10.5. Customizing Desktop Backgrounds

Using the dconf utility, you can configure the default background, add extra backgrounds, or add multiple backgrounds.
If the users of the system will not be permitted to change these settings from the defaults, then system administrators need to lock the settings using the locks directory. Otherwise each user will be able to customize the setting to suit their own preferences. For more information, see Section 9.5.1, “Locking Down Specific Settings”.

10.5.1. Customizing the Default Desktop Background

You can configure the default desktop background and its appearance by setting the relevant GSettings keys in the org.gnome.desktop.background schema.
For more information about GSettings, see Chapter 9, Configuring Desktop with GSettings and dconf.

Procedure 10.10. Setting the Default Background

  1. Create a local database for machine-wide settings in /etc/dconf/db/local.d/00-background: 
    # Specify the dconf path
[org/gnome/desktop/background]

# Specify the path to the desktop background image file
picture-uri='file:///usr/local/share/backgrounds/wallpaper.jpg'
# Specify one of the rendering options for the background image:
# 'none', 'wallpaper', 'centered', 'scaled', 'stretched', 'zoom', 'spanned'
picture-options='scaled'
# Specify the left or top color when drawing gradients or the solid color
primary-color='000000'
# Specify the right or bottom color when drawing gradients
secondary-color='FFFFFF'
  2. Override the user's setting to prevent the user from changing it in /etc/dconf/db/local.d/locks/background: 
    # List the keys used to configure the desktop background
/org/gnome/desktop/background/picture-uri
/org/gnome/desktop/background/picture-options
/org/gnome/desktop/background/primary-color
/org/gnome/desktop/background/secondary-color
    For more information, see Section 9.5.1, “Locking Down Specific Settings”.
  3. Update the system databases: 
    # dconf update
  4. Users must log out and back in again before the system-wide settings take effect.

10.5.2. Adding Extra Backgrounds

You can make extra backgrounds available to users on your system.
  1. Create a filename.xml file (there are no requirements for file names) specifying your extra background's appearance using the org.gnome.desktop.background schemas. Here is a list of the most frequently used schemas:

    Table 10.1. org.gnome.desktop.background schemas GSettings Keys

    Key NamePossible ValuesDescription
    picture-options"none", "wallpaper", "centered", "scaled", "stretched", "zoom", "spanned"Determines how the image set by wallpaper_filename is rendered.
    color-shading-type"horizontal", "vertical", and "solid"How to shade the background color.
    primary-colordefault: #023c88Left or Top color when drawing gradients, or the solid color.
    secondary-colordefault: #5789caRight or Bottom color when drawing gradients, not used for solid color.
    The full range of options is to be found in the dconf-editor GUI or gsettings command-line utility. For more information, see Section 9.3, “Browsing GSettings Values for Desktop Applications”.
  2. Store the filename.xml file in the /usr/share/gnome-background-properties/ directory.
When the user clicks their name in the top right corner, chooses Settings, and in the Personal section of the table selects Background, they will see the new background available.
Look at the example and see how org.gnome.desktop.background GSettings keys are implemented practically:

Example 10.4. Extra Backgrounds File

<?xml version="1.0" encoding="UTF-8"?>
<!DOCTYPE wallpapers SYSTEM "gnome-wp-list.dtd">
<wallpapers>
  <wallpaper deleted="false">
    <name>Company Background</name>
    <name xml:lang="de">Firmenhintergrund</name>
    <filename>/usr/local/share/backgrounds/company-wallpaper.jpg</filename>
    <options>zoom</options>
    <shade_type>solid</shade_type>
    <pcolor>#ffffff</pcolor>
    <scolor>#000000</scolor>
  </wallpaper>
</wallpapers>
In one configuration file, you can specify multiple <wallpaper> elements to add more backgrounds.
See the following example which shows an .xml file with two <wallpaper> elements, adding two different backgrounds:

Example 10.5. Extra Backgrounds File with Two Wallpaper Elements

<?xml version="1.0" encoding="UTF-8"?>
<!DOCTYPE wallpapers SYSTEM "gnome-wp-list.dtd">
<wallpapers>
  <wallpaper deleted="false">
    <name>Company Background</name>
    <name xml:lang="de">Firmenhintergrund</name>
    <filename>/usr/local/share/backgrounds/company-wallpaper.jpg</filename>
    <options>zoom</options>
    <shade_type>solid</shade_type>
    <pcolor>#ffffff</pcolor>
    <scolor>#000000</scolor>
  </wallpaper>
  <wallpaper deleted="false">
    <name>Company Background 2</name>
    <name xml:lang="de">Firmenhintergrund 2</name>
    <filename>/usr/local/share/backgrounds/company-wallpaper-2.jpg</filename>
    <options>zoom</options>
    <shade_type>solid</shade_type>
    <pcolor>#ff0000</pcolor>
    <scolor>#00ffff</scolor>
  </wallpaper>
</wallpapers>

10.5.3. Setting the Screen Shield

Screen Shield is the screen that quickly slides down when the system is locked. It is controlled by the org.gnome.desktop.screensaver.picture-uri GSettings key. Since GDM uses its own dconf profile, you can set the default background by changing the settings in that profile.
For more information about GSettings and dconf, see Chapter 9, Configuring Desktop with GSettings and dconf.

Procedure 10.11. Adding a Logo to the Screen Shield

  1. Create a gdm database for machine-wide settings in /etc/dconf/db/gdm.d/01-screensaver: 
    [org/gnome/desktop/screensaver]
picture-uri='file:///opt/corp/background.jpg'
    Replace /opt/corp/background.jpg with the path to the image file you want to use as the Screen Shield.
    Supported formats are PNG, JPG, JPEG, and TGA. The image will be scaled if necessary to fit the screen.
  2. Update the system databases: 
    # dconf update
  3. You must log out before the system-wide settings take effect.
Next time you lock the screen, the new Screen Shield will show in the background. In the foreground, time, date and the current day of the week will be displayed.

10.5.3.1. What If the Screen Shield Does Not Update?

Make sure that you have run the dconf update command as root to update the system databases.
In case the background does not update, try restarting GDM. For more information, see Section 14.1.1, “Restarting GDM”.