timelineobject: Add a method to add a GESAsset

+ Avoid to assume function arguments are correct before actually testing
      them in ges_timeline_object_add_track_object

API: ges_timeline_object_add_asset

docs/libs/ges-sections.txt

@@ -336,6 +336,7 @@ ges_timeline_object_set_duration
 ges_timeline_object_get_layer
 ges_timeline_object_find_track_object
 ges_timeline_object_add_track_object
+ges_timeline_object_add_asset
 ges_timeline_object_get_top_effects
 ges_timeline_object_get_top_effect_position
 ges_timeline_object_move_to_layer

ges/ges-timeline-object.c

@@ -572,16 +572,19 @@ gboolean
 ges_timeline_object_add_track_object (GESTimelineObject * object, GESTrackObject
     * trobj)
 {
-  ObjectMapping *mapping;
   GList *tmp;
+  gboolean is_effect;
+  ObjectMapping *mapping;
   guint max_prio, min_prio;
-  GESTimelineObjectPrivate *priv = object->priv;
+  GESTimelineObjectClass *klass;
-  gboolean is_effect = GES_IS_TRACK_EFFECT (trobj);
+  GESTimelineObjectPrivate *priv;
-  GESTimelineObjectClass *klass = GES_TIMELINE_OBJECT_GET_CLASS (object);
 
   g_return_val_if_fail (GES_IS_TIMELINE_OBJECT (object), FALSE);
   g_return_val_if_fail (GES_IS_TRACK_OBJECT (trobj), FALSE);
 
+  priv = object->priv;
+  is_effect = GES_IS_TRACK_EFFECT (trobj);
+
   GST_LOG ("Got a TrackObject : %p , setting the timeline object as its"
       "creator. Is a TrackEffect %i", trobj, is_effect);
 
@@ -637,6 +640,7 @@ ges_timeline_object_add_track_object (GESTimelineObject * object, GESTrackObject
   ges_track_object_set_inpoint (trobj, object->inpoint);
   ges_track_object_set_max_duration (trobj, object->priv->maxduration);
 
+  klass = GES_TIMELINE_OBJECT_GET_CLASS (object);
   if (klass->track_object_added) {
     GST_DEBUG ("Calling track_object_added subclass method");
     klass->track_object_added (object, trobj);
@@ -1942,6 +1946,34 @@ ges_timeline_object_trim_start (GESTimelineObject * object, guint64 start)
   return ret;
 }
 
+/**
+ * ges_timeline_object_add_asset:
+ * @object: a #GESTimelineObject
+ * @asset: a #GESAsset with #GES_TYPE_TRACK_OBJECT as extractable_type
+ *
+ * Extracts a #GESTrackObject from @asset and adds it to the @object.
+ * Should only be called in order to add operations to a #GESTimelineObject,
+ * ni other cases TrackObject are added automatically when adding the
+ * #GESTimelineObject/#GESAsset to a layer.
+ *
+ * Takes a reference on @trobj.
+ *
+ * Returns: %TRUE on success, %FALSE on failure.
+ */
+
+gboolean
+ges_timeline_object_add_asset (GESTimelineObject * object,
+    GESAsset * asset)
+{
+  g_return_val_if_fail (GES_IS_TIMELINE_OBJECT (object), FALSE);
+  g_return_val_if_fail (GES_IS_ASSET (asset), FALSE);
+  g_return_val_if_fail (g_type_is_a (ges_asset_get_extractable_type
+          (asset), GES_TYPE_TRACK_OBJECT), FALSE);
+
+  return ges_timeline_object_add_track_object (object,
+      GES_TRACK_OBJECT (ges_asset_extract (asset, NULL)));
+}
+
 static void
 update_height (GESTimelineObject * object)
 {

ges/ges-timeline-object.h

@@ -256,6 +256,7 @@ ges_timeline_object_create_track_objects    (GESTimelineObject * object,
 gboolean
 ges_timeline_object_release_track_object    (GESTimelineObject * object,
 					  GESTrackObject * trackobject);
+gboolean ges_timeline_object_add_asset               (GESTimelineObject *object, GESAsset       *asset);
 
 gboolean
 ges_timeline_object_fill_track_object       (GESTimelineObject * object,