Ubuntu 18.04, separate X-screens

1
Dear Mario and list,

sorry, slightly off-topic: We are testing Ubuntu 18.04 for our stimulation PC. So far we have used Xfce/Xubuntu but as the default desktop changed to Gnome in 18.04 we actually would prefer using regular Ubuntu (on Xorg).

We have two monitors configured as separate X-screens. PTB can open its window on the second screen without any problems. However, I do not succeed making the second screen available for the desktop environment. The screen remains completely black. The only thing I can do is moving the mouse to the screen (x-shaped without any functionality). We would like to show at least a wallpaper or have a colored desktop to be sure at first glance and without extensive testing that the second monitor is switched on and configured correctly.

xrandr finds the second screen when used with -d :0.1. Card is Nvidia with open-source Nouveau driver.

We would appreciate any hint how to configure the second screen. Thank you!
Andreas
2
<widmann@...> wrote :

Dear Mario and list,

sorry, slightly off-topic: We are testing Ubuntu 18.04 for our stimulation PC. So far we have used Xfce/Xubuntu but as the default desktop changed to Gnome in 18.04 we actually would prefer using regular Ubuntu (on Xorg).

We have two monitors configured as separate X-screens. PTB can open its window on the second screen without any problems. However, I do not succeed making the second screen available for the desktop environment. The screen remains completely black. The only thing I can do is moving the mouse to the screen (x-shaped without any functionality). We would like to show at least a wallpaper or have a colored desktop to be sure at first glance and without extensive testing that the second monitor is switched on and configured correctly.

xrandr finds the second screen when used with -d :0.1. Card is Nvidia with open-source Nouveau driver.

We would appreciate any hint how to configure the second screen. Thank you!
Andreas

-> Different X-Screens are logically almost completely separate from the pov of the OS. They only share the mouse-cursor and its general location - and some global layout to allow meaningful movement of the cursor from one screen to the other.

-> You can use the -display :0.x switch or DISPLAY=:0.x applicationname with x being the x-screen number to start a specific app on X-Screen 1. E.g., DISPLAY=:0.1 myfavoriteimageviewer to start an image viewer on screen 1. That would be one way to get some wallpaper there.

-> The current desktop GUI's seem to be often not set up to display anything on secondary X-Screens, not even a wallpaper. How to set them up to manage other X-Screens than 0 is dependent on the desktop GUI and OS. Ubuntu 18.04 LTS, like many other recent distros, has switched to a different login manager, way to manage the GUI's, and to systemd as the service manager to control such things. I'm not yet that experienced with the new way of things myself - it's not yet part of my "muscle memory" what is where. But something that might work - untested so far.

The folder ~/.config/autostart-scripts/
allows to store scripts to be executed at login, so you could add something there to launch applications, e.g., maybe "gnome-shell --screen 1" to start a 2nd separate instance of the UI on screen 1.

Or for keeping X-Screen 1 free from resource intense graphics applications or UI's, a "xeyes -display :0.1"  for a cute way to indicate if the monitor is on, without using much graphics resources on the stimulation display? Or instead "xsetroot -display :0.1 ...." with proper options for a more boring status indicator like a grey background, or background image?

-mario


3
Dear Mario,

> E.g., DISPLAY=:0.1 myfavoriteimageviewer to start an image viewer on
> screen 1. That would be one way to get some wallpaper there.
Perfect, thank you! A "display -display :0.1 -window root
wallpaper.png" in autostart-scripts shows a wallpaper on the separate
X-screen. This was what I was searching for (ok, better integration in
the desktop environment as in Xfce would be even better but we can
well live with this solution for now :).

Thank you! Best,
Andreas

Zitat von "mario.kleiner@... [PSYCHTOOLBOX]"
<PSYCHTOOLBOX@yahoogroups.com>:

> <widmann@...> wrote :
>
> Dear Mario and list,
>
> sorry, slightly off-topic: We are testing Ubuntu 18.04 for our
> stimulation PC. So far we have used Xfce/Xubuntu but as the default
> desktop changed to Gnome in 18.04 we actually would prefer using
> regular Ubuntu (on Xorg).
>
> We have two monitors configured as separate X-screens. PTB can open
> its window on the second screen without any problems. However, I do
> not succeed making the second screen available for the desktop
> environment. The screen remains completely black. The only thing I
> can do is moving the mouse to the screen (x-shaped without any
> functionality). We would like to show at least a wallpaper or have a
> colored desktop to be sure at first glance and without extensive
> testing that the second monitor is switched on and configured
> correctly.
>
> xrandr finds the second screen when used with -d :0.1. Card is
> Nvidia with open-source Nouveau driver.
>
> We would appreciate any hint how to configure the second screen. Thank you!
> Andreas
>
>
> -> Different X-Screens are logically almost completely separate
> from the pov of the OS. They only share the mouse-cursor and its
> general location - and some global layout to allow meaningful
> movement of the cursor from one screen to the other.
>
>
> -> You can use the -display :0.x switch or DISPLAY=:0.x
> applicationname with x being the x-screen number to start a specific
> app on X-Screen 1. E.g., DISPLAY=:0.1 myfavoriteimageviewer to start
> an image viewer on screen 1. That would be one way to get some
> wallpaper there.
>
>
> -> The current desktop GUI's seem to be often not set up to display
> anything on secondary X-Screens, not even a wallpaper. How to set
> them up to manage other X-Screens than 0 is dependent on the desktop
> GUI and OS. Ubuntu 18.04 LTS, like many other recent distros, has
> switched to a different login manager, way to manage the GUI's, and
> to systemd as the service manager to control such things. I'm not
> yet that experienced with the new way of things myself - it's not
> yet part of my "muscle memory" what is where. But something that
> might work - untested so far.
>
>
>
>
> The folder ~/.config/autostart-scripts/
> allows to store scripts to be executed at login, so you could add
> something there to launch applications, e.g., maybe "gnome-shell
> --screen 1" to start a 2nd separate instance of the UI on screen 1.
>
>
> Or for keeping X-Screen 1 free from resource intense graphics
> applications or UI's, a "xeyes -display :0.1" for a cute way to
> indicate if the monitor is on, without using much graphics resources
> on the stimulation display? Or instead "xsetroot -display :0.1 ...."
> with proper options for a more boring status indicator like a grey
> background, or background image?
>
>
>
> -mario