Modernizing kmscon

Modernizing kmscon

[Skyler Ferris]

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Hello,

I am writing to see if the project is interested in using an updated version of kmscon. I ran across this information because I have started using kmscon as the main interface on my Guix machine, and ended up digging into it a bit. I am sending this email only because I think it is polite to offer information upstream, if you are not interested in this then I can keep everything locally without any problems. I am currently keeping the code in a separate repository, but if you are interested in it then I can add it to the Guix repository and send a patch. There are 3 areas I will discuss: the elogind dependency, updating to a more recent Aetf version, and some additional patches I wrote which you may or may not want.

# elogind dependency

As a result of the work I will discuss below, I noticed that the current version of kmscon does not actually have multi-seat support enabled, which can be seen in the log output on the CI platform (1):

Miscellaneous Options:
                debug: yes (yes: )
        optimizations: yes (yes: )
           multi-seat: no (no: libsystemd)

Although, there is a different line farther up in the file indicating that multi-seat support is desired. I assume that this does not cause any practical issues because a cursory search of the issue tracker doesn't show anyone discussing it. But the substitute* snippets changing the systemd dependency to an elogind dependency imply that someone wanted this at some point, so I'm mentioning it in case it's relevant. I tried building the tip of Aetf's tree with multi-seat support enabled and some changes based on the substitute* snippets. However, there was a fatal error when kmscon called `sd_login_monitor_new`. I don't know why this happened and I didn't look into it because I don't need multi-seat support and I don't have multi-seat equipment in any case.

# Aetf version

The current kmscon package uses the Aetf repository as the source, with a note that the old one is unmaintained. However, the commit that is specified is from the old repository. This means that Aetf's improvements, such as the ability to select a color palette, are not available. The package definition needs to use the meson-build-system and there are some new or updated dependencies (2). It seems to work on my machine, but currently kmscon is used in the installer where stability is critical so that users have a good first experience. So it might make sense to have a separate kmscon package with the updates and a keep the current package for the installer. I don't know how widely Aetf's version has been used, and it turns out that the automated test suite does very little (there are several files meant for interactive testing, but `meson test` only runs one test which checks some string parsing logic).

# Additional patches

I have 3 patches implementing 2 changes in my personal fork (3). The first change adds command-line options to set the desired width and height of the viewport. I added this because running kmscon in my VM did not fill the available space. This is implemented across 2 commits, but I could squash them into one patch if you want it. I was careful to preserve existing behavior if these options are not specified so it should not cause any regressions. However, I don't know if you want to keep a patch that adds a feature in your repository. Most of the patches I've seen have been about compatibility with Guix, not adding new features. I did open a pull request with the upstream repository, but I do not think it is maintained any more. The most recent commit is from last year, and there are pull requests more than 6 months old which have not received any reply from the developer.

I expect that you will want the other change if you want the updated kmscon. There were some warnings emitted by the current version of meson about deprecated functionality in the build files, I just changed it to conform to the new version. This did not require any functional changes. It just makes the build log a little bit quieter, which is generally a good thing.

Sincerely,
Skyler

(1) http://ci.guix.gnu.org/build/1396560/log/raw
(2) https://git.sr.ht/~skyvine/personal-code/tree/c525f74c64b27a793aca088489d7c9cfe7090581/item/src/scheme/guile/guix/packages.scm#L81
(3) https://git.sr.ht/~skyvine/kmscon/log

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