vendor-customisation.md

Vendor customisation of GNOME Software

GNOME Software is in an unusual position in a distribution, as it lies at the interface of the GNOME project and the distribution’s packaging and release infrastructure. GNOME Software is the user interface which a lot of users will use to see updates and new releases from their distribution. Distributions understandably want to be able to put some of their own branding on this interface, both to publicise their distribution and to confer some level of official authority on the updates being provided.

For this reason, GNOME Software has a few ways which vendors can use to customise its appearance.

A variety of different customisations have been implemented in the past, some of which have been removed and others are still present. This document aims to document the ones which are still present and supported. This document is not necessarily complete. It will be added to over time as different customisations are refreshed and updated.

If there is a supported customisation method which is not in this document, please submit a merge request to document it.

Likewise, if your distribution would like to customise gnome-software in a way which isn’t currently supported, please open a new issue to discuss it. We don’t guarantee to implement anything, and customisations are limited to adding branding in specific areas.

Principles

The principles which guide vendor customisation features in GNOME Software are:

• Avoid requiring vendor specific code.
  • Otherwise vendors have to maintain and test GNOME Software plugins, which is a lot of work.
• Don’t use GSettings unless customisations really should be per-user.
  • While GSettings overrides are convenient, they are designed for user preferences, not packaging customisation.
• Don’t require downstream patching of GNOME Software, although configure-time arguments are OK.
  • Many distributions are derived from other ones and would not like to have to maintain a packaging fork in order to make small customisations.
• Be mindful of release cadences.
  • If customisations related to a new OS version were tied to the release cycle of GNOME Software, a new GNOME Software packaging release would have to be done by a distribution in advance of making their new OS release, which is a burden.
  • It’s easier to allow distributions to put customisations specific to a new OS version into a separate package.

Upgrade background image

The background image which is shown when a new OS upgrade is available is customisable in several ways. It’s displayed by the GsUpgradeBanner widget, and shown on the updates page.

If your distribution has a specific GNOME Software plugin providing its upgrade information, that plugin can provide CSS for rendering the background. See the fedora-pkgdb-collections plugin for an example of this.

Otherwise, the background image is looked up from several well-known locations, in order:

• ${DATADIR}/gnome-software/backgrounds/${os_id}-${version}.png
• ${DATADIR}/gnome-software/backgrounds/${os_id}.png

${DATADIR} is the configured data directory (typically /usr/share). ${os_id} is the ID= value from /etc/os-release, and ${version} is the version string being upgraded to.

Featured apps and Editor’s Choice

There are several ways to promote and highlight specific applications in GNOME Software. On the overview page, there’s a carousel of featured applications (featured_carousel), and an “Editor’s Choice” section (box_curated). Both of them highlight curated sets of applications. The same is true on each category page: a carousel (top_carousel) and an “Editor’s Choice” section (featured_flow_box) are present.

Both pages also have a “New & Updated” section (box_recent or recently_updated_flow_box) presented below “Editor’s Choice”. The applications listed in the new and updated section are not curated: they are chosen as the applications which have had a recent release, according to the component/releases/release[@timestamp] attribute in their metainfo. Technically these are the results of a GsPlugin.list_apps_async() query with GsAppQuery:released-since set.

Applications are included in any of the curated sets through having special metadata in their metainfo. The required metadata is different for the different sections:

• Carousel on the overview page: Applications are included if they have component/custom/value[@key='GnomeSoftware::FeatureTile] or component/custom/value[@key='GnomeSoftware::FeatureTile-css] set in their metainfo. They are also required to have a high-resolution icon, and the set of applications shown in the carousel is randomised and limited to (for example) 5. Technically these are the results of a GsPlugin.list_apps_async() query with GsAppQuery:is-featured set.
• “Editor’s Choice” on the overview page: Applications are included if they have component/kudos/kudo[text()='GnomeSoftware::popular'] set in their metainfo. Technically these are the results of a GsPlugin.list_apps_async() query with GsAppQuery:is-curated set.
• Carousel on the category page: Applications are included if they are in the Featured subcategory of the displayed category. They are also required to have a high-resolution icon, and the set of applications shown in the carousel is randomised and limited to (for example) 5.
• “Editor’s Choice” on the category page: Applications are included if they meet the requirements for being in the carousel, but weren’t chosen as part of the randomisation process.

Example:

<?xml version="1.0" encoding="UTF-8"?>
<components>
  <component merge="append">
    <!-- The ID must always be present to allow merging -->
    <id>org.gnome.Podcasts</id>

    <!-- Make the app a candidate for inclusion in the carousel on the
         overview page (if it has a hi-res icon). -->
    <custom>
      <value key="GnomeSoftware::FeatureTile">True</value>
    </custom>

    <!-- Include the app in the “Editor’s Choice” section on the overview page. -->
    <kudos>
      <kudo>GnomeSoftware::popular</kudo>
    </kudos>

    <!-- Make the app a candidate for inclusion in the carousel or
         “Editor’s Choice” section on category pages (if it has a hi-res icon). -->
    <categories>
      <!-- Note that, due to a bug (https://gitlab.gnome.org/GNOME/gnome-software/-/issues/1649),
           currently all the other categories for the app must also be listed
           here, as well as the additional ‘Featured’ category. -->
      <category>AudioVideo</category>
      <category>Player</category>
      <!-- This category has been added: -->
      <category>Featured</category>
    </categories>
  </component>
  <!-- more components -->
</components>

There are several ways to modify the metainfo for applications so that they are highlighted as required, all of which involve providing an additional appstream file which sets the additional metainfo for those applications.

The main approach is to ship an additional distro-specific appstream file in ${DATADIR}/swcatalog/xml, providing and updating it via normal distribution channels. For example, by packaging it in its own package which is updated regularly.

For distributions which can’t do regular updates of individual files – such as image-based distributions – GNOME Software can download distro-specific appstream files from the internet. List them in the external-appstream-urls GSetting in /org/gnome/software, typically via a distribution-provided GSettings override. Each URL must be HTTPS, and must point to a valid appstream file. GNOME Software must be configured with -Dexternal_appstream=true for this to work.

GNOME Software will periodically check and download any updates to these files, and will cache them locally. Ensure the If-Modified-Since HTTP header functions correctly on your server, or GNOME Software’s caching will be ineffective.

The external-appstream-urls mechanism may change in future.

GNOME Software ships a default list of featured applications, chosen to match the GNOME Circle. See data/assets/org.gnome.Software.Featured.xml for this list, and for an example of the metainfo XML needed to feature or highlight applications. See data/assets/org.gnome.Software.Curated.xml for a default hard-coded list of curated high quality applications, which is displayed in the “Editor’s Choice” section of the overview page.

Pass -Ddefault_featured_apps=false when configuring GNOME Software to disable the default list of featured applications. Pass -Dhardcoded_curated=false to disable the default list of “Editor’s Choice” applications.

Deployment Featured Apps

Deployments can feature their own applications, which will be shown in the Explore page in its own section. To have the section shown, two files need to be provided. The number of deployment-featured apps is limited in the UI, and if not enough deployment-featured apps are found, then the section will not be shown at all.

The first file is org.gnome.Software.DeploymentFeatured.xml, which works similarly to org.gnome.Software.Featured.xml and should be saved beside it in an appstream directory. It sets the GnomeSoftware::DeploymentFeatured key on apps which should be featured for this distribution or deployment. The value of this key is a string containing the deployment name as an identifier.

The second file is deployment-featured.ini, which contains a human-readable title and the selector for the section. The title is a localized key, and is used to set the heading for the section on the Explore page. When the title is not provided, a fallback title "Available for ${distro-name}" is used. The selector defines which apps should be picked. It is a semicolon-separated list of GnomeSoftware::DeploymentFeatured key values, thus the deployment can feature apps from zero or more vendors.

The deployment-featured.ini file should be saved in one of the sysconfdir, system config dirs or system data dirs. They are checked, in that order, for existence of the gnome-software/deployment-featured.ini file. The first directory containing it will be used. The relevant file names are /etc/xdg/gnome-software/deployment-featured.ini, /usr/local/share/gnome-software/deployment-featured.ini and /usr/share/gnome-software/deployment-featured.ini.

Any changes to these files, including adding or removing them, will only be noticed when gnome-software is restarted.

Example files can be found in the contrib/ directory.