input/libinput: make udev optional

[illiliti]

trafficstars

See also https://gitlab.freedesktop.org/wlroots/wlroots/-/merge_requests/3490

[emersion]

We can probably make this depend on wlroots.get_variable('have_session') == 'true' as a first step now that wlroots!3874 is merged.

[emersion]

Actually since this is only used for libinput backend stuff, have_libinput_backend would be more appropriate.

[illiliti]

What exactly should depend on have_libinput_backend? dependency('libudev')?

[emersion]

Yeah

[illiliti]

So udev will be assumed dependency if libinput is present, right? It doesn't make sense to me since I patched out udev dependency from libinput in my branch.

By the way, isn't sway has mandatory dependency on libinput and session backends?

[emersion]

So udev will be assumed dependency if libinput is present, right? It doesn't make sense to me since I patched out udev dependency from libinput in my branch.

It would be a first step.

By the way, isn't sway has mandatory dependency on libinput and session backends?

Nope

[illiliti]

The better first step would be cooperating with libinput to implement sway_libinput_device_is_builtin there. Then udev would just go away from sway.

But anyway, feel free to open another PR and do your own thing. I'll keep this PR as is since I don't want to make udev mandatory with libinput backend enabled.

By the way, isn't sway has mandatory dependency on libinput and session backends?

Nope

I see at least three wlr/backend/session.h header includes. As of libinput, it is literally everywhere.