backend: add signals for reporting suspend and resume

This commit adds "suspending" and "resuming" signals
to MetaBackend.

It's preliminary work needed for tracking when to purge
and recreate all textures (needed by nvidia).

src/backends/meta-backend.c

@@ -26,6 +26,8 @@
 
 #include <stdlib.h>
 
+#include <gio/gunixfdlist.h>
+
 #include <clutter/clutter-mutter.h>
 #include <meta/meta-backend.h>
 #include <meta/main.h>
@@ -60,7 +62,8 @@ enum
   KEYMAP_CHANGED,
   KEYMAP_LAYOUT_GROUP_CHANGED,
   LAST_DEVICE_CHANGED,
-
+  SUSPENDING,
+  RESUMING,
   N_SIGNALS
 };
 
@@ -550,6 +553,20 @@ meta_backend_class_init (MetaBackendClass *klass)
                   0,
                   NULL, NULL, NULL,
                   G_TYPE_NONE, 1, G_TYPE_INT);
+  signals[SUSPENDING] =
+    g_signal_new ("suspending",
+                  G_TYPE_FROM_CLASS (object_class),
+                  G_SIGNAL_RUN_LAST,
+                  0,
+                  NULL, NULL, NULL,
+                  G_TYPE_NONE, 0);
+  signals[RESUMING] =
+    g_signal_new ("resuming",
+                  G_TYPE_FROM_CLASS (object_class),
+                  G_SIGNAL_RUN_LAST,
+                  0,
+                  NULL, NULL, NULL,
+                  G_TYPE_NONE, 0);
 
   mutter_stage_views = g_getenv ("MUTTER_STAGE_VIEWS");
   stage_views_disabled = g_strcmp0 (mutter_stage_views, "0") == 0;
@@ -584,15 +601,66 @@ lid_is_closed_changed_cb (UpClient   *client,
   meta_idle_monitor_reset_idletime (meta_idle_monitor_get_core ());
 }
 
+static void
+inhibit_sleep (MetaBackend *backend)
+{
+  MetaBackendPrivate *priv = meta_backend_get_instance_private (backend);
+  g_autoptr (GVariant) fd_variant = NULL;
+  g_autoptr (GUnixFDList) fd_list = NULL;
+  g_autoptr (GError) error = NULL;
+  int handle, fd;
+
+  if (priv->inhibit_sleep_fd >= 0)
+    return;
+
+  if (!login1_manager_call_inhibit_sync (priv->logind_proxy,
+                                         "sleep",
+                                         "Display Server",
+                                         "Prepare for suspend",
+                                         "delay",
+                                         NULL,
+                                         &fd_variant,
+                                         &fd_list,
+                                         priv->cancellable,
+                                         &error))
+    {
+      g_warning ("Failed to inhibit sleep: %s", error->message);
+      return;
+    }
+
+  handle = g_variant_get_handle (fd_variant);
+  fd = g_unix_fd_list_get (fd_list, handle, &error);
+
+  if (fd < 0)
+    {
+      g_warning ("Failed to fetch sleep inhibitor fd: %s", error->message);
+      return;
+    }
+
+  priv->inhibit_sleep_fd = fd;
+}
+
+static void
+uninhibit_sleep (MetaBackend *backend)
+{
+  MetaBackendPrivate *priv = meta_backend_get_instance_private (backend);
+
+  close (priv->inhibit_sleep_fd);
+  priv->inhibit_sleep_fd = -1;
+}
+
 static void
 prepare_for_sleep_cb (MetaBackend *backend,
                       gboolean     suspending)
 {
-  gboolean suspending;
+  if (suspending) {
-
+    g_signal_emit (backend, signals[SUSPENDING], 0);
-  g_variant_get (parameters, "(b)", &suspending);
+    uninhibit_sleep (backend);
-  if (suspending)
     return;
+  }
+
+  inhibit_sleep (backend);
+  g_signal_emit (backend, signals[RESUMING], 0);
   meta_idle_monitor_reset_idletime (meta_idle_monitor_get_core ());
 }
 
@@ -619,6 +687,7 @@ system_bus_gotten_cb (GObject      *object,
                       GAsyncResult *res,
                       gpointer      user_data)
 {
+  MetaBackend *backend = META_BACKEND (user_data);
   MetaBackendPrivate *priv;
   g_autoptr (GError) error = NULL;
   GDBusConnection *bus;
@@ -630,15 +699,21 @@ system_bus_gotten_cb (GObject      *object,
   priv = meta_backend_get_instance_private (user_data);
   priv->system_bus = bus;
   priv->logind_proxy = get_logind_proxy (priv->cancellable, &error);
+  priv->inhibit_sleep_fd = -1;
 
   if (!priv->logind_proxy)
-    g_warning ("Failed to get logind proxy: %s", error->message);
+    {
-
+      g_warning ("Failed to get logind proxy: %s", error->message);
-  g_signal_connect_object (priv->logind_proxy,
+    }
-                           "prepare-for-sleep",
+  else
-                           G_CALLBACK (prepare_for_sleep_cb),
+    {
-                           user_data,
+      inhibit_sleep (backend);
-                           G_CONNECT_SWAPPED);
+      g_signal_connect_object (priv->logind_proxy,
+                               "prepare-for-sleep",
+                               G_CALLBACK (prepare_for_sleep_cb),
+                               user_data,
+                               G_CONNECT_SWAPPED);
+    }
 }
 
 static gboolean