device: Take advantage of the DBus skeleton properties caching

The device DBus skeleton interface already implements caching for the
properties and can smartly handle their update sending (batched) dbus
events on changes.

Even if the default properties are only read only and we don't care, we
are going to introduce properties that will change values, and so having
the skeleton to handle this for us is quite convenient.

Given that we don't really need to override those properties, we can
just set them at start and leave the skeleton cache to handle the rest.

In case we'd ever need to override them, however the skeleton also
provides a way to override all the properties and to get a reference of
the number of properties it defines, ensuring to keep the order they are
defined.
This would allow us to get back the parent's properties IDs and to use
this to implement ours properties getters/setters using the parent one
as fallback.

src/device.c

@@ -29,6 +29,7 @@
 #include <pwd.h>
 #include <errno.h>
 
+#include "fprintd-dbus.h"
 #include "fprintd.h"
 #include "storage.h"
 
@@ -118,9 +119,6 @@ G_DEFINE_TYPE_WITH_CODE (FprintDevice, fprint_device,
 enum fprint_device_properties {
   FPRINT_DEVICE_CONSTRUCT_DEV = 1,
   FPRINT_DEVICE_IN_USE,
-  FPRINT_DEVICE_NAME,
-  FPRINT_DEVICE_NUM_ENROLL,
-  FPRINT_DEVICE_SCAN_TYPE
 };
 
 enum fprint_device_signals {
@@ -289,41 +287,75 @@ fprint_device_get_property (GObject *object, guint property_id,
       g_value_set_boolean (value, g_hash_table_size (priv->clients) != 0);
       break;
 
-    case FPRINT_DEVICE_NAME:
-      g_value_set_static_string (value, fp_device_get_name (priv->dev));
-      break;
-
-    case FPRINT_DEVICE_NUM_ENROLL:
-      if (priv->dev)
-        g_value_set_int (value, fp_device_get_nr_enroll_stages (priv->dev));
-      else
-        g_value_set_int (value, -1);
-      break;
-
-    case FPRINT_DEVICE_SCAN_TYPE: {
-        const char *type;
-
-        if (fp_device_get_scan_type (priv->dev) == FP_SCAN_TYPE_PRESS)
-          type = "press";
-        else
-          type = "swipe";
-
-        g_value_set_static_string (value, type);
-        break;
-      }
-
     default:
       G_OBJECT_WARN_INVALID_PROPERTY_ID (object, property_id, pspec);
       break;
     }
 }
 
+static void
+on_nr_enroll_stages_changed (FprintDevice *rdev,
+                             GParamSpec   *spec,
+                             FpDevice     *device)
+{
+  FprintDBusDevice *dbus_dev = FPRINT_DBUS_DEVICE (rdev);
+  gint nr_enroll_stages;
+
+  nr_enroll_stages = fp_device_get_nr_enroll_stages (device);
+
+  g_debug ("Device %s enroll stages changed to %d",
+           fp_device_get_name (device),
+           nr_enroll_stages);
+
+  fprint_dbus_device_set_num_enroll_stages (dbus_dev, nr_enroll_stages);
+}
+
+static void
+on_scan_type_changed (FprintDevice *rdev,
+                      GParamSpec   *spec,
+                      FpDevice     *device)
+{
+  FprintDBusDevice *dbus_dev = FPRINT_DBUS_DEVICE (rdev);
+
+  if (fp_device_get_scan_type (device) == FP_SCAN_TYPE_PRESS)
+    fprint_dbus_device_set_scan_type (dbus_dev, "press");
+  else if (fp_device_get_scan_type (device) == FP_SCAN_TYPE_SWIPE)
+    fprint_dbus_device_set_scan_type (dbus_dev, "swipe");
+
+  g_debug ("Device %s scan type changed to '%s'",
+           fp_device_get_name (device),
+           fprint_dbus_device_get_scan_type (dbus_dev));
+}
+
+static void
+fprint_device_constructed (GObject *object)
+{
+  FprintDevice *rdev = FPRINT_DEVICE (object);
+  FprintDBusDevice *dbus_dev = FPRINT_DBUS_DEVICE (rdev);
+  FprintDevicePrivate *priv = fprint_device_get_instance_private (rdev);
+
+  fprint_dbus_device_set_name (dbus_dev, fp_device_get_name (priv->dev));
+
+  g_signal_connect_object (priv->dev, "notify::scan-type",
+                           G_CALLBACK (on_scan_type_changed),
+                           rdev, G_CONNECT_SWAPPED);
+  on_scan_type_changed (rdev, NULL, priv->dev);
+
+  g_signal_connect_object (priv->dev, "notify::nr-enroll-stages",
+                           G_CALLBACK (on_nr_enroll_stages_changed),
+                           rdev, G_CONNECT_SWAPPED);
+  on_nr_enroll_stages_changed (rdev, NULL, priv->dev);
+
+  G_OBJECT_CLASS (fprint_device_parent_class)->constructed (object);
+}
+
 static void
 fprint_device_class_init (FprintDeviceClass *klass)
 {
   GObjectClass *gobject_class = G_OBJECT_CLASS (klass);
   GParamSpec *pspec;
 
+  gobject_class->constructed = fprint_device_constructed;
   gobject_class->dispose = fprint_device_dispose;
   gobject_class->finalize = fprint_device_finalize;
   gobject_class->set_property = fprint_device_set_property;
@@ -342,18 +374,6 @@ fprint_device_class_init (FprintDeviceClass *klass)
   g_object_class_install_property (gobject_class,
                                    FPRINT_DEVICE_IN_USE, pspec);
 
-  g_object_class_override_property (gobject_class,
-                                    FPRINT_DEVICE_NAME,
-                                    "name");
-
-  g_object_class_override_property (gobject_class,
-                                    FPRINT_DEVICE_SCAN_TYPE,
-                                    "scan-type");
-
-  g_object_class_override_property (gobject_class,
-                                    FPRINT_DEVICE_NUM_ENROLL,
-                                    "num-enroll-stages");
-
   signals[SIGNAL_VERIFY_STATUS] =
     g_signal_lookup ("verify-status", FPRINT_TYPE_DEVICE);
   signals[SIGNAL_ENROLL_STATUS] =