[gxml] Ported Serializable.serialize_property to GXml.Node

[Daniel Espinosa Ortiz <despinosa src gnome org>]

commit 642f2da48d9f6a8be8e644f4de2257550e2fae38
Author: Daniel Espinosa <esodan gmail com>
Date:   Fri Apr 24 14:43:12 2015 -0500

    Ported Serializable.serialize_property to GXml.Node

 gxml/Serializable.vala              |    2 +-
 gxml/SerializableGeeArrayList.vala  |    4 ++--
 gxml/SerializableGeeDualKeyMap.vala |    4 ++--
 gxml/SerializableGeeHashMap.vala    |    4 ++--
 gxml/SerializableGeeTreeMap.vala    |    4 ++--
 gxml/SerializableJson.vala          |    4 +++-
 gxml/SerializableObjectModel.vala   |    6 ++++--
 7 files changed, 16 insertions(+), 12 deletions(-)
---
diff --git a/gxml/Serializable.vala b/gxml/Serializable.vala
index 5028eba..edaa570 100644
--- a/gxml/Serializable.vala
+++ b/gxml/Serializable.vala
@@ -160,7 +160,7 @@ namespace GXml {
      * This method is called recursivally by { link serialize} method over all properties
      * to be serialized.
      */
-    public abstract GXml.xNode? serialize_property (GXml.xElement element,
+    public abstract GXml.Node? serialize_property (GXml.Node element,
                                                    GLib.ParamSpec prop)
                                                    throws GLib.Error;
 
diff --git a/gxml/SerializableGeeArrayList.vala b/gxml/SerializableGeeArrayList.vala
index 645fcda..24288d5 100644
--- a/gxml/SerializableGeeArrayList.vala
+++ b/gxml/SerializableGeeArrayList.vala
@@ -99,13 +99,13 @@ public class GXml.SerializableArrayList<G> : Gee.ArrayList<G>, Serializable, Ser
     }
     return node;
   }
-  public virtual GXml.xNode? serialize_property (GXml.xElement element,
+  public virtual GXml.Node? serialize_property (GXml.Node element,
                                         GLib.ParamSpec prop)
                                         throws GLib.Error
   {
     return default_serialize_property (element, prop);
   }
-  public GXml.xNode? default_serialize_property (GXml.xElement element,
+  public GXml.Node? default_serialize_property (GXml.Node element,
                                         GLib.ParamSpec prop)
                                         throws GLib.Error
   {
diff --git a/gxml/SerializableGeeDualKeyMap.vala b/gxml/SerializableGeeDualKeyMap.vala
index eae37d9..d1d84e3 100644
--- a/gxml/SerializableGeeDualKeyMap.vala
+++ b/gxml/SerializableGeeDualKeyMap.vala
@@ -178,13 +178,13 @@ public class GXml.SerializableDualKeyMap<P,S,V> : Object, Serializable, Serializ
     }
     return node;
   }
-  public virtual GXml.xNode? serialize_property (GXml.xElement element,
+  public virtual GXml.Node? serialize_property (GXml.Node element,
                                         GLib.ParamSpec prop)
                                         throws GLib.Error
   {
     return default_serialize_property (element, prop);
   }
-  public GXml.xNode? default_serialize_property (GXml.xElement element,
+  public GXml.Node? default_serialize_property (GXml.Node element,
                                         GLib.ParamSpec prop)
                                         throws GLib.Error
   {
diff --git a/gxml/SerializableGeeHashMap.vala b/gxml/SerializableGeeHashMap.vala
index aaba248..7f53ec7 100644
--- a/gxml/SerializableGeeHashMap.vala
+++ b/gxml/SerializableGeeHashMap.vala
@@ -95,13 +95,13 @@ public class GXml.SerializableHashMap<K,V> : Gee.HashMap<K,V>, Serializable, Ser
     }
     return node;
   }
-  public virtual GXml.xNode? serialize_property (GXml.xElement element,
+  public virtual GXml.Node? serialize_property (GXml.Node element,
                                         GLib.ParamSpec prop)
                                         throws GLib.Error
   {
     return default_serialize_property (element, prop);
   }
-  public GXml.xNode? default_serialize_property (GXml.xElement element,
+  public GXml.Node? default_serialize_property (GXml.Node element,
                                         GLib.ParamSpec prop)
                                         throws GLib.Error
   {
diff --git a/gxml/SerializableGeeTreeMap.vala b/gxml/SerializableGeeTreeMap.vala
index d28f2bd..79f8448 100644
--- a/gxml/SerializableGeeTreeMap.vala
+++ b/gxml/SerializableGeeTreeMap.vala
@@ -98,13 +98,13 @@ public class GXml.SerializableTreeMap<K,V> : Gee.TreeMap<K,V>, Serializable, Ser
     }
     return node;
   }
-  public virtual GXml.xNode? serialize_property (GXml.xElement element,
+  public virtual GXml.Node? serialize_property (GXml.Node element,
                                         GLib.ParamSpec prop)
                                         throws GLib.Error
   {
     return default_serialize_property (element, prop);
   }
-  public GXml.xNode? default_serialize_property (GXml.xElement element,
+  public GXml.Node? default_serialize_property (GXml.Node element,
                                         GLib.ParamSpec prop)
                                         throws GLib.Error
   {
diff --git a/gxml/SerializableJson.vala b/gxml/SerializableJson.vala
index cbc4d1b..5eec3e0 100644
--- a/gxml/SerializableJson.vala
+++ b/gxml/SerializableJson.vala
@@ -139,10 +139,12 @@ public class GXml.SerializableJson : GLib.Object, GXml.Serializable
     return root;
   }
 
-  public virtual GXml.xNode? serialize_property (xElement element, 
+  public virtual GXml.Node? serialize_property (GXml.Node node, 
                                         GLib.ParamSpec prop)
                                         throws GLib.Error
+                                        requires (node is xElement)
   {
+    xElement element = (xElement) node;
     Type type;
     Value val;
     GXml.xNode value_node = null;
diff --git a/gxml/SerializableObjectModel.vala b/gxml/SerializableObjectModel.vala
index 46691c4..41d394a 100644
--- a/gxml/SerializableObjectModel.vala
+++ b/gxml/SerializableObjectModel.vala
@@ -153,11 +153,13 @@ public abstract class GXml.SerializableObjectModel : Object, Serializable
     return element;
   }
 
-  public virtual GXml.xNode? serialize_property (GXml.xElement element,
+  public virtual GXml.Node? serialize_property (GXml.Node element,
                                         GLib.ParamSpec prop)
                                         throws GLib.Error
   {
-    return default_serialize_property (element, prop);
+    if (element is xElement)
+      return default_serialize_property ((xElement) element, prop);
+    return null;
   }
   public GXml.xNode? default_serialize_property (GXml.xElement element,
                                         GLib.ParamSpec prop)