[Lazarus] Gtk2 Linux detect user logoff?

[Michael Van Canneyt]

On Mon, 23 Mar 2020, Anthony Walter via lazarus wrote:

> Does anyone here know how to detect user log off and gracefully terminate
> under Gtk2 Linux? I have an app which uses some temporary files (in /tmp)
> and I want to ensure those files are deleted when the user logs off. The
> application query/end session events don't seem to be connected when using
> the Gtk2 widgetset.
>
>> From this stack overflow answer it would seem there is a 'save-yourself'
> sinal to notify you when the user logs off, but I don't know what the LCL
> value of client might be. Could it be application handle? Is there a better
> way to detect user log off on Gtk2?
>
> https://stackoverflow.com/a/2519829/269630

I suspect this is a dbus signal. 
Maybe gnome API interfaces expose an api for the signals of the session
manager. I doubt GTK handles these signals, and I don't think Lazarus uses
the Gnome signals or the Gnome API.

So I would attempt to connect to the gnome session manager using dbus. 
FPC has a DBUS client component, so this should not be too hard.

I have some uncommitted example programs that may help you if you decide to
go this path.

Michael.