The xdg-app story

[Alexander Larsson]

On tor, 2016-03-24 at 13:56 +0100, Alexander Larsson wrote:
> 
> So, supposing we rename the project. What would that mean in terms of
> breakage. We don't really have much internet presence yet, so a new
> webpage for zapp would be no problem at all. However, there are some
> things that we do have. In order of how problematic to change these
> are:
> 
> * xdg-app at lists.freedesktop.org
> * bugzilla @ freedesktop
> * git repo @ freedesktop
> * xdg-app commandline tools
> * libxdgapp soname
> * org.freedesktop.XdgApp dbus service
> * ~/.local/share/xdg-app & /var/lib/xdg-app directory names
> 
> Do we change all of these too? or just some? if so, which ones?

So, I've been thinking about this, and I think we should change as much
as possible, leaving very little of the xdg-app name. However, we want
*some* level of backwards compat:

1) Already existing xdg-app repos should (mostly) work.

This is pretty easy, as there are not a lot of xdg-app references in
the repo. 

One is the origin="xdg-app", type="xdg-app" and X-XdgApp-Tags=.. in the
appdata. Richard would know if changing this is a problem? 

The second is that the summary has a "xa.title" metadata extension in
the summary. However, that can be rewritten during zapp remote-update,
and it is completely optional, so it doesn't affect anything important.

There is also "xdg-app" in the bundle header, but I don't think there
are any live bundles out there, so we can change that.

2) Already installed per-user apps/runtimes should work after switching
over to zapp.

In practice this means that the first time zapp runs, if
~/.local/share/xdg-app exists, but not ~/.local/share/zapp, then we
should move it over and rename any internal references to xdg-app in
it.  These are: 
* re-run the exports so that the exported desktop and dbus service
files have Exec=zapp
* ostree repo config extensions should change from xa.* to xzapp.*

3) Already existing software using xdg-app apis should not break.

Note: this doesn't include gnome-software which would need some serious
changes to handle the new name for libxdg-app anyway.

All I know that uses the dbus APIs is gnome-control-center, which uses
the org.freedesktop.XdgApp.PermissionStore dbus api. So, we should keep
listening to the old name for this too.

Also, geoclue looks for "xdg-app-*.scope" as the cgroup name to detect
containerized apps. If we change this to zapp-*.scope we have to update
geoclue too, but this is not a breakage in anything, it just means that
until you update geoclue zapp apps will be "trusted" (i.e. we report
the name the app claimed it was rather than the verified app id).

This isn't a lot, and in fact, we could probably keep the "xa.*"
namespace making it even less.


That brings us to the more important question. 

Pronunciation!

Is it "zap!", or is it "zee-app"?
Opinions?

-- 
=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=
 Alexander Larsson                                            Red Hat, Inc 
       alexl at redhat.com            alexander.larsson at gmail.com 
He's an impetuous one-eyed barbarian on the edge. She's a cold-hearted 
snooty widow from a family of eight older brothers. They fight crime!