The GNOME extension, referred to internally as gnome, helps build snaps that use GTK
3, GNOME 42 and higher, and GLib. This extension provides many of the components needed
for general desktop apps, making it useful for a broader set of apps outside of those
tailored for the GNOME desktop.
This extension is compatible with the core22 and core24 bases.
When this extension is used, the following plugs are connected for the app. The paths slightly differ between core24 and core22 bases.
.. tabs::
.. group-tab:: core24
.. collapse:: Included snap-wide plugs
.. code-block:: yaml
:caption: snapcraft.yaml
plugs:
desktop:
mount-host-font-cache: false
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
gnome-46-2404:
interface: content
target: $SNAP/gnome-platform
default-provider: gnome-46-2404
gpu-2404:
interface: content
target: $SNAP/gpu-2404
default-provider: mesa-2404
.. group-tab:: core22
.. collapse:: Included snap-wide plugs
.. code-block:: yaml
:caption: snapcraft.yaml
plugs:
desktop:
mount-host-font-cache: false
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
gnome-42-2204:
interface: content
target: $SNAP/gnome-platform
default-provider: gnome-42-2204
The extension also connects the following plugs to all apps that use it.
.. collapse:: Included app plugs
.. code-block:: yaml
:caption: snapcraft.yaml
plugs:
- desktop
- desktop-legacy
- gsettings
- opengl
- wayland
- x11
- mount-observe
- calendar-service
The GNOME extension is derived from two separate snaps -- a build snap and a platform snap.
The build snap compiles libraries from source that are commonly used across GNOME apps. Examples include GLib, GTK, and gnome-desktop. These are built to provide newer versions of these packages that exist in either the core24 or core22 base snaps (a subset of their respective Ubuntu archives).
The platform snap takes the build snap and makes all of those libraries available at build time to snaps using this extension. This way, snap authors don't need to include the pieces of the build snap that are unnecessary at runtime, like compilers, in the final snap.
In addition to using the build and platform snaps, this extension sets several environment variables, links, and default plugs for the app to use, and a default build-environment for each part in your snap to use.
The following build environment variables are added to each part in a snap that uses this extension.
You can declare additional variables in the build-environment key. Furthermore,
these default variables can be overridden by declaring them in the project file.
The paths differ slightly between core24 and core22 bases.
.. tabs::
.. group-tab:: core24
.. collapse:: Included build environment variables
.. code-block:: yaml
:caption: snapcraft.yaml
build-environment:
- PATH: /snap/gnome-46-2404-sdk/current/usr/bin${PATH:+:$PATH}
- XDG_DATA_DIRS: $CRAFT_STAGE/usr/share:/snap/gnome-46-2404-sdk/current/usr/share:/usr/share${XDG_DATA_DIRS:+:$XDG_DATA_DIRS}
- C_INCLUDE_PATH: $CRAFT_STAGE/usr/include:/snap/gnome-46-2404-sdk/current/usr/include:/snap/core24/current/usr/include${C_INCLUDE_PATH:+:$C_INCLUDE_PATH}
- LD_LIBRARY_PATH: /snap/gnome-46-2404-sdk/current/lib/$CRAFT_ARCH_TRIPLET_BUILD_FOR:/snap/gnome-46-2404-sdk/current/usr/lib/$CRAFT_ARCH_TRIPLET_BUILD_FOR:/snap/gnome-46-2404-sdk/current/usr/lib:/snap/gnome-46-2404-sdk/current/usr/lib/vala-current:/snap/gnome-46-2404-sdk/current/usr/lib/$CRAFT_ARCH_TRIPLET_BUILD_FOR/pulseaudio${LD_LIBRARY_PATH:+:$LD_LIBRARY_PATH}
- PKG_CONFIG_PATH: /snap/gnome-46-2404-sdk/current/usr/lib/$CRAFT_ARCH_TRIPLET_BUILD_FOR/pkgconfig:/snap/gnome-46-2404-sdk/current/usr/lib/pkgconfig:/snap/gnome-46-2404-sdk/current/usr/share/pkgconfig${PKG_CONFIG_PATH:+:$PKG_CONFIG_PATH}
- GETTEXTDATADIRS: /snap/gnome-46-2404-sdk/current/usr/share/gettext-current${GETTEXTDATADIRS:+:$GETTEXTDATADIRS}
- GDK_PIXBUF_MODULE_FILE: /snap/gnome-46-2404-sdk/current/usr/lib/$CRAFT_ARCH_TRIPLET_BUILD_FOR/gdk-pixbuf-current/loaders.cache
- ACLOCAL_PATH: /snap/gnome-46-2404-sdk/current/usr/share/aclocal${ACLOCAL_PATH:+:$ACLOCAL_PATH}
- PYTHONPATH: /snap/gnome-46-2404-sdk/current/usr/lib/python3.10:/snap/gnome-46-2404-sdk/current/usr/lib/python3/dist-packages:/snap/gnome-46-2404-sdk/current/usr/lib/$CRAFT_ARCH_TRIPLET_BUILD_FOR/gobject-introspection${PYTHONPATH:+:$PYTHONPATH}
- GI_TYPELIB_PATH: /snap/gnome-46-2404-sdk/current/usr/lib/girepository-1.0:/snap/gnome-46-2404-sdk/current/usr/lib/$CRAFT_ARCH_TRIPLET_BUILD_FOR/girepository-1.0${GI_TYPELIB_PATH:+:$GI_TYPELIB_PATH}
.. group-tab:: core22
.. collapse:: Included build environment variables
.. code-block:: yaml
:caption: snapcraft.yaml
build-environment:
- PATH: /snap/gnome-42-2204-sdk/current/usr/bin${PATH:+:$PATH}
- XDG_DATA_DIRS: $SNAPCRAFT_STAGE/usr/share:/snap/gnome-42-2204-sdk/current/usr/share:/usr/share${XDG_DATA_DIRS:+:$XDG_DATA_DIRS}
- LD_LIBRARY_PATH: /snap/gnome-42-2204-sdk/current/lib/$CRAFT_ARCH_TRIPLET:/snap/gnome-42-2204-sdk/current/usr/lib/$CRAFT_ARCH_TRIPLET:/snap/gnome-42-2204-sdk/current/usr/lib:/snap/gnome-42-2204-sdk/current/usr/lib/vala-current:/snap/gnome-42-2204-sdk/current/usr/lib/$CRAFT_ARCH_TRIPLET/pulseaudio${LD_LIBRARY_PATH:+:$LD_LIBRARY_PATH}
- PKG_CONFIG_PATH: /snap/gnome-42-2204-sdk/current/usr/lib/$CRAFT_ARCH_TRIPLET/pkgconfig:/snap/gnome-42-2204-sdk/current/usr/lib/pkgconfig:/snap/gnome-42-2204-sdk/current/usr/share/pkgconfig${PKG_CONFIG_PATH:+:$PKG_CONFIG_PATH}
- GETTEXTDATADIRS: /snap/gnome-42-2204-sdk/current/usr/share/gettext-current${GETTEXTDATADIRS:+:$GETTEXTDATADIRS}
- GDK_PIXBUF_MODULE_FILE: /snap/gnome-42-2204-sdk/current/usr/lib/$CRAFT_ARCH_TRIPLET/gdk-pixbuf-current/loaders.cache
- ACLOCAL_PATH: /snap/gnome-42-2204-sdk/current/usr/share/aclocal${ACLOCAL_PATH:+:$ACLOCAL_PATH}
- PYTHONPATH: /snap/gnome-42-2204-sdk/current/usr/lib/python3.10:/snap/gnome-42-2204-sdk/current/usr/lib/python3/dist-packages:/snap/gnome-42-2204-sdk/current/usr/lib/$CRAFT_ARCH_TRIPLET/gobject-introspection${PYTHONPATH:+:$PYTHONPATH}
The following environment variables are exported when the app runs:
.. collapse:: Environment variables
.. code-block:: yaml
:caption: snapcraft.yaml
environment:
SNAP_DESKTOP_RUNTIME: $SNAP/gnome-platform
GTK_USE_PORTAL: '1'
This extension uses layouts to access files on the host. The platform snap's GNOME JavaScript (GJS), webkit2gtk-4.0, and iso-codes are used so they don't need to be packaged as part of the snap and would greatly inflate the size.
.. tabs::
.. group-tab:: core24
.. collapse:: Included layouts
.. code-block:: yaml
:caption: snapcraft.yaml
layout:
/usr/lib/$CRAFT_ARCH_TRIPLET_BUILD_FOR/webkit2gtk-4.0:
bind: $SNAP/gnome-platform/usr/lib/$CRAFT_ARCH_TRIPLET_BUILD_FOR/webkit2gtk-4.0
/usr/lib/$CRAFT_ARCH_TRIPLET_BUILD_FOR/webkit2gtk-4.1:
bind: $SNAP/gnome-platform/usr/lib/$CRAFT_ARCH_TRIPLET_BUILD_FOR/webkit2gtk-4.1
/usr/share/xml/iso-codes:
bind: $SNAP/gnome-platform/usr/share/xml/iso-codes
/usr/share/libdrm:
bind: $SNAP/gpu-2404/libdrm
/usr/share/drirc.d:
symlink: $SNAP/gpu-2404/drirc.d
/usr/share/X11/XErrorDB:
symlink: $SNAP/gpu-2404/X11/XErrorDB
.. group-tab:: core22
.. collapse:: Included layouts
.. code-block:: yaml
:caption: snapcraft.yaml
layout:
/usr/lib/$SNAPCRAFT_ARCH_TRIPLET/libgweather-4:
symlink: $SNAP/usr/lib/$SNAPCRAFT_ARCH_TRIPLET/libgweather-4
/usr/lib/evolution-data-server:
symlink: $SNAP/usr/lib/evolution-data-server
/usr/bin/gnome-control-center:
symlink: $SNAP/usr/bin/gnome-control-center
/usr/lib/$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
/usr/share/libdrm:
bind: $SNAP/gnome-platform/usr/share/libdrm
Here's an example of the result of Snapcraft expanding a core24-based project file, as immediately prior to build. It demonstrates the added plugs, packages, variables, and layouts that the GNOME extension includes in a project.
The original files were for the GNOME System Monitor snap. These texts contain the difference between the original file and the output of the :ref:`snapcraft expand-extensions <ref_commands_expand-extensions>` command. Some of the text has been altered for ease of reading.
.. tabs::
.. group-tab:: core24
.. collapse:: Expanded project file for GNOME System Monitor
.. literalinclude:: code/gnome-extension-gnome-system-monitor-core-24-expanded.diff
:language: diff
:lines: 3-
:emphasize-lines: 57-66, 78-87, 100-150, 158-163, 171-173, 180-201, 210-212
.. group-tab:: core22
.. collapse:: Expanded project file for GNOME System Monitor
.. literalinclude:: code/gnome-extension-gnome-system-monitor-core-22-expanded.diff
:language: diff
:lines: 3-
:emphasize-lines: 60-69, 81-90, 103-155, 159-160, 164-170, 178-179, 186-207