why toLatin1? I would expect a toUtf8?

random suggestion: use a wayland-protocols compliant license right from the start? Just in case it ever goes upstream...

5.XX

5.XX, though I think you don't need to change it. I'm quite certain we make 5.41

a conceptional alternative could be to delegate this through the SurfaceInterface like how it was done for idleInhibit protocol. I'm fine with both approaches.

Please add some documentation.

documentation missing.

Wayland strings can be UTF-8 but DBus service names and object paths can only be ASCII.

I figured it was best to avoid any potential locale issues.

I'm also fine with either, kwayland has a bit of both. This mostly copies the ServerSideDecoration style.

My rationale was that this isn't double-buffered against the surface commits, so didn't proxy it, but I don't mind either way.

Fair enough. I wasn't aware of the DBus restriction. I suggest to add it to the protocol definition. E.g. in Wayland protocols we find: "The string must be encoded in UTF-8. " So I suggest to do something similar, just to be sure.

I just noticed that this is missing documentation. The wayland protocol generator is not happy if the documentation is missing and emits warnings.

Could you please add "The string must be encoded in latin-1".