The Mir project has always been about how best to develop a shell for the modern desktop. It was about addressing concerns like a security model for desktop environments; convergence (which has implications for app lifecycles); and, making efficient use of modern hardware. It has never been only about Unity8, that was just the first of (hopefully) many shells written using Mir. To that end, the Mir developers have tried to ensure that the code wasn’t too tightly coupled to Unity8 (e.g. by developing demo servers with alternative behaviors).
There have been many reasons that no other shells used Mir but to tackle some of them I started a “hobby project” (MirAL) last year. MirAL aimed to make it easier to build shells other than Unity8 with Mir, and one of the examples I produced, miral-kiosk, proved important to Canonical’s support for graphics for the “Internet of Things”. Even on the Internet of Things Mir is more than just a way of getting pixels onscreen, it also fits the security model needed. That secures a future for Mir at Canonical.
In Canonical the principle target for Mir is now Ubuntu Core, and that is currently based on the 16.04LTS. We’ve recently released Mir 0.26.3 to this series and will be upgrading it to Mir 1.0 when that comes out.
Outside Canonical there are other projects that are making use of Mir.
UBports is taking forward the work begun by Canonical to support phones and tablets. Their current stack is based on an old release of Mir (0.17) but they are migrating to Ubuntu 16.04LTS and will get the latest release of Mir with that.
Yunit is taking forward the work begun by Canonical on “convergence”. They are still in an exploratory phase, but the debs they’ve created for Debian Unstable use the current Mir 0.26 release.
As reported elsewhere there have been discussions with other projects who are interested in using Mir. It remains to see if, and in what way, those discussions develop.
For all of these projects the Mir team must be more responsive than it has been to the needs of those outside Canonical. I think, with the work done on MirAL, much of the technical side of that has been addressed. But we still have to prove ourselves in other ways.
There’s a new (0.27) release of Mir undergoing testing for release to the Ubuntu 17.10 series. This delivers a lot of the work that was “in progress” before Canonical’s focus shifted from Unity8 to miral-kiosk and marks the point of departure from our previous plans for a Mir 1.0. Mir 0.27 will not be released to other series, as we expect to ship Mir 1.0 in 17.10.
The other thing 0.27 offers is based on the efforts we’ve seen in UBports (and a PR from a former Mir developer that has joined the project): we’ve published the APIs needed to develop a “mir platform” out of the Mir source tree. That means, for example, developing a mir-on-wayland platform doesn’t require forking the whole of Mir. One specific platform that is now out-of-tree is the “mir-on-android” platform – from my experience with MirAL I know that having a real out-of-tree project helps prove things really work.
In addition, while we won’t be releasing Mir 0.27 to 17.04, I’ve included testing there, along with the Unity8 desktop to ensure that all the features required by a “real shell” remain intact.
Beyond Mir 0.27 the plan towards 1.0 diverges from past discussions. We are no longer planning to remove deprecated functions from the libmirclient ABI, instead we are working towards supporting Wayland clients directly.