Ubports relies on Mir for a large part of the graphics stack and Mir has been changing in ways that make that problematic. In particular:
- Mir 2.x has made some server APIs private and these are used by the UBPorts QtMir and unity-system-compositor (unless that's been renamed to lomiri-system-compositor); and,
- The other problem is that some features exposed by the mirclient API are not supported by Mir's Wayland support.
Andrew Koenig's "Fundamental Theorem of Software Engineering" says that "we can solve any problem by introducing an extra level of indirection." Miroil is an extra level of indirection that solves the problem of Lomiri depending on features that Mir no longer offers.
A bit of history
While Canonical was working on Ubuntu Touch there was a plan to update QtMir to remove the direct dependencies on mirserver and migrate some code into the (then separate) MirAL project that would provide the functionality QtMir needed from mirserver. As a first step much of the code that depended on mirserver was moved to a
src/platforms/mirserver/miral directory in QtMir. This has been updated and extended over the years, but the intended move of the code out of QtMir into MirAL never happened.
A similar exercise for code in unity-system-compositor was started by @WebDrake and that too stalled before code was moved.
Because of events this year I have a few more vacation days to use by the end of the year than I normally have. So I've decided to start a project to complete the work described above. (Although Miroil lives in the Mir repository it isn't going to be a significant part of my "day job" as Mir development lead.)
The point of Miroil is to provide the support from Mir needed for Ubuntu Touch to move to Mir 2.x and Wayland. This will require further input from downstream before it is fully functional and I'm appealing for any interested developers to help.
Current status of Miroil
I've created a feature branch from Mir "master" that included this new library and APIs and added the work already completed in QtMir.
I've taken a look at the unity-system-compositor work, but that is still incomplete and I don't currently have the time to bring that to a state ready to move into Miroil.
The future of Miroil
For any interested developers, it is possible to work on Miroil on "desktop" and test with QtMir, Lomiri and unity-system-compositor.
While the current work in progress is based on Mir 2.x it is sufficiently isolated from the rest of Mir to make a backport to Mir 1.x a simple "cherry-pick" once it reaches a sufficient level of maturity to be of interest to Lomiri development. (And doing that would simplify Lomiri migration to Mir 2.x.)
With my "hobby project" hat on, I've still got some (but not much) vacation time left to spend on this, and plan to look into providing a Wayland extension that maps easily to the "trusted prompt session" APIs from mirclient.
With my "Mir team lead" hat on, I'm happy to accept something like Miroil into the Mir source tree to support Lomiri development. And ensuring that it continues to build, pass tests and deploy. But further development will be a very low priority for a small team with other responsibilities.
Miroil needs you!
I won't have time to do everything that needs doing. But I will try to help anyone interested in joining this effort and am trying to provide a template to follow for the different aspects of work needed, in particular, server APIs and Wayland extensions.
If anyone has the time to document how to build QtMir on the desktop and how to run the test program the project contains that would reduce the barrier for others interested in helping. (Also the same for unity-system-compositor and Lomiri.)
|General advice on developing Mir||https://mir-server.io/doc/getting_involved_in_mir.html|
|The Miroil PR||https://github.com/MirServer/mir/pull/1820|
|The unity-system-compositor PR||https://github.com/ubports/unity-system-compositor/pull/4|