🔟Metadata

Every app comes with two metadata files that we can generate using an online tool. Open AppStream Metainfo Creator and fill out the form with your app's info:

AppStream MetaInfo Creator

When you get the section titled "Launchables", make sure to select "Generate a .desktop file for me".

Don't worry about generating Meson snippets, as we'll cover that in the next section. After you select "Generate", you should have two resulting files that you can copy.

MetaInfo

First is a MetaInfo file. This file contains all the information needed to list your app in App shop. It should look something like this:

<?xml version="1.0" encoding="UTF-8"?>
<component type="desktop-application">
  <id>com.github.myteam.myapp</id>

  <name>My App</name>
  <summary>Proves that we can use Vala and Gtk</summary>

  <metadata_license>CC-BY-4.0</metadata_license>
  <project_license>GPL-3.0-or-later</project_license>

  <description>
    <p>
      A quick summary of your app's main selling points and features. Just a couple sentences per paragraph is best
    </p>
  </description>

  <launchable type="desktop-id">com.github.myteam.myapp.desktop</launchable>
</component>

In your project's root, create a new folder called "data", and save your MetaInfo to a new file called "hello-again.metainfo.xml".

Below are some of the most important fields for publishing in AppCenter, but there are even more optional fields that you can read about

Screenshots

For the purposes of this tutorial, screenshots are optional, but they are required for publishing in App Shop. Screenshots should only show your app on a transparent background and not contain any additional text or illustrations. You can use the caption tag to provide translatable and accessible descriptions of your screenshots.

<screenshots>
  <screenshot type="default">
    <caption>The most important feature of my app</caption>
    <image>https://raw.githubusercontent.com/myteam/myapp/1.0.0/data/screenshot.png</image>
  </screenshot>
</screenshots>

You can use the built-in Screenshot app on elementary OS with the "grab the current window" option or secondary-click on your app's title area and select "Take Screenshot" to get transparent window-only screenshots of your app

Content Warnings

We use the Open Age Rating Service (OARS) standard to describe sensitive content that may be present in your app so that people using it can be informed and actively consent to seeing that content. OARS data is required and can be generated by taking a short survey:

OARS: Open Age Ratings Service

Branding

You can also specify a brand color for your app by adding the branding tag inside the component tag. Colors must be in hexadecimal, starting with #. The background will automatically be given a slight gradient in your app's banner.

<branding>
  <color type="primary">#f37329</color>
</branding>

Releases

Your app must have a release tag for every version you wish to publish in AppCenter. Release notes show up in App shop and should be aimed at the people who use your app. Avoid technical language and developer-facing changes and focus more on what people can expect to see in this update.

<releases>
  <release version="1.0.0" date="2022-09-08" urgency="medium">
    <description>
      <p>New features:</p>
      <ul>
        <li>My app can now do a great new thing</li>
      </ul>
      <p>Fixes:</p>
      <ul>
        <li>An annoying behavior no longer occurs</li>
      </ul>
    </description>
  </release>
</releases>

Previous release tags can remain in your MetaInfo file forever, and we encourage it; App shop may use them to show changes across multiple releases of your app

You can read more about the release tag here, including more features and formatting options.

Desktop Entry

This file contains all the information needed to display your app in the Applications Menu and in the Dock. The one generated from AppStream Metainfo Creator looks something like this:

[Desktop Entry]
Version=1.0
Type=Application

Name=My App
Comment=Proves that we can use Vala and Gtk
Categories=Development;Education;

Icon=com.github.myteam.myapp
Exec=com.github.myteam.myapp
Terminal=false

Copy the contents of your Desktop Entry and save it to the data folder you created earlier. Name this new file "hello-again.desktop".

For more info about crafting .desktop files, check out this HIG entry.

Mark Your Progress

Each time we add a new file or make a significant change it's a good idea to commit a new revision and push to GitHub. Keep in mind that this acts as a backup system as well; when we push our work to GitHub, we know it's safe and we can always revert to a known good revision if we mess up later.

Add all of these files to git and commit a revision:

git add data/
git commit -am "Add Metadata files"
git push

Now that we've got all these swanky files laying around, we need a way to tell the computer what to do with them. Ready for the next chapter? Let's do this!