Tag Archives: appdata

Add metadata to your app to say what inputs and display sizes it supports

The appstream specification, used for appdata files for apps on Linux, supports specifying what input devices and display sizes an app requires or supports. GNOME Software 41 will hopefully be able to use that information to show whether an app supports your computer. Currently, though, almost no apps include this metadata in their appdata.xml file.

Please consider taking 5 minutes to add the information to the appdata.xml files you care about. Thanks!

If your app supports (and is tested with) touch devices, plus keyboard and mouse, add:

<recommends>
  <control>keyboard</control>
  <control>pointing</control>
  <control>touch</control>
</recommends>

If your app is only tested against keyboard and mouse, add:

<requires>
  <control>keyboard</control>
  <control>pointing</control>
</requires>

If it supports gamepads, add:

<recommends>
  <control>gamepad</control>
</recommends>

If your app is only tested on desktop screens (the majority of cases):

<requires>
  <display_length compare="ge">medium</display_length>
</requires>

If your app is adaptive and works on mobile device screens through to desktops, add:

<requires>
  <display_length compare="ge">small</display_length>
</requires>

Or, if you’ve developed your app to work at a specific size (mostly relevant for mobile devices), you can specify that explicitly:

<requires>
  <display_length compare="ge">360</display_length>
</requires>

Note that there may be updates to the definition of display_length in appstream in future for small display sizes (phones), so this might change slightly.

Another example is what I’ve added for Hitori, which supports touch and mouse input (but not keyboard input) and which works on small and large screens.

See the full specification for more unusual situations and additional examples.

Don’t (generally) put documentation license in appdata

There have been a few instances recently where people have pointed out that GNOME Software marks some apps as not free software when they are. This is a bug in the appdata files provided by those applications, which typically includes something like

<project_license>GPL-3.0+ and CC-BY-SA-3.0</project_license>

This is generally an attempt to list the license of the code and of the documentation. However, the resulting SPDX expression means to apply the most restrictive interpretation of both licenses. As a result, the expression as a whole is considered not free software (CC-BY-SA-3.0 is not a free software license as per the FSF or OSI lists).

Instead, those apps should probably just list the ‘main’ license for the project:

<project_license>GPL-3.0+</project_license>

and document the license for their documentation separately. As far as I know, the appdata format doesn’t currently have a way of listing the documentation license in a machine readable way.

If you maintain an app, or want to help out, please check the licensing is correctly listed in your app’s appdata.

There’s an issue open against the appdata spec for improving how licenses are documented in future — contributions also welcome there.

(To avoid doubt, I think CC-BY-SA-3.0 is a fine license for documentation; it’s just problematic to include it in the ‘main’ appdata license statement for an app.)