From 952d32609f9bceee444fa2690afb4d28539b4b92 Mon Sep 17 00:00:00 2001
From: Lennart Poettering <lennart@poettering.net>
Date: Mon, 19 May 2014 09:03:20 +0900
Subject: [PATCH] logind: fix Display property of user objects

When we dropped support for creating a per-user to the "main" X11
display we stopped returning useful data in the "Display" user property.
With this change this is fixed and we again expose an appropriate
(graphical session) in the property that is useful as the "main" one, if
one is needed.
---
 src/login/logind-session.c   |    8 ++++++--
 src/login/logind-session.h   |    2 ++
 src/login/logind-user-dbus.c |    2 +-
 src/login/logind-user.c      |   37 +++++++++++++++++++++++++++++++++++++
 src/login/logind-user.h      |    1 +
 5 files changed, 47 insertions(+), 3 deletions(-)

diff --git src/login/logind-session.c src/login/logind-session.c
index 4fb229e..9a54101 100644
--- src/login/logind-session.c
+++ 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 src/login/logind-session.h src/login/logind-session.h
index f78f309..81957df 100644
--- src/login/logind-session.h
+++ 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 src/login/logind-user-dbus.c src/login/logind-user-dbus.c
index 6266ccb..51793f6 100644
--- src/login/logind-user-dbus.c
+++ 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 src/login/logind-user.c src/login/logind-user.c
index 5fffa65..fdbccb3 100644
--- src/login/logind-user.c
+++ 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 src/login/logind-user.h src/login/logind-user.h
index f237d2a..4e0568f 100644
--- src/login/logind-user.h
+++ 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);
-- 
1.7.9.2