Bug#874514: gnome-shell: cannot configure displays under Wayland/mutter

[Simon McVittie]

On Wed, 06 Sep 2017 at 11:53:00 -0700, Abhijit Hoskeri wrote:
> After updating to mutter/gnome-shell to 3.25.91, I am not able to
> rearrange display layout.

I would guess that this is because we don't have gnome-control-center
3.25.x yet, and gnome-control-center 3.24 is looking for old gnome-shell
APIs that no longer exist. Strictly speaking, when we get the new g-c-c,
gnome-shell or mutter should probably have a versioned Breaks to get
them upgraded in lockstep - but it would be premature to add that before
the new gnome-control-center is even available in experimental.

> This appears to be because of a new
> mutter/wayland dbus service being missing:
> 
>  gnome-control-c[2853]: Error applying configuration: GDBus.Error:org.freedesktop.DBus.Error.UnknownMethod: \
>         Method ApplyConfiguration is not implemented on interface org.gnome.Mutter.DisplayConfig

This indicates that gnome-control-center is talking to the D-Bus peer
to which it wants to be talking, but that peer does not implement the
org.gnome.Mutter.DisplayConfig interface at the expected object path...

> I looked for the corresponding service using busctl and could not find
> it. I could not find any corresponding dbus service config either.

... which means that looking for bus names will not help you here.

The hierarchy is:

    * bus name (vaguely analogous to an Internet server domain name)
        * has 0 or more objects (vaguely analogous to HTTP paths)
            * has 0 or more methods (vaguely analogous to GET/POST/PUT)

Looking for services (well-known bus names) with busctl is like looking
for a HTTP server with ping. It is sometimes a useful thing to do,
but it will never give you useful information about, for example, whether
that server implements POST at /cgi-bin/enter_bug.cgi.

Regards,
    smcv