Craft a GTK4 app

This how-to guide covers the steps, decisions, and implementation details that are unique when crafting a snap of an app built using GTK4 and GNOME. We’ll work through the aspects unique to GTK4-based apps by examining an existing project file.

Example gnome-text-editor project file

The following code comprises the project file of a GTK4 app, gnome-text-editor. This project is the default text editor of the GNOME desktop environment.

gnome-text-editor project file
snapcraft.yaml
name: gnome-text-editor
grade: stable
adopt-info: gnome-text-editor
license: GPL-3.0+

base: core22
confinement: strict

apps:
  gnome-text-editor:
    extensions: [gnome]
    command: usr/bin/gnome-text-editor
    desktop: usr/share/applications/org.gnome.TextEditor.desktop
    common-id: org.gnome.TextEditor.desktop
    plugs:
      - gsettings
      - cups

parts:
  gnome-text-editor:
    source: https://gitlab.gnome.org/GNOME/gnome-text-editor
    source-tag: "42.2"
    source-type: git
    plugin: meson
    meson-parameters:
      - --prefix=/usr
      - --buildtype=release
    parse-info: [usr/share/metainfo/org.gnome.TextEditor.appdata.xml]

slots:
  gnome-text-editor:
    interface: dbus
    bus: session
    name: org.gnome.TextEditor

Add an app that uses GNOME

snapcraft.yaml
apps:
  gnome-text-editor:
    extensions: [gnome]
    command: usr/bin/gnome-text-editor
    desktop: usr/share/applications/org.gnome.TextEditor.desktop
    common-id: org.gnome.TextEditor.desktop
    plugs:
      - gsettings
      - cups

Apps that use GTK4 and GNOME as runtime libraries require the GNOME extension. The extension configures the runtime environment of the app so that all desktop functionality is correctly initialised. As desktop environment apps, they also need special configuration for AppStream and .desktop file compatibility.

To add a GTK4 app:

  1. Declare the general app keys, such as command, plugs, after, and so on.

  2. For extensions, add gnome.

  3. Set common-id to the app’s unique AppStream ID. Doing so links the app to the .desktop launcher specified in the AppStream file.

Add a part written for GTK4

snapcraft.yaml
parts:
  gnome-text-editor:
    source: https://gitlab.gnome.org/GNOME/gnome-text-editor
    source-tag: "42.2"
    source-type: git
    plugin: meson
    meson-parameters:
      - --prefix=/usr
      - --buildtype=release
    parse-info: [usr/share/metainfo/org.gnome.TextEditor.appdata.xml]

GTK4 parts are built with the Meson plugin.

To add a GTK4 part:

  1. Declare the general part keys, such as source, override-build, build-packages, and so on.

  2. Set plugin: meson.

  3. So that the app has access to its AppStream metadata, for parse-info add a path to the AppStream .xml file on the host system. Since we set adopt-info: gnome-text-editor at the start of the project file, the AppStream file of the gnome-text-editor part will be used to fill in the summary, description and icon of this snap and copy the AppStream file. See AppStream for technical details about how this works.

Add required slots

snapcraft.yaml
slots:
  gnome-text-editor:
    interface: dbus
    bus: session
    name: org.gnome.TextEditor

Many GTK4 apps require access to D-Bus in order to run correctly. If your app does, you need to explicitly grant it access as a slot:

  1. Declare the slot key.

  2. Set interface: dbus and bus: session.

  3. Set name to the app’s AppStream ID.