The gnome-3-34 extension

The gnome-3-34 extension helps with the creation of snaps that use GTK 3, GNOME 3.34, and/or GLib. It’s an updated version of the gnome-3-28 extension.

This extension provides many of the components needed for general desktop applications making it useful for a broader set of applications outside of those tailored for the GNOME desktop.

:information_source: Snapcraft extensions enable snap developers to easily incorporate a set of common requirements into a snap. See Snapcraft extensions for further details.

How to use it

This extension currently only works with the core18 base snap (see Base snaps for details). To use it, add extensions: [gnome-3-34] to the application definition in your snapcraft.yaml file. For instance:

apps:
    tali:
        extensions: [gnome-3-34]
        command: usr/bin/tali
[...]

See GTK3 applications for a comprehensive overview of using extensions with GNOME applications.

Interface connections

The following plugs are provided by the extension and implicitly included in your snapcraft.yaml:

plugs:
    gtk-3-themes:
        interface: content
        target: $SNAP/data-dir/themes
        default-provider: gtk-common-themes
    icon-themes:
            interface: content
            target: $SNAP/data-dir/icons
            default-provider: gtk-common-themes
    sound-themes:
            interface: content
            target: $SNAP/data-dir/sounds
            default-provider: gtk-common-themes
    platform_snap:
            interface: content
            target: $SNAP/gnome-platform
            default-provider: gnome-3-34-1804

Your app may still need additional plugs, but you can expect the following plugs to be automatically available to your apps as well:

plugs: [ desktop, desktop-legacy, gsettings, wayland, x11 ]

See Adding interfaces for more details.

Included packages

The GNOME extension is derived from two separate snaps; a build snap and a platform snap.

The build snap builds 35 libraries from source that are commonly used across GNOME applications. Examples include glib, gtk, and gnome-desktop. These are built to provide newer versions of these packages that exist in the core18 base snap (a subset of the Ubuntu 18.04 archive).

It is common for GNOME applications to release a gnome-3-34 branch of their project when the 3.34 version of GNOME is released (or shortly thereafter). Keeping this in mind, the build snap looks for this first to provide access to various GNOME libraries on their gnome-3-34 branch, to distribute the latest stable version that corresponds to the GNOME 3.34 release.

The platform snap takes the build snap and makes all of those libraries available to your snap at build time without needing to include the pieces of the build snap that are unnecessary at runtime (like compilers) in your final snap.

The libraries built in the gnome-3-34-1804-sdk build snap are:

gnome-3-34-1804-sdk libraries
  • libtool
  • libffi
  • glib (2.62)
  • pixman (0.38.4)
  • cairo (1.16.0)
  • gobject-introspection (gnome-3-34 branch)
  • vala (0.46)
  • gee (0.20.2)
  • atk (gnome-3-34 branch)
  • at-spi2-core (2.34.0)
  • at-spi2-atk (2.34.1)
  • fribidi (1.0.7)
  • harfbuzz (2.6.2)
  • pango (1.44.6-2)
  • librsvg (2.44)
  • gdk-pixbuf (2.38)
  • epoxy (1.5.3)
  • json-glib (1.4)
  • libpsl (0.21.0)
  • libsoup (2.68.2)
  • librest (0.7)
  • gtk (3.24.10)
  • gtk-locales
  • mm-common (1.0.0)
  • glibmm (2.62.0)
  • cairomm (1.12.2)
  • pangomm (2.42.0)
  • atkmm (2.28.0)
  • gtkmm (3.24.2)
  • gtksourceview (4.4.0)
  • libdazzle (3.34)
  • libcanberra
  • gsettings-desktop-schemas (gnome-3-34 branch)
  • gnome-desktop (gnome-3-34 branch)
  • cogl (1.22)
  • clutter
  • clutter-gtk (1.8.4)
  • libpeas (1.22.0)
  • pycairo (1.18.1)
  • pygobject (3.34)
  • libhandy (libhandy-0-0 branch)

There are also several packages included from the Ubuntu 18.04 apt repository:

additional packages
  • gcc
  • pkg-config
  • libpcre3-dev
  • zlib1g-dev
  • libmount-dev
  • libxml2-dev
  • libsqlite3-dev
  • libbrotli-dev
  • libthai-dev
  • libfontconfig1-dev
  • libxrender-dev
  • libxft-dev
  • libxcb-shm0-dev
  • libxcb-render0-dev
  • libxext-dev
  • libxi-dev
  • libxrandr-dev
  • libxcursor-dev
  • libxcomposite-dev
  • libxdamage-dev
  • libxinerama-dev
  • libwayland-dev
  • wayland-protocols
  • libxkbcommon-dev
  • libgl1-mesa-dev
  • libegl1-mesa-dev
  • libdbus-1-dev
  • libxtst-dev
  • gettext
  • shared-mime-info
  • libwebkit2gtk-4.0-dev
  • libgcr-3-dev
  • libnotify-dev
  • libsecret-1-dev
  • itstool
  • libudev-dev
  • libseccomp-dev
  • libjpeg-dev
  • liblcms2-dev
  • libgspell-1-dev
  • python3-minimal
  • libxml2-utils
  • libgtksourceview-3.0-dev
  • libtdb1
  • libvorbisfile3
  • libegl-mesa0

Environment variables

In addition to using the build and platform snaps, the gnome-3-34 extension also sets a collection of environment variables, links, default plugs for the app to use, and a default build-environment for each part in your snap to use.

Build variables

The following “build-environment” section is made available to each part built in your snap.

If you define other build-environment variables, then those will get added to these and the set is used. If you define another value for one of these variables, then the value you’ve defined will be used instead of the value defined within the extension.

build-environment:
   - PATH: /snap/gnome-3-34-1804-sdk/current/usr/bin:$PATH
   - XDG_DATA_DIRS: /snap/gnome-3-34-1804-sdk/current/usr/share:/usr/share:$XDG_DATA_DIRS
   - LD_LIBRARY_PATH:/snap/gnome-3-34-1804-sdk/current/lib/$SNAPCRAFT_ARCH_TRIPLET:/snap/gnome-3-34-1804-sdk/current/usr/lib/$SNAPCRAFT_ARCH_TRIPLET:/snap/gnome-3-34-1804-sdk/current/usr/lib:/snap/gnome-3-34-1804-sdk/current/usr/lib/vala-current:$LD_LIBRARY_PATH
   - PKG_CONFIG_PATH: /snap/gnome-3-34-1804-sdk/current/usr/lib/$SNAPCRAFT_ARCH_TRIPLET/pkgconfig:/snap/gnome-3-34-1804-sdk/current/usr/lib/pkgconfig:/snap/gnome-3-34-1804-sdk/current/usr/share/pkgconfig:$PKG_CONFIG_PATH
   - GETTEXTDATADIRS:/snap/gnome-3-34-1804-sdk/current/usr/share/gettext-current:$GETTEXTDATADIRS
   - GDK_PIXBUF_MODULE_FILE: /snap/gnome-3-34-1804-sdk/current/usr/lib/$SNAPCRAFT_ARCH_TRIPLET/gdk-pixbuf-current/loaders.cache

Runtime variables

The following environment is set when your application is run:

 environment:
   - SNAP_DESKTOP_RUNTIME: $SNAP/gnome-platform
   - GTK_USE_PORTALS: 1

Layouts set

The host’s gjs, webkit2gtk-4.0, and iso-codes are used so they don’t need to be packaged as part of the snap (would greatly inflate the size).

layout:
    /usr/lib/$SNAPCRAFT_ARCH_TRIPLET/webkit2gtk-4.0:
        bind: $SNAP/gnome-platform/usr/lib/$SNAPCRAFT_ARCH_TRIPLET/webkit2gtk-4.0
    /usr/share/xml/iso-codes:
        bind: $SNAP/gnome-platform/usr/share/xml/iso-codes

See Snap layouts for further details.

Last updated 2 months ago. Help improve this document in the forum.