manager: Don't reuse the same X server when we have a display server

GNOME is going to need a mode of operation in GDM where it manages its
own display.  In this mode of operation, we won't morph the login
screen into a user session by reusing the same X server.  Instead, we
reset the login screen to prepare it for a future login, and then let
GNOME activate its session on its own.

This commit adds the prerequisite work needed to gdm-manager.c, but
only as dead code, since the way to "turn it on" is stubbed out to
always return FALSE.

https://bugzilla.gnome.org/show_bug.cgi?id=726380

3 files changed, 26 insertions, 1 deletions

diff --git a/daemon/gdm-manager.c b/daemon/gdm-manager.c
index f55d11e0..5c59dc91 100644
--- a/daemon/gdm-manager.c
+++ b/daemon/gdm-manager.c
@@ -870,7 +870,25 @@ on_start_user_session (StartUserSessionOperation *operation)
         }
 
         display = get_display_for_user_session (operation->session);
-        gdm_display_stop_greeter_session (display);
+
+        if (gdm_session_has_own_display_server (operation->session)) {
+                uid_t allowed_uid;
+
+                g_debug ("GdmManager: session has its display server, reusing our server for another login screen");
+
+                /* The seed session is going to follow the session worker
+                 * into the new display. Untie it from this display and
+                 * create a new seed session for us. */
+                allowed_uid = gdm_session_get_allowed_user (operation->session);
+                g_object_set_data (G_OBJECT (display), "gdm-seed-session", NULL);
+                g_object_set_data (G_OBJECT (operation->session), "gdm-display", NULL);
+                create_seed_session_for_display (operation->manager, display, allowed_uid);
+        } else {
+                /* In this case, the greeter's display is morphing into
+                 * the user session display. Kill the greeter on this session
+                 * and let the seed session follow the same display. */
+                gdm_display_stop_greeter_session (display);
+        }
 
         start_user_session (operation->manager, operation);
 
diff --git a/daemon/gdm-session.c b/daemon/gdm-session.c
index 7b6b5e27..45b8acc1 100644
--- a/daemon/gdm-session.c
+++ b/daemon/gdm-session.c
@@ -2691,6 +2691,12 @@ out:
         return bypasses_xsession;
 }
 
+gboolean
+gdm_session_has_own_display_server (GdmSession *self)
+{
+        return FALSE;
+}
+
 void
 gdm_session_select_program (GdmSession *self,
                             const char *text)
diff --git a/daemon/gdm-session.h b/daemon/gdm-session.h
index d953302b..1d264f40 100644
--- a/daemon/gdm-session.h
+++ b/daemon/gdm-session.h
@@ -111,6 +111,7 @@ const char       *gdm_session_get_display_device          (GdmSession     *sessi
 const char       *gdm_session_get_display_seat_id         (GdmSession     *session);
 const char       *gdm_session_get_session_id              (GdmSession     *session);
 gboolean          gdm_session_bypasses_xsession           (GdmSession     *session);
+gboolean          gdm_session_has_own_display_server      (GdmSession     *session);
 
 void              gdm_session_start_conversation          (GdmSession *session,
                                                            const char *service_name);