launcher: Add session-active property to decouple from backend native

By connecting to changes of the new property in backend native itself.
This removes the dependency on the native backend and allows us to move
it to the generic backend.

Part-of: <https://gitlab.gnome.org/GNOME/mutter/-/merge_requests/4130>

src/backends/native/meta-backend-native.c

@@ -734,6 +734,17 @@ on_started (MetaContext *context,
   meta_seat_native_start (META_SEAT_NATIVE (seat));
 }
 
+static void
+on_session_active_changed (MetaLauncher      *launcher,
+                           GParamSpec        *pspec,
+                           MetaBackendNative *native)
+{
+  if (meta_launcher_is_session_active (launcher))
+    meta_backend_native_resume (native);
+  else
+    meta_backend_native_pause (native);
+}
+
 static gboolean
 meta_backend_native_init_basic (MetaBackend  *backend,
                                 GError      **error)
@@ -776,6 +787,10 @@ meta_backend_native_init_basic (MetaBackend  *backend,
           priv->mode = META_BACKEND_NATIVE_MODE_HEADLESS;
           g_message ("No seat assigned, running headlessly");
         }
+
+      g_signal_connect (priv->launcher, "notify::session-active",
+                        G_CALLBACK (on_session_active_changed),
+                        native);
     }
 
   priv->device_pool = meta_device_pool_new (native);

src/backends/native/meta-launcher.c

@@ -33,10 +33,20 @@
 
 #include "backends/meta-backend-private.h"
 #include "backends/meta-dbus-utils.h"
-#include "backends/native/meta-backend-native.h"
 
 #include "meta-dbus-login1.h"
 
+enum
+{
+  PROP_0,
+
+  PROP_SESSION_ACTIVE,
+
+  N_PROPS
+};
+
+static GParamSpec *obj_props[N_PROPS];
+
 struct _MetaLauncher
 {
   GObject parent;
@@ -59,6 +69,25 @@ meta_launcher_get_seat_id (MetaLauncher *launcher)
   return launcher->seat_id;
 }
 
+static void
+meta_launcher_get_property (GObject    *object,
+                            guint       prop_id,
+                            GValue     *value,
+                            GParamSpec *pspec)
+{
+  MetaLauncher *launcher = META_LAUNCHER (object);
+
+  switch (prop_id)
+    {
+    case PROP_SESSION_ACTIVE:
+      g_value_set_boolean (value, launcher->session_active);
+      break;
+    default:
+      G_OBJECT_WARN_INVALID_PROPERTY_ID (object, prop_id, pspec);
+      break;
+    }
+}
+
 static void
 meta_launcher_dispose (GObject *object)
 {
@@ -77,6 +106,15 @@ meta_launcher_class_init (MetaLauncherClass *klass)
   GObjectClass *object_class = G_OBJECT_CLASS (klass);
 
   object_class->dispose = meta_launcher_dispose;
+  object_class->get_property = meta_launcher_get_property;
+
+  obj_props[PROP_SESSION_ACTIVE] =
+    g_param_spec_boolean ("session-active", NULL, NULL,
+                          TRUE,
+                          G_PARAM_READABLE |
+                          G_PARAM_STATIC_STRINGS);
+
+  g_object_class_install_properties (object_class, N_PROPS, obj_props);
 }
 
 static void
@@ -334,8 +372,6 @@ get_seat_proxy (char          *seat_id,
 static void
 sync_active (MetaLauncher *self)
 {
-  MetaBackend *backend = self->backend;
-  MetaBackendNative *backend_native = META_BACKEND_NATIVE (backend);
   MetaDBusLogin1Session *session_proxy = self->session_proxy;
   gboolean active;
 
@@ -344,11 +380,8 @@ sync_active (MetaLauncher *self)
     return;
 
   self->session_active = active;
-
-  if (active)
-    meta_backend_native_resume (backend_native);
-  else
-    meta_backend_native_pause (backend_native);
+  g_object_notify_by_pspec (G_OBJECT (self),
+                            obj_props[PROP_SESSION_ACTIVE]);
 }
 
 static void
@@ -454,6 +487,7 @@ meta_launcher_new (MetaBackend  *backend,
     }
 
   g_signal_connect (self->session_proxy, "notify::active", G_CALLBACK (on_active_changed), self);
+  sync_active (self);
 
   return self;
 
@@ -477,6 +511,12 @@ meta_launcher_activate_vt (MetaLauncher  *launcher,
                                                     NULL, error);
 }
 
+gboolean
+meta_launcher_is_session_active (MetaLauncher *launcher)
+{
+  return launcher->session_active;
+}
+
 MetaBackend *
 meta_launcher_get_backend (MetaLauncher *launcher)
 {

src/backends/native/meta-launcher.h

@@ -38,6 +38,8 @@ gboolean meta_launcher_activate_vt (MetaLauncher  *self,
                                     signed char    vt,
                                     GError       **error);
 
+gboolean meta_launcher_is_session_active (MetaLauncher *launcher);
+
 const char * meta_launcher_get_seat_id (MetaLauncher *launcher);
 
 MetaDBusLogin1Session * meta_launcher_get_session_proxy (MetaLauncher *launcher);