ephyr -ac :1 -screen 1024x768

export DISPLAY=:1
openbox & firefox

root@web-browser:/# openbox & firefox
[1] 192
Openbox-Message: Failed to open the display from the DISPLAY environment variable.
Failed to connect to Mir: Failed to connect to server socket: No such file or directory
Unable to init server: Could not connect: Connection refused
Error: cannot open display: :1
[1]+  Exit 1                  openbox

#! /bin/sh

set -e

if ! hash gresource 2>/dev/null; then
  echo "gresource binary not found. "
  echo " "
  echo "Please install glib2 or glib2-devel"
  echo " "
  echo "Fedora:"
  echo "# dnf install glib2-devel"
  exit 1
fi

if [ "$#" -eq "0" ]; then
  echo 'Usage:'
  echo '  set-gdm-wallpaper [FLAG] /path/to/image    Set login screen wallpaper'
  echo '    Flags:'
  echo '      --css 'css data'                       Replace css params inside #lockDialogGroup block. Ex: background-size: 1920px 1080px;'
  echo '      --resize 0..6 (default: 2)             Use built-in css template for image resize and alignment. Try this option for fix multi monitor issue. Use 0 for disable resize.'
  echo '        0 - background-repeat: repeat;'
  echo '        1 - background-repeat: no-repeat;'
  echo '        2 - background-repeat: no-repeat;background-size: cover;'
  echo '        3 - background-size: 1920px 1080px;'
  echo '        4 - background-size: 1920px 1080px;background-repeat: repeat;'
  echo '        5 - background-position: 0 0;background-size: 1920px 1080px;background-repeat: repeat;'
  echo '        6 - background-repeat: no-repeat;background-size: cover;background-position: center;'
  echo '  set-gdm-wallpaper --uninstall              Remove changes and set original wallpaper (original gresource file)'
  exit 1
fi

if [ "$1" = "--uninstall" ]; then
  # Restore file if current gresource file is modified by this script.
  # If wallpaper-gdm.png text inside gresource file, then this is modified file.
  if grep -q "wallpaper-gdm.png" /usr/share/gnome-shell/gnome-shell-theme.gresource; then
    cp -f /usr/share/gnome-shell/gnome-shell-theme.gresource.backup /usr/share/gnome-shell/gnome-shell-theme.gresource

    echo 'gnome-shell-theme.gresource recovered'
  fi

  exit
fi

image_parameters="background-repeat: no-repeat;background-size: cover;"
if [ "$1" = "--css" ]; then
  image_parameters="$2;"
  shift;shift;
fi

if [ "$1" = "--resize" ]; then
  case "$2" in
    0) image_parameters="background-repeat: repeat;";;
    1) image_parameters="background-repeat: no-repeat;";;
    2) image_parameters="background-repeat: no-repeat;background-size: cover;";;
    3) image_parameters="background-size: 1920px 1080px;";;
    4) image_parameters="background-size: 1920px 1080px;background-repeat: repeat;";;
    5) image_parameters="background-position: 0 0;background-size: 1920px 1080px;background-repeat: repeat;";;
    6) image_parameters="background-repeat: no-repeat;background-size: cover;background-position: center;";;
    *)
      echo "Error: unknown --resize value"
      exit 1;;
  esac
  shift;shift;
fi

  if [ "$#" -ne "1" ]; then
    echo "Error: Illegal argument $1"
    exit 1
  fi

image="$(realpath "$1")"

if [ ! -f "$image" ]; then
  echo "File not found: \"$image\" "
  exit 1
fi

echo "Updating wallpaper..."

# Restore gresource from backup if current gresource is modified
if grep -q "wallpaper-gdm.png" /usr/share/gnome-shell/gnome-shell-theme.gresource; then
  cp -f /usr/share/gnome-shell/gnome-shell-theme.gresource.backup /usr/share/gnome-shell/gnome-shell-theme.gresource
fi

workdir=$(mktemp -d)
cd "$workdir"

# Creating gnome-shell-theme.gresource.xml with theme file list and add header
echo '<?xml version="1.0" encoding="UTF-8"?>' >"$workdir/gnome-shell-theme.gresource.xml"
echo '<gresources><gresource>' >>"$workdir/gnome-shell-theme.gresource.xml"

for res_file in $(gresource list /usr/share/gnome-shell/gnome-shell-theme.gresource); do
  # create dir for theme file inside temp dir
  mkdir -p "$(dirname "$workdir$res_file")"

  if [ "$res_file" != "/org/gnome/shell/theme/wallpaper-gdm.png" ]; then
    # extract file ($res_file) from current theme and write it to temp dir ($workdir)
    gresource extract /usr/share/gnome-shell/gnome-shell-theme.gresource "$res_file" >"$workdir$res_file"

    # add extracted file name to gnome-shell-theme.gresource.xml
    echo "<file>${res_file#\/}</file>" >>"$workdir/gnome-shell-theme.gresource.xml"
  fi
done

# add our image ($image) to theme path and to xml file
echo "<file>org/gnome/shell/theme/wallpaper-gdm.png</file>" >>"$workdir/gnome-shell-theme.gresource.xml"
cp -f "$image" "$workdir/org/gnome/shell/theme/wallpaper-gdm.png"

# add footer to xml file
echo '</gresource></gresources>' >>"$workdir/gnome-shell-theme.gresource.xml"


# find #lockDialogGroup block inside gnome-shell.css and replace with new_theme_params with our image
# and add image_parameters
new_theme_params="background: #2e3436 url(resource:\/\/\/org\/gnome\/shell\/theme\/wallpaper-gdm.png);$image_parameters"
sed -i -z -E "s/#lockDialogGroup \{[^}]+/#lockDialogGroup \{$new_theme_params/g" "$workdir/org/gnome/shell/theme/gnome-shell.css"

# create gresource file with file list inside gnome-shell-theme.gresource.xml
glib-compile-resources "$workdir/gnome-shell-theme.gresource.xml"

# Do backup only for original gresource file, not modified by this script.
# If wallpaper-gdm.png text inside gresource file, then this is modified file.
if ! grep -q "wallpaper-gdm.png" /usr/share/gnome-shell/gnome-shell-theme.gresource; then
  cp -f /usr/share/gnome-shell/gnome-shell-theme.gresource /usr/share/gnome-shell/gnome-shell-theme.gresource.backup
  echo "Backup"
fi

cp -f "$workdir/gnome-shell-theme.gresource" /usr/share/gnome-shell/

# Strange but safe from bug
rm -rf "$workdir/org"
rm -f "$workdir/gnome-shell-theme.gresource.xml"
rm -f "$workdir/gnome-shell-theme.gresource"
rm -r "$workdir"

echo "Done!"

ildar@ROBOT-1:~$ lsb_release -a
No LSB modules are available.
Distributor ID:    Ubuntu
Description:    Ubuntu 19.10
Release:    19.10
Codename:    eoan
ildar@ROBOT-1:~$ 

<?xml version="1.0"?>
<mime-info xmlns="http://www.freedesktop.org/standards/shared-mime-info">
<mime-type type="user/mod">
<comment>video files MOD</comment>
<glob pattern="*.mod"/>
</mime-type>
</mime-info>