`session`

The login session and the machine's power, from logind (org.freedesktop.login1): a power menu. Each can_* says whether logind allows it, so a menu greys out what it does not; an action that fails (polkit refused it, no login session, no logind) is session.failed.

Field	Type
`can_suspend`	`bool`	Suspending is allowed (logind's `CanSuspend` is `yes`, or `challenge`: polkit asks for a password first).
`can_hibernate`	`bool`	Hibernating is allowed (`CanHibernate`, as `can_suspend`).
`can_reboot`	`bool`	Rebooting is allowed (`CanReboot`, as `can_suspend`).
`can_power_off`	`bool`	Powering off is allowed (`CanPowerOff`, as `can_suspend`).
`available`	`bool`	logind answers: false without it (or without a system bus), when every action fails with `session.failed`.

Method
`action suspend()`	Suspends the machine.
`action hibernate()`	Hibernates the machine.
`action reboot()`	Reboots the machine.
`action power_off()`	Powers the machine off.
`action lock()`	Asks logind to lock this session: the locker that follows logind puts its lock up, and `lock_requested` fires, so a shell's own `lock` can follow too.
`action log_out()`	Ends this login session (logind's `TerminateSession`): every app in it is closed.

Event
`on session.lock_requested()`	logind asks this session's locker to lock it (`session.lock()`, `loginctl lock-session`, an idle daemon): `on session.lock_requested { locked = true }` puts a shell's own `lock` up.
`on session.failed(action: text, error: text)`	An action failed (polkit refused it, no login session to lock or end, logind or the system bus missing): `on session.failed(action, error) { … }`, `action` as written (`"reboot"`). A power action waiting on polkit's password dialog has not failed: it fails only when logind refuses it.