[gnome-shell/wip/laney/systemd-user: 1/2] loginManager: Get the session ID from logind if XDG_SESSION_ID unset

[Iain Lane <iainl src gnome org>]

commit a02ce7e881108178df6c81f79cfe3a2d908ac75a
Author: Iain Lane <iain orangesquash org uk>
Date:   Mon Jan 8 14:23:52 2018 +0000

    loginManager: Get the session ID from logind if XDG_SESSION_ID unset
    
    If we're started by systemd, we won't be in the user's display session.
    However, this is still the session that will get locked & unlocked. Ask
    logind what the 'display' session is, and watch for the Unlock signal
    for that session to know when to unlock.

 js/misc/loginManager.js |   21 +++++++++++++++++++--
 1 files changed, 19 insertions(+), 2 deletions(-)
---
diff --git a/js/misc/loginManager.js b/js/misc/loginManager.js
index d2c7290..6caef2b 100644
--- a/js/misc/loginManager.js
+++ b/js/misc/loginManager.js
@@ -46,8 +46,15 @@ const SystemdLoginSessionIface = '<node> \
 </interface> \
 </node>';
 
+const SystemdLoginUserIface = '<node> \
+<interface name="org.freedesktop.login1.User"> \
+<property name="Display" type="(so)" access="read" /> \
+</interface> \
+</node>';
+
 const SystemdLoginManager = Gio.DBusProxy.makeProxyWrapper(SystemdLoginManagerIface);
 const SystemdLoginSession = Gio.DBusProxy.makeProxyWrapper(SystemdLoginSessionIface);
+const SystemdLoginUser = Gio.DBusProxy.makeProxyWrapper(SystemdLoginUserIface);
 
 function haveSystemd() {
     return GLib.access("/run/systemd/seats", 0) >= 0;
@@ -109,6 +116,9 @@ var LoginManagerSystemd = new Lang.Class({
         this._proxy = new SystemdLoginManager(Gio.DBus.system,
                                               'org.freedesktop.login1',
                                               '/org/freedesktop/login1');
+        this._userProxy = new SystemdLoginUser(Gio.DBus.system,
+                                               'org.freedesktop.login1',
+                                               '/org/freedesktop/login1/user/self');
         this._proxy.connectSignal('PrepareForSleep',
                                   Lang.bind(this, this._prepareForSleep));
     },
@@ -121,8 +131,15 @@ var LoginManagerSystemd = new Lang.Class({
 
         let sessionId = GLib.getenv('XDG_SESSION_ID');
         if (!sessionId) {
-            log('Unset XDG_SESSION_ID, getCurrentSessionProxy() called outside a user session.');
-            return;
+            log('Unset XDG_SESSION_ID, getCurrentSessionProxy() called outside a user session. Asking logind 
directly.');
+            let [session, session_object_path] = this._userProxy.Display;
+            if (session) {
+                    log('Will monitor session ' + session);
+                    sessionId = session;
+            } else {
+                    log('Failed to get session from logind.');
+                    return;
+            }
         }
 
         this._proxy.GetSessionRemote(sessionId, Lang.bind(this,