JSON has problems, but that's why we have TOML:

    [gamma_size]
    type = "event"
    args = [
       { name = "size", type = "uint" }
    ]

XML isn't what I would choose here because there's no need for text markup. TOML is both simpler and friendlier than XML in this case.

I do agree that it doesn't matter much.

We have TOML in the sense that TOML is currently v0.4.0 and bears an explicit warning that the specification is unstable should be treated accordingly.

That's unfortunate, but there are a lot of projects out there that depend on TOML, and it hasn't changed since 2015. It's de facto stable at this point.

The author has said as much: https://github.com/toml-lang/toml/issues/330

Wayland predates TOML, and I think TOML would be worse than XML for this use case.

I'd be happy to know your reasons why.

Overall, XML is too verbose; in particular, the text markup features of XML are needless complexity.

It's not. It's barely more verbose than JSON and a hell of a lot more readable. JSON is appropriate for machines to talk with. XML is appropriate for writing documentation or API specs.

Thanks for the insight. Some of the comments revealed why xml was picked. I personally agree that depending on the problem you must pick the right tools and what might be a good suit in a context it might not be the best fit in another. Moreover, there are probably more mature and performant parsing libs in c for xml than for json.

However, XML might be overkill as it might be too complex for this particular scenario. XML parsing it's complicated and from time to time there are bugs in those parsers. A simpler format might also get the job done and might be safer. However XML might provide flexibility to scale.

Finally, this is what Torvalds said about XML when someone suggested to use it in git:

> XML is crap. Really. There are no excuses. XML is nasty to parse for humans, and it's a disaster to parse even for computers. There's just no reason for that horrible crap to exist.

Relevant xkcd: https://xkcd.com/927

It's USB-C ;)