[gxml] Now unknown elements/attributes initialization done only if required

[Daniel Espinosa Ortiz <despinosa src gnome org>]

commit 9dbaba201908d8ebcd9f79e620c85e95996c5a34
Author: Daniel Espinosa <esodan gmail com>
Date:   Thu Jun 18 05:45:25 2015 -0500

    Now unknown elements/attributes initialization done only if required
    
    * This fixes memory resources upto 60-75% when using SerializableObjectModel

 gxml/SerializableObjectModel.vala |   19 +++++++++++--------
 1 files changed, 11 insertions(+), 8 deletions(-)
---
diff --git a/gxml/SerializableObjectModel.vala b/gxml/SerializableObjectModel.vala
index 202c432..50dec7f 100644
--- a/gxml/SerializableObjectModel.vala
+++ b/gxml/SerializableObjectModel.vala
@@ -38,32 +38,34 @@ using Gee;
 public abstract class GXml.SerializableObjectModel : Object, Serializable
 {
   // holds all unknown nodes
-  protected GXml.TwDocument _doc;
+  protected GXml.TwDocument _doc = null;
   /* Serializable interface properties */
   protected ParamSpec[] properties { get; set; }
   public GLib.HashTable<string,GLib.ParamSpec> ignored_serializable_properties { get; protected set; }
   public string? serialized_xml_node_value { get; protected set; default=null; }
   public virtual bool get_enable_unknown_serializable_property () { return false; }
+  /**
+   * All unknown nodes, will be stored in a per-object { link GXml.Document}
+   * in its { link GXml.Element} root. Then, all unknown properties will be
+   * stored as properties in document's root and all unknown childs { link GXml.Node}
+   * as root's childs.
+   */
   public Gee.Map<string,GXml.Attribute> unknown_serializable_properties
   {
     get {
+      if (_doc == null) init_unknown_doc ();
       return (Gee.Map<string,GXml.Attribute>) _doc.root.attrs;
     }
   }
   public Gee.Collection<GXml.Node> unknown_serializable_nodes
   {
     get {
+      if (_doc == null) init_unknown_doc ();
       return _doc.root.childs;
     }
   }
 
-  /**
-   * All unknown nodes, will be stored in a per-object { link GXml.Document}
-   * in its { link GXml.Element} root. Then, all unknown properties will be
-   * stored as properties in document's root and all unknown childs { link GXml.Node}
-   * as root's childs.
-   */
-  construct
+  private void init_unknown_doc ()
   {
     _doc = new TwDocument ();
     var r = _doc.create_element ("root");
@@ -374,6 +376,7 @@ public abstract class GXml.SerializableObjectModel : Object, Serializable
     if (prop == null) {
       // FIXME: Event emit
       if (get_enable_unknown_serializable_property ()) {
+        if (_doc == null) init_unknown_doc ();
         if (property_node is GXml.Attribute) {
 #if DEBUG
           GLib.message (@"Adding unknown attribute $(property_node.name) to $(get_type ().name ())\n");