Merge pull request #4 from Ralf1108/master

Write fill attribute value if it differs from parent element, as a temporal fix.

Source/Document Structure/SvgGroup.cs

@@ -26,7 +26,7 @@ namespace Svg
         [SvgAttribute("fill")]
         public override SvgPaintServer Fill
         {
-            get { return (this.Attributes["Fill"] == null) ? new SvgColourServer(Color.Transparent) : (SvgPaintServer)this.Attributes["Fill"]; }
+            get { return (this.Attributes["Fill"] == null) ? null : (SvgPaintServer)this.Attributes["Fill"]; }
             set { this.Attributes["Fill"] = value; }
         }
 

Source/Painting/SvgColourServer.cs

@@ -61,5 +61,18 @@ namespace Svg
 
 		}
 
+        public override bool Equals(object obj)
+        {
+            var objColor = obj as SvgColourServer;
+            if (objColor == null)
+                return false;
+
+            return this.GetHashCode() == objColor.GetHashCode();
+        }
+
+        public override int GetHashCode()
+        {
+            return _colour.GetHashCode();
+        }
     }
 }

Source/SvgElement.cs

@@ -357,12 +357,26 @@ namespace Svg
                 {
                     object propertyValue = attr.Property.GetValue(this);
 
+                    var forceWrite = false;
+                    if ((attr.Attribute.Name == "fill") && (Parent != null))
+                    {
+                        object parentValue;
+                        if (TryResolveParentAttributeValue(attr.Attribute.Name, out parentValue))
+                        {
+                            if ((parentValue == propertyValue) 
+                                || ((parentValue != null) &&  parentValue.Equals(propertyValue)))
+                                continue;
+                            
+                            forceWrite = true;
+                        }
+                    }
+
                     if (propertyValue != null)
                     {
                         var type = propertyValue.GetType();
                         string value = (string)attr.Property.Converter.ConvertTo(propertyValue, typeof(string));
 
-                        if (!SvgDefaults.IsDefault(attr.Attribute.Name, value))
+                        if (!SvgDefaults.IsDefault(attr.Attribute.Name, value) || forceWrite)
                         {
                             writer.WriteAttributeString(attr.Attribute.NamespaceAndName, value);
                         }
@@ -380,7 +394,29 @@ namespace Svg
             {
                 writer.WriteAttributeString(item.Key, item.Value);
             }
+        }
+
+        private bool TryResolveParentAttributeValue(string attributeKey, out object parentAttributeValue)
+        {
+            parentAttributeValue = null;
+
+            attributeKey = char.ToUpper(attributeKey[0]) + attributeKey.Substring(1);
+
+            var currentParent = Parent;
+            var resolved = false;
+            while (currentParent != null)
+            {
+                if (currentParent.Attributes.ContainsKey(attributeKey))
+                {
+                    resolved = true;
+                    parentAttributeValue = currentParent.Attributes[attributeKey];
+                    if (parentAttributeValue != null)
+                        break;
+                }
+                currentParent = currentParent.Parent;
+            }
 
+            return resolved;
         }
 
         protected virtual void Write(XmlTextWriter writer)