Allow building with elogind

[craftyguy]

This makes the runtime systemd dep requirement optional when building with -Dsystemd=true so that colord can be built with support for libsystemd on distros that use elogind. There should be no impact here when building colord on distros that use systemd, both libsystemd and systemd should exist in that case.

[hughsie]

Why can't we use -Dsystemd=disabled for the elogind case?

[craftyguy]

@hughsie because the meson doesn't pull in libsystemd (and HAVE_SYSTEMD is unset for the #ifdef in code) if that option is not enabled, so elogind isn't actually used for the seat stuff, etc

Sorry this might not be obvious, but elogind provides libsystemd.pc and is compatible with libsystemd

[hughsie]

but elogind provides libsystemd.pc and is compatible with libsystemd

Then I'm double confused; why can't systems using elogind just use -Dsystemd=enabled??

[craftyguy]

Because dependency('systemd') fails, nothing from elogind provides that, and you only use it to determine install paths for unit files, which is a runtime thing.

So this patch makes that 'systemd' dependency optional so it builds on systems with elogind, but still supports finding libsystemd (which elogind can provide) when using -Dsystemd=true for supporting the api

[hughsie]

I think elogind either needs to provide full compatibility with systemd or none; providing one of the two pkg-config files is super weird and adds to the maintenance burden.

[craftyguy]

Ya I don't disagree, but I'm in no position to change elogind's behavior and patching colord this way was much simpler and straight forward. It's fine if you want to NAK this patch, we are using it anyways in Alpine Linux, I just thought you might want it since we aren't the only distro using elogind (and no systemd) 😁

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On January 9, 2025 3:37:03 AM PST, Richard Hughes ***@***.***> wrote: I think elogind either needs to provide full compatibility with systemd or none; providing one of the two pkg-config files is super weird and adds to the maintenance burden.