[gxml] Implemented better support for GXml.Node.parent to TwNode

[Daniel Espinosa Ortiz <despinosa src gnome org>]

commit f67dc16f1cae0143c25621c05f9ef0b1dfa61cdc
Author: Daniel Espinosa <esodan gmail com>
Date:   Thu Feb 18 18:33:43 2016 -0600

    Implemented better support for GXml.Node.parent to TwNode

 gxml/TwElement.vala |    6 ++++--
 gxml/TwNode.vala    |   17 +++++++++++++++--
 2 files changed, 19 insertions(+), 4 deletions(-)
---
diff --git a/gxml/TwElement.vala b/gxml/TwElement.vala
index c88b596..8721578 100644
--- a/gxml/TwElement.vala
+++ b/gxml/TwElement.vala
@@ -27,7 +27,7 @@ using Gee;
 public class GXml.TwElement : GXml.TwNode, GXml.Element
 {
   protected Gee.HashMap<string,GXml.Node> _attrs;
-  protected Gee.ArrayList<GXml.Node> _children;
+  protected TwNode.TwChildrenList _children;
   protected Gee.ArrayList<GXml.Node> _namespaces;
   private string _content = null;
   public TwElement (GXml.Document d, string name)
@@ -53,7 +53,7 @@ public class GXml.TwElement : GXml.TwNode, GXml.Element
   }
   public override Gee.BidirList<GXml.Node> children {
     owned get {
-      if (_children == null) _children  = new Gee.ArrayList<GXml.Node> ();
+      if (_children == null) _children  = new TwChildrenList (this);
       return _children.ref () as Gee.BidirList<GXml.Node>;
     }
   }
@@ -68,6 +68,7 @@ public class GXml.TwElement : GXml.TwNode, GXml.Element
   {
     if (":" in name) return;
     var att = new TwAttribute (document, name, value);
+    att.set_parent (this);
     attrs.set (name, att);
   }
   public GXml.Node get_attr (string name) { return attrs.get (name); }
@@ -82,6 +83,7 @@ public class GXml.TwElement : GXml.TwNode, GXml.Element
   public void set_ns_attr (Namespace ns, string name, string value) {
     var att = new TwAttribute (document, name, value);
     att.set_namespace (ns.uri, ns.prefix);
+    att.set_parent (this);
     attrs.set (name, att);
   }
   public void remove_attr (string name) {
diff --git a/gxml/TwNode.vala b/gxml/TwNode.vala
index c37b85f..0bd0ef3 100644
--- a/gxml/TwNode.vala
+++ b/gxml/TwNode.vala
@@ -29,6 +29,7 @@ public abstract class GXml.TwNode : Object, GXml.Node
   protected string _name = null;
   protected string _value = null;
   protected GXml.Document _doc;
+  protected GXml.Node _parent;
   internal Xml.TextWriter *tw;
 
        construct { Init.init (); }
@@ -52,11 +53,23 @@ public abstract class GXml.TwNode : Object, GXml.Node
   }
   public virtual string to_string () { return get_type ().name (); }
   public virtual Gee.Map<string,GXml.Node> attrs { owned get { return new Gee.HashMap<string,GXml.Node> (); 
} }
-  public virtual Gee.BidirList<GXml.Node> children { owned get { return new Gee.ArrayList<GXml.Node> (); } }
+  public virtual Gee.BidirList<GXml.Node> children { owned get { return new TwChildrenList (this); } }
   public virtual GXml.Document document { get { return _doc; } }
   public virtual string name { owned get { return _name.dup (); } }
   public virtual Gee.List<GXml.Namespace> namespaces { owned get { return new Gee.ArrayList<GXml.Node> (); } 
}
   public virtual GXml.NodeType type_node { get { return GXml.NodeType.DOCUMENT; } }
   public virtual string value { owned get { return _value.dup (); } set  { _value = value; } }
-  public virtual GXml.Node parent { owned get { return null; } }
+  public virtual GXml.Node parent { owned get { return _parent; } }
+  public virtual void set_parent (GXml.Node node) { _parent = node; }
+  
+  protected class TwChildrenList : Gee.ArrayList<GXml.Node> {
+    GXml.Node _parent;
+    protected TwChildrenList (GXml.Node e) {
+      _parent = e;
+    }
+    protected new bool add (GXml.Node node) {
+      (node as GXml.TwNode).set_parent (_parent);
+      return base.add (node);
+    }
+  }
 }