5 files changed, 47 insertions, 3 deletions

diff --git a/src/login/logind-session.c b/src/login/logind-session.c
index 4fb229e354..9a54101301 100644
--- a/src/login/logind-session.c
+++ b/src/login/logind-session.c
@@ -545,6 +545,8 @@ int session_start(Session *s) {
 
         s->started = true;
 
+        user_elect_display(s->user);
+
         /* Save data */
         session_save(s);
         user_save(s->user);
@@ -553,7 +555,7 @@ int session_start(Session *s) {
 
         /* Send signals */
         session_send_signal(s, true);
-        user_send_changed(s->user, "Sessions", NULL);
+        user_send_changed(s->user, "Sessions", "Display", NULL);
         if (s->seat) {
                 if (s->seat->active == s)
                         seat_send_changed(s->seat, "Sessions", "ActiveSession", NULL);
@@ -612,6 +614,8 @@ int session_stop(Session *s, bool force) {
 
         s->stopping = true;
 
+        user_elect_display(s->user);
+
         session_save(s);
         user_save(s->user);
 
@@ -660,7 +664,7 @@ int session_finalize(Session *s) {
         }
 
         user_save(s->user);
-        user_send_changed(s->user, "Sessions", NULL);
+        user_send_changed(s->user, "Sessions", "Display", NULL);
 
         return r;
 }
diff --git a/src/login/logind-session.h b/src/login/logind-session.h
index f78f30956d..81957dfa78 100644
--- a/src/login/logind-session.h
+++ b/src/login/logind-session.h
@@ -60,6 +60,8 @@ typedef enum SessionType {
         _SESSION_TYPE_INVALID = -1
 } SessionType;
 
+#define SESSION_TYPE_IS_GRAPHICAL(type) IN_SET(type, SESSION_X11, SESSION_WAYLAND, SESSION_MIR)
+
 enum KillWho {
         KILL_LEADER,
         KILL_ALL,
diff --git a/src/login/logind-user-dbus.c b/src/login/logind-user-dbus.c
index 6266ccb0f0..51793f6dad 100644
--- a/src/login/logind-user-dbus.c
+++ b/src/login/logind-user-dbus.c
@@ -220,7 +220,7 @@ const sd_bus_vtable user_vtable[] = {
         SD_BUS_PROPERTY("RuntimePath", "s", NULL, offsetof(User, runtime_path), SD_BUS_VTABLE_PROPERTY_CONST),
         SD_BUS_PROPERTY("Service", "s", NULL, offsetof(User, service), SD_BUS_VTABLE_PROPERTY_CONST),
         SD_BUS_PROPERTY("Slice", "s", NULL, offsetof(User, slice), SD_BUS_VTABLE_PROPERTY_CONST),
-        SD_BUS_PROPERTY("Display", "(so)", property_get_display, 0, SD_BUS_VTABLE_PROPERTY_CONST),
+        SD_BUS_PROPERTY("Display", "(so)", property_get_display, 0, SD_BUS_VTABLE_PROPERTY_EMITS_CHANGE),
         SD_BUS_PROPERTY("State", "s", property_get_state, 0, 0),
         SD_BUS_PROPERTY("Sessions", "a(so)", property_get_sessions, 0, SD_BUS_VTABLE_PROPERTY_EMITS_CHANGE),
         SD_BUS_PROPERTY("IdleHint", "b", property_get_idle_hint, 0, SD_BUS_VTABLE_PROPERTY_EMITS_CHANGE),
diff --git a/src/login/logind-user.c b/src/login/logind-user.c
index 5fffa651a3..fdbccb364c 100644
--- a/src/login/logind-user.c
+++ b/src/login/logind-user.c
@@ -713,6 +713,43 @@ int user_kill(User *u, int signo) {
         return manager_kill_unit(u->manager, u->slice, KILL_ALL, signo, NULL);
 }
 
+void user_elect_display(User *u) {
+        Session *graphical = NULL, *text = NULL, *s;
+
+        assert(u);
+
+        /* This elects a primary session for each user, which we call
+         * the "display". We try to keep the assignment stable, but we
+         * "upgrade" to better choices. */
+
+        LIST_FOREACH(sessions_by_user, s, u->sessions) {
+
+                if (s->class != SESSION_USER)
+                        continue;
+
+                if (s->stopping)
+                        continue;
+
+                if (SESSION_TYPE_IS_GRAPHICAL(s->type))
+                        graphical = s;
+                else
+                        text = s;
+        }
+
+        if (graphical &&
+            (!u->display ||
+             u->display->class != SESSION_USER ||
+             u->display->stopping ||
+             !SESSION_TYPE_IS_GRAPHICAL(u->display->type)))
+                u->display = graphical;
+
+        if (text &&
+            (!u->display ||
+             u->display->class != SESSION_USER ||
+             u->display->stopping))
+                u->display = text;
+}
+
 static const char* const user_state_table[_USER_STATE_MAX] = {
         [USER_OFFLINE] = "offline",
         [USER_OPENING] = "opening",
diff --git a/src/login/logind-user.h b/src/login/logind-user.h
index f237d2a6b9..4e0568fea9 100644
--- a/src/login/logind-user.h
+++ b/src/login/logind-user.h
@@ -80,6 +80,7 @@ int user_save(User *u);
 int user_load(User *u);
 int user_kill(User *u, int signo);
 int user_check_linger_file(User *u);
+void user_elect_display(User *u);
 
 extern const sd_bus_vtable user_vtable[];
 int user_node_enumerator(sd_bus *bus, const char *path, void *userdata, char ***nodes, sd_bus_error *error);