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2.2. Desktop Applications

2.2.1. Introduction

A desktop application is an application which has a graphical user interface and is commonly used with mouse and keyboard. It also ships a Freedesktop .desktop file to be visible in application menus.
AppStream generators may pull data from the preexisting .desktop files to represent an application in the AppStream metadata pool. Upstream projects should ship a metainfo file containing additional metadata to describe their application though, to enhance the available metadata. This data includes things like screenshots, long descriptions, icon information and various other things needed to present the application properly to the user. For some distributions, the presence of this metadata is a prerequisite for the application showing up in the metadata pool and being presented in software centers.
The file described in this document is built upon the generic component metadata with fields specific for desktop applications (see Section 2.1, “Generic Component”).
The metainfo files override any values which are automatically fetched from other sources by the AppStream data generator, which means that its data will always take precedence over data which has already been defined in a .desktop file. Applications can ship one or more files in /usr/share/metainfo/%{id}.appdata.xml.
Data will only be fetched from a desktop file if one <launchable/> tag is present to define a .desktop file ID. If multiple launch tags are defined, no data will be merged in from .desktop files.

Note

If you are looking for some quickstart guide to just get your application to ship AppStream metadata quickly, this document might not be for you. You might want to take a look at Section 4.1, “For GUI application upstream maintainers” instead.

2.2.2. File specification

The basic structure for a generic component as described at Section 2.1.3, “XML Specification” applies. Note that the XML root must have the type property set to desktop-application, while in a generic component this property can be omitted. This clearly identifies this metainfo document as describing an application.

Note

All tags defined in the generic component specification are valid for desktop-application components as well. An application is just a specialized component, allowing tools like software centers to filter out the component types they want to display.

Note

The desktop-application component type is the same as the desktop component type - desktop is the older type identifier for desktop-applications and should not be used for new metainfo files, unless compatibility with very old AppStream tools (pre 2016) is still wanted.
The following list describes the special tags for application upstream metadata and provides some additional information about the values the tags are expected to have. If no information is given about a tag, refer to the respective tag in Section 2.1, “Generic Component”.
<id/>
For desktop applications, the <id/> tag value must follow the reverse-DNS scheme as described in <id/>.

Note

In previous AppStream releases, the <id/> was used to associate metainfo files with their .desktop files to merge in data from .desktop files into the AppStream generator's final output. In modern metainfo files, the component-ID for desktop-application components can be an arbitrary string (matching the naming rules applying to all AppStream metadata), while the <launchable/> tag is used to associate .desktop files with their metainfo files.
<metadata_license/>
The <metadata_license/> tag as described in <metadata_license/> must be present.
<name/>
The human-readable name of the application. This is the name you want users to see prior to installing the application.
<summary/>
A short summary on what this application does, roughly equivalent to the Comment field of the accompanying .desktop file of the application.
<launchable/>
It is recommended that a <launchable/> tag is present in desktop-application metainfo files. The tag is described in detail at <launchable/>.
If only one launchable entry of type desktop-id is present, AppStream metadata generators might decide to merge metadata from .desktop files referenced by the tag into their final output.
The launchable tag is optional, but if omitted software centers will not be able to launch the application directly after it was installed.
<screenshots/>
A screenshot presents your application to the outside world, and could be seen by hundreds or thousands of people.
The <screenshots/> tag should look like it is described at <screenshots/>.
Screenshot size, shape and format recommendations for applications:
  • All screenshots should have a 16:9 aspect ratio, and should have a width that is no smaller than 620px (software center applications will be able to fill in the screenshots in the space they provide for that more easily then).
    Ideally the window will be resized to a 16:9 aspect ratio, but screenshots can also be cropped if only a small area of the window needs to be shown.
  • Screenshots should be in PNG or JPEG format. PNG is the preferred format; JPEG should only be used when screenshots include large photographs or other images where a lossy format like JPEG may compress better.
  • Do not scale screenshots below their original size.
You can find a lot more information on how to create good screenshots in the quickstart guide on applications.
<project_group/>
This tag is described for generic components at Section 2.1.3, “XML Specification”. You should use it for your application if appropriate.
<provides/>
This tag is described in detail for generic components at <provides/>.
If your application ships a binary in a location in the default PATH, you should add at least a child of type <binary/> to make that new executable known to the distribution.
<releases/>
The application metainfo should at least provide one <releases/> tag, which has one or more <release/> childs to define the version and release date of this application. For details, see <releases/> .
For a component of type desktop-application, the following tags are required and must always be present: <id/>, <name/>, <summary/>, <description/>, <metadata_license/>.