Friday, 14 June 2013

Re: non-Unity flavours and Mir

Hi all,

On Fri, Jun 14, 2013 at 5:07 PM, Stéphane Graber <> wrote:
> 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).

That's exactly right, XMir will wire up X to talk to Mir (in its
instance as a system-level compositor). In the final setup, Mir will
come up early on in the boot process and act as system-level
compositor. User sessions then talk to this system-level Mir instance,
including Mir itself. But to state this clearly, XMir will support the
X session scenario on top of Mir.



> 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
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> ubuntu-devel mailing list
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