?id=264701   
      
      # Surround and Eyefinity aren't in here...   
      
      https://wiki.archlinux.org/title/Xrandr   
      
      # Example of shenanigans, before Window Managers starts and after X starts   
      
      ~/.xinitrc   
      ...   
      { sleep 2; xrandr xrandr_parameters } &   
      
   The question then would be, does the Xserver need to be concatenated before   
   the Windows Manager starts ? Or can displays be concatenated after the   
   Windows Manager is running ?   
      
   Matrox (a graphics card company in Canada), made adapter boxes.   
   One supports one monitor signal in, driving two surround monitors.   
   The other product could drive three monitors. The three monitor   
   one would claim to the OS to be a "5760x1080" monitor, and then   
   the video card was not doing any fancy crossbar shit. The external   
   box did it.   
      
      TripleHeadToGo   
      
      https://video.matrox.com/en/products/gxm/triplehead2go-series/dp-edition   
      
          (discontinued, replace by QuadHeadToGo)   
      
          https://video.matrox.com/en/media/1616/download   
      
      QuadHeadToGo (looks commercial rather than consumer-oriented, follow the   
   money)   
      
      https://video.matrox.com/en/products/video-walls/quadhead2go-series   
      
   That would be one way to fool a computer into doing the right thing.   
      
      Paul   
      
   --- SoupGate-Win32 v1.05   
    * Origin: you cannot sedate... all the things you hate (1:229/2)