Setup: Ubuntu, Openbox, notebook, occasionally an external screen.

I’ve set things up so that if an external monitor is attached when I start my notebook, a script (run by Openbox’s autostart), xrandr makes that the primary monitor.

What I’d like to do is run that script when I turn off or otherwise disconnect that external monitor, so that I can make the notebook’s built-in screen the primary again. Does anyone here have any ideas how to do that automatically?

  • Helix 🧬@feddit.de
    2·
    3 years ago

    there’s a file called status in cat /sys/class/drm/card0-CONNECTION where CONNECTION is the name xrandr --listmonitors shows on the right. So e.g. for me it looks like this:

    $ xrandr --listmonitors
Monitors: 2
 0: +*DP-3 2560/553x1440/311+0+430  DP-3
 1: +DP-5 1440/553x2560/311+2560+0  DP-5

$ cat /sys/class/drm/card0-DP-3/status 
connected

    You can watch this file with inotifywatch -e modify. You can put this in a systemd.path unit which calls your script as a one-shot or with an environment parameter.

    You can also use srandrd but IMHO that’s a bit overkill when you can do it with pid0 tools 😅

    • N0b3dOP
      1·
      3 years ago

      Hmm. Maybe I’m doing something wrong but doing

      inotifywatch -e modify /sys/class/drm/card0-HDMI-A-2/status

      only gives me “No events occurred.” (after ctrl-c stops it). Oddly, I can see the file contents change (connected to disconnected and back again) if I cat it in a separate term window so I don’t know what’s going on.

      • Helix 🧬@feddit.de
        1·
        3 years ago

        hm, maybe you need another event type. What GPU is it?

        Events:
        access          file or directory contents were read
        modify          file or directory contents were written
        attrib          file or directory attributes changed
        close_write     file or directory closed, after being opened in
                        writeable mode
        close_nowrite   file or directory closed, after being opened in
                        read-only mode
        close           file or directory closed, regardless of read/write mode
        open            file or directory opened
        moved_to        file or directory moved to watched directory
        moved_from      file or directory moved from watched directory
        move            file or directory moved to or from watched directory
        move_self               A watched file or directory was moved.
        create          file or directory created within watched directory
        delete          file or directory deleted within watched directory
        delete_self     file or directory was deleted
        unmount         file system containing file or directory unmounted

        May be create or delete