Add the "url" launchable type

[dchristidis]

From my initial PR on appstream-glib:

The Telegram web application opens its homepage. Instead, it should open this location. As it stands, a user has to perform unnecessary clicks each time the application is launched. Another example is Skype (homepage, web app), which would be a wonderful addition once WebKitGTK+ can support it.

I suggest adding a new, optional type AS_URL_KIND_WEB_APP. If this is acceptable, I will submit a patch to GNOME Software so that it prefers it over AS_URL_KIND_HOMEPAGE during the web application installation.

I’m hoping that the justification is reasonable and the implementation correct.

[aleixpol]

The fact that it has a web-app could be circumstancial. Sounds like it should be the value of the a <bundle type="webapp>https://...`.

See https://www.freedesktop.org/software/appstream/docs/chap-CollectionData.html

<url> is usually from before deciding to adopt the software.

[ximion]

This needs some discussion first. Web applications have never been properly defined in AppStream, and it has been a long-time item on my todo list.
I actually thought about using the bundle tag for this as well, because a bundle is a way of distributing the app, while the URL tag just exists for additional information on the app.
@hughsie What do you think?

[hughsie]

Web apps don't really have a bundle, they're not bundled blobs, they really are just a URL and some metadata already in the AppStream XML.

[ximion]

@hughsie Jup, that's my problem with using <bundle/> as well. But the <url/> tag is thought to be additional, informative weblinks that have nothing to do with the delivery method of an app. The very purpose of the <bundle/> tag however is to describe how software can be made to work.

So, from that standpoint is see webapp-URLs being closer to bundle than to URL. In order for this to go into AppStream properly, we would also need to determine what a webapp is exactly, and how a software center should deal with it (just open the URL in a webbrowser? or something different?).

[ximion]

Actually, the intended purpose here is closest in spirit to the <launchable/> tag.
So, as for the spec, I propose a <launchable type="url">https://example.com</launchable> tag addition that is required for all components of type web-application.

As for how software centers should handle this, there are still open questions (should they use a dedicated browser? what is the difference from a web app compared to a simple hyperlink? which websites actually are apps?) I also wonder how we distinguish the current web-application components from things like Wordpress and NextCloud, which people might also occasionally want to install from a software store.

[hughsie]

Launchable makes sense to me too.

[hughsie]

I also wonder how we distinguish the current web-application components

It's a different component type for sure.

[ximion]

@hughsie At the moment, those are of the "service" component-type, because they essentially are services that run in the background. But let's not worry about that yet.

[dchristidis]

Thank you for discussing this issue. I have submitted a new patch for which I’m hoping to receive feedback on.

I’m not sure where to state that a launchable tag of type url is required for components of type web-application. It looks like there’s a need for a new section in chapter 2, but I don’t feel qualified to write it.

[ximion]

I’m not sure where to state that a launchable tag of type url is required for components of type web-application. It looks like there’s a need for a new section in chapter 2, but I don’t feel qualified to write it.

Exactly. Web applications were not really supported in AppStream until now and were more of a hidden feature. It's likely time to change that, and I already started drafting the new section in the spec.

Your patch looks fine to me, thanks!