library: Add Session Monitor and Inhibit entry

[AkshayWarrier]

Closes #496 and closes #497

[AkshayWarrier]

I have tried to replicate ASPHD demo. I tested the session inhibits for LOGOUT and IDLE and they seem to work fine, but I'm not sure how USER_SWITCH and SUSPEND is supposed to work. Whenever I try to suspend or switch user, nothing happens. I even tried comparing it to ASPHD Demo and nothing happens there either.

Also, I'm activating the session_inihibit(s) as soon as the session starts as opposed to when session-state-change is triggered. I'm not sure what's the correct method but when I try to do the latter, the inhibition always happens late and I have to logout a second time to see it.

[sonnyp]

nothing happens there either.

It might simply not be implemented in GNOME?

Also, I'm activating the session_inihibit(s) as soon as the session starts as opposed to when session-state-change is triggered. I'm not sure what's the correct method but when I try to do the latter, the inhibition always happens late and I have to logout a second time to see it.

Why would you wait for a session state change?

[AkshayWarrier]

Why would you wait for a session state change?

It's because in multiple places the doc mentioned something like that.
https://libportal.org/enum.LoginSessionState.html

XDP_LOGIN_SESSION_QUERY_END The session is in the query end phase, during which applications can save their state or inhibit the session from ending.

https://libportal.org/method.Portal.session_monitor_query_end_response.html

This method should be called within one second of receiving a XdpPortal::session-state-changed signal with the ‘Query End’ state, to acknowledge that they have handled the state change.
Possible ways to handle the state change are either to call xdp_portal_session_inhibit() to prevent the session from ending, or to save your state and get ready for the session to end.

[sonnyp]

Ha, I thought it was about something else.

Hmm if ASHPD also exhibits the same problem then maybe it's a bug in the xdg portal ?

Could you open an issue on https://gitlab.gnome.org/GNOME/xdg-desktop-portal-gnome/-/issues with steps to reproduce using ASHPD?

[sonnyp]

For reference

[sonnyp]

Nice!

I made some small changes 6e0559f