# Ported from gnome-session git commit 53cb8b5d6deb2f6425a388e46c58f097fe126904
# (30.6.2019) - " gsm-systemd: Find user's graphical session, not the current pid's session"
# (https://github.com/GNOME/gnome-session/commit/53cb8b5):
# =============================================================================
# If we're started by systemd --user, we won't be in the XDG session of
# the user. The session will still exist, and we want to monitor when it
# closes so that we know when to die ourselves.
#

diff -up mate-session-manager-f56f8cd63d330e576aeabd09a0600a8da2e02392/mate-session/gsm-systemd.c~ mate-session-manager-f56f8cd63d330e576aeabd09a0600a8da2e02392/mate-session/gsm-systemd.c
--- mate-session-manager-f56f8cd63d330e576aeabd09a0600a8da2e02392/mate-session/gsm-systemd.c~	2021-05-17 10:22:07.111952069 +0200
+++ mate-session-manager-f56f8cd63d330e576aeabd09a0600a8da2e02392/mate-session/gsm-systemd.c	2021-05-17 10:22:07.193952605 +0200
@@ -44,6 +44,8 @@
 #define SD_SEAT_INTERFACE    "org.freedesktop.login1.Seat"
 #define SD_SESSION_INTERFACE "org.freedesktop.login1.Session"
 
+#define SYSTEMD_SESSION_REQUIRE_ONLINE 0 /* active or online sessions only */
+
 typedef struct
 {
     DBusGConnection *dbus_connection;
@@ -292,6 +294,104 @@ gsm_systemd_on_name_owner_changed (DBusG
     gsm_systemd_ensure_sd_connection (manager, NULL);
 }
 
+static gboolean
+_systemd_session_is_graphical (const char *session_id)
+{
+        const gchar * const graphical_session_types[] = { "wayland", "x11", "mir", NULL };
+        int saved_errno;
+        g_autofree gchar *type = NULL;
+
+        saved_errno = sd_session_get_type (session_id, &type);
+        if (saved_errno < 0) {
+                g_warning ("Couldn't get type for session '%s': %s",
+                           session_id,
+                           g_strerror (-saved_errno));
+                return FALSE;
+        }
+
+        if (!g_strv_contains (graphical_session_types, type)) {
+                g_debug ("Session '%s' is not a graphical session (type: '%s')",
+                         session_id,
+                         type);
+                return FALSE;
+        }
+
+        return TRUE;
+}
+
+static gboolean
+_systemd_session_is_active (const char *session_id)
+{
+        const gchar * const active_states[] = { "active", "online", NULL };
+        int saved_errno;
+        g_autofree gchar *state = NULL;
+
+        /*
+         * display sessions can be 'closing' if they are logged out but some
+         * processes are lingering; we shouldn't consider these (this is
+         * checking for a race condition since we specified
+         * SYSTEMD_SESSION_REQUIRE_ONLINE)
+         */
+        saved_errno = sd_session_get_state (session_id, &state);
+        if (saved_errno < 0) {
+                g_warning ("Couldn't get state for session '%s': %s",
+                           session_id,
+                           g_strerror (-saved_errno));
+                return FALSE;
+        }
+
+        if (!g_strv_contains (active_states, state)) {
+                g_debug ("Session '%s' is not active or online", session_id);
+                return FALSE;
+        }
+
+        return TRUE;
+}
+
+static gboolean
+gsm_systemd_find_session (char **session_id)
+{
+        char *local_session_id = NULL;
+        g_auto(GStrv) sessions = NULL;
+        int n_sessions;
+
+        g_return_val_if_fail (session_id != NULL, FALSE);
+
+        g_debug ("Finding a graphical session for user %d", getuid ());
+
+        n_sessions = sd_uid_get_sessions (getuid (),
+                                          SYSTEMD_SESSION_REQUIRE_ONLINE,
+                                          &sessions);
+
+        if (n_sessions < 0) {
+                g_critical ("Failed to get sessions for user %d", getuid ());
+                return FALSE;
+        }
+
+        for (int i = 0; i < n_sessions; ++i) {
+                g_debug ("Considering session '%s'", sessions[i]);
+
+                if (!_systemd_session_is_graphical (sessions[i]))
+                        continue;
+
+                if (!_systemd_session_is_active (sessions[i]))
+                        continue;
+
+                /*
+                 * We get the sessions from newest to oldest, so take the last
+                 * one we find that's good
+                 */
+                local_session_id = sessions[i];
+        }
+
+        if (local_session_id == NULL)
+                return FALSE;
+
+        *session_id = g_strdup (local_session_id);
+
+        return TRUE;
+}
+
 static void
 gsm_systemd_init (GsmSystemd *manager)
 {
@@ -428,13 +528,15 @@ gsm_systemd_is_last_session_for_user (Gs
         int ret, i;
 
 #ifdef HAVE_SYSTEMD
-        ret = sd_pid_get_session (getpid (), &session);
+        ret = gsm_systemd_find_session (&session);
 #endif
 
         if (session == NULL) {
                 return FALSE;
         }
 
+        g_debug ("Found session ID: %s", session);
+
         if (ret != 0) {
                 free (session);
                 return FALSE;
@@ -584,12 +686,14 @@ gsm_systemd_get_session_path (DBusConnec
     gchar          *session_id = NULL;
 
 #ifdef HAVE_SYSTEMD
-    sd_pid_get_session (getpid (), &session_id);
+    gsm_systemd_find_session (&session_id);
 #endif
 
     if (session_id == NULL)
         return;
 
+    g_debug ("Found session ID: %s", session_id);
+
     reply = NULL;
 
     dbus_error_init (&local_error);
@@ -710,12 +814,14 @@ gsm_systemd_can_switch_user (GsmSystemd
     }
 
 #ifdef HAVE_SYSTEMD
-    sd_pid_get_session (getpid (), &session_id);
+    gsm_systemd_find_session (&session_id);
 #endif
 
     if (session_id == NULL)
         return FALSE;
 
+    g_debug ("Found session ID: %s", session_id);
+
 #ifdef HAVE_SYSTEMD
     sd_session_get_seat (session_id, &seat_id);
     ret = sd_seat_can_multi_session (seat_id);
@@ -989,12 +1095,14 @@ gsm_systemd_get_current_session_type (Gs
     }
 
 #ifdef HAVE_SYSTEMD
-    sd_pid_get_session (getpid (), &session_id);
+    gsm_systemd_find_session (&session_id);
 #endif
 
     if (session_id == NULL)
         return NULL;
 
+    g_debug ("Found session ID: %s", session_id);
+
 #ifdef HAVE_SYSTEMD
     res = sd_session_get_class (session_id, &session_class);
     if (res < 0) {