Friday, 14 June 2013

Re: non-Unity flavours and Mir

On Fri, Jun 14, 2013 at 03:54:32PM +0100, Jonathan Riddell wrote:
> Here's a discussion I half started as part of vUDS.
> The switch to Mir in Ubuntu seems pretty risky for the existance of
> Kubuntu, I wonder if other flavours have the same probable problem.
> KWin dev has opinions on the subject
> From the architecture section on that blog post:
> "Mir's architecture is centered around Unity. It is difficult to really
> understand the architecture of Mir as the specification is so full of
> buzz-words that I don't understand it [5]. From all I can see and
> understand Unity Next is a combination of window manager and desktop
> shell implemented on top of Mir. How exactly this is going to look
> like I do not know. Anyway it does not fit our design of having
> desktop shell and window manager separated and we do not know whether
> Mir would support that. We also do not know whether Mir would allow
> any other desktop shell except Unity Next, given that this is the main
> target. Wayland on the other hand is designed to have more than one
> compositor implementations. Using KWin as a session compositor is an
> example in the spec."
> and on protocol
> "But it gets worse, the protocol between Mir server and Mir clients
> is defined as not being stable. In fact it's promised that it will
> break. That's a huge problem, I would even call it a showstopper....
> Given that the protocol may change any time and given that the whole
> thing is developed for the needs of Unity we have to expect that the
> server libraries are not binary compatible or that old version of the
> server libraries cannot talk with the latest client libraries"
> Canonical was going to port LightDM to Wayland but now does not plan
> to so someone else would have to do this. KDE might be interested
> but more likely will switch to SDDM.
> For Kubuntu the options are:
> - Use Mir - infeasable as upstream can't support it as described above
> - Use Wayland with packages from Debian and hope we can make those packages
> live with Mir as best as possible
> - End of Kubuntu
> The second options is the one I'm expecting. It's completely unknown
> how much it means Kubuntu and other flavours will need to maintain X
> and Wayland packages, hopefully not much (it's hardly our speciality)
> and hopefully Debian and Ubuntu Desktop will support it enough.
> I don't think there's a public timeline for Mir so we don't know when
> this will hit us, presumably in the next year.
> Other flavours I think are this:
> Mythbuntu: not evaluated, hope to do so once NVideo and AMD provide drivers
> Lubuntu: not evaluated, hope to use X and GTK
> ubuntustudio: I've heard both that they use xfce based on xubuntu and
> will follow them, and "aiming for users to choose whatever desktop
> environment they want"
> Any other flavours got an opinions?
> Are there any misconceptions I have in the above?
> Jonathan

Hi Jonathan,

Edubuntu currently ships with both Unity and gnome-fallback, so we also have an
interest in keeping working X sessions for that last one.

Anyway, my understanding was that Mir would become the system compositor and
act as the main compositor for Unity, but that for the other sessions, one
could simply run X with the Mir driver on top of Mir and then run a standard
accelerated X session (I understand that the accelerated part is still work in
progress at the moment).

Might be worth having one of the Unity/Mir guys confirm this though and maybe
get a clearer picture of how that'd work per-session (on a system that ships
both Unity and a non-Mir desktop environment).

Stéphane Graber
Ubuntu developer